WO2024055162A1 - Negative electrode sheet, method for manufacturing negative electrode sheet, secondary battery and electric device - Google Patents

Negative electrode sheet, method for manufacturing negative electrode sheet, secondary battery and electric device Download PDF

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WO2024055162A1
WO2024055162A1 PCT/CN2022/118484 CN2022118484W WO2024055162A1 WO 2024055162 A1 WO2024055162 A1 WO 2024055162A1 CN 2022118484 W CN2022118484 W CN 2022118484W WO 2024055162 A1 WO2024055162 A1 WO 2024055162A1
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negative electrode
film layer
electrode film
porosity
thickness
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PCT/CN2022/118484
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French (fr)
Chinese (zh)
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李玲
宋书涛
张小细
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宁德时代新能源科技股份有限公司
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Priority to PCT/CN2022/118484 priority Critical patent/WO2024055162A1/en
Publication of WO2024055162A1 publication Critical patent/WO2024055162A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application belongs to the technical field of electrochemistry, and specifically relates to a negative electrode plate, a method for preparing a negative electrode plate, a secondary battery and an electrical device.
  • Secondary batteries represented by lithium-ion batteries, are widely used in all aspects of today's life due to their advantages such as no memory effect, long cycle life, and environmental protection. In recent years, secondary batteries have developed rapidly in the fields of new energy vehicles and large-scale energy storage. In current secondary batteries, conventional negative electrode sheets usually have low porosity and poor electrolyte wetting properties, resulting in poor rate performance of secondary batteries.
  • the purpose of this application is to provide a negative electrode sheet, a method for preparing the negative electrode sheet, a secondary battery and an electrical device, aiming to improve the electrolyte wetting performance of the negative electrode sheet and the rate performance of the secondary battery.
  • the first aspect of the present application provides a negative electrode sheet, including: a negative electrode current collector; and a negative electrode film layer disposed on at least one side of the negative electrode current collector, and the negative electrode film layer includes a negative electrode film layer disposed close to the The first negative electrode film layer on the surface of the negative electrode current collector and the second negative electrode film layer disposed on the surface of the first negative electrode film layer away from the negative electrode current collector, wherein the first negative electrode film layer
  • the thickness is D1, the thickness of the second negative electrode film layer is D2, and D1>D2; the porosity of the first negative electrode film layer is P1, the porosity of the second negative electrode film layer is P2, and P1 ⁇ P2.
  • the negative electrode sheet provided in this application has a double film layer structure, in which the porosity of the first negative electrode film layer is smaller than the porosity of the second negative electrode film layer, that is, the surface film layer of the negative electrode sheet (the second negative electrode film layer)
  • the pore distribution of the inner membrane layer of the pole piece (the first negative electrode membrane layer) is relatively small.
  • the pores in the surface film layer are distributed more, which is conducive to the large-scale diffusion and penetration of the electrolyte on the surface of the pole piece, thereby improving the liquid absorption capacity of the pole piece; while the pore distribution in the inner film layer is relatively Less, it can form a differentiated structure of pore distribution in the inner and outer film layers.
  • This differentiated structure can give full play to the role of the pores in the film layer and increase the diffusion rate of electrolyte and active ions in the negative electrode piece, thereby improving the electrode piece. While absorbing liquid, it can also increase the electrolyte infiltration rate of the pole piece, and ultimately improve the rate performance of the secondary battery.
  • the thickness of the first negative electrode film layer is thicker than the thickness of the second negative electrode film layer, that is, the thickness of the internal film layer of the negative electrode plate (the first negative electrode film layer) is thicker than the thickness of the surface film layer (the second negative electrode film layer). Greater thickness.
  • This thickness setting can ensure a sufficiently high bonding force between the negative electrode film layer and the negative electrode current collector, ensure that the negative electrode plate has sufficient bonding performance, reduce the shedding of active material on the electrode plate, and thereby increase the capacity of the secondary battery.
  • the surface film layer (second negative electrode film layer) is thinner than the internal film layer (first negative electrode film layer), which is also conducive to reducing the diffusion distance of the electrolyte on the surface of the electrode piece when the surface film layer diffuses and penetrates in large amounts. , and through synergy with the above-mentioned differentiated structure of pore distribution in the inner and outer membrane layers, further accelerate the diffusion rate of the electrolyte and increase the electrolyte infiltration rate of the pole piece
  • the ratio of the thickness of the first negative electrode film layer to the thickness of the second negative electrode film layer is 3 ⁇ D1/D2 ⁇ 10, optionally 5 ⁇ D1/D2 ⁇ 8.
  • the ratio of the thickness of the first negative electrode film layer to the thickness of the second negative electrode film layer is within an appropriate range, which can reduce the impact of the pore structure in the film layer on the bonding performance of the negative electrode film layer, wherein the pores of the first negative electrode film layer
  • the rate is lower and the thickness is thicker.
  • the porosity of the second negative electrode film layer is higher and the thickness is thinner. Therefore, the first negative electrode film layer contains more binding material per unit volume than the second negative electrode film layer, and is closely related to the negative electrode current collector. The adhesiveness is also stronger.
  • the negative electrode film layer can be
  • the negative electrode current collector has sufficient bonding force to improve the bonding performance of the negative electrode sheet. It can also further leverage the differentiated structure of the pore distribution of the first negative electrode film layer and the second negative electrode film layer in the negative electrode film layer. The synergistic effect further improves the electrolyte infiltration rate of the pole piece.
  • the ratio of the porosity of the second negative electrode film layer to the porosity of the first negative electrode film layer is 1 ⁇ P2/P1 ⁇ 5, optionally 3 ⁇ P2/P1 ⁇ 4 .
  • the ratio of the porosity of the second negative electrode film layer to the porosity of the first negative electrode film layer is within an appropriate range, which is conducive to further increasing the diffusion and penetration of the electrolyte in the surface film layer of the electrode piece, and further improving the liquid absorption capacity of the electrode piece.
  • controlling the ratio of porosity within the above range can better form a differentiated structure of pore distribution in the inner and outer film layers, and more fully play the role of pores in this differentiated structure, improving the electrolyte in the negative electrode piece. Diffusion rate, thereby further increasing the electrolyte infiltration rate of the pole piece, and ultimately improving the rate performance of the secondary battery.
  • the first negative electrode film layer meets at least one of the following conditions:
  • the thickness of the first negative electrode film layer is 80 ⁇ m ⁇ D1 ⁇ 2250 ⁇ m, optionally 100 ⁇ m ⁇ D1 ⁇ 2000 ⁇ m;
  • the porosity of the first negative electrode film layer is 20% ⁇ P1 ⁇ 40%, optionally 25% ⁇ P1 ⁇ 35%.
  • the thickness of the first negative electrode film layer is within a suitable range, which is beneficial to minimizing the diffusion distance of the electrolyte while ensuring adhesion, increasing the transmission rate of active ions (such as lithium ions), thereby improving the rate performance of the secondary battery .
  • the porosity of the first negative electrode film layer is within an appropriate range, which is conducive to the formation of the aforementioned differentiated structure of pore distribution between the inner and outer film layers with the second negative electrode film layer, and allows this differentiated structure to more fully exert itself in the film layer.
  • the role of pores increases the diffusion rate of electrolyte in the negative electrode piece, thereby increasing the electrolyte infiltration rate of the electrode piece.
  • the second negative electrode film layer satisfies at least one of the following conditions:
  • the thickness of the second negative electrode film layer is 8 ⁇ m ⁇ D2 ⁇ 750 ⁇ m, optionally 10 ⁇ m ⁇ D2 ⁇ 700 ⁇ m;
  • the porosity of the second negative electrode film layer is 40% ⁇ P2 ⁇ 70%, optionally 45% ⁇ P2 ⁇ 65%.
  • the thickness of the second negative electrode film layer is controlled within the above range, which is beneficial to reducing the diffusion distance of the electrolyte on the surface of the electrode piece when it diffuses into the surface film layer, further accelerating the diffusion rate, reducing the interface resistance, thereby further improving the performance of the electrode piece Electrolyte infiltration rate and rate performance of secondary batteries.
  • the porosity of the second negative electrode film layer is within the above range, which is conducive to the diffusion and penetration of a large amount of electrolyte on the surface of the electrode piece, thereby improving the liquid absorption capacity of the electrode piece.
  • the total porosity of the negative electrode film layer is P0, and 30% ⁇ P0 ⁇ 60%, optionally 35% ⁇ P0 ⁇ 55%.
  • the total porosity of the negative electrode film layer is within an appropriate range, which is beneficial to improving the liquid absorption capacity of the electrode piece and improving the conductivity of active ions (such as lithium ions) in the negative electrode piece.
  • the total thickness of the negative electrode film layer is D0, and 100 ⁇ m ⁇ D0 ⁇ 3000 ⁇ m, optionally 150 ⁇ m ⁇ D0 ⁇ 2500 ⁇ m.
  • the total thickness of the negative electrode film layer is within an appropriate range, which can ensure the bonding performance of the negative electrode piece, shorten the diffusion path and diffusion distance of the electrolyte in the electrode piece, and improve the electrolyte wettability of the electrode piece.
  • the single-sided coating weight of the negative electrode piece is 0.1g/1540.25mm 2 to 0.4g/1540.25mm 2 , optionally 0.15g/1540.25mm 2 to 0.35g/1540.25mm 2 .
  • the single-sided coating weight of the negative electrode piece is within an appropriate range, which can shorten the diffusion path and diffusion distance of the electrolyte in the electrode piece, which is conducive to increasing the infiltration rate of the electrolyte, thereby improving the transmission efficiency of active ions (such as lithium ions) , while ensuring that the secondary battery has a high energy density.
  • a second aspect of the present application provides a method for preparing a negative electrode sheet, including: a film forming step, including forming a first negative electrode film layer and a second negative electrode film layer on at least one side of the negative electrode current collector to obtain a negative electrode sheet ; wherein, the first negative electrode film layer is located on a surface close to the negative electrode current collector, and the second negative electrode film layer is located on a surface of the first negative electrode film layer away from the negative electrode current collector;
  • the thickness of a negative electrode film layer is D1, the thickness of the second negative electrode film layer is D2, and D1>D2;
  • the porosity of the first negative electrode film layer is P1, and the porosity of the second negative electrode film layer is P1 P2, and P1 ⁇ P2.
  • a double-film layer structure composed of a first negative electrode film layer and a second negative electrode film layer is formed on at least one side of the negative electrode current collector.
  • the pore distribution of the second negative electrode film layer is relatively small. It is conducive to the large amount of electrolyte diffusion and penetration on the surface of the pole piece, which can improve the liquid absorption capacity of the pole piece.
  • the pore distribution of the first negative electrode film layer is relatively small, which can form a differentiated structure of the pore distribution of the inner and outer film layers in the negative electrode piece. This differentiated structure can give full play to the role of the pores in the film layer and improve the electrolyte and activity.
  • the diffusion rate of ions in the negative electrode plate increases the electrolyte infiltration rate of the electrode plate and ultimately improves the rate performance of the secondary battery.
  • the film forming step further includes: coating a first negative electrode slurry on at least one side of the negative electrode current collector to form a first coating layer; Coating a second negative electrode slurry on the second negative electrode slurry to form a second coating, wherein the second negative electrode slurry includes 1,2-dihydroxy-3-trityl-propane; and to the first coating
  • the second coating layer is dried and cold-pressed to form the first negative electrode film layer and the second negative electrode film layer.
  • the second slurry includes the thermal sublimation material 1,2-dihydroxy-3-trityl-propane, which is used as a pore-forming agent for the second negative electrode film layer in the process of formation.
  • the mass percentage of the 1,2-dihydroxy-3-trityl-propane is 0.1% to 30%. Choose from 1% to 25%.
  • the method satisfies at least one of the following conditions:
  • the first negative electrode slurry includes a negative active material and an optional first component, wherein the first component includes a conductive agent, a binder, a thickener, a solvent, or a combination thereof;
  • the second negative electrode slurry also includes a negative active material and an optional second component, wherein the second component includes a conductive agent, a binder, a thickener, a solvent, or a combination thereof.
  • a third aspect of this application provides a secondary battery, including the negative electrode piece described in the first aspect of this application or the negative electrode piece produced by the method described in the second aspect of this application.
  • a fourth aspect of this application provides a battery module, including the secondary battery described in the third aspect of this application.
  • a fifth aspect of this application provides a battery pack, including the battery module described in the fourth aspect of this application.
  • a sixth aspect of this application provides an electrical device, including at least one of the secondary battery described in the third aspect of this application, the battery module described in the fourth aspect, or the battery pack described in the fifth aspect of this application.
  • the battery modules, battery packs and electrical devices of the present application include the secondary battery provided by the present application, and thus have at least the same advantages as the secondary battery.
  • Figure 1 is a schematic structural diagram of an embodiment of the negative electrode plate of the present application.
  • FIG. 2 is a schematic diagram of an embodiment of the secondary battery of the present application.
  • FIG. 3 is an exploded schematic diagram of an embodiment of the secondary battery of the present application.
  • FIG. 4 is a schematic diagram of an embodiment of the battery module of the present application.
  • FIG. 5 is a schematic diagram of an embodiment of the battery pack of the present application.
  • FIG. 6 is an exploded view of FIG. 5 .
  • FIG. 7 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of the present application.
  • any lower limit can be combined with any upper limit to form an unexpressed range; and any lower limit can be combined with other lower limits to form an unexpressed range, and likewise any upper limit can be combined with any other upper limit to form an unexpressed range.
  • each individually disclosed point or single value may itself serve as a lower or upper limit in combination with any other point or single value or with other lower or upper limits to form a range not expressly recited.
  • a list of items connected by the terms “at least one of,” “at least one of,” “at least one of,” or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, the phrase “at least one of A and B” means only A; only B; or A and B. In another example, if the items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B and C.
  • Item A may contain a single component or multiple components.
  • Item B may contain a single component or multiple components.
  • Item C may contain a single component or multiple components.
  • the porosity of the negative electrode sheet of the secondary battery is usually not high, resulting in poor rate performance of the secondary battery.
  • conventional methods usually include: (1) using a pore-forming agent to create pores, and adjusting the proportion of the pore-forming agent to regulate the porosity of the negative electrode sheet to obtain a porous negative electrode sheet ; (2) Use graphite with a larger specific surface area as the negative electrode active material, such as natural graphite, to increase the porosity of the negative electrode sheet through the porosity of the graphite itself.
  • the method (1) 1) After using a pore-forming agent to create pores, the pores in the negative electrode sheet are usually irregularly distributed. This irregular distribution cannot effectively take advantage of the pores and increase the infiltration rate of the electrolyte. Moreover, the porous structure formed in the negative electrode piece may affect the bonding performance of the electrode piece and easily cause the active material on the electrode piece to fall off, resulting in a decrease in the capacity of the secondary battery.
  • the conventional pore-forming agent used in method (1) is easily decomposed during the reaction to produce harmful corrosive gases. This corrosive gas will produce side reactions in the battery core and reduce the performance of the battery core.
  • method (2) after the negative electrode piece is cold-pressed, the pores of the graphite itself will be compacted, so the porosity of the electrode piece cannot be effectively improved; and using graphite with a larger specific surface area will generate more SEI film, leading to deterioration of gas production and affecting the cycle performance of secondary batteries.
  • the inventor proposed a negative electrode sheet through extensive research and cleverly designed the structure of the negative electrode film layer in the negative electrode sheet.
  • the negative electrode sheet includes a negative electrode current collector and a double membrane provided on the negative electrode current collector.
  • layer structure in which the film layer close to the negative electrode current collector is relatively thick and has fewer pores, ensuring that the electrode piece has a sufficiently high bonding force; the film layer away from the negative electrode current collector is relatively thin and has more pores, ensuring that the electrode piece has Higher ability to absorb electrolyte (liquid absorption capacity).
  • the electrolyte absorption capacity (liquid absorption capacity) of the negative electrode plate can be improved.
  • the electrolyte infiltration rate of the pole piece is increased, which is beneficial to improving the rate performance of the secondary battery and ensuring that the pole piece has sufficiently high bonding performance.
  • the first aspect of the embodiment of the present application provides a negative electrode sheet, see Figure 1, including: a negative electrode current collector 1; and a negative electrode film layer 2 provided on at least one side of the negative electrode current collector, the negative electrode film layer includes The first negative electrode film layer 21 is disposed on the surface close to the negative electrode current collector and the second negative electrode film layer 22 is disposed on the surface of the first negative electrode film layer away from the negative electrode current collector, wherein, the The thickness of the first negative electrode film layer 21 is D1, the thickness of the second negative electrode film layer 22 is D2, and D1>D2; the porosity of the first negative electrode film layer 21 is P1, and the thickness of the second negative electrode film layer 22 is D2.
  • the porosity of 22 is P2, and P1 ⁇ P2.
  • the inventor found that the liquid absorbing ability of the electrode piece is a behavior driven by capillary force.
  • the flow rate of electrolyte and active ion diffusion on the surface of the electrode piece is greater.
  • the diffusion flow rate of the electrolyte and active ions inside the pole piece will decrease rapidly.
  • the present application sets up the above-mentioned double-layer structure, in which the porosity of the first negative electrode film layer is smaller than the porosity of the second negative electrode film layer, that is, the surface film layer of the negative electrode sheet (the third The pore distribution of the two negative electrode film layers) is relatively large, while the pore distribution of the internal film layer of the pole piece (the first negative electrode film layer) is relatively small.
  • the pores in the surface film layer are distributed more, which is conducive to the large-scale diffusion and penetration of the electrolyte on the surface of the pole piece, thereby improving the liquid absorption capacity of the pole piece; while the pore distribution in the inner film layer is relatively Less, it can form a differentiated structure of pore distribution in the inner and outer film layers.
  • This differentiated structure can give full play to the role of the pores in the film layer and increase the diffusion rate of electrolyte and active ions in the negative electrode piece, thereby improving the electrode piece. While absorbing liquid, it can also increase the electrolyte infiltration rate of the pole piece, and ultimately improve the rate performance of the secondary battery.
  • the thickness of the first negative electrode film layer is thicker than the thickness of the second negative electrode film layer, that is, the thickness of the internal film layer of the negative electrode plate (the first negative electrode film layer) is thicker than the thickness of the surface film layer (the second negative electrode film layer) The thickness is greater.
  • This thickness setting can ensure a sufficiently high bonding force between the negative electrode film layer and the negative electrode current collector, ensure that the negative electrode plate has sufficient bonding performance, reduce the shedding of active material on the electrode plate, and thereby increase the capacity of the secondary battery. .
  • the surface film layer (the second negative electrode film layer) is thinner than the internal film layer (the first negative electrode film layer), which is also beneficial to reducing the diffusion distance of the electrolyte on the surface of the electrode piece when a large amount of the electrolyte diffuses and penetrates into the surface film layer.
  • the diffusion rate of the electrolyte is further accelerated and the electrolyte infiltration rate of the pole piece is increased.
  • the ratio of the thickness of the first negative electrode film layer to the thickness of the second negative electrode film layer is 3 ⁇ D1/D2 ⁇ 10.
  • the ratio of the thickness of the first negative electrode film layer to the thickness of the second negative electrode film layer may be 3 ⁇ D1/D2 ⁇ 9, 3 ⁇ D1/D2 ⁇ 8, 3 ⁇ D1/D2 ⁇ 7, 3 ⁇ D1/D2 ⁇ 6, 3 ⁇ D1/D2 ⁇ 5, 3 ⁇ D1/D2 ⁇ 4, 4 ⁇ D1/D2 ⁇ 10, 4 ⁇ D1/D2 ⁇ 9, 4 ⁇ D1/D2 ⁇ 7, 4 ⁇ D1 /D2 ⁇ 6, 4 ⁇ D1/D2 ⁇ 5, 5 ⁇ D1/D2 ⁇ 10, 5 ⁇ D1/D2 ⁇ 9, 5 ⁇ D1/D2 ⁇ 8, 5 ⁇ D1/D2 ⁇ 7, 5 ⁇ D1/D2 ⁇ 6, 6 ⁇ D1/D2 ⁇ 10, 6 ⁇ D1/D2 ⁇ 9, 6 ⁇ D1/D2 ⁇ 8, 6 ⁇ D1/D2 ⁇ 7, 7 ⁇ D1/D2 ⁇ 10, 7 ⁇ D1/D2 ⁇ 9
  • the ratio of the thickness of the first negative electrode film layer to the thickness of the second negative electrode film layer is within an appropriate range, which is conducive to further improving the bonding force between the negative electrode film layer and the negative electrode current collector, thereby further improving the negative electrode plate adhesive properties. Moreover, controlling the thickness ratio within the above range is also conducive to enhancing the synergistic effect with the differentiated structure of the pore distribution of the inner and outer membrane layers, and further improving the electrolyte infiltration rate of the pole piece.
  • the ratio of the porosity of the second negative electrode film layer to the porosity of the first negative electrode film layer is 1 ⁇ P2/P1 ⁇ 5.
  • the ratio of the porosity of the second negative electrode film layer to the porosity of the first negative electrode film layer may be 1 ⁇ P2/P1 ⁇ 4, 1 ⁇ P2/P1 ⁇ 3, 1 ⁇ P2/P1 ⁇ 2 , 2 ⁇ P2/P1 ⁇ 5, 2 ⁇ P2/P1 ⁇ 4, 2 ⁇ P2/P1 ⁇ 3, 3 ⁇ P2/P1 ⁇ 5, 3 ⁇ P2/P1 ⁇ 4 or 4 ⁇ P2/P1 ⁇ 5.
  • the ratio of the porosity of the second negative electrode film layer to the porosity of the first negative electrode film layer is 3 ⁇ P2/P1 ⁇ 4.
  • the ratio of the porosity of the second negative electrode film layer to the porosity of the first negative electrode film layer is within an appropriate range, which is conducive to further increasing the diffusion and penetration amount of the electrolyte in the surface film layer of the pole piece, and further improving the electrolyte diffusion and penetration of the pole piece. Aspiration capacity. Moreover, controlling the ratio of porosity within the above range can better form a differentiated structure of pore distribution in the inner and outer membrane layers, and more fully play the role of pores in this differentiated structure, improving the electrolyte in the negative electrode piece. Diffusion rate, thereby further increasing the electrolyte infiltration rate of the pole piece, and ultimately improving the rate performance of the secondary battery.
  • the thickness of the first negative electrode film layer is 80 ⁇ m ⁇ D1 ⁇ 2250 ⁇ m.
  • the thickness of the first negative electrode film layer may be 100 ⁇ m, 200 ⁇ m, 400 ⁇ m, 600 ⁇ m, 800 ⁇ m, 1200 ⁇ m, 100 ⁇ m, 1400 ⁇ m, 1600 ⁇ m, 1800 ⁇ m, 2000 ⁇ m, 2200 ⁇ m or within the range of any of the above values.
  • the thickness of the first negative electrode film layer is 100 ⁇ m ⁇ D1 ⁇ 2000 ⁇ m.
  • the thickness of the first negative electrode film layer in this application has a well-known meaning in the art, and can be measured using methods known in the art, such as using a multimeter (for example, Mitutoyo 293-100 type, with an accuracy of 0.1 ⁇ m).
  • the thickness of the first negative electrode film layer is within a suitable range. On the one hand, it is helpful to ensure the bonding force between the negative electrode film layer and the negative electrode current collector, thereby improving the bonding performance of the negative electrode plate. On the other hand, it is also beneficial to minimize the diffusion distance of the electrolyte while ensuring adhesion, and increase the transmission rate of active ions (such as lithium ions), thereby improving the rate performance of the secondary battery.
  • the porosity of the first negative electrode film layer is 20% ⁇ P1 ⁇ 40%.
  • the porosity of the first negative electrode film layer may be 22%, 24%, 26%, 28%, 30%, 32%, 34%, 32%, 36%, 38% or any of the above values. In the range.
  • the porosity of the first negative electrode film layer is 25% ⁇ P1 ⁇ 35%.
  • the porosity of the first negative electrode film layer in this application has a well-known meaning in the art, and can be tested using methods known in the art, for example, cutting the negative electrode sheet containing only the first negative electrode film layer into discs with a diameter of 10 mm. , use the gas replacement method to test the porosity of the negative active material layer.
  • the porosity of the first negative electrode film layer is within an appropriate range, which is conducive to the formation of the aforementioned differentiated structure of pore distribution between the inner and outer film layers with the second negative electrode film layer, and allows this differentiated structure to more fully exert itself in the film layer.
  • the role of pores increases the diffusion rate of electrolyte in the negative electrode piece, thereby increasing the electrolyte infiltration rate of the electrode piece.
  • the thickness of the second negative electrode film layer is 8 ⁇ m ⁇ D2 ⁇ 750 ⁇ m.
  • the thickness of the second negative electrode film layer can be 10 ⁇ m, 50 ⁇ m, 100 ⁇ m, 150 ⁇ m, 200 ⁇ m, 250 ⁇ m, 300 ⁇ m, 350 ⁇ m, 400 ⁇ m, 450 ⁇ m, 500 ⁇ m, 550 ⁇ m, 600 ⁇ m, 650 ⁇ m, 700 ⁇ m or any combination thereof. within the range.
  • the thickness of the second negative electrode film layer is 10 ⁇ m ⁇ D2 ⁇ 700 ⁇ m.
  • the thickness of the second negative electrode film layer in this application has a well-known meaning in the art, and can be measured using methods known in the art, such as using a multimeter (for example, Mitutoyo 293-100 type, with an accuracy of 0.1 ⁇ m).
  • the thickness of the second negative electrode film layer is controlled within the above range, which is beneficial to reducing the diffusion distance of the electrolyte on the surface of the electrode piece when it diffuses into the surface film layer, further accelerating the diffusion rate, reducing the interface resistance, thereby further improving the performance of the electrode piece Electrolyte infiltration rate and rate performance of secondary batteries.
  • the porosity of the second negative electrode film layer is 40% ⁇ P2 ⁇ 70%.
  • the porosity of the second negative electrode film layer may be 43%, 46%, 49%, 52%, 55%, 58%, 61%, 64%, 67% or within the range of any of the above values.
  • the porosity of the second negative electrode film layer is 45% ⁇ P2 ⁇ 65%.
  • the porosity of the second negative electrode film layer in this application has a well-known meaning in the art, and can be tested using methods known in the art, for example, cutting the negative electrode sheet containing only the second negative electrode film layer into discs with a diameter of 10 mm. , use the gas replacement method to test the porosity of the negative active material layer.
  • the porosity of the second negative electrode film layer is within the above range, which is conducive to the large-scale diffusion and penetration of the electrolyte on the surface of the electrode piece, thereby improving the liquid absorption capacity of the electrode piece; at the same time, it is also conducive to the formation of a gap between the second negative electrode film layer and the first negative electrode film layer.
  • the aforementioned differentiated structure of pore distribution in the inner and outer film layers enables this differentiated structure to fully play the role of the pores in the film layer and increase the diffusion rate of electrolyte in the negative electrode plate, thus improving the liquid absorbing capacity of the electrode plate.
  • the electrolyte infiltration rate of the pole piece is increased.
  • the total porosity of the negative electrode film layer is P0, and 30% ⁇ P0 ⁇ 60%.
  • the total porosity of the negative electrode film layer may be 33%, 36%, 39%, 42%, 45%, 48%, 51%, 54%, 57% or within the range of any of the above values.
  • the total porosity of the negative electrode film layer is 35% ⁇ P0 ⁇ 55%.
  • the total porosity of the negative electrode film layer is within an appropriate range, which is beneficial to improving the liquid absorption capacity of the electrode piece and improving the conductivity of active ions (such as lithium ions) in the negative electrode piece.
  • the total porosity of the negative electrode film layer can be tested using methods known in the art.
  • the negative electrode piece is cut into discs with a diameter of 10 mm, and the gas replacement method is used to test the porosity of the negative electrode active material layer.
  • the total thickness of the negative electrode film layer is D0, and 100 ⁇ m ⁇ D0 ⁇ 3000 ⁇ m.
  • the total thickness of the negative electrode film layer may be 200 ⁇ m, 500 ⁇ m, 800 ⁇ m, 1100 ⁇ m, 1400 ⁇ m, 1700 ⁇ m, 2000 ⁇ m, 2300 ⁇ m, 2600 ⁇ m, 2900 ⁇ m or within the range of any of the above values.
  • the total thickness of the negative electrode film layer is 150 ⁇ m ⁇ D0 ⁇ 2500 ⁇ m.
  • the total thickness of the negative electrode film layer is within an appropriate range, which can ensure the bonding performance of the negative electrode piece, shorten the diffusion path and diffusion distance of the electrolyte in the electrode piece, and improve the electrolyte wettability of the electrode piece.
  • the total thickness of the negative electrode film layer can be measured using methods known in the art, such as using a multimeter (for example, Mitutoyo 293-100 type, with an accuracy of 0.1 ⁇ m).
  • the single-sided coating weight of the negative electrode sheet is 0.1g/1540.25mm 2 to 0.4g/1540.25mm 2 .
  • the single-sided coating weight of the negative electrode piece can be 0.15g/1540.25mm 2 , 0.20g/1540.25mm 2 , 0.25g/1540.25mm 2 , 0.30g/1540.25mm 2 , 0.35g/1540.25mm 2 , 0.40g/1540.25mm 2 or within the range of any of the above values.
  • the single-sided coating weight of the negative electrode piece is 0.15g/1540.25mm 2 to 0.35g/1540.25mm 2 .
  • the single-sided coating weight of the negative electrode sheet is a well-known meaning in the art and can be tested by methods known in the art. For example, cut five dried negative electrode sheets with an area of 1540.25 mm2 , measure the thickness of the negative electrode sheets with a micrometer, record it as d0cm, scrape off the negative electrode active material layer in the negative electrode sheet with a scraper, weigh the mass of the negative electrode active material layer with a balance, record it as m (mg), which is the mass of the negative electrode active material layer on the area of 1540.25 mm2 .
  • the single-sided coating weight of the negative electrode piece is within an appropriate range, which can shorten the diffusion path and diffusion distance of the electrolyte in the electrode piece, which is conducive to increasing the infiltration rate of the electrolyte, thereby improving the transmission efficiency of active ions (such as lithium ions) , while ensuring that the secondary battery has a high energy density.
  • each negative electrode piece (such as the coating weight on one side) given in this application refer to the parameters of one side of the negative electrode current collector.
  • the negative active material layer is disposed on both sides of the negative current collector, if the parameters on either side meet the requirements of this application, it is deemed to fall within the protection scope of this application.
  • a second aspect of the embodiment of the present application provides a method for preparing a negative electrode sheet, including:
  • the film forming step includes forming a first negative electrode film layer and a second negative electrode film layer on at least one side of the negative electrode current collector to obtain a negative electrode sheet; wherein the first negative electrode film layer is located close to the surface of the negative electrode current collector , the second negative electrode film layer is located on the surface of the first negative electrode film layer away from the negative electrode current collector; the thickness of the first negative electrode film layer is D1, and the thickness of the second negative electrode film layer is D2, and D1>D2; the porosity of the first negative electrode film layer is P1, and the porosity of the second negative electrode film layer is P2, and P1 ⁇ P2.
  • a double-film layer structure composed of a first negative electrode film layer and a second negative electrode film layer is formed on at least one side of the negative electrode current collector.
  • the pore distribution of the second negative electrode film layer is relatively small. It is conducive to the large amount of electrolyte diffusion and penetration on the surface of the pole piece, which can improve the liquid absorption capacity of the pole piece.
  • the pore distribution of the first negative electrode film layer is relatively small, which can form a differentiated structure of the pore distribution of the inner and outer film layers in the negative electrode piece. This differentiated structure can give full play to the role of the pores in the film layer and improve the electrolyte and activity.
  • the diffusion rate of ions in the negative electrode plate increases the electrolyte infiltration rate of the electrode plate and ultimately improves the rate performance of the secondary battery.
  • the thickness setting relationship between the first negative electrode film layer and the second negative electrode film layer can ensure a sufficiently high bonding force between the negative electrode film layer and the negative electrode current collector, and ensure that the negative electrode plate has sufficient bonding performance. Reduce the shedding of active materials on the pole pieces, thereby ensuring the capacity of the secondary battery.
  • the film forming step further includes:
  • the second slurry of the present application includes the thermal sublimation material 1,2-dihydroxy-3-trityl-propane, which is used as a pore-forming agent in the formation process of the second negative electrode film layer.
  • the above-mentioned pore-forming agents used in this application will not produce harmful corrosive gases and have no side reactions during use, thereby reducing the side effects of conventional pore-forming agents.
  • the influence of the battery core improves the performance of the battery core.
  • the recovery rate of the above-mentioned pore-forming agent can be monitored to determine whether the pore-forming agent has been completely removed, so as to avoid the remaining pore-forming agent from sublimating again during the subsequent drying process to increase gas production and improve Safety performance of secondary batteries.
  • the mass percentage content of the 1,2-dihydroxy-3-trityl-propane is 0.1% to 30% based on the total mass of the second negative electrode slurry.
  • the mass percentage of 1,2-dihydroxy-3-trityl-propane can be 0.5%, 1%, 3%, 5%, 10%, 12%, 15%, 18%, 20%, 23%, 25%, 27% or within the range of any of the above values.
  • the mass percentage of 1,2-dihydroxy-3-trityl-propane is 1% to 25%.
  • the porosity of the second negative electrode membrane layer can be maintained within the aforementioned appropriate range, which is conducive to the large-scale diffusion and infiltration of the electrolyte on the surface of the electrode piece, thereby improving the electrode The liquid absorption capacity of the tablet.
  • the first negative electrode slurry includes a negative active material and an optional first component, wherein the first component includes a conductive agent, a binder, a thickener, a solvent, or the like. combination.
  • the second negative electrode slurry further includes a negative active material and an optional second component, wherein the second component includes a conductive agent, a binder, a thickener, a solvent or its combination.
  • the negative active material may be a negative active material known in the art for secondary batteries.
  • the negative active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon carbon composites, silicon nitrogen composites and silicon alloys.
  • the tin-based material may be selected from at least one of elemental tin, tin oxide compounds and tin alloys.
  • the present application is not limited to these materials, and other traditional materials that can be used as battery negative electrode active materials can also be used. Only one type of these negative electrode active materials may be used alone, or two or more types may be used in combination.
  • the first negative electrode slurry and the second negative electrode slurry optionally further include a conductive agent.
  • the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the first negative electrode slurry and the second negative electrode slurry optionally further include a binder.
  • the binder can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polysodium acrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), poly At least one of methacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the first negative electrode slurry and the second negative electrode slurry optionally further include a thickener.
  • the thickening agent may be sodium carboxymethylcellulose (CMC-Na).
  • the first negative electrode slurry and the second negative electrode slurry optionally further include a solvent.
  • the solvent may be N-methylpyrrolidone (NMP) or deionized water.
  • the negative electrode current collector has two surfaces opposite in its own thickness direction, and the negative electrode active material layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material.
  • the composite current collector can be formed by forming metal materials (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative active materials, conductive agents, binders and any other components in a solvent (such as deionized water) to form a first negative electrode slurry; the first negative electrode slurry is coated on the negative electrode current collector to form a first coating layer.
  • a solvent such as deionized water
  • a second negative electrode slurry is formed; the second negative electrode slurry is coated on the first coating layer to form a second coating layer. After drying, cold pressing and other processes, a negative electrode sheet including a first negative electrode film layer and a second negative electrode film layer can be obtained.
  • the negative electrode sheet of the present application does not exclude other additional functional layers in addition to the negative electrode film layer.
  • the negative electrode sheet of the present application also includes a conductive undercoat layer (for example, composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector.
  • the negative electrode sheet of the present application further includes a protective layer covering the surface of the negative electrode film layer.
  • a third aspect of the embodiment of the present application provides a secondary battery, including any device in which an electrochemical reaction occurs to convert chemical energy and electrical energy into each other, and specific examples thereof include all kinds of lithium primary batteries or lithium secondary batteries.
  • the lithium secondary battery includes a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery or a lithium ion polymer secondary battery.
  • the secondary battery of the present application includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte.
  • active ions are inserted and detached back and forth between the positive and negative electrodes.
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the isolation film is placed between the positive electrode piece and the negative electrode piece. It mainly prevents the positive and negative electrodes from short-circuiting and allows ions to pass through.
  • the negative electrode sheet used in the secondary battery of the present application is the negative electrode sheet of the first aspect of the embodiment of the present application or the negative electrode sheet produced by the method of the second aspect of the embodiment of the present application.
  • the material, composition and manufacturing method of the positive electrode sheet used in the secondary battery of the present application may include any technology known in the prior art.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector and including a positive electrode active material.
  • the positive electrode current collector has two surfaces facing each other in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode film layer includes a positive electrode active material.
  • the specific type of the positive electrode active material is not specifically limited and can be selected according to requirements.
  • the cathode active material may include one or more of lithium transition metal oxides, lithium-containing phosphates with an olivine structure, and their respective modified compounds.
  • the modified compound of each positive electrode active material mentioned above may be doping modification, surface coating modification, or doping and surface coating modification of the positive electrode active material.
  • lithium transition metal oxides may include lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, One or more of lithium nickel cobalt aluminum oxide and its modified compounds.
  • the lithium-containing phosphate with an olivine structure may include lithium iron phosphate, a composite of lithium iron phosphate and carbon, a lithium manganese phosphate, a composite of lithium manganese phosphate and carbon, a lithium manganese iron phosphate, a lithium manganese iron phosphate and carbon One or more of the composite materials and their modified compounds. Only one type of these positive electrode active materials may be used alone, or two or more types may be used in combination.
  • the positive electrode film layer optionally further includes a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the positive electrode film layer optionally further includes a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene At least one of ethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • a metal foil aluminum foil can be used as the positive electrode current collector.
  • the composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer.
  • the metal material may be selected from one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy.
  • the polymer material base layer may be selected from polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.
  • the positive electrode piece in this application can be prepared according to conventional methods in this field.
  • the positive electrode film layer is usually formed by coating the positive electrode slurry on the positive electrode current collector, drying, and cold pressing.
  • the cathode slurry is usually formed by dispersing the cathode active material, optional conductive agent, optional binder and any other components in a solvent and stirring evenly.
  • the solvent may be N-methylpyrrolidone (NMP), but is not limited thereto.
  • the positive electrode sheet of the present application does not exclude other additional functional layers in addition to the positive electrode film layer.
  • the positive electrode sheet of the present application also includes a conductive undercoat layer (for example, composed of a conductive agent and a binder) sandwiched between the positive electrode current collector and the positive electrode film layer and disposed on the surface of the positive electrode current collector.
  • the positive electrode sheet of the present application further includes a protective layer covering the surface of the positive electrode film layer.
  • the electrolyte plays a role in conducting active ions between the positive electrode piece and the negative electrode piece.
  • the electrolyte solution that can be used in the secondary battery of the present application can be an electrolyte solution known in the art.
  • the electrolyte solution includes an organic solvent, a lithium salt and optional additives.
  • organic solvent a lithium salt and optional additives.
  • the types of the organic solvent, lithium salt and additives are not specifically limited and can be selected according to needs.
  • the lithium salts include, but are not limited to, LiPF 6 (lithium hexafluorophosphate), LiBF 4 (lithium tetrafluoroborate), LiClO 4 (lithium perchlorate), LiFSI (lithium bisfluorosulfonimide) ), LiTFSI (lithium bistrifluoromethanesulfonimide), LiTFS (lithium trifluoromethanesulfonate), LiDFOB (lithium difluoromethanesulfonate), LiBOB (lithium difluoromethanesulfonate), LiPO 2 F 2 (difluorophosphoric acid Lithium), LiDFOP (lithium difluorodioxalate phosphate) and LiTFOP (lithium tetrafluorooxalate phosphate).
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium tetrafluoroborate
  • LiClO 4 lithium perchlorate
  • LiFSI
  • the organic solvent includes, but is not limited to, ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), carbonic acid Dimethyl ester (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate Ester (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), Methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS)
  • EC ethylene carbon
  • the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain properties of the battery, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance. wait.
  • the additives include, but are not limited to, fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), vinyl sulfate (DTD), propylene sulfate, vinyl sulfite Ester (ES), 1,3-propene sultone (PS), 1,3-propene sultone (PST), sulfonate cyclic quaternary ammonium salt, succinic anhydride, succinonitrile (SN) , at least one of adiponitrile (AND), tris(trimethylsilane)phosphate (TMSP), and tris(trimethylsilane)borate (TMSB).
  • FEC fluoroethylene carbonate
  • VC vinylene carbonate
  • VEC vinyl ethylene carbonate
  • DTD vinyl sulfate
  • ES vinyl sulfite Ester
  • PS 1,3-propene sultone
  • PST 1,3-propene sultone
  • the electrolyte solution can be prepared according to conventional methods in the art.
  • the organic solvent, lithium salt, and optional additives can be mixed evenly to obtain an electrolyte.
  • the materials There is no particular restriction on the order in which the materials are added. For example, add lithium salt and optional additives to the organic solvent and mix evenly to obtain an electrolyte; or add lithium salt to the organic solvent first, and then add the optional additives.
  • the additives are added to the organic solvent and mixed evenly to obtain an electrolyte.
  • the isolation film is placed between the positive electrode piece and the negative electrode piece. It mainly prevents the positive and negative electrodes from short-circuiting and allows active ions to pass through.
  • isolation membrane There is no particular restriction on the type of isolation membrane in this application. Any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be used.
  • the material of the isolation membrane can be selected from one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride, but is not limited to these.
  • the isolation film can be a single-layer film or a multi-layer composite film. When the isolation film is a multi-layer composite film, the materials of each layer may be the same or different. In some embodiments, a ceramic coating or a metal oxide coating can also be provided on the isolation film.
  • the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.
  • the secondary battery may include an outer packaging.
  • the outer packaging can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag.
  • the material of the soft bag can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.
  • FIG. 2 shows an example of a square-structured secondary battery 5 .
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity.
  • the housing 51 has an opening communicating with the accommodation cavity, and the cover plate 53 is used to cover the opening to close the accommodation cavity.
  • the positive electrode piece, the negative electrode piece and the isolation film can be formed into the electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the containing cavity.
  • the electrolyte soaks into the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or several, and can be adjusted according to needs.
  • secondary batteries can be assembled into battery modules, and the number of secondary batteries contained in the battery module can be multiple. The specific number can be adjusted according to the application and capacity of the battery module.
  • FIG. 4 is a battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 .
  • the plurality of secondary batteries 5 can be fixed by fasteners.
  • the battery module 4 may further include a housing having a receiving space in which a plurality of secondary batteries 5 are received.
  • the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box 2 and a lower box 3 .
  • the upper box 2 is used to cover the lower box 3 and form a closed space for accommodating the battery module 4 .
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • a fifth aspect of the embodiments of the present application provides an electrical device, which device includes at least one of a secondary battery, a battery module, or a battery pack of the present application.
  • the secondary battery, battery module or battery pack may be used as a power source for the device or as an energy storage unit for the device.
  • the device may be, but is not limited to, mobile equipment, electric vehicles, electric trains, ships and satellites, energy storage systems, etc.
  • a notebook computer For example, a notebook computer, a pen input type computer, a mobile computer, an e-book player, a portable telephone, a portable fax machine, a portable copy machine, a portable printer, a stereo headset, a video recorder, an LCD TV, a portable cleaner, a portable CD player, mini CD, transceiver, electronic notepad, calculator, memory card, portable recorder, radio, backup power supply, motor, automobile, motorcycle, power-assisted bicycle, bicycle, lighting equipment, toys, game consoles, clocks, electric Tools, flashlights, cameras, large household batteries and lithium-ion capacitors, etc.
  • the device can select secondary batteries, battery modules or battery packs according to its usage requirements.
  • Figure 7 is an example device.
  • the device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc.
  • battery packs or battery modules can be used.
  • cathode active material LiCoO 2 , conductive carbon black, and binder PVDF according to the mass ratio of 96.7:1.7:1.6, add an appropriate amount of solvent NMP, and use it in a vacuum mixer to obtain a cathode slurry; apply the cathode slurry evenly on the cathode on both surfaces of the current collector aluminum foil; then vacuum dried at 70°C for 12 hours, and then cut into strips to obtain the positive electrode piece.
  • EC ethylene carbonate
  • EMC ethyl methyl carbonate
  • DEC diethyl carbonate
  • FEC fluoroethylene carbonate
  • PE porous film is used as the isolation membrane.
  • the lithium-ion battery is obtained through processes such as formation, degassing, and trimming.
  • the preparation method of the lithium-ion battery is similar to Example 1, except that the negative electrode plate and related parameters in the preparation process are adjusted.
  • the specific parameters are shown in Table 1 and Table 2, where "/" means that the negative electrode plate and the relevant parameters in the preparation process are not included. substance.
  • the charge-discharge rate refers to the current value required when the battery discharges its rated capacity within a specified period of time, expressed in C. 1C means charging or discharging is completed in 1 hour, and 1/3C means charging or discharging is completed in 3 hours.
  • set the current values to 0.2C, 0.5C, 1C, 2C, and 3C respectively, and cycle 5 times at each current.
  • Table 3 gives the performance test results of Examples 1 to 11 and Comparative Examples 1 to 4.
  • Comparative analysis of Example 1 and Comparative Example 1, Example 6 and Comparative Example 2, and Example 9 and Comparative Example 3 respectively shows that compared with a single film layer, the negative electrode sheet provided by the present application has a lower liquid absorption capacity and electrolyte The infiltration rate and the 3C charging rate capacity retention rate of lithium-ion batteries are higher, indicating that the double-layer structure of the present application can indeed improve the liquid absorption capacity of the negative electrode plate, the infiltration performance of the electrolyte and the rate performance of the secondary battery. .
  • Comparative analysis of Example 2 and Comparative Example 4 shows that, compared with the conventional film layer arrangement structure, the double film layer structure provided by the present application can also improve the negative electrode while ensuring that the negative electrode plate has sufficiently high adhesion.
  • Comparative analysis of Examples 1 to 3 shows that when the ratio P2/P1 of the porosity of the second negative electrode film layer to the porosity of the first negative electrode film layer changes, the liquid absorption amount of the negative electrode plate, the electrolyte infiltration rate, and the battery's The capacity retention rate of the 3C charging rate will change; and the larger P2/P1, that is, the greater the porosity difference between the second negative electrode film layer and the first negative electrode film layer, the liquid absorption capacity of the electrode piece, the electrolyte infiltration performance and the battery The higher the white-green performance.
  • Comparative analysis of Examples 2, 4 and 5 shows that the ratio D1/D2 of the thickness of the first negative electrode film layer to the thickness of the second negative electrode film layer will have an impact on the bonding performance of the electrode piece.
  • a comparative analysis of Examples 1, 6, and 9 shows that the total thickness of the negative electrode film layer provided by the present application will also affect the liquid absorption capacity of the negative electrode sheet, the wetting performance of the electrolyte, and the rate performance of the secondary battery.

Abstract

Provided in the present application are a negative electrode sheet, a method for manufacturing the negative electrode sheet, a secondary battery and an electric device. The negative electrode sheet comprises a negative electrode current collector; and a negative electrode film layer arranged on at least one side of the negative electrode current collector, the negative electrode film layer comprising a first negative electrode film layer arranged on the surface close to the negative electrode current collector and a second negative electrode film layer arranged on the surface of the side of the first negative electrode film layer away from the negative electrode current collector, the thickness of the first negative electrode film layer being D1, the thickness of the second negative electrode film layer being D2, D1>D2, the porosity of the first negative electrode film layer being P1, the porosity of the second negative electrode film layer being P2, and P1<P2. The negative electrode sheet provided by the present application can improve the electrolyte absorption capacity of the electrode sheet, and can also improve the electrolyte wetting rate of the electrode sheet, thereby improving the rate capability of the secondary battery.

Description

负极极片、用于制备负极极片的方法、二次电池和用电装置Negative electrode plate, method for preparing negative electrode plate, secondary battery and electrical device 技术领域Technical field
本申请属于电化学技术领域，具体涉及一种负极极片、用于制备负极极片的方法、二次电池和用电装置。The present application belongs to the technical field of electrochemistry, and specifically relates to a negative electrode plate, a method for preparing a negative electrode plate, a secondary battery and an electrical device.
背景技术Background technique
以锂离子电池为代表的二次电池因无记忆效应、长循环寿命、绿色环保等优点，广泛应用在如今生活的各个方面。近年来，二次电池更是在新能源汽车和大规模储能领域得到了迅猛发展。在目前的二次电池中，常规的负极极片通常孔隙率不高，电解液的浸润性能不佳，使得二次电池的倍率性能较差。Secondary batteries, represented by lithium-ion batteries, are widely used in all aspects of today's life due to their advantages such as no memory effect, long cycle life, and environmental protection. In recent years, secondary batteries have developed rapidly in the fields of new energy vehicles and large-scale energy storage. In current secondary batteries, conventional negative electrode sheets usually have low porosity and poor electrolyte wetting properties, resulting in poor rate performance of secondary batteries.
发明内容Contents of the invention
本申请的目的在于提供一种负极极片、用于制备负极极片的方法、二次电池及用电装置，旨在提升负极极片的电解液浸润性能及二次电池的倍率性能。The purpose of this application is to provide a negative electrode sheet, a method for preparing the negative electrode sheet, a secondary battery and an electrical device, aiming to improve the electrolyte wetting performance of the negative electrode sheet and the rate performance of the secondary battery.
为了实现上述发明目的，本申请第一方面提供一种负极极片，包括：负极集流体；和设置于所述负极集流体至少一侧的负极膜层，所述负极膜层包括设置于靠近所述负极集流体的表面的第一负极膜层和设置于所述第一负极膜层远离所述负极集流体一侧的表面上的第二负极膜层，其中，所述第一负极膜层的厚度为D1，所述第二负极膜层的厚度为D2，且D1>D2；所述第一负极膜层的孔隙率为P1，所述第二负极膜层的孔隙率为P2，且P1<P2。In order to achieve the above-mentioned object of the invention, the first aspect of the present application provides a negative electrode sheet, including: a negative electrode current collector; and a negative electrode film layer disposed on at least one side of the negative electrode current collector, and the negative electrode film layer includes a negative electrode film layer disposed close to the The first negative electrode film layer on the surface of the negative electrode current collector and the second negative electrode film layer disposed on the surface of the first negative electrode film layer away from the negative electrode current collector, wherein the first negative electrode film layer The thickness is D1, the thickness of the second negative electrode film layer is D2, and D1>D2; the porosity of the first negative electrode film layer is P1, the porosity of the second negative electrode film layer is P2, and P1< P2.
本申请提供的负极极片中设置了双膜层结构，其中，第一负极膜层的孔隙率相较于第二负极膜层的孔隙率更小，即负极极片表面膜层(第二负极膜层)的孔隙分布较多，而极片内部膜层(第一负极膜层)的孔隙分布相对较少。在这种双膜层结构中，表面膜层的孔隙分布较多，有利于极片表面的电解液的大量扩散渗入，由此能够提升极片的吸液能力；而内部膜层的孔隙分布相对较少，能够形成内外膜层孔隙分布的差异化结构，这种差异化结构能够充分发挥膜层中孔隙的作用，提升电解液和活性离子在负极极片中的扩散速率，从而在提升极片吸液能力的同时，还可以提升极片的电解液浸润速率，并最终提升二次电池的倍率性能。此外，第一负极膜层的厚度相较于第二负极膜层的厚度更厚，即负极极片内部膜层(第一负极膜层)的厚度比表面膜层(第二负极膜层)的厚度更大。这种厚度的设置能够保证负极膜层与负极集流体之间具备足够高的粘结力，保证负极极片具备足够的粘结性能，减少极片上活性物质的脱落，从而提升二次电池的容 量。进一步的，表面膜层(第二负极膜层)比内部膜层(第一负极膜层)更薄，也有利于减小极片表面的电解液在表面膜层进行大量扩散渗入时的扩散距离，并通过与上述的内外膜层孔隙分布的差异化结构的相互协同配合，进一步加快电解液的扩散速率并提升极片的电解液浸润速率The negative electrode sheet provided in this application has a double film layer structure, in which the porosity of the first negative electrode film layer is smaller than the porosity of the second negative electrode film layer, that is, the surface film layer of the negative electrode sheet (the second negative electrode film layer) The pore distribution of the inner membrane layer of the pole piece (the first negative electrode membrane layer) is relatively small. In this double-membrane structure, the pores in the surface film layer are distributed more, which is conducive to the large-scale diffusion and penetration of the electrolyte on the surface of the pole piece, thereby improving the liquid absorption capacity of the pole piece; while the pore distribution in the inner film layer is relatively Less, it can form a differentiated structure of pore distribution in the inner and outer film layers. This differentiated structure can give full play to the role of the pores in the film layer and increase the diffusion rate of electrolyte and active ions in the negative electrode piece, thereby improving the electrode piece. While absorbing liquid, it can also increase the electrolyte infiltration rate of the pole piece, and ultimately improve the rate performance of the secondary battery. In addition, the thickness of the first negative electrode film layer is thicker than the thickness of the second negative electrode film layer, that is, the thickness of the internal film layer of the negative electrode plate (the first negative electrode film layer) is thicker than the thickness of the surface film layer (the second negative electrode film layer). Greater thickness. This thickness setting can ensure a sufficiently high bonding force between the negative electrode film layer and the negative electrode current collector, ensure that the negative electrode plate has sufficient bonding performance, reduce the shedding of active material on the electrode plate, and thereby increase the capacity of the secondary battery. . Furthermore, the surface film layer (second negative electrode film layer) is thinner than the internal film layer (first negative electrode film layer), which is also conducive to reducing the diffusion distance of the electrolyte on the surface of the electrode piece when the surface film layer diffuses and penetrates in large amounts. , and through synergy with the above-mentioned differentiated structure of pore distribution in the inner and outer membrane layers, further accelerate the diffusion rate of the electrolyte and increase the electrolyte infiltration rate of the pole piece
在本申请任意实施方式中，所述第一负极膜层的厚度与所述第二负极膜层的厚度的比值为3≤D1/D2≤10，可选为5≤D1/D2≤8。In any embodiment of the present application, the ratio of the thickness of the first negative electrode film layer to the thickness of the second negative electrode film layer is 3≤D1/D2≤10, optionally 5≤D1/D2≤8.
第一负极膜层的厚度与第二负极膜层的厚度的比值在合适范围内，能够减小膜层中的孔隙结构对负极膜层粘结性能的影响，其中，第一负极膜层的孔隙率较低且厚度较厚，第二负极膜层的孔隙率较高且厚度较薄，因而单位体积中第一负极膜层包含的粘结物质较第二负极膜层更多，与负极集流体的粘结性也更强。由此通过控制第一负极膜层的厚度与第二负极膜层的厚度的比值在合适范围内，并且通过负极膜层间厚度的比值与孔隙率设置的相互协同配合，可以使负极膜层与负极集流体之间具备足够粘结力、提升负极极片的粘结性能的同时，还能进一步发挥负极膜层中第一负极膜层和第二负极膜层的孔隙分布的差异化结构的相互协同配合作用，进一步提升极片的电解液浸润速率。The ratio of the thickness of the first negative electrode film layer to the thickness of the second negative electrode film layer is within an appropriate range, which can reduce the impact of the pore structure in the film layer on the bonding performance of the negative electrode film layer, wherein the pores of the first negative electrode film layer The rate is lower and the thickness is thicker. The porosity of the second negative electrode film layer is higher and the thickness is thinner. Therefore, the first negative electrode film layer contains more binding material per unit volume than the second negative electrode film layer, and is closely related to the negative electrode current collector. The adhesiveness is also stronger. Therefore, by controlling the ratio of the thickness of the first negative electrode film layer to the thickness of the second negative electrode film layer within an appropriate range, and through the synergistic cooperation between the thickness ratio between the negative electrode film layers and the porosity setting, the negative electrode film layer can be The negative electrode current collector has sufficient bonding force to improve the bonding performance of the negative electrode sheet. It can also further leverage the differentiated structure of the pore distribution of the first negative electrode film layer and the second negative electrode film layer in the negative electrode film layer. The synergistic effect further improves the electrolyte infiltration rate of the pole piece.
在本申请任意实施方式中，所述第二负极膜层的孔隙率与所述第一负极膜层的孔隙率的比值为1≤P2/P1≤5，可选为3≤P2/P1≤4。In any embodiment of the present application, the ratio of the porosity of the second negative electrode film layer to the porosity of the first negative electrode film layer is 1≤P2/P1≤5, optionally 3≤P2/P1≤4 .
第二负极膜层的孔隙率与第一负极膜层的孔隙率的比值在合适范围内，有利于进一步提升极片表面膜层的电解液的扩散渗入量，进一步提升极片的吸液能力。而且孔隙率的比值控制在上述范围内，能更好的形成内外膜层孔隙分布的差异化结构，并更加充分地发挥这种差异化结构中孔隙的作用，提升电解液在负极极片中的扩散速率，从而进一步提升极片的电解液浸润速率，并最终提升二次电池的倍率性能。The ratio of the porosity of the second negative electrode film layer to the porosity of the first negative electrode film layer is within an appropriate range, which is conducive to further increasing the diffusion and penetration of the electrolyte in the surface film layer of the electrode piece, and further improving the liquid absorption capacity of the electrode piece. Moreover, controlling the ratio of porosity within the above range can better form a differentiated structure of pore distribution in the inner and outer film layers, and more fully play the role of pores in this differentiated structure, improving the electrolyte in the negative electrode piece. Diffusion rate, thereby further increasing the electrolyte infiltration rate of the pole piece, and ultimately improving the rate performance of the secondary battery.
在本申请任意实施方式中，所述第一负极膜层满足如下条件中的至少一者：In any embodiment of the present application, the first negative electrode film layer meets at least one of the following conditions:
(1)所述第一负极膜层的厚度为80μm≤D1≤2250μm，可选为100μm≤D1≤2000μm；(1) The thickness of the first negative electrode film layer is 80μm≤D1≤2250μm, optionally 100μm≤D1≤2000μm;
(2)所述第一负极膜层的孔隙率为20％≤P1≤40％，可选为25％≤P1≤35％。(2) The porosity of the first negative electrode film layer is 20%≤P1≤40%, optionally 25%≤P1≤35%.
第一负极膜层的厚度在合适范围内，有利于在保证粘结性的同时尽量减小电解液的扩散距离，提升活性离子(例如锂离子)的传输速率，从而提高二次电池的倍率性能。The thickness of the first negative electrode film layer is within a suitable range, which is beneficial to minimizing the diffusion distance of the electrolyte while ensuring adhesion, increasing the transmission rate of active ions (such as lithium ions), thereby improving the rate performance of the secondary battery .
第一负极膜层的孔隙率在合适范围内，有利于同第二负极膜层之间形成前述的内外膜层孔隙分布的差异化结构，并使这种差异化结构更加充分的发挥膜层中孔隙的作用，提升电解液在负极极片中的扩散速率，从而提升极片的电解液浸润速率。The porosity of the first negative electrode film layer is within an appropriate range, which is conducive to the formation of the aforementioned differentiated structure of pore distribution between the inner and outer film layers with the second negative electrode film layer, and allows this differentiated structure to more fully exert itself in the film layer. The role of pores increases the diffusion rate of electrolyte in the negative electrode piece, thereby increasing the electrolyte infiltration rate of the electrode piece.
在本申请任意实施方式中，所述第二负极膜层满足如下条件中的至少一者：In any embodiment of the present application, the second negative electrode film layer satisfies at least one of the following conditions:
(1)所述第二负极膜层的厚度为8μm≤D2≤750μm，可选为10μm≤D2≤700μm；(1) The thickness of the second negative electrode film layer is 8μm≤D2≤750μm, optionally 10μm≤D2≤700μm;
(2)所述第二负极膜层的孔隙率为40％≤P2≤70％，可选为45％≤P2≤65％。(2) The porosity of the second negative electrode film layer is 40%≤P2≤70%, optionally 45%≤P2≤65%.
第二负极膜层的厚度控制在上述范围内，有利于减小极片表面的电解液在扩散进入表面膜层时的扩散距离，进一步加快扩散速率，减小界面电阻，从而进一步提升极片 的电解液浸润速率及二次电池的倍率性能。此外，第二负极膜层的孔隙率在上述范围内，有利于极片表面的电解液的大量扩散渗入，由此提升极片的吸液能力。The thickness of the second negative electrode film layer is controlled within the above range, which is beneficial to reducing the diffusion distance of the electrolyte on the surface of the electrode piece when it diffuses into the surface film layer, further accelerating the diffusion rate, reducing the interface resistance, thereby further improving the performance of the electrode piece Electrolyte infiltration rate and rate performance of secondary batteries. In addition, the porosity of the second negative electrode film layer is within the above range, which is conducive to the diffusion and penetration of a large amount of electrolyte on the surface of the electrode piece, thereby improving the liquid absorption capacity of the electrode piece.
在本申请任意实施方式中，所述负极膜层的总孔隙率为P0，且30％≤P0≤60％，可选为35％≤P0≤55％。In any embodiment of the present application, the total porosity of the negative electrode film layer is P0, and 30%≤P0≤60%, optionally 35%≤P0≤55%.
负极膜层的总孔隙率在合适范围内，有利于提升极片的吸液能力，提升活性离子(如锂离子)在负极极片中的传导性。The total porosity of the negative electrode film layer is within an appropriate range, which is beneficial to improving the liquid absorption capacity of the electrode piece and improving the conductivity of active ions (such as lithium ions) in the negative electrode piece.
在本申请任意实施方式中，所述负极膜层的总厚度为D0，且100μm≤D0≤3000μm，可选为150μm≤D0≤2500μm。In any embodiment of the present application, the total thickness of the negative electrode film layer is D0, and 100 μm≤D0≤3000 μm, optionally 150 μm≤D0≤2500 μm.
负极膜层的总厚度在合适范围内，能够在保证负极极片粘结性能的同时，缩短电解液在极片中的扩散路径和扩散距离，提升极片的电解液浸润性。The total thickness of the negative electrode film layer is within an appropriate range, which can ensure the bonding performance of the negative electrode piece, shorten the diffusion path and diffusion distance of the electrolyte in the electrode piece, and improve the electrolyte wettability of the electrode piece.
在本申请任意实施方式中，所述负极极片的单面涂布重量为0.1g/1540.25mm 2至0.4g/1540.25mm 2，可选为0.15g/1540.25mm 2至0.35g/1540.25mm 2。 In any embodiment of the present application, the single-sided coating weight of the negative electrode piece is 0.1g/1540.25mm 2 to 0.4g/1540.25mm 2 , optionally 0.15g/1540.25mm 2 to 0.35g/1540.25mm 2 .
负极极片的单面涂布重量在合适范围内，能够缩短电解液在极片中的扩散路径和扩散距离，有利于提升电解液的浸润速率，从而提高活性离子(如锂离子)的传输效率，同时保证二次电池具备较高的能量密度。The single-sided coating weight of the negative electrode piece is within an appropriate range, which can shorten the diffusion path and diffusion distance of the electrolyte in the electrode piece, which is conducive to increasing the infiltration rate of the electrolyte, thereby improving the transmission efficiency of active ions (such as lithium ions) , while ensuring that the secondary battery has a high energy density.
本申请第二方面提供一种用于制备负极极片的方法，包括：成膜步骤，包括在负极集流体的至少一侧上形成第一负极膜层和第二负极膜层，得到负极极片；其中，所述第一负极膜层位于靠近所述负极集流体的表面，所述第二负极膜层位于所述第一负极膜层远离所述负极集流体一侧的表面上；所述第一负极膜层的厚度为D1，所述第二负极膜层的厚度为D2，且D1>D2；所述第一负极膜层的孔隙率为P1，所述第二负极膜层的孔隙率为P2，且P1<P2。A second aspect of the present application provides a method for preparing a negative electrode sheet, including: a film forming step, including forming a first negative electrode film layer and a second negative electrode film layer on at least one side of the negative electrode current collector to obtain a negative electrode sheet ; wherein, the first negative electrode film layer is located on a surface close to the negative electrode current collector, and the second negative electrode film layer is located on a surface of the first negative electrode film layer away from the negative electrode current collector; The thickness of a negative electrode film layer is D1, the thickness of the second negative electrode film layer is D2, and D1>D2; the porosity of the first negative electrode film layer is P1, and the porosity of the second negative electrode film layer is P1 P2, and P1<P2.
本申请通过在负极集流体的至少一侧上形成由第一负极膜层和第二负极膜层组成的双膜层结构，在这种双膜层结构中，第二负极膜层的孔隙分布较多，有利于极片表面的电解液的大量扩散渗入，由此能够提升极片的吸液能力。而第一负极膜层的孔隙分布相对较少，能够在负极极片中形成内外膜层孔隙分布的差异化结构，这种差异化结构能够充分发挥膜层中孔隙的作用，提升电解液和活性离子在负极极片中的扩散速率，从而提升极片的电解液浸润速率，并最终提升二次电池的倍率性能。In this application, a double-film layer structure composed of a first negative electrode film layer and a second negative electrode film layer is formed on at least one side of the negative electrode current collector. In this double-film layer structure, the pore distribution of the second negative electrode film layer is relatively small. It is conducive to the large amount of electrolyte diffusion and penetration on the surface of the pole piece, which can improve the liquid absorption capacity of the pole piece. The pore distribution of the first negative electrode film layer is relatively small, which can form a differentiated structure of the pore distribution of the inner and outer film layers in the negative electrode piece. This differentiated structure can give full play to the role of the pores in the film layer and improve the electrolyte and activity. The diffusion rate of ions in the negative electrode plate increases the electrolyte infiltration rate of the electrode plate and ultimately improves the rate performance of the secondary battery.
在本申请任意实施方式中，所述成膜步骤进一步包括：在所述负极集流体的至少一侧上涂布第一负极浆料，形成第一涂层；在所述第一涂层的表面上涂布第二负极浆料，形成第二涂层，其中，所述第二负极浆料中包括1,2-二羟基-3-三苯甲基-丙烷；和对所述第一涂层和所述第二涂层做烘干冷压处理，形成所述第一负极膜层和所述第二负极膜层。In any embodiment of the present application, the film forming step further includes: coating a first negative electrode slurry on at least one side of the negative electrode current collector to form a first coating layer; Coating a second negative electrode slurry on the second negative electrode slurry to form a second coating, wherein the second negative electrode slurry includes 1,2-dihydroxy-3-trityl-propane; and to the first coating The second coating layer is dried and cold-pressed to form the first negative electrode film layer and the second negative electrode film layer.
本申请的上述成膜步骤中，第二浆料中包括热升华材料1,2-二羟基-3-三苯甲基-丙烷，该材料是作为造孔剂而应用于第二负极膜层的形成过程中。通过将热升华材料1,2-二 羟基-3-三苯甲基-丙烷作为造孔剂添加到浆料中，并经涂布冷压之后再烘干极片的方式去除造孔剂，能够减小冷压工序对孔隙的影响，有效提高负极极片的孔隙率。In the above film-forming step of the present application, the second slurry includes the thermal sublimation material 1,2-dihydroxy-3-trityl-propane, which is used as a pore-forming agent for the second negative electrode film layer in the process of formation. By adding the thermal sublimation material 1,2-dihydroxy-3-trityl-propane to the slurry as a pore-forming agent, and removing the pore-forming agent by applying cold pressing and then drying the pole piece, Reduce the impact of the cold pressing process on pores and effectively increase the porosity of the negative electrode piece.
在本申请任意实施方式中，基于所述第二负极浆料的总质量，所述1,2-二羟基-3-三苯甲基-丙烷的质量百分含量为0.1％至30％，可选为1％至25％。In any embodiment of the present application, based on the total mass of the second negative electrode slurry, the mass percentage of the 1,2-dihydroxy-3-trityl-propane is 0.1% to 30%. Choose from 1% to 25%.
通过将第二负极浆料中的1,2-二羟基-3-三苯甲基-丙烷的质量百分含量控制在上述范围内，并在上述范围内对1,2-二羟基-3-三苯甲基-丙烷的质量百分含量进行调控，能够使第二负极膜层的孔隙率保持在前述的合适范围内，从而有利于极片表面的电解液的大量扩散渗入，由此提升极片的吸液能力。By controlling the mass percentage of 1,2-dihydroxy-3-trityl-propane in the second negative electrode slurry within the above range, and controlling 1,2-dihydroxy-3-tritylpropane within the above range. Adjusting the mass percentage of trityl-propane can keep the porosity of the second negative electrode film layer within the aforementioned appropriate range, which is conducive to the large-scale diffusion and infiltration of the electrolyte on the surface of the electrode piece, thereby improving the electrode The liquid absorption capacity of the tablet.
在本申请任意实施方式中，所述方法满足如下条件中的至少一者：In any embodiment of the present application, the method satisfies at least one of the following conditions:
(1)所述第一负极浆料中包括负极活性材料和可选的第一组分，其中，所述第一组分包括导电剂、粘结剂、增稠剂、溶剂或其组合；(1) The first negative electrode slurry includes a negative active material and an optional first component, wherein the first component includes a conductive agent, a binder, a thickener, a solvent, or a combination thereof;
(2)所述第二负极浆料中还包括负极活性材料和可选的第二组分，其中，所述第二组分包括导电剂、粘结剂、增稠剂、溶剂或其组合。(2) The second negative electrode slurry also includes a negative active material and an optional second component, wherein the second component includes a conductive agent, a binder, a thickener, a solvent, or a combination thereof.
本申请第三方面提供一种二次电池，包括本申请第一方面所述的负极极片或通过本申请第二方面所述的方法制得的负极极片。A third aspect of this application provides a secondary battery, including the negative electrode piece described in the first aspect of this application or the negative electrode piece produced by the method described in the second aspect of this application.
本申请第四方面提供一种电池模块，包括本申请第三方面所述的二次电池。A fourth aspect of this application provides a battery module, including the secondary battery described in the third aspect of this application.
本申请第五方面提供一种电池包，包括本申请第四方面所述的电池模块。A fifth aspect of this application provides a battery pack, including the battery module described in the fourth aspect of this application.
本申请第六方面提供一种用电装置，包括本申请第三方面所述的二次电池、第四方面所述的电池模块或本申请第五方面所述的电池包中的至少一种。A sixth aspect of this application provides an electrical device, including at least one of the secondary battery described in the third aspect of this application, the battery module described in the fourth aspect, or the battery pack described in the fifth aspect of this application.
本申请的电池模块、电池包和用电装置包括本申请提供的二次电池，因而至少具有与所述二次电池相同的优势。The battery modules, battery packs and electrical devices of the present application include the secondary battery provided by the present application, and thus have at least the same advantages as the secondary battery.
附图说明Description of drawings
图1是本申请的负极极片的一实施方式的结构示意图。Figure 1 is a schematic structural diagram of an embodiment of the negative electrode plate of the present application.
图2是本申请的二次电池的一实施方式的示意图。FIG. 2 is a schematic diagram of an embodiment of the secondary battery of the present application.
图3是本申请的二次电池的一实施方式的分解示意图。FIG. 3 is an exploded schematic diagram of an embodiment of the secondary battery of the present application.
图4是本申请的电池模块的一实施方式的示意图。FIG. 4 is a schematic diagram of an embodiment of the battery module of the present application.
图5是本申请的电池包的一实施方式的示意图。Figure 5 is a schematic diagram of an embodiment of the battery pack of the present application.
图6是图5的分解图。FIG. 6 is an exploded view of FIG. 5 .
图7是本申请的二次电池作为电源的用电装置的一实施方式的示意图。FIG. 7 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of the present application.
具体实施方式Detailed ways
为使本申请的目的、技术方案和优点更加清楚，下面将结合实施例对本申请的技术方案进行清楚、完整地描述，显然，所描述的实施例是本申请一部分实施例，而不是 全部的实施例。在此所描述的有关实施例为说明性质的且用于提供对本申请的基本理解。本申请的实施例不应该被解释为对本申请的限制。In order to make the purpose, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present application, not all implementations. example. The related embodiments described herein are illustrative in nature and are intended to provide a basic understanding of the present application. The embodiments of the present application should not be construed as limitations of the present application.
为了简明，本文仅具体地公开了一些数值范围。然而，任意下限可以与任何上限组合形成未明确记载的范围；以及任意下限可以与其它下限组合形成未明确记载的范围，同样任意上限可以与任意其它上限组合形成未明确记载的范围。此外，每个单独公开的点或单个数值自身可以作为下限或上限与任意其它点或单个数值组合或与其它下限或上限组合形成未明确记载的范围。For the sake of simplicity, only certain numerical ranges are specifically disclosed herein. However, any lower limit can be combined with any upper limit to form an unexpressed range; and any lower limit can be combined with other lower limits to form an unexpressed range, and likewise any upper limit can be combined with any other upper limit to form an unexpressed range. Furthermore, each individually disclosed point or single value may itself serve as a lower or upper limit in combination with any other point or single value or with other lower or upper limits to form a range not expressly recited.
在本文的描述中，除非另有说明，“以上”、“以下”包含本数。In the description herein, “above” and “below” include the numbers unless otherwise stated.
除非另有说明，本申请中使用的术语具有本领域技术人员通常所理解的公知含义。除非另有说明，本申请中提到的各参数的数值可以用本领域常用的各种测量方法进行测量(例如，可以按照在本申请的实施例中给出的方法进行测试)。Unless otherwise stated, terms used in this application have their commonly understood meanings as generally understood by those skilled in the art. Unless otherwise stated, the values of each parameter mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the examples of this application).
术语“中的至少一者”、“中的至少一个”、“中的至少一种”或其他相似术语所连接的项目的列表可意味着所列项目的任何组合。例如，如果列出项目A及B，那么短语“A及B中的至少一者”意味着仅A；仅B；或A及B。在另一实例中，如果列出项目A、B及C，那么短语“A、B及C中的至少一者”意味着仅A；或仅B；仅C；A及B(排除C)；A及C(排除B)；B及C(排除A)；或A、B及C的全部。项目A可包含单个组分或多个组分。项目B可包含单个组分或多个组分。项目C可包含单个组分或多个组分。A list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if the items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B and C. Item A may contain a single component or multiple components. Item B may contain a single component or multiple components. Item C may contain a single component or multiple components.
目前，在以锂离子电池为代表的二次电池中，二次电池的负极极片的孔隙率通常不高，使得二次电池的倍率性能不佳。为了提升二次电池负极极片的孔隙率，常规的方法通常包括：(1)使用造孔剂造孔，通过调节造孔剂的比例而调控负极极片的孔隙率，得到多孔的负极极片；(2)使用比表面积更大的石墨作为负极活性材料，例如天然石墨，通过石墨本身的孔隙率来增加负极极片的孔隙率。Currently, in secondary batteries represented by lithium-ion batteries, the porosity of the negative electrode sheet of the secondary battery is usually not high, resulting in poor rate performance of the secondary battery. In order to improve the porosity of the negative electrode sheet of secondary batteries, conventional methods usually include: (1) using a pore-forming agent to create pores, and adjusting the proportion of the pore-forming agent to regulate the porosity of the negative electrode sheet to obtain a porous negative electrode sheet ; (2) Use graphite with a larger specific surface area as the negative electrode active material, such as natural graphite, to increase the porosity of the negative electrode sheet through the porosity of the graphite itself.
但发明人在研究过程中发现，方法(1)中使用造孔剂造孔后，虽然可以提升负极极片的孔隙率，并在一定程度上提高极片的吸收电解液的能力，但方法(1)中使用造孔剂造孔后，负极极片中的孔隙通常无规律分布，这种无规律的分布并不能有效发挥孔隙优势而提高电解液的浸润速率。而且负极极片中形成的多孔结构可能会影响极片的粘结性能，容易使极片上的活性物质脱落，导致二次电池的容量下降。此外，方法(1)中使用的常规造孔剂在反应过程中易分解而产生有害的腐蚀性气体，这种腐蚀性气体在电芯中会产生副反应而降低电芯的性能。另外在方法(1)中，无法监控造孔剂是否全部升华，遗留的造孔剂可能会在后续的烘干过程中再次升华而增加产气，影响二次电池的安全性。而在方法(2)中，负极极片经过冷压之后，石墨本身的孔隙会被压实，因此并不能有效提高极片的孔隙率；且使用比表面积更大的石墨，会生成更多的SEI膜，导致产气恶化，影响二次电池的循环性能。However, during the research process, the inventor found that after using a pore-forming agent to create pores in method (1), although the porosity of the negative electrode piece can be increased and the ability of the electrode piece to absorb electrolyte can be improved to a certain extent, the method (1) 1) After using a pore-forming agent to create pores, the pores in the negative electrode sheet are usually irregularly distributed. This irregular distribution cannot effectively take advantage of the pores and increase the infiltration rate of the electrolyte. Moreover, the porous structure formed in the negative electrode piece may affect the bonding performance of the electrode piece and easily cause the active material on the electrode piece to fall off, resulting in a decrease in the capacity of the secondary battery. In addition, the conventional pore-forming agent used in method (1) is easily decomposed during the reaction to produce harmful corrosive gases. This corrosive gas will produce side reactions in the battery core and reduce the performance of the battery core. In addition, in method (1), it is impossible to monitor whether all the pore-forming agents have sublimated. The remaining pore-forming agents may sublimate again during the subsequent drying process to increase gas production and affect the safety of the secondary battery. In method (2), after the negative electrode piece is cold-pressed, the pores of the graphite itself will be compacted, so the porosity of the electrode piece cannot be effectively improved; and using graphite with a larger specific surface area will generate more SEI film, leading to deterioration of gas production and affecting the cycle performance of secondary batteries.
为了解决上述问题，发明人通过大量研究提出了一种负极极片，巧妙地设计了负极极片中负极膜层的结构，该负极极片包括负极集流体和在负极集流体上设置的双膜层结构，其中，靠近负极集流体的膜层相对较厚且孔隙较少，保证极片具备足够高的粘结力；远离负极集流体的膜层相对较薄且孔隙较多，保证极片具备较高的吸收电解液的能力(吸液能力)。由此，通过设置这种表层膜层孔隙分布较多且较薄、里层膜层孔隙分布较少且较厚的膜层结构，能够在提升负极极片的吸收电解液能力(吸液能力)的同时，提升极片的电解液浸润速率，进而有利于提升二次电池的倍率性能，并且保证极片具备足够高的粘结性能。In order to solve the above problems, the inventor proposed a negative electrode sheet through extensive research and cleverly designed the structure of the negative electrode film layer in the negative electrode sheet. The negative electrode sheet includes a negative electrode current collector and a double membrane provided on the negative electrode current collector. layer structure, in which the film layer close to the negative electrode current collector is relatively thick and has fewer pores, ensuring that the electrode piece has a sufficiently high bonding force; the film layer away from the negative electrode current collector is relatively thin and has more pores, ensuring that the electrode piece has Higher ability to absorb electrolyte (liquid absorption capacity). Therefore, by setting up a film structure in which the surface film layer has more pores and is thinner, and the inner film layer has less pores and is thicker, the electrolyte absorption capacity (liquid absorption capacity) of the negative electrode plate can be improved. At the same time, the electrolyte infiltration rate of the pole piece is increased, which is beneficial to improving the rate performance of the secondary battery and ensuring that the pole piece has sufficiently high bonding performance.
负极极片Negative pole piece
本申请实施方式的第一方面提供了一种负极极片，参见图1，包括：负极集流1；和设置于所述负极集流体至少一侧的负极膜层2，所述负极膜层包括设置于靠近所述负极集流体的表面的第一负极膜层21和设置于所述第一负极膜层远离所述负极集流体一侧的表面上的第二负极膜层22，其中，所述第一负极膜层21的厚度为D1，所述第二负极膜层22的厚度为D2，且D1>D2；所述第一负极膜层21的孔隙率为P1，所述第二负极膜层22的孔隙率为P2，且P1<P2。The first aspect of the embodiment of the present application provides a negative electrode sheet, see Figure 1, including: a negative electrode current collector 1; and a negative electrode film layer 2 provided on at least one side of the negative electrode current collector, the negative electrode film layer includes The first negative electrode film layer 21 is disposed on the surface close to the negative electrode current collector and the second negative electrode film layer 22 is disposed on the surface of the first negative electrode film layer away from the negative electrode current collector, wherein, the The thickness of the first negative electrode film layer 21 is D1, the thickness of the second negative electrode film layer 22 is D2, and D1>D2; the porosity of the first negative electrode film layer 21 is P1, and the thickness of the second negative electrode film layer 22 is D2. The porosity of 22 is P2, and P1<P2.
并非意在受限于任何理论，发明人发现极片的吸液能力是毛细管力驱动的行为，在二次电池的负极极片中，极片表面的电解液和活性离子扩散的流量更大，而随着电解液和活性离子向极片内部的渗入，极片内部的电解液和活性离子扩散的流量会迅速减小。因此，基于前述发现，本申请设置了上述的双膜层结构，其中，第一负极膜层的孔隙率相较于第二负极膜层的孔隙率更小，即负极极片表面膜层(第二负极膜层)的孔隙分布较多，而极片内部膜层(第一负极膜层)的孔隙分布相对较少。在这种双膜层结构中，表面膜层的孔隙分布较多，有利于极片表面的电解液的大量扩散渗入，由此能够提升极片的吸液能力；而内部膜层的孔隙分布相对较少，能够形成内外膜层孔隙分布的差异化结构，这种差异化结构能够充分发挥膜层中孔隙的作用，提升电解液和活性离子在负极极片中的扩散速率，从而在提升极片吸液能力的同时，还可以提升极片的电解液浸润速率，并最终提升二次电池的倍率性能。Without intending to be bound by any theory, the inventor found that the liquid absorbing ability of the electrode piece is a behavior driven by capillary force. In the negative electrode piece of the secondary battery, the flow rate of electrolyte and active ion diffusion on the surface of the electrode piece is greater. As the electrolyte and active ions penetrate into the interior of the pole piece, the diffusion flow rate of the electrolyte and active ions inside the pole piece will decrease rapidly. Therefore, based on the aforementioned findings, the present application sets up the above-mentioned double-layer structure, in which the porosity of the first negative electrode film layer is smaller than the porosity of the second negative electrode film layer, that is, the surface film layer of the negative electrode sheet (the third The pore distribution of the two negative electrode film layers) is relatively large, while the pore distribution of the internal film layer of the pole piece (the first negative electrode film layer) is relatively small. In this double-membrane structure, the pores in the surface film layer are distributed more, which is conducive to the large-scale diffusion and penetration of the electrolyte on the surface of the pole piece, thereby improving the liquid absorption capacity of the pole piece; while the pore distribution in the inner film layer is relatively Less, it can form a differentiated structure of pore distribution in the inner and outer film layers. This differentiated structure can give full play to the role of the pores in the film layer and increase the diffusion rate of electrolyte and active ions in the negative electrode piece, thereby improving the electrode piece. While absorbing liquid, it can also increase the electrolyte infiltration rate of the pole piece, and ultimately improve the rate performance of the secondary battery.
进一步地，第一负极膜层的厚度相较于第二负极膜层的厚度更厚，即负极极片内部膜层(第一负极膜层)的厚度比表面膜层(第二负极膜层)的厚度更大。这种厚度的设置能够保证负极膜层与负极集流体之间具备足够高的粘结力，保证负极极片具备足够的粘结性能，减少极片上活性物质的脱落，从而提升二次电池的容量。另外，表面膜层(第二负极膜层)比内部膜层(第一负极膜层)更薄，也有利于减小极片表面的电解液在表面膜层进行大量扩散渗入时的扩散距离，并通过与上述的内外膜层孔隙分布的差异化结构的相互协同配合，进一步加快电解液的扩散速率并提升极片的电解液浸润速率。Further, the thickness of the first negative electrode film layer is thicker than the thickness of the second negative electrode film layer, that is, the thickness of the internal film layer of the negative electrode plate (the first negative electrode film layer) is thicker than the thickness of the surface film layer (the second negative electrode film layer) The thickness is greater. This thickness setting can ensure a sufficiently high bonding force between the negative electrode film layer and the negative electrode current collector, ensure that the negative electrode plate has sufficient bonding performance, reduce the shedding of active material on the electrode plate, and thereby increase the capacity of the secondary battery. . In addition, the surface film layer (the second negative electrode film layer) is thinner than the internal film layer (the first negative electrode film layer), which is also beneficial to reducing the diffusion distance of the electrolyte on the surface of the electrode piece when a large amount of the electrolyte diffuses and penetrates into the surface film layer. And by cooperating with the above-mentioned differentiated structure of pore distribution in the inner and outer membrane layers, the diffusion rate of the electrolyte is further accelerated and the electrolyte infiltration rate of the pole piece is increased.
在一些实施方式中，所述第一负极膜层的厚度与所述第二负极膜层的厚度的比值为3≤D1/D2≤10。例如，所述第一负极膜层的厚度与所述第二负极膜层的厚度的比值可以为3≤D1/D2≤9，3≤D1/D2≤8，3≤D1/D2≤7，3≤D1/D2≤6，3≤D1/D2≤5，3≤D1/D2≤4，4≤D1/D2≤10，4≤D1/D2≤9，4≤D1/D2≤7，4≤D1/D2≤6，4≤D1/D2≤5，5≤D1/D2≤10，5≤D1/D2≤9，5≤D1/D2≤8，5≤D1/D2≤7，5≤D1/D2≤6，6≤D1/D2≤10，6≤D1/D2≤9，6≤D1/D2≤8，6≤D1/D2≤7，7≤D1/D2≤10，7≤D1/D2≤9，7≤D1/D2≤8，8≤D1/D2≤10，8≤D1/D2≤9或9≤D1/D2≤10。可选的，所述第一负极膜层的厚度与所述第二负极膜层的厚度的比值为5≤D1/D2≤8。In some embodiments, the ratio of the thickness of the first negative electrode film layer to the thickness of the second negative electrode film layer is 3≤D1/D2≤10. For example, the ratio of the thickness of the first negative electrode film layer to the thickness of the second negative electrode film layer may be 3≤D1/D2≤9, 3≤D1/D2≤8, 3≤D1/D2≤7, 3 ≤D1/D2≤6, 3≤D1/D2≤5, 3≤D1/D2≤4, 4≤D1/D2≤10, 4≤D1/D2≤9, 4≤D1/D2≤7, 4≤D1 /D2≤6, 4≤D1/D2≤5, 5≤D1/D2≤10, 5≤D1/D2≤9, 5≤D1/D2≤8, 5≤D1/D2≤7, 5≤D1/D2 ≤6, 6≤D1/D2≤10, 6≤D1/D2≤9, 6≤D1/D2≤8, 6≤D1/D2≤7, 7≤D1/D2≤10, 7≤D1/D2≤9 , 7≤D1/D2≤8, 8≤D1/D2≤10, 8≤D1/D2≤9 or 9≤D1/D2≤10. Optionally, the ratio of the thickness of the first negative electrode film layer to the thickness of the second negative electrode film layer is 5≤D1/D2≤8.
所述第一负极膜层的厚度与所述第二负极膜层的厚度的比值在合适范围内，有利于进一步提升负极膜层与负极集流体之间的粘结力，从而进一步提升负极极片的粘结性能。而且厚度的比值控制在上述范围内，也有利于增强与前述的内外膜层孔隙分布的差异化结构的相互协同配合作用，进一步提升极片的电解液浸润速率。The ratio of the thickness of the first negative electrode film layer to the thickness of the second negative electrode film layer is within an appropriate range, which is conducive to further improving the bonding force between the negative electrode film layer and the negative electrode current collector, thereby further improving the negative electrode plate adhesive properties. Moreover, controlling the thickness ratio within the above range is also conducive to enhancing the synergistic effect with the differentiated structure of the pore distribution of the inner and outer membrane layers, and further improving the electrolyte infiltration rate of the pole piece.
在一些实施方式中，所述第二负极膜层的孔隙率与所述第一负极膜层的孔隙率的比值为1≤P2/P1≤5。例如，所述第二负极膜层的孔隙率与所述第一负极膜层的孔隙率的比值可以为1≤P2/P1≤4，1≤P2/P1≤3，1≤P2/P1≤2，2≤P2/P1≤5，2≤P2/P1≤4，2≤P2/P1≤3，3≤P2/P1≤5，3≤P2/P1≤4或4≤P2/P1≤5。可选的，所述第二负极膜层的孔隙率与所述第一负极膜层的孔隙率的比值为3≤P2/P1≤4。In some embodiments, the ratio of the porosity of the second negative electrode film layer to the porosity of the first negative electrode film layer is 1≤P2/P1≤5. For example, the ratio of the porosity of the second negative electrode film layer to the porosity of the first negative electrode film layer may be 1≤P2/P1≤4, 1≤P2/P1≤3, 1≤P2/P1≤2 , 2≤P2/P1≤5, 2≤P2/P1≤4, 2≤P2/P1≤3, 3≤P2/P1≤5, 3≤P2/P1≤4 or 4≤P2/P1≤5. Optionally, the ratio of the porosity of the second negative electrode film layer to the porosity of the first negative electrode film layer is 3≤P2/P1≤4.
所述第二负极膜层的孔隙率与所述第一负极膜层的孔隙率的比值在合适范围内，有利于进一步提升极片表面膜层的电解液的扩散渗入量，进一步提升极片的吸液能力。而且孔隙率的比值控制在上述范围内，能更好的形成内外膜层孔隙分布的差异化结构，并更加充分地发挥这种差异化结构中孔隙的作用，提升电解液在负极极片中的扩散速率，从而进一步提升极片的电解液浸润速率，并最终提升二次电池的倍率性能。The ratio of the porosity of the second negative electrode film layer to the porosity of the first negative electrode film layer is within an appropriate range, which is conducive to further increasing the diffusion and penetration amount of the electrolyte in the surface film layer of the pole piece, and further improving the electrolyte diffusion and penetration of the pole piece. Aspiration capacity. Moreover, controlling the ratio of porosity within the above range can better form a differentiated structure of pore distribution in the inner and outer membrane layers, and more fully play the role of pores in this differentiated structure, improving the electrolyte in the negative electrode piece. Diffusion rate, thereby further increasing the electrolyte infiltration rate of the pole piece, and ultimately improving the rate performance of the secondary battery.
在一些实施方式中，所述第一负极膜层的厚度为80μm≤D1≤2250μm。例如，所述第一负极膜层的厚度可以为100μm，200μm，400μm，600μm，800μm，1200μm，100μm，1400μm，1600μm，1800μm，2000μm，2200μm或处于以上任何数值所组成的范围内。可选的，所述第一负极膜层的厚度为100μm≤D1≤2000μm。In some embodiments, the thickness of the first negative electrode film layer is 80 μm≤D1≤2250 μm. For example, the thickness of the first negative electrode film layer may be 100 μm, 200 μm, 400 μm, 600 μm, 800 μm, 1200 μm, 100 μm, 1400 μm, 1600 μm, 1800 μm, 2000 μm, 2200 μm or within the range of any of the above values. Optionally, the thickness of the first negative electrode film layer is 100 μm ≤ D1 ≤ 2000 μm.
本申请中第一负极膜层的厚度为本领域公知的含义，可采用本领域已知的方法测试，例如采用万分尺(例如Mitutoyo293-100型，精度为0.1μm)进行测试。The thickness of the first negative electrode film layer in this application has a well-known meaning in the art, and can be measured using methods known in the art, such as using a multimeter (for example, Mitutoyo 293-100 type, with an accuracy of 0.1 μm).
第一负极膜层的厚度在合适范围内，一方面，有利于保证负极膜层与负极集流体之间的粘结力，从而提升负极极片的粘结性能。另一方面，也有利于在保证粘结性的同时尽量减小电解液的扩散距离，提升活性离子(例如锂离子)的传输速率，从而提高二次电池的倍率性能。The thickness of the first negative electrode film layer is within a suitable range. On the one hand, it is helpful to ensure the bonding force between the negative electrode film layer and the negative electrode current collector, thereby improving the bonding performance of the negative electrode plate. On the other hand, it is also beneficial to minimize the diffusion distance of the electrolyte while ensuring adhesion, and increase the transmission rate of active ions (such as lithium ions), thereby improving the rate performance of the secondary battery.
在一些实施方式中，所述第一负极膜层的孔隙率为20％≤P1≤40％。例如，所述第一负极膜层的孔隙率可以为22％，24％，26％，28％，30％，32％，34％，32％，36％，38％ 或处于以上任何数值所组成的范围内。可选的，所述第一负极膜层的孔隙率为25％≤P1≤35％。In some embodiments, the porosity of the first negative electrode film layer is 20%≤P1≤40%. For example, the porosity of the first negative electrode film layer may be 22%, 24%, 26%, 28%, 30%, 32%, 34%, 32%, 36%, 38% or any of the above values. In the range. Optionally, the porosity of the first negative electrode film layer is 25%≤P1≤35%.
本申请中第一负极膜层的孔隙率为本领域公知的含义，可采用本领域已知的方法测试，例如将仅包含第一负极膜层的负极极片裁成直径大小为10mm的圆片，采用气体置换法测试负极活性材料层的孔隙率，孔隙率的计算公式为：P＝(V-V0)/V*100％，其中P为孔隙率，V0为极片涂层真体积，V为极片涂层表观体积。The porosity of the first negative electrode film layer in this application has a well-known meaning in the art, and can be tested using methods known in the art, for example, cutting the negative electrode sheet containing only the first negative electrode film layer into discs with a diameter of 10 mm. , use the gas replacement method to test the porosity of the negative active material layer. The calculation formula of porosity is: P=(V-V0)/V*100%, where P is the porosity, V0 is the true volume of the electrode coating, V is the apparent volume of the pole piece coating.
第一负极膜层的孔隙率在合适范围内，有利于同第二负极膜层之间形成前述的内外膜层孔隙分布的差异化结构，并使这种差异化结构更加充分的发挥膜层中孔隙的作用，提升电解液在负极极片中的扩散速率，从而提升极片的电解液浸润速率。The porosity of the first negative electrode film layer is within an appropriate range, which is conducive to the formation of the aforementioned differentiated structure of pore distribution between the inner and outer film layers with the second negative electrode film layer, and allows this differentiated structure to more fully exert itself in the film layer. The role of pores increases the diffusion rate of electrolyte in the negative electrode piece, thereby increasing the electrolyte infiltration rate of the electrode piece.
在一些实施方式中，所述第二负极膜层的厚度为8μm≤D2≤750μm。例如，所述第二负极膜层的厚度可以为10μm，50μm，100μm，150μm，200μm，250μm，300μm，350μm，400μm，450μm，500μm，550μm，600μm，650μm，700μm或处于以上任何数值所组成的范围内。可选的，所述第二负极膜层的厚度为10μm≤D2≤700μm。In some embodiments, the thickness of the second negative electrode film layer is 8 μm≤D2≤750 μm. For example, the thickness of the second negative electrode film layer can be 10 μm, 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm, 500 μm, 550 μm, 600 μm, 650 μm, 700 μm or any combination thereof. within the range. Optionally, the thickness of the second negative electrode film layer is 10 μm ≤ D2 ≤ 700 μm.
本申请中第二负极膜层的厚度为本领域公知的含义，可采用本领域已知的方法测试，例如采用万分尺(例如Mitutoyo293-100型，精度为0.1μm)进行测试。The thickness of the second negative electrode film layer in this application has a well-known meaning in the art, and can be measured using methods known in the art, such as using a multimeter (for example, Mitutoyo 293-100 type, with an accuracy of 0.1 μm).
第二负极膜层的厚度控制在上述范围内，有利于减小极片表面的电解液在扩散进入表面膜层时的扩散距离，进一步加快扩散速率，减小界面电阻，从而进一步提升极片的电解液浸润速率及二次电池的倍率性能。The thickness of the second negative electrode film layer is controlled within the above range, which is beneficial to reducing the diffusion distance of the electrolyte on the surface of the electrode piece when it diffuses into the surface film layer, further accelerating the diffusion rate, reducing the interface resistance, thereby further improving the performance of the electrode piece Electrolyte infiltration rate and rate performance of secondary batteries.
在一些实施方式中，所述第二负极膜层的孔隙率为40％≤P2≤70％。例如，所述第二负极膜层的孔隙率可以为43％，46％，49％，52％，55％，58％，61％，64％，67％或处于以上任何数值所组成的范围内。可选的，所述第二负极膜层的孔隙率为45％≤P2≤65％。In some embodiments, the porosity of the second negative electrode film layer is 40%≤P2≤70%. For example, the porosity of the second negative electrode film layer may be 43%, 46%, 49%, 52%, 55%, 58%, 61%, 64%, 67% or within the range of any of the above values. . Optionally, the porosity of the second negative electrode film layer is 45%≤P2≤65%.
本申请中第二负极膜层的孔隙率为本领域公知的含义，可采用本领域已知的方法测试，例如将仅包含第二负极膜层的负极极片裁成直径大小为10mm的圆片，采用气体置换法测试负极活性材料层的孔隙率，孔隙率的计算公式为：P＝(V-V0)/V*100％，其中P为孔隙率，V0为极片涂层真体积，V为极片涂层表观体积。The porosity of the second negative electrode film layer in this application has a well-known meaning in the art, and can be tested using methods known in the art, for example, cutting the negative electrode sheet containing only the second negative electrode film layer into discs with a diameter of 10 mm. , use the gas replacement method to test the porosity of the negative active material layer. The calculation formula of porosity is: P=(V-V0)/V*100%, where P is the porosity, V0 is the true volume of the electrode coating, V is the apparent volume of the pole piece coating.
第二负极膜层的孔隙率在上述范围内，有利于极片表面的电解液的大量扩散渗入，由此提升极片的吸液能力；同时，还有利于与第一负极膜层之间形成前述的内外膜层孔隙分布的差异化结构，并使这种差异化结构更加充分的发挥膜层中孔隙的作用，提升电解液在负极极片中的扩散速率，从而在提升极片吸液能力的同时提升极片的电解液浸润速率。The porosity of the second negative electrode film layer is within the above range, which is conducive to the large-scale diffusion and penetration of the electrolyte on the surface of the electrode piece, thereby improving the liquid absorption capacity of the electrode piece; at the same time, it is also conducive to the formation of a gap between the second negative electrode film layer and the first negative electrode film layer. The aforementioned differentiated structure of pore distribution in the inner and outer film layers enables this differentiated structure to fully play the role of the pores in the film layer and increase the diffusion rate of electrolyte in the negative electrode plate, thus improving the liquid absorbing capacity of the electrode plate. At the same time, the electrolyte infiltration rate of the pole piece is increased.
在一些实施方式中，所述负极膜层的总孔隙率为P0，且30％≤P0≤60％。例如，所述负极膜层的总孔隙率可以为33％，36％，39％，42％，45％，48％，51％，54％，57％或处于以上任何数值所组成的范围内。可选的，所述负极膜层的总孔隙率为35％≤P0≤55％。 负极膜层的总孔隙率在合适范围内，有利于提升极片的吸液能力，提升活性离子(如锂离子)在负极极片中的传导性。In some embodiments, the total porosity of the negative electrode film layer is P0, and 30%≤P0≤60%. For example, the total porosity of the negative electrode film layer may be 33%, 36%, 39%, 42%, 45%, 48%, 51%, 54%, 57% or within the range of any of the above values. Optionally, the total porosity of the negative electrode film layer is 35%≤P0≤55%. The total porosity of the negative electrode film layer is within an appropriate range, which is beneficial to improving the liquid absorption capacity of the electrode piece and improving the conductivity of active ions (such as lithium ions) in the negative electrode piece.
本申请中，负极膜层的总孔隙率可采用本领域已知的方法测试，例如将负极极片裁成直径大小为10mm的圆片，采用气体置换法测试负极活性材料层的孔隙率，孔隙率的计算公式为：P＝(V-V0)/V*100％，其中P为孔隙率，V0为极片涂层真体积，V为极片涂层表观体积。In this application, the total porosity of the negative electrode film layer can be tested using methods known in the art. For example, the negative electrode piece is cut into discs with a diameter of 10 mm, and the gas replacement method is used to test the porosity of the negative electrode active material layer. The porosity The calculation formula of the rate is: P=(V-V0)/V*100%, where P is the porosity, V0 is the true volume of the pole piece coating, and V is the apparent volume of the pole piece coating.
在一些实施方式中，所述负极膜层的总厚度为D0，且100μm≤D0≤3000μm。例如，所述负极膜层的总厚度可以为200μm，500μm，800μm，1100μm，1400μm，1700μm，2000μm，2300μm，2600μm，2900μm或处于以上任何数值所组成的范围内。可选的，所述负极膜层的总厚度为150μm≤D0≤2500μm。负极膜层的总厚度在合适范围内，能够在保证负极极片粘结性能的同时，缩短电解液在极片中的扩散路径和扩散距离，提升极片的电解液浸润性。In some embodiments, the total thickness of the negative electrode film layer is D0, and 100 μm≤D0≤3000 μm. For example, the total thickness of the negative electrode film layer may be 200 μm, 500 μm, 800 μm, 1100 μm, 1400 μm, 1700 μm, 2000 μm, 2300 μm, 2600 μm, 2900 μm or within the range of any of the above values. Optionally, the total thickness of the negative electrode film layer is 150 μm ≤ D0 ≤ 2500 μm. The total thickness of the negative electrode film layer is within an appropriate range, which can ensure the bonding performance of the negative electrode piece, shorten the diffusion path and diffusion distance of the electrolyte in the electrode piece, and improve the electrolyte wettability of the electrode piece.
本申请中，负极膜层的总厚度指的是第一负极膜层与第二负极膜层的厚度之和，即D0＝D1+D2。负极膜层的总厚度可采用本领域已知的方法测试，例如采用万分尺(例如Mitutoyo293-100型，精度为0.1μm)进行测试。In this application, the total thickness of the negative electrode film layer refers to the sum of the thicknesses of the first negative electrode film layer and the second negative electrode film layer, that is, D0=D1+D2. The total thickness of the negative electrode film layer can be measured using methods known in the art, such as using a multimeter (for example, Mitutoyo 293-100 type, with an accuracy of 0.1 μm).
在一些实施方式中，所述负极极片的单面涂布重量为0.1g/1540.25mm 2至0.4g/1540.25mm 2。例如，所述负极极片的单面涂布重量可以为0.15g/1540.25mm 2，0.20g/1540.25mm 2，0.25g/1540.25mm 2，0.30g/1540.25mm 2，0.35g/1540.25mm 2，0.40g/1540.25mm 2或处于以上任何数值所组成的范围内。可选的，所述负极极片的单面涂布重量为0.15g/1540.25mm 2至0.35g/1540.25mm 2。 In some embodiments, the single-sided coating weight of the negative electrode sheet is 0.1g/1540.25mm 2 to 0.4g/1540.25mm 2 . For example, the single-sided coating weight of the negative electrode piece can be 0.15g/1540.25mm 2 , 0.20g/1540.25mm 2 , 0.25g/1540.25mm 2 , 0.30g/1540.25mm 2 , 0.35g/1540.25mm 2 , 0.40g/1540.25mm 2 or within the range of any of the above values. Optionally, the single-sided coating weight of the negative electrode piece is 0.15g/1540.25mm 2 to 0.35g/1540.25mm 2 .
负极极片的单面涂布重量为本领域公知的含义，可采用本领域已知的方法测试。例如，将烘干的负极极片裁切面积为1540.25mm 2的极片5片，通过万分尺分别测量负极极片的厚度，记为d0cm，用刮刀刮下负极极片中的负极活性材料层，通过天平称量负极活性材料层的质量，记为m(mg)，即为负极活性材料层1540.25mm 2面积上的质量。 The single-sided coating weight of the negative electrode sheet is a well-known meaning in the art and can be tested by methods known in the art. For example, cut five dried negative electrode sheets with an area of 1540.25 mm2 , measure the thickness of the negative electrode sheets with a micrometer, record it as d0cm, scrape off the negative electrode active material layer in the negative electrode sheet with a scraper, weigh the mass of the negative electrode active material layer with a balance, record it as m (mg), which is the mass of the negative electrode active material layer on the area of 1540.25 mm2 .
负极极片的单面涂布重量在合适范围内，能够缩短电解液在极片中的扩散路径和扩散距离，有利于提升电解液的浸润速率，从而提高活性离子(如锂离子)的传输效率，同时保证二次电池具备较高的能量密度。The single-sided coating weight of the negative electrode piece is within an appropriate range, which can shorten the diffusion path and diffusion distance of the electrolyte in the electrode piece, which is conducive to increasing the infiltration rate of the electrolyte, thereby improving the transmission efficiency of active ions (such as lithium ions) , while ensuring that the secondary battery has a high energy density.
需要说明的是，本申请所给的各负极极片参数(例如单面涂布重量)均指负极集流体单侧的参数。当负极活性材料层设置在负极集流体的两侧时，其中任意一侧的参数满足本申请，即认为落入本申请的保护范围内。It should be noted that the parameters of each negative electrode piece (such as the coating weight on one side) given in this application refer to the parameters of one side of the negative electrode current collector. When the negative active material layer is disposed on both sides of the negative current collector, if the parameters on either side meet the requirements of this application, it is deemed to fall within the protection scope of this application.
本申请实施方式的第二方面提供了一种用于制备负极极片的方法，包括：A second aspect of the embodiment of the present application provides a method for preparing a negative electrode sheet, including:
成膜步骤，包括在负极集流体的至少一侧上形成第一负极膜层和第二负极膜层，得到负极极片；其中，所述第一负极膜层位于靠近所述负极集流体的表面，所述第二负极膜层位于所述第一负极膜层远离所述负极集流体一侧的表面上；所述第一负极膜层的 厚度为D1，所述第二负极膜层的厚度为D2，且D1>D2；所述第一负极膜层的孔隙率为P1，所述第二负极膜层的孔隙率为P2，且P1<P2。The film forming step includes forming a first negative electrode film layer and a second negative electrode film layer on at least one side of the negative electrode current collector to obtain a negative electrode sheet; wherein the first negative electrode film layer is located close to the surface of the negative electrode current collector , the second negative electrode film layer is located on the surface of the first negative electrode film layer away from the negative electrode current collector; the thickness of the first negative electrode film layer is D1, and the thickness of the second negative electrode film layer is D2, and D1>D2; the porosity of the first negative electrode film layer is P1, and the porosity of the second negative electrode film layer is P2, and P1<P2.
本申请通过在负极集流体的至少一侧上形成由第一负极膜层和第二负极膜层组成的双膜层结构，在这种双膜层结构中，第二负极膜层的孔隙分布较多，有利于极片表面的电解液的大量扩散渗入，由此能够提升极片的吸液能力。而第一负极膜层的孔隙分布相对较少，能够在负极极片中形成内外膜层孔隙分布的差异化结构，这种差异化结构能够充分发挥膜层中孔隙的作用，提升电解液和活性离子在负极极片中的扩散速率，从而提升极片的电解液浸润速率，并最终提升二次电池的倍率性能。另外，第一负极膜层与第二负极膜层之间的厚度的设置关系能够保证负极膜层与负极集流体之间具备足够高的粘结力，保证负极极片具备足够的粘结性能，减少极片上活性物质的脱落，从而保证二次电池的容量。In this application, a double-film layer structure composed of a first negative electrode film layer and a second negative electrode film layer is formed on at least one side of the negative electrode current collector. In this double-film layer structure, the pore distribution of the second negative electrode film layer is relatively small. It is conducive to the large amount of electrolyte diffusion and penetration on the surface of the pole piece, which can improve the liquid absorption capacity of the pole piece. The pore distribution of the first negative electrode film layer is relatively small, which can form a differentiated structure of the pore distribution of the inner and outer film layers in the negative electrode piece. This differentiated structure can give full play to the role of the pores in the film layer and improve the electrolyte and activity. The diffusion rate of ions in the negative electrode plate increases the electrolyte infiltration rate of the electrode plate and ultimately improves the rate performance of the secondary battery. In addition, the thickness setting relationship between the first negative electrode film layer and the second negative electrode film layer can ensure a sufficiently high bonding force between the negative electrode film layer and the negative electrode current collector, and ensure that the negative electrode plate has sufficient bonding performance. Reduce the shedding of active materials on the pole pieces, thereby ensuring the capacity of the secondary battery.
在一些实施方式中，所述成膜步骤进一步包括：In some embodiments, the film forming step further includes:
S10、在所述负极集流体的至少一侧上涂布第一负极浆料，形成第一涂层；S10. Coat the first negative electrode slurry on at least one side of the negative electrode current collector to form a first coating;
S20、在所述第一涂层的表面上涂布第二负极浆料，形成第二涂层，其中，所述第二负极浆料中包括1,2-二羟基-3-三苯甲基-丙烷；S20. Coat a second negative electrode slurry on the surface of the first coating layer to form a second coating layer, wherein the second negative electrode slurry includes 1,2-dihydroxy-3-trityl. -propane;
S30、对所述第一涂层和所述第二涂层做烘干冷压处理，形成所述第一负极膜层和所述第二负极膜层。S30. Perform a drying and cold pressing process on the first coating layer and the second coating layer to form the first negative electrode film layer and the second negative electrode film layer.
本申请的第二浆料中包括热升华材料1,2-二羟基-3-三苯甲基-丙烷，该材料是作为造孔剂而应用于第二负极膜层的形成过程中。通过将热升华材料1,2-二羟基-3-三苯甲基-丙烷作为造孔剂添加到浆料中，并经涂布冷压之后再烘干极片的方式去除造孔剂，能够减小冷压工序对孔隙的影响，有效提高负极极片的孔隙率。The second slurry of the present application includes the thermal sublimation material 1,2-dihydroxy-3-trityl-propane, which is used as a pore-forming agent in the formation process of the second negative electrode film layer. By adding the thermal sublimation material 1,2-dihydroxy-3-trityl-propane to the slurry as a pore-forming agent, and removing the pore-forming agent by applying cold pressing and then drying the pole piece, Reduce the impact of the cold pressing process on pores and effectively increase the porosity of the negative electrode piece.
此外，与常规的造孔剂相比，本申请使用的上述造孔剂在使用过程中不会产生有害的腐蚀性气体，无副反应发生，由此可以减小常规造孔剂的副反应对电芯的影响，提升电芯的性能。而且在负极极片的制备过程中，可通过监控上述造孔剂的回收率去判断造孔剂是否除尽，避免遗留的造孔剂在后续的烘干过程中再次升华而增加产气，提升二次电池的安全性能。In addition, compared with conventional pore-forming agents, the above-mentioned pore-forming agents used in this application will not produce harmful corrosive gases and have no side reactions during use, thereby reducing the side effects of conventional pore-forming agents. The influence of the battery core improves the performance of the battery core. Moreover, during the preparation process of the negative electrode piece, the recovery rate of the above-mentioned pore-forming agent can be monitored to determine whether the pore-forming agent has been completely removed, so as to avoid the remaining pore-forming agent from sublimating again during the subsequent drying process to increase gas production and improve Safety performance of secondary batteries.
在一些实施方式中，基于所述第二负极浆料的总质量，所述1,2-二羟基-3-三苯甲基-丙烷的质量百分含量为0.1％至30％。例如，所述1,2-二羟基-3-三苯甲基-丙烷的质量百分含量可以为0.5％，1％，3％，5％，10％，12％，15％，18％，20％，23％，25％，27％或处于以上任何数值所组成的范围内。可选的，所述1,2-二羟基-3-三苯甲基-丙烷的质量百分含量为1％至25％。In some embodiments, the mass percentage content of the 1,2-dihydroxy-3-trityl-propane is 0.1% to 30% based on the total mass of the second negative electrode slurry. For example, the mass percentage of 1,2-dihydroxy-3-trityl-propane can be 0.5%, 1%, 3%, 5%, 10%, 12%, 15%, 18%, 20%, 23%, 25%, 27% or within the range of any of the above values. Optionally, the mass percentage of 1,2-dihydroxy-3-trityl-propane is 1% to 25%.
通过将第二负极浆料中的1,2-二羟基-3-三苯甲基-丙烷的质量百分含量控制在上述范围内，并在上述范围内对1,2-二羟基-3-三苯甲基-丙烷的质量百分含量进行调控，能够 使第二负极膜层的孔隙率保持在前述的合适范围内，从而有利于极片表面的电解液的大量扩散渗入，由此提升极片的吸液能力。By controlling the mass percentage of 1,2-dihydroxy-3-trityl-propane in the second negative electrode slurry within the above range, and controlling 1,2-dihydroxy-3-tritylpropane within the above range. By regulating the mass percentage of trityl-propane, the porosity of the second negative electrode membrane layer can be maintained within the aforementioned appropriate range, which is conducive to the large-scale diffusion and infiltration of the electrolyte on the surface of the electrode piece, thereby improving the electrode The liquid absorption capacity of the tablet.
在一些实施方式中，所述第一负极浆料中包括负极活性材料和可选的第一组分，其中，所述第一组分包括导电剂、粘结剂、增稠剂、溶剂或其组合。In some embodiments, the first negative electrode slurry includes a negative active material and an optional first component, wherein the first component includes a conductive agent, a binder, a thickener, a solvent, or the like. combination.
在一些实施方式中，所述第二负极浆料中还包括负极活性材料和可选的第二组分，其中，所述第二组分包括导电剂、粘结剂、增稠剂、溶剂或其组合。In some embodiments, the second negative electrode slurry further includes a negative active material and an optional second component, wherein the second component includes a conductive agent, a binder, a thickener, a solvent or its combination.
在一些实施方式中，所述负极活性材料可采用本领域公知的用于二次电池的负极活性材料。作为示例，负极活性材料可包括以下材料中的至少一种：人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂等。所述硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的至少一种。所述锡基材料可选自单质锡、锡氧化合物以及锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性材料的传统材料。这些负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。In some embodiments, the negative active material may be a negative active material known in the art for secondary batteries. As an example, the negative active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon carbon composites, silicon nitrogen composites and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as battery negative electrode active materials can also be used. Only one type of these negative electrode active materials may be used alone, or two or more types may be used in combination.
在一些实施方式中，所述第一负极浆料和第二负极浆料中还可选的包括导电剂。所述导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。In some embodiments, the first negative electrode slurry and the second negative electrode slurry optionally further include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
在一些实施方式中，所述第一负极浆料和第二负极浆料中还可选的包括粘结剂。所述粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。In some embodiments, the first negative electrode slurry and the second negative electrode slurry optionally further include a binder. The binder can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polysodium acrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), poly At least one of methacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
在一些实施方式中，所述第一负极浆料和第二负极浆料中还可选的包括增稠剂。例如增稠剂可以是羧甲基纤维素钠(CMC-Na)。In some embodiments, the first negative electrode slurry and the second negative electrode slurry optionally further include a thickener. For example, the thickening agent may be sodium carboxymethylcellulose (CMC-Na).
在一些实施方式中，所述第一负极浆料和第二负极浆料中还可选的包括溶剂。例如，溶剂可以是N-甲基吡咯烷酮(NMP)或去离子水。In some embodiments, the first negative electrode slurry and the second negative electrode slurry optionally further include a solvent. For example, the solvent may be N-methylpyrrolidone (NMP) or deionized water.
在一些实施方式中，负极集流体具有在其自身厚度方向相对的两个表面，负极活性材料层设置在负极集流体相对的两个表面中的任意一者或两者上。In some embodiments, the negative electrode current collector has two surfaces opposite in its own thickness direction, and the negative electrode active material layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
在一些实施方式中，所述负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, copper foil can be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material. The composite current collector can be formed by forming metal materials (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子 水)中，形成第一负极浆料；将第一负极浆料涂覆在负极集流体上，形成第一涂层。将上述用于制备负极极片的组分，例如负极活性材料、导电剂、粘结剂、造孔剂1,2-二羟基-3-三苯甲基-丙烷和任意其他组分分散于溶剂(例如去离子水)中，形成第二负极浆料；将第二负极浆料涂覆在第一涂层上，形成第二涂层。经烘干、冷压等工序后，即可得到包含第一负极膜层和第二负极膜层的负极极片。In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative active materials, conductive agents, binders and any other components in a solvent (such as deionized water) to form a first negative electrode slurry; the first negative electrode slurry is coated on the negative electrode current collector to form a first coating layer. Disperse the above-mentioned components for preparing the negative electrode sheet, such as negative active material, conductive agent, binder, pore-forming agent 1,2-dihydroxy-3-trityl-propane and any other components in a solvent (for example, deionized water), a second negative electrode slurry is formed; the second negative electrode slurry is coated on the first coating layer to form a second coating layer. After drying, cold pressing and other processes, a negative electrode sheet including a first negative electrode film layer and a second negative electrode film layer can be obtained.
本申请的负极极片并不排除除了负极膜层之外的其他附加功能层。例如，在一些实施方式中，本申请的负极极片还包括夹在负极集流体和负极膜层之间、设置于负极集流体表面的导电底涂层(例如由导电剂和粘结剂组成)。在另外一些实施方式中，本申请的负极极片还包括覆盖在负极膜层表面的保护层。The negative electrode sheet of the present application does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode sheet of the present application also includes a conductive undercoat layer (for example, composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. . In other embodiments, the negative electrode sheet of the present application further includes a protective layer covering the surface of the negative electrode film layer.
二次电池secondary battery
本申请实施方式的第三方面提供一种二次电池，包括其中发生电化学反应以将化学能与电能互相转化的任何装置，它的具体实例包括所有种类的锂一次电池或锂二次电池。特别地，锂二次电池包括锂金属二次电池、锂离子二次电池、锂聚合物二次电池或锂离子聚合物二次电池。A third aspect of the embodiment of the present application provides a secondary battery, including any device in which an electrochemical reaction occurs to convert chemical energy and electrical energy into each other, and specific examples thereof include all kinds of lithium primary batteries or lithium secondary batteries. In particular, the lithium secondary battery includes a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery or a lithium ion polymer secondary battery.
在一些实施方式中，本申请的二次电池包括正极极片、负极极片、隔离膜和电解液。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之间起到传导离子的作用。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使离子通过。In some embodiments, the secondary battery of the present application includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte. During the charging and discharging process of the battery, active ions are inserted and detached back and forth between the positive and negative electrodes. The electrolyte plays a role in conducting ions between the positive and negative electrodes. The isolation film is placed between the positive electrode piece and the negative electrode piece. It mainly prevents the positive and negative electrodes from short-circuiting and allows ions to pass through.
[负极极片][Negative pole piece]
本申请的二次电池中使用的负极极片为本申请实施方式第一方面的负极极片或通过本申请实施方式第二方面的方法制得的负极极片。The negative electrode sheet used in the secondary battery of the present application is the negative electrode sheet of the first aspect of the embodiment of the present application or the negative electrode sheet produced by the method of the second aspect of the embodiment of the present application.
[正极极片][Positive pole piece]
本申请的二次电池中使用的正极极片的材料、构成和其制造方法可包括任何现有技术中公知的技术。The material, composition and manufacturing method of the positive electrode sheet used in the secondary battery of the present application may include any technology known in the prior art.
正极极片包括正极集流体以及设置在正极集流体至少一个表面上且包括正极活性材料的正极膜层。作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector and including a positive electrode active material. As an example, the positive electrode current collector has two surfaces facing each other in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
在一些实施方式中，正极膜层包括正极活性材料，正极活性材料的具体种类不受到具体的限制，可根据需求进行选择。例如，正极活性材料可以包括锂过渡金属氧化物、橄榄石结构的含锂磷酸盐及其各自的改性化合物中的一种或几种。在本申请的二次电池中，上述各正极活性材料的改性化合物可以是对正极活性材料进行掺杂改性、表面包覆改性、或掺杂同时表面包覆改性。In some embodiments, the positive electrode film layer includes a positive electrode active material. The specific type of the positive electrode active material is not specifically limited and can be selected according to requirements. For example, the cathode active material may include one or more of lithium transition metal oxides, lithium-containing phosphates with an olivine structure, and their respective modified compounds. In the secondary battery of the present application, the modified compound of each positive electrode active material mentioned above may be doping modification, surface coating modification, or doping and surface coating modification of the positive electrode active material.
作为示例，锂过渡金属氧化物可以包括锂钴氧化物、锂镍氧化物、锂锰氧化物、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物、锂镍钴铝氧化物及其 改性化合物中的一种或几种。作为示例，橄榄石结构的含锂磷酸盐可以包括磷酸铁锂、磷酸铁锂与碳的复合材料、磷酸锰锂、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料及其改性化合物中的一种或几种。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。As examples, lithium transition metal oxides may include lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, One or more of lithium nickel cobalt aluminum oxide and its modified compounds. As examples, the lithium-containing phosphate with an olivine structure may include lithium iron phosphate, a composite of lithium iron phosphate and carbon, a lithium manganese phosphate, a composite of lithium manganese phosphate and carbon, a lithium manganese iron phosphate, a lithium manganese iron phosphate and carbon One or more of the composite materials and their modified compounds. Only one type of these positive electrode active materials may be used alone, or two or more types may be used in combination.
在一些实施方式中，正极膜层还可选的包括导电剂。作为示例，所述导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。In some embodiments, the positive electrode film layer optionally further includes a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
在一些实施方式中，正极膜层还可选的包括粘结剂。作为示例，所述粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。In some embodiments, the positive electrode film layer optionally further includes a binder. As examples, the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene At least one of ethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
在一些实施方式中，正极集流体可采用金属箔片或复合集流体。作为金属箔片的示例，正极集流体可采用铝箔。复合集流体可包括高分子材料基层以及形成于高分子材料基层至少一个表面上的金属材料层。作为示例，金属材料可选自铝、铝合金、镍、镍合金、钛、钛合金、银、银合金中的一种或几种。作为示例，高分子材料基层可选自聚丙烯、聚对苯二甲酸乙二醇酯、聚对苯二甲酸丁二醇酯、聚苯乙烯、聚乙烯等。In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, aluminum foil can be used as the positive electrode current collector. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may be selected from one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may be selected from polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.
本申请中正极极片可以按照本领域常规方法制备。例如，正极膜层通常是将正极浆料涂布在正极集流体上，经干燥、冷压而成的。正极浆料通常是将正极活性材料、可选的导电剂、可选的粘结剂以及任意的其他组分分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)，但不限于此。The positive electrode piece in this application can be prepared according to conventional methods in this field. For example, the positive electrode film layer is usually formed by coating the positive electrode slurry on the positive electrode current collector, drying, and cold pressing. The cathode slurry is usually formed by dispersing the cathode active material, optional conductive agent, optional binder and any other components in a solvent and stirring evenly. The solvent may be N-methylpyrrolidone (NMP), but is not limited thereto.
本申请的正极极片并不排除除了正极膜层之外的其他附加功能层。例如，在一些实施方式中，本申请的正极极片还包括夹在正极集流体和正极膜层之间、设置于正极集流体表面的导电底涂层(例如由导电剂和粘结剂组成)。在另外一些实施方式中，本申请的正极极片还包括覆盖在正极膜层表面的保护层。The positive electrode sheet of the present application does not exclude other additional functional layers in addition to the positive electrode film layer. For example, in some embodiments, the positive electrode sheet of the present application also includes a conductive undercoat layer (for example, composed of a conductive agent and a binder) sandwiched between the positive electrode current collector and the positive electrode film layer and disposed on the surface of the positive electrode current collector. . In other embodiments, the positive electrode sheet of the present application further includes a protective layer covering the surface of the positive electrode film layer.
[电解液][Electrolyte]
电解液在正极极片和负极极片之间起到传导活性离子的作用。可用于本申请二次电池的电解液可以为现有技术已知的电解液。The electrolyte plays a role in conducting active ions between the positive electrode piece and the negative electrode piece. The electrolyte solution that can be used in the secondary battery of the present application can be an electrolyte solution known in the art.
在一些实施方式中，所述电解液包括有机溶剂、锂盐和可选的添加剂，有机溶剂、锂盐和添加剂的种类均不受到具体的限制，可根据需求进行选择。In some embodiments, the electrolyte solution includes an organic solvent, a lithium salt and optional additives. The types of the organic solvent, lithium salt and additives are not specifically limited and can be selected according to needs.
在一些实施方式中，作为示例，所述锂盐包括但不限于LiPF 6(六氟磷酸锂)、LiBF 4(四氟硼酸锂)、LiClO 4(高氯酸锂)、LiFSI(双氟磺酰亚胺锂)、LiTFSI(双三氟甲磺酰亚胺锂)、LiTFS(三氟甲磺酸锂)、LiDFOB(二氟草酸硼酸锂)、LiBOB(二草酸硼酸锂)、LiPO 2F 2(二氟磷酸锂)、LiDFOP(二氟二草酸磷酸锂)及LiTFOP (四氟草酸磷酸锂)中的至少一种。上述锂盐可以单独使用一种，也可以同时使用两种或两种以上。 In some embodiments, as examples, the lithium salts include, but are not limited to, LiPF 6 (lithium hexafluorophosphate), LiBF 4 (lithium tetrafluoroborate), LiClO 4 (lithium perchlorate), LiFSI (lithium bisfluorosulfonimide) ), LiTFSI (lithium bistrifluoromethanesulfonimide), LiTFS (lithium trifluoromethanesulfonate), LiDFOB (lithium difluoromethanesulfonate), LiBOB (lithium difluoromethanesulfonate), LiPO 2 F 2 (difluorophosphoric acid Lithium), LiDFOP (lithium difluorodioxalate phosphate) and LiTFOP (lithium tetrafluorooxalate phosphate). One type of the above-mentioned lithium salt may be used alone, or two or more types may be used simultaneously.
在一些实施方式中，作为示例，所述有机溶剂包括但不限于碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸亚丁酯(BC)、氟代碳酸亚乙酯(FEC)、甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)、丁酸乙酯(EB)、1,4-丁内酯(GBL)、环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)及二乙砜(ESE)中的至少一种。上述有机溶剂可以单独使用一种，也可以同时使用两种或两种以上。可选地，上述有机溶剂同时使用两种或两种以上。In some embodiments, as examples, the organic solvent includes, but is not limited to, ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), carbonic acid Dimethyl ester (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate Ester (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), Methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and diethyl sulfone (ESE) ) at least one of the following. One type of the above-mentioned organic solvent may be used alone, or two or more types may be used simultaneously. Optionally, two or more of the above organic solvents are used simultaneously.
在一些实施方式中，所述添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。In some embodiments, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain properties of the battery, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance. wait.
作为示例，所述添加剂包括但不限于氟代碳酸乙烯酯(FEC)、碳酸亚乙烯酯(VC)、乙烯基碳酸乙烯酯(VEC)、硫酸乙烯酯(DTD)、硫酸丙烯酯、亚硫酸乙烯酯(ES)、1,3-丙磺酸内酯(PS)、1,3-丙烯磺酸内酯(PST)、磺酸酯环状季铵盐、丁二酸酐、丁二腈(SN)、己二腈(AND)、三(三甲基硅烷)磷酸酯(TMSP)、三(三甲基硅烷)硼酸酯(TMSB)中的至少一种。As examples, the additives include, but are not limited to, fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), vinyl sulfate (DTD), propylene sulfate, vinyl sulfite Ester (ES), 1,3-propene sultone (PS), 1,3-propene sultone (PST), sulfonate cyclic quaternary ammonium salt, succinic anhydride, succinonitrile (SN) , at least one of adiponitrile (AND), tris(trimethylsilane)phosphate (TMSP), and tris(trimethylsilane)borate (TMSB).
电解液可以按照本领域常规的方法制备。例如，可以将有机溶剂、锂盐、可选的添加剂混合均匀，得到电解液。各物料的添加顺序并没有特别的限制，例如，将锂盐、可选的添加剂加入到有机溶剂中混合均匀，得到电解液；或者，先将锂盐加入有机溶剂中，然后再将可选的添加剂加入有机溶剂中混合均匀，得到电解液。The electrolyte solution can be prepared according to conventional methods in the art. For example, the organic solvent, lithium salt, and optional additives can be mixed evenly to obtain an electrolyte. There is no particular restriction on the order in which the materials are added. For example, add lithium salt and optional additives to the organic solvent and mix evenly to obtain an electrolyte; or add lithium salt to the organic solvent first, and then add the optional additives. The additives are added to the organic solvent and mixed evenly to obtain an electrolyte.
[隔离膜][Isolation film]
隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使活性离子通过。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。The isolation film is placed between the positive electrode piece and the negative electrode piece. It mainly prevents the positive and negative electrodes from short-circuiting and allows active ions to pass through. There is no particular restriction on the type of isolation membrane in this application. Any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be used.
在一些实施方式中，隔离膜的材质可以选自玻璃纤维、无纺布、聚乙烯、聚丙烯、聚偏氟乙烯中的一种或几种，但不仅限于这些。隔离膜可以是单层薄膜，也可以是多层复合薄膜。隔离膜为多层复合薄膜时，各层的材料相同或不同。在一些实施例方式中，隔离膜上还可以设置陶瓷涂层、金属氧化物涂层。In some embodiments, the material of the isolation membrane can be selected from one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride, but is not limited to these. The isolation film can be a single-layer film or a multi-layer composite film. When the isolation film is a multi-layer composite film, the materials of each layer may be the same or different. In some embodiments, a ceramic coating or a metal oxide coating can also be provided on the isolation film.
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.
在一些实施方式中，二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。In some embodiments, the secondary battery may include an outer packaging. The outer packaging can be used to package the above-mentioned electrode assembly and electrolyte.
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，如聚丙烯(PP)、聚对苯二甲酸丁二醇酯(PBT)、聚丁二酸丁二醇酯(PBS)等中的一种或几种。In some embodiments, the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag. The material of the soft bag can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。如图2是作为一个示例的方形结构的二次电池5。This application has no particular limitation on the shape of the secondary battery, which can be cylindrical, square or any other shape. FIG. 2 shows an example of a square-structured secondary battery 5 .
在一些实施方式中，参照图3，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53用于盖设所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或几个，可根据需求来调节。In some embodiments, referring to FIG. 3 , the outer package may include a housing 51 and a cover 53 . The housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity. The housing 51 has an opening communicating with the accommodation cavity, and the cover plate 53 is used to cover the opening to close the accommodation cavity. The positive electrode piece, the negative electrode piece and the isolation film can be formed into the electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is packaged in the containing cavity. The electrolyte soaks into the electrode assembly 52 . The number of electrode assemblies 52 contained in the secondary battery 5 can be one or several, and can be adjusted according to needs.
在一些实施方式中，二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为多个，具体数量可根据电池模块的应用和容量来调节。In some embodiments, secondary batteries can be assembled into battery modules, and the number of secondary batteries contained in the battery module can be multiple. The specific number can be adjusted according to the application and capacity of the battery module.
图4是作为一个示例的电池模块4。参照图4，在电池模块4中，多个二次电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池5进行固定。Figure 4 is a battery module 4 as an example. Referring to FIG. 4 , in the battery module 4 , a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 . Of course, it can also be arranged in any other way. Furthermore, the plurality of secondary batteries 5 can be fixed by fasteners.
可选地，电池模块4还可以包括具有容纳空间的外壳，多个二次电池5容纳于该容纳空间。Optionally, the battery module 4 may further include a housing having a receiving space in which a plurality of secondary batteries 5 are received.
在一些实施方式中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以根据电池包的应用和容量进行调节。In some embodiments, the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.
图5和图6是作为一个示例的电池包1。参照图5和图6，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2用于盖设下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。Figures 5 and 6 show the battery pack 1 as an example. Referring to FIGS. 5 and 6 , the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box 2 and a lower box 3 . The upper box 2 is used to cover the lower box 3 and form a closed space for accommodating the battery module 4 . Multiple battery modules 4 can be arranged in the battery box in any manner.
用电设备Electrical equipment
本申请实施方式的第五方面提供了一种用电装置，所述装置包括本申请的二次电池、电池模块、或电池包中的至少一种。所述二次电池、电池模块或电池包可以用作所述装置的电源，也可以用作所述装置的能量存储单元。所述装置可以但不限于是移动设备、电动车辆、电气列车、船舶及卫星、储能***等。例如，可以为笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、 电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池和锂离子电容器等。A fifth aspect of the embodiments of the present application provides an electrical device, which device includes at least one of a secondary battery, a battery module, or a battery pack of the present application. The secondary battery, battery module or battery pack may be used as a power source for the device or as an energy storage unit for the device. The device may be, but is not limited to, mobile equipment, electric vehicles, electric trains, ships and satellites, energy storage systems, etc. For example, a notebook computer, a pen input type computer, a mobile computer, an e-book player, a portable telephone, a portable fax machine, a portable copy machine, a portable printer, a stereo headset, a video recorder, an LCD TV, a portable cleaner, a portable CD player, mini CD, transceiver, electronic notepad, calculator, memory card, portable recorder, radio, backup power supply, motor, automobile, motorcycle, power-assisted bicycle, bicycle, lighting equipment, toys, game consoles, clocks, electric Tools, flashlights, cameras, large household batteries and lithium-ion capacitors, etc.
所述装置可以根据其使用需求来选择二次电池、电池模块或电池包。The device can select secondary batteries, battery modules or battery packs according to its usage requirements.
图7是作为一个示例的装置。该装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该装置对高功率和高能量密度的需求，可以采用电池包或电池模块。Figure 7 is an example device. The device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. To meet the device's requirements for high power and energy density, battery packs or battery modules can be used.
实施例Example
下述实施例更具体地描述了本发明公开的内容，这些实施例仅仅用于阐述性说明，因为在本发明公开内容的范围内进行各种修改和变化对本领域技术人员来说是明显的。除非另有声明，以下实施例中所报道的所有份、百分比、和比值都是基于质量计，而且实施例中使用的所有试剂都可商购获得或是按照常规方法进行合成获得，并且可直接使用而无需进一步处理，以及实施例中使用的仪器均可商购获得。The present disclosure is more particularly described in the following examples, which are intended to be illustrative only, as it will be apparent to those skilled in the art that various modifications and changes can be made within the scope of the present disclosure. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods, and can be directly were used without further processing and the equipment used in the examples is commercially available.
实施例1Example 1
负极极片的制备Preparation of negative electrode plates
将人造石墨、导电剂碳黑、粘结剂羧甲基纤维素(CMC)和丁苯橡胶(SBR)以及溶剂水按照重量比93:2:2:3:100均匀混合得到浆料A。将人造石墨、导电剂碳黑、粘结剂羧甲基纤维素(CMC)、丁苯橡胶(SBR)和造孔剂1,2-二羟基-3-三苯甲基-丙烷以及溶剂水按照重量比92:2:2:3:1:100均匀混合得到浆料B。先将浆料A均匀涂覆在铜集流体上，形成第一涂层；再将浆料B均匀涂覆在第一涂层上，形成第二涂层；在110℃下烘干，经冷压处理后形成第一负极膜层和第二负极膜层，获得负极极片。Mix artificial graphite, conductive agent carbon black, binders carboxymethylcellulose (CMC) and styrene-butadiene rubber (SBR) and solvent water uniformly in a weight ratio of 93:2:2:3:100 to obtain slurry A. Combine artificial graphite, conductive agent carbon black, binder carboxymethylcellulose (CMC), styrene-butadiene rubber (SBR), pore-forming agent 1,2-dihydroxy-3-trityl-propane and solvent water according to the The weight ratio of 92:2:2:3:1:100 was uniformly mixed to obtain slurry B. First, apply slurry A evenly on the copper current collector to form the first coating; then apply slurry B evenly on the first coating to form the second coating; dry it at 110°C and cool it. After pressure treatment, a first negative electrode film layer and a second negative electrode film layer are formed to obtain a negative electrode piece.
正极极片的制备Preparation of positive electrode plates
将正极活性材料LiCoO 2、导电炭黑、粘结剂PVDF按照质量比96.7:1.7:1.6进行混合，加入适量的溶剂NMP，在真空搅拌机作用获得正极浆料；将正极浆料均匀涂覆在正极集流体铝箔的两个表面上；然后经过70℃真空干燥12h，分条裁片后得到正极极片。 Mix the cathode active material LiCoO 2 , conductive carbon black, and binder PVDF according to the mass ratio of 96.7:1.7:1.6, add an appropriate amount of solvent NMP, and use it in a vacuum mixer to obtain a cathode slurry; apply the cathode slurry evenly on the cathode on both surfaces of the current collector aluminum foil; then vacuum dried at 70°C for 12 hours, and then cut into strips to obtain the positive electrode piece.
电解液的制备Preparation of electrolyte
将碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)及碳酸二乙酯(DEC)按照体积比为1:1:1进行混合，得到有机溶剂；将LiPF 6溶解在上述有机溶剂中，再加入氟代碳酸乙烯酯(FEC)混合均匀，得到电解液；其中，LiPF 6的浓度为1mol/L。 Mix ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) at a volume ratio of 1:1:1 to obtain an organic solvent; dissolve LiPF 6 in the above organic solvent, and then Add fluoroethylene carbonate (FEC) and mix evenly to obtain an electrolyte; the concentration of LiPF 6 is 1 mol/L.
隔离膜的制备Preparation of isolation film
采用PE多孔薄膜作为隔离膜。PE porous film is used as the isolation membrane.
锂离子电池的制备Preparation of lithium-ion batteries
将正极极片、隔离膜、负极极片依次叠好，使隔离膜处于正负极中间起到隔离的作用，并卷绕得到电极组件；将电极组件置于外包装中，注入配好的电解液后并封装，经过化成、脱气、切边等工艺流程得到锂离子电池。Stack the positive electrode piece, isolation film, and negative electrode piece in order, so that the isolation film is between the positive and negative electrodes for isolation, and wind it to obtain the electrode assembly; place the electrode assembly in the outer packaging, and inject the prepared electrolyte After liquidization and packaging, the lithium-ion battery is obtained through processes such as formation, degassing, and trimming.
实施例2至11和对比例1至4Examples 2 to 11 and Comparative Examples 1 to 4
锂离子电池的制备方法与实施例1类似，不同之处在于：调整了负极极片及其制备过程中的相关参数，具体参数详见表1和表2，其中，“/”表示不包含该物质。The preparation method of the lithium-ion battery is similar to Example 1, except that the negative electrode plate and related parameters in the preparation process are adjusted. The specific parameters are shown in Table 1 and Table 2, where "/" means that the negative electrode plate and the relevant parameters in the preparation process are not included. substance.
表1Table 1
Figure PCTCN2022118484-appb-000001
Figure PCTCN2022118484-appb-000001
表2Table 2
Figure PCTCN2022118484-appb-000002
Figure PCTCN2022118484-appb-000002
测试部分test part
(1)负极极片的吸液量和电解液浸润速率测试(1) Test of the liquid absorption capacity and electrolyte infiltration rate of the negative electrode piece
裁取负极极片，宽5cm，高15cm，每组极片裁取3片。将极片浸泡在液面高度为1cm的电解液中进行吸液，记录电解液在一定时间内的爬液高度，即为负极极片的吸液量，爬液高度随时间变化曲线的斜率即为电解液浸润速率。Cut the negative pole pieces, 5cm wide and 15cm high, and cut 3 pieces from each set of pole pieces. Immerse the electrode piece in the electrolyte with a liquid level of 1cm to absorb the liquid. Record the liquid climbing height of the electrolyte within a certain period of time, which is the liquid absorption volume of the negative electrode piece. The slope of the curve of the liquid climbing height with time is: is the electrolyte infiltration rate.
(2)负极极片的粘结力测试(2) Adhesion test of negative electrode piece
裁取负极极片，宽3cm，高15cm，将所裁取的极片用双面胶贴于钢板上，测试面朝下，在极片下方贴上纸带完成制样。将钢板未贴极片的一端用下夹具固定，纸带线上翻折用上夹具固定，使用拉力机进行测试。Cut the negative electrode piece with a width of 3cm and a height of 15cm. Paste the cut piece on the steel plate with double-sided tape, with the test side facing down. Paste a paper tape under the electrode piece to complete the sample preparation. Fix the end of the steel plate that is not attached to the pole piece with the lower clamp, fold the paper tape on the line and fix it with the upper clamp, and use a tensile machine for testing.
(3)锂离子电池的充放电倍率性能测试(3) Charge and discharge rate performance test of lithium-ion batteries
充放电倍率是指电池在规定的时间内放出其额定容量时所需要的电流值，以C表示。1C表示1h完成充电或放电，1/3C表示3h完成充电或放电。电池充放电倍率性能测试时，分别设置电流大小为0.2C、0.5C、1C、2C、3C，每个电流下循环5圈。The charge-discharge rate refers to the current value required when the battery discharges its rated capacity within a specified period of time, expressed in C. 1C means charging or discharging is completed in 1 hour, and 1/3C means charging or discharging is completed in 3 hours. When testing the battery charge and discharge rate performance, set the current values to 0.2C, 0.5C, 1C, 2C, and 3C respectively, and cycle 5 times at each current.
表3给出实施例1至11和对比例1至4的性能测试结果。Table 3 gives the performance test results of Examples 1 to 11 and Comparative Examples 1 to 4.
表3table 3
Figure PCTCN2022118484-appb-000003
Figure PCTCN2022118484-appb-000003
分别对比分析实施例1与对比例1、实施例6与对比例2及实施例9与对比例3可知，与单层膜层相比，本申请提供的负极极片的吸液量、电解液的浸润速率以及锂离子电池的3C充电倍率容量保持率更高，说明本申请双膜层结构的设置确实能够同时提升负极极片的吸液能力、电解液的浸润性能和二次电池的倍率性能。Comparative analysis of Example 1 and Comparative Example 1, Example 6 and Comparative Example 2, and Example 9 and Comparative Example 3 respectively shows that compared with a single film layer, the negative electrode sheet provided by the present application has a lower liquid absorption capacity and electrolyte The infiltration rate and the 3C charging rate capacity retention rate of lithium-ion batteries are higher, indicating that the double-layer structure of the present application can indeed improve the liquid absorption capacity of the negative electrode plate, the infiltration performance of the electrolyte and the rate performance of the secondary battery. .
对比分析实施例2与对比例4可知，与常规的膜层设置结构相比，本申请提供的双膜层结构在保证负极极片具备足够高的粘接力的条件下，还能同时提升负极极片的吸液能力和电解液浸润性能。Comparative analysis of Example 2 and Comparative Example 4 shows that, compared with the conventional film layer arrangement structure, the double film layer structure provided by the present application can also improve the negative electrode while ensuring that the negative electrode plate has sufficiently high adhesion. The liquid absorption capacity and electrolyte wetting performance of the pole piece.
对比分析实施例1至3可知，第二负极膜层的孔隙率与第一负极膜层的孔隙率的比值P2/P1发生变化时，负极极片的吸液量、电解液浸润速率以及电池的3C充电倍率容量保持率均会发生变化；而且P2/P1越大，即第二负极膜层与第一负极膜层的孔隙率差异越大，极片的吸液能力、电解液浸润性能和电池的白绿性能越高。Comparative analysis of Examples 1 to 3 shows that when the ratio P2/P1 of the porosity of the second negative electrode film layer to the porosity of the first negative electrode film layer changes, the liquid absorption amount of the negative electrode plate, the electrolyte infiltration rate, and the battery's The capacity retention rate of the 3C charging rate will change; and the larger P2/P1, that is, the greater the porosity difference between the second negative electrode film layer and the first negative electrode film layer, the liquid absorption capacity of the electrode piece, the electrolyte infiltration performance and the battery The higher the white-green performance.
对比分析实施例2、4和5可知，第一负极膜层的厚度与第二负极膜层的厚度的比值D1/D2会对极片的粘结性能产生影响。另外，对比分析实施例1、6、9可知，本申请提供的负极膜层的总厚度也会对负极极片的吸液能力、电解液的浸润性能和二次电池的倍率性能产生影响。Comparative analysis of Examples 2, 4 and 5 shows that the ratio D1/D2 of the thickness of the first negative electrode film layer to the thickness of the second negative electrode film layer will have an impact on the bonding performance of the electrode piece. In addition, a comparative analysis of Examples 1, 6, and 9 shows that the total thickness of the negative electrode film layer provided by the present application will also affect the liquid absorption capacity of the negative electrode sheet, the wetting performance of the electrolyte, and the rate performance of the secondary battery.
以上所述，仅为本申请的具体实施方式，但本申请的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本申请揭露的技术范围内，可轻易想到各种等效的修改或替换，这些修改或替换都应涵盖在本申请的保护范围之内。因此，本申请的保护范围应以权利要求的保护范围为准。The above are only specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person familiar with the technical field can easily think of various equivalent methods within the technical scope disclosed in the present application. Modification or replacement, these modifications or replacements shall be covered by the protection scope of this application. Therefore, the protection scope of this application should be subject to the protection scope of the claims.

Claims (14)

  1. 一种负极极片，包括：A negative electrode piece, including:
    负极集流体；和negative electrode current collector; and
    设置于所述负极集流体至少一侧的负极膜层，a negative electrode film layer disposed on at least one side of the negative electrode current collector,
    所述负极膜层包括设置于靠近所述负极集流体的表面的第一负极膜层和设置于所述第一负极膜层远离所述负极集流体一侧的表面上的第二负极膜层，The negative electrode film layer includes a first negative electrode film layer disposed on a surface close to the negative electrode current collector and a second negative electrode film layer disposed on a surface of the first negative electrode film layer away from the negative electrode current collector,
    其中，所述第一负极膜层的厚度为D1，所述第二负极膜层的厚度为D2，且D1>D2；所述第一负极膜层的孔隙率为P1，所述第二负极膜层的孔隙率为P2，且P1<P2。Wherein, the thickness of the first negative electrode film layer is D1, the thickness of the second negative electrode film layer is D2, and D1>D2; the porosity of the first negative electrode film layer is P1, and the thickness of the second negative electrode film The porosity of the layer is P2, and P1<P2.
  2. 根据权利要求1所述的负极极片，其中，所述第一负极膜层的厚度与所述第二负极膜层的厚度的比值为3≤D1/D2≤10，可选为5≤D1/D2≤8。The negative electrode plate according to claim 1, wherein the ratio of the thickness of the first negative electrode film layer to the thickness of the second negative electrode film layer is 3≤D1/D2≤10, optionally 5≤D1/ D2≤8.
  3. 根据权利要求1或2所述的负极极片，其中，所述第二负极膜层的孔隙率与所述第一负极膜层的孔隙率的比值为1≤P2/P1≤5，可选为3≤P2/P1≤4。The negative electrode sheet according to claim 1 or 2, wherein the ratio of the porosity of the second negative electrode film layer to the porosity of the first negative electrode film layer is 1≤P2/P1≤5, optionally 3≤P2/P1≤4.
  4. 根据权利要求1至3任一项所述的负极极片，其中，所述第一负极膜层满足如下条件中的至少一者：The negative electrode sheet according to any one of claims 1 to 3, wherein the first negative electrode film layer satisfies at least one of the following conditions:
    (1)所述第一负极膜层的厚度为80μm≤D1≤2250μm，可选为100μm≤D1≤2000μm；(1) The thickness of the first negative electrode film layer is 80μm≤D1≤2250μm, optionally 100μm≤D1≤2000μm;
    (2)所述第一负极膜层的孔隙率为20％≤P1≤40％，可选为25％≤P1≤35％。(2) The porosity of the first negative electrode film layer is 20%≤P1≤40%, optionally 25%≤P1≤35%.
  5. 根据权利要求1至4任一项所述的负极极片，其中，所述第二负极膜层满足如下条件中的至少一者：The negative electrode sheet according to any one of claims 1 to 4, wherein the second negative electrode film layer satisfies at least one of the following conditions:
    (1)所述第二负极膜层的厚度为8μm≤D2≤750μm，可选为10μm≤D2≤700μm；(1) The thickness of the second negative electrode film layer is 8μm≤D2≤750μm, optionally 10μm≤D2≤700μm;
    (2)所述第二负极膜层的孔隙率为40％≤P2≤70％，可选为45％≤P2≤65％。(2) The porosity of the second negative electrode film layer is 40%≤P2≤70%, optionally 45%≤P2≤65%.
  6. 根据权利要求1至5任一项所述的负极极片，其中，所述负极膜层的总孔隙率为P0，且30％≤P0≤60％，可选为35％≤P0≤55％。The negative electrode piece according to any one of claims 1 to 5, wherein the total porosity of the negative electrode film layer is P0, and 30%≤P0≤60%, optionally 35%≤P0≤55%.
  7. 根据权利要求1至6任一项所述的负极极片，其中，所述负极膜层的总厚度为D0，且100μm≤D0≤3000μm，可选为150μm≤D0≤2500μm。The negative electrode plate according to any one of claims 1 to 6, wherein the total thickness of the negative electrode film layer is D0, and 100 μm≤D0≤3000 μm, optionally 150 μm≤D0≤2500 μm.
  8. 根据权利要求1至7任一项所述的负极极片，其中，所述负极极片的单面涂布重量为0.1g/1540.25mm 2至0.4g/1540.25mm 2，可选为0.15g/1540.25mm 2至0.35g/1540.25mm 2。 The negative electrode piece according to any one of claims 1 to 7, wherein the single-sided coating weight of the negative electrode piece is 0.1g/1540.25mm 2 to 0.4g/1540.25mm 2 , optionally 0.15g/ 1540.25mm 2 to 0.35g/1540.25mm 2 .
  9. 一种用于制备负极极片的方法，包括：A method for preparing negative electrode plates, including:
    成膜步骤，包括在负极集流体的至少一侧上形成第一负极膜层和第二负极膜层，得到负极极片；The film forming step includes forming a first negative electrode film layer and a second negative electrode film layer on at least one side of the negative electrode current collector to obtain a negative electrode plate;
    其中，所述第一负极膜层位于靠近所述负极集流体的表面，所述第二负极膜层位于所述第一负极膜层远离所述负极集流体一侧的表面上；所述第一负极膜层的厚度为D1，所述第二负极膜层的厚度为D2，且D1>D2；所述第一负极膜层的孔隙率为P1，所述第二负极膜层的孔隙率为P2，且P1<P2。Wherein, the first negative electrode film layer is located on a surface close to the negative electrode current collector, and the second negative electrode film layer is located on a surface of the first negative electrode film layer away from the negative electrode current collector; The thickness of the negative electrode film layer is D1, the thickness of the second negative electrode film layer is D2, and D1>D2; the porosity of the first negative electrode film layer is P1, and the porosity of the second negative electrode film layer is P2 , and P1<P2.
  10. 根据权利要求9所述的方法，其中，所述成膜步骤进一步包括：The method of claim 9, wherein the film forming step further includes:
    在所述负极集流体的至少一侧上涂布第一负极浆料，形成第一涂层；Coating a first negative electrode slurry on at least one side of the negative electrode current collector to form a first coating;
    在所述第一涂层的表面上涂布第二负极浆料，形成第二涂层，其中，所述第二负极浆料中包括1,2-二羟基-3-三苯甲基-丙烷；和Coating a second negative electrode slurry on the surface of the first coating layer to form a second coating layer, wherein the second negative electrode slurry includes 1,2-dihydroxy-3-trityl-propane ;and
    对所述第一涂层和所述第二涂层做烘干冷压处理，形成所述第一负极膜层和所述第二负极膜层。The first coating layer and the second coating layer are dried and cold-pressed to form the first negative electrode film layer and the second negative electrode film layer.
  11. 根据权利要求10所述的方法，其中，基于所述第二负极浆料的总质量，所述1,2-二羟基-3-三苯甲基-丙烷的质量百分含量为0.1％至30％，可选为1％至25％。The method according to claim 10, wherein the mass percentage of the 1,2-dihydroxy-3-trityl-propane is 0.1% to 30 based on the total mass of the second negative electrode slurry. %, optional from 1% to 25%.
  12. 根据权利要求10或11所述的方法，其中，所述方法满足如下条件中的至少一者：The method according to claim 10 or 11, wherein the method satisfies at least one of the following conditions:
    (1)所述第一负极浆料中包括负极活性材料和可选的第一组分，其中，所述第一组分包括导电剂、粘结剂、增稠剂、溶剂或其组合；(1) The first negative electrode slurry includes a negative active material and an optional first component, wherein the first component includes a conductive agent, a binder, a thickener, a solvent, or a combination thereof;
    (2)所述第二负极浆料中还包括负极活性材料和可选的第二组分，其中，所述第二组分包括导电剂、粘结剂、增稠剂、溶剂或其组合。(2) The second negative electrode slurry also includes a negative active material and an optional second component, wherein the second component includes a conductive agent, a binder, a thickener, a solvent, or a combination thereof.
  13. 一种二次电池，包括权利要求1至8任一项所述的负极极片或通过权利要求9至12任一项所述的方法制得的负极极片。A secondary battery including the negative electrode sheet according to any one of claims 1 to 8 or the negative electrode sheet produced by the method according to any one of claims 9 to 12.
  14. 一种用电装置，包括权利要求14所述的二次电池。An electrical device comprising the secondary battery according to claim 14.
PCT/CN2022/118484 2022-09-13 2022-09-13 Negative electrode sheet, method for manufacturing negative electrode sheet, secondary battery and electric device WO2024055162A1 (en)

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