WO2023216013A1 - 负极极片、负极极片的制备方法、二次电池、电池模块、电池包及用电装置 - Google Patents
负极极片、负极极片的制备方法、二次电池、电池模块、电池包及用电装置 Download PDFInfo
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- WO2023216013A1 WO2023216013A1 PCT/CN2022/091367 CN2022091367W WO2023216013A1 WO 2023216013 A1 WO2023216013 A1 WO 2023216013A1 CN 2022091367 W CN2022091367 W CN 2022091367W WO 2023216013 A1 WO2023216013 A1 WO 2023216013A1
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- Prior art keywords
- film
- salt
- negative electrode
- lithium metal
- composite protective
- Prior art date
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- 229910002102 lithium manganese oxide Inorganic materials 0.000 description 1
- FRMOHNDAXZZWQI-UHFFFAOYSA-N lithium manganese(2+) nickel(2+) oxygen(2-) Chemical compound [O-2].[Mn+2].[Ni+2].[Li+] FRMOHNDAXZZWQI-UHFFFAOYSA-N 0.000 description 1
- MHCFAGZWMAWTNR-UHFFFAOYSA-M lithium perchlorate Chemical compound [Li+].[O-]Cl(=O)(=O)=O MHCFAGZWMAWTNR-UHFFFAOYSA-M 0.000 description 1
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- VDVLPSWVDYJFRW-UHFFFAOYSA-N lithium;bis(fluorosulfonyl)azanide Chemical compound [Li+].FS(=O)(=O)[N-]S(F)(=O)=O VDVLPSWVDYJFRW-UHFFFAOYSA-N 0.000 description 1
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- URIIGZKXFBNRAU-UHFFFAOYSA-N lithium;oxonickel Chemical compound [Li].[Ni]=O URIIGZKXFBNRAU-UHFFFAOYSA-N 0.000 description 1
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- ISPYRSDWRDQNSW-UHFFFAOYSA-L manganese(II) sulfate monohydrate Chemical compound O.[Mn+2].[O-]S([O-])(=O)=O ISPYRSDWRDQNSW-UHFFFAOYSA-L 0.000 description 1
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Images
Classifications
-
- 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
- H01M4/139—Processes of manufacture
- H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
-
- 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
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
-
- 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
- This application belongs to the technical field of electrochemistry, and specifically relates to a negative electrode plate, a preparation method of the negative electrode plate, a secondary battery, a battery module, a battery pack 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.
- secondary batteries have developed rapidly in the fields of new energy vehicles and large-scale energy storage.
- lithium metal anode has become the best choice for the next generation of high-specific-energy secondary battery anode materials due to its high theoretical specific capacity (3860mAh/g).
- 3860mAh/g the high theoretical specific capacity
- due to the high activity of the lithium metal anode it is easy to react with environmental media in secondary batteries, resulting in poor cycle performance of the secondary battery, which greatly limits its large-scale application in secondary batteries.
- the purpose of this application is to provide a negative electrode plate, a negative electrode plate used in a secondary battery, a secondary battery and a power consumption device, aiming to improve the cycle performance and safety performance of the secondary battery.
- the first aspect of the present application provides a negative electrode sheet, including: a lithium metal layer, and a composite protective film located on at least one surface of the lithium metal layer, wherein the composite protective film includes a precipitated salt film layer and an oxide film layer, at least a part of the oxide film layer is distributed in the precipitated salt film layer.
- the composite protective film formed by the precipitated salt film layer and the oxide film layer in this application is very dense. In the secondary battery, it can isolate the organic solvent in the electrolyte and the contact between the lithium salt anion and the lithium metal, reducing the irreversible loss of the electrolyte. This can achieve the purpose of protecting lithium metal during the charge and discharge cycle.
- the precipitated salt film layer includes (M 1 ) x1 (PO 4 ) y1 , (M 1 ) x2 (CO 3 ) y2 , or a combination thereof, where M 1 is Li, Mn, Mg , Ba, Ca and Sr, x 1 , y 1 and x 2 , y 2 make the net charge of the compound zero.
- the precipitated salt film layer is mainly composed of inorganic phosphates and carbonates. It has good lithium ion conductivity and can isolate electrons, so it can provide a migration channel for lithium ions to induce uniform lithium ion dispersion. deposition, thereby reducing the generation of lithium dendrites and improving the safety performance of secondary batteries.
- the oxide film layer includes (M 1 ) m On , where M 1 is Li, Mn, Mg, Ba, Ca, Sr or a combination thereof, and m and n are such that the metal The net charge of oxides is zero.
- the oxide film layer and the precipitated salt film layer in this application are compounded/mixed together to form a composite protective film of the lithium metal layer.
- the composite protective film is a solid electrolyte layer, has high mechanical strength, and can act on the lithium metal layer. It has a strong isolation and protection effect, and can also induce uniform deposition of lithium metal during charge and discharge cycles, inhibit the growth of lithium dendrites, and improve the cycle performance and safety performance of secondary batteries.
- the oxide film layer is located on a side of the composite protective film close to the lithium metal layer, and the precipitated salt film layer is located on a side of the composite protective film away from the lithium metal layer. side.
- the thickness of the composite protective film is 1 ⁇ m to 25 ⁇ m, optionally 3 ⁇ m to 20 ⁇ m.
- the thickness of the oxide film layer ranges from 50 nm to 200 nm, optionally from 70 nm to 160 nm.
- the thickness of the oxide film layer and the composite protective film is within an appropriate range, which can not only provide a good migration channel for lithium ions, but also enable lithium ions to have better conductivity in the composite protective film, thereby reducing the interface impedance and inducing lithium metal.
- Uniform deposition can reduce or avoid the growth of lithium dendrites; it can also effectively isolate the contact between organic solvents and lithium salt anions in the electrolyte and lithium metal, reducing the irreversible loss of the electrolyte, thereby protecting lithium metal during charge and discharge cycles. the goal of.
- the passivation interval of the composite protective film is 110 mV to 420 mV.
- the passivation interval of the composite protective film is within the above range, indicating that the composite protective film in this application has good high voltage resistance and will not be easily decomposed even under high voltage, because it can play a long-lasting role in protecting the lithium metal layer.
- the protective effect is beneficial to improving the cycle performance of secondary batteries.
- a second aspect of the present application provides a method for preparing a negative electrode sheet, including: a film forming step, including reacting a lithium metal layer with a film-forming liquid to form a composite protective film to obtain a negative electrode sheet, wherein the composite protective film It includes a precipitated salt film layer and an oxide film layer, at least part of the oxide film layer is distributed in the precipitated salt film layer; the film-forming liquid includes precipitated salt cations, precipitated salt anions dissolved in an inert solvent, Oxidizing oxygen acid salts, complexing agents and catalysts.
- a controllable, high-temperature film-forming liquid can be formed on the surface of the lithium metal layer.
- Voltage inorganic salt composite protective film This composite protective film can effectively isolate the organic solvent in the electrolyte and the contact between lithium salt anions and lithium metal, reduce the irreversible loss of the electrolyte, thereby achieving the purpose of protecting the lithium metal layer during the charge and discharge cycle. .
- the preparation method further includes a step of providing a film-forming liquid.
- the step of providing a film-forming liquid includes: combining the first film-forming salt containing the precipitation salt cation, the complexing agent and the The catalyst is dissolved in a first inert solvent to obtain a first solution; the second film-forming salt containing the precipitation salt anion and the oxidizing oxygen acid salt are dissolved in a second inert solvent to obtain a second solution; The first solution and the second solution are mixed evenly to obtain the film-forming liquid.
- the first film-forming salt includes MnCl 2 , Mn(NO 3 ) 2 , MnSO 4 ⁇ H 2 O, MgSO 4 , Ca(NO 3 ) 2 , Ba(NO 3 ) 2 , Sr(NO 3 ) 2 or combinations thereof.
- the second film-forming salt includes carbonate, phosphate or a combination thereof, optionally (M 2 ) 2 CO 3 , (M 2 ) x3 H y3 (PO4) z3 , ( M 2 ) x4 H y4 (P 2 O 7 ) z4 or a combination thereof, where M 2 is Li, Na, K or a combination thereof, x 3 , y 3 , z 3 and x 4 , y 4 , z 4 make all The net charge of the second film-forming salt is zero.
- the complexing agent includes ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, ethanolamine or a combination thereof.
- the oxidizing oxygen-containing acid salt includes nitrate, inorganic salt (M 2 ) x5 (M 3 ) y5 O z5 or a combination thereof, optionally NaNO 3 , KNO 3 , Ca(NO 3 ) 2 , KMnO 4 , Na 2 FeO 4 , K 2 Cr 2 O 7 , NaCoO 2 , NaVO 2 or combinations thereof, where M 2 is Li, Na, K or combinations thereof, M 3 is V, Cr, Mn , Fe, Co, Ni or combinations thereof, z 5 is 1 to 7, x 5 , y 5 , z 5 make the net charge of the oxidizing oxo acid salt be zero.
- M 2 Li, Na, K or combinations thereof
- M 3 is V, Cr, Mn , Fe, Co, Ni or combinations thereof
- z 5 is 1 to 7, x 5 , y 5 , z 5 make the net charge of the oxidizing oxo acid salt be zero.
- the catalyst includes an ammonium salt, which may be NH 4 NO 3 , (NH 4 ) 2 SO 4 , NH 4 Cl or a combination thereof.
- the concentration of the first film-forming salt, the second film-forming salt, the complexing agent and the oxidizing oxygen acid salt is 10 g /L to 50g/L
- the concentration of the catalyst is 10g/L to 30g/L.
- a dense solid electrolyte composite protective film that can conduct lithium ions but not electrons can be converted in situ on the surface of lithium metal.
- the composite protective film has low interface impedance, strong interface bonding force, and high mechanical strength. It can isolate the reaction between the electrolyte and lithium metal, weaken or avoid the irreversible loss of the electrolyte, and can induce uniform deposition of lithium metal during the cycle, inhibiting The growth of lithium dendrites improves the cycle performance and safety performance of secondary batteries.
- the pH value of the film-forming liquid is 5 to 7.
- the acidity of the film-forming liquid can be reduced and its alkalinity can be increased, thereby increasing the number of basic acid radicals in the solution, which is beneficial to promoting the formation of the precipitated salt film layer.
- a third aspect of this application provides a secondary battery, including the negative electrode sheet described in the first aspect of this application or the negative electrode sheet produced by the preparation 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 surface morphology diagram of an embodiment of the composite protective film in the negative electrode sheet 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.
- lithium metal anode 3860mAh/g
- the theoretical specific capacity of lithium metal anode 3860mAh/g is extremely high, making it the best choice for the next generation of high-specific-energy secondary battery anode materials.
- the inventor found that lithium metal has extremely high activity. On the one hand, it easily undergoes oxidation-reduction reactions with environmental media during storage and transportation and becomes ineffective. It is also more likely to react violently with aqueous solutions, thus limiting the secondary battery preparation process. Many inorganic salt film-forming liquids are used; on the other hand, during the charging and discharging process of secondary batteries, it is easy to react with the electrolyte to form an SEI film.
- the SEI film will gradually thicken, resulting in an interface
- the impedance increases and leads to the generation of dead lithium, which in turn causes capacity loss and affects the cycle performance of the secondary battery.
- uneven lithium deposition can lead to the generation of lithium dendrites.
- the growth of lithium dendrites may puncture the separator and cause the battery to short-circuit or even explode.
- the existing technology mostly adopts the method of coating a layer of polymer on the surface of lithium metal.
- this method has complex process and high cost, and the main link between the polymer and lithium metal is organic. -It is combined by inorganic bonds, and the binding force is poor; in addition, the polymer protective film has many defects and has poor protection ability for lithium metal anodes.
- the polymer film layer is not resistant to high voltage and is easy to decompose under high voltage, so Limited ability to protect lithium metal.
- the inventor proposed a negative electrode sheet through extensive research.
- the film-forming liquid is configured according to the reaction mechanism of the deposited film, and the lithium metal and lithium metal are controlled by spraying.
- the reaction speed of the film-forming liquid deposits a composite protective film with controllable thickness and high voltage resistance on the surface of lithium metal.
- This composite protective film can achieve the purpose of protecting lithium metal during the charge and discharge cycle of the secondary battery, and can Promote the uniform deposition of lithium metal, which is beneficial to improving the cycle performance and safety performance of secondary batteries.
- a first aspect of the embodiment of the present application provides a negative electrode sheet, including: a lithium metal layer, and a composite protective film located on at least one surface of the lithium metal layer, wherein the composite protective film includes a precipitated salt film layer and an oxide film layer, at least a portion of the oxide film layer being distributed in the precipitated salt film layer.
- the composite protective film formed by the precipitated salt film layer and the oxide film layer in the present application is very dense and can isolate the organic solvent in the electrolyte and the lithium salt anion from the secondary battery.
- the contact of lithium metal reduces the irreversible loss of the electrolyte, thereby achieving the purpose of protecting lithium metal during the charge and discharge cycle; at the same time, the composite protective film can induce the uniform deposition of lithium metal during the charge and discharge cycle and reduce the growth of lithium dendrites. and the generation of dead lithium, which is beneficial to improving the capacity, cycle performance and safety performance of secondary batteries.
- the precipitated salt film layer and the oxide film layer in the composite protective film are mixed and distributed, wherein the precipitated salt film layer is located on the side of the composite protective film away from the lithium metal layer, and the oxide film layer is located on the side of the composite protective film away from the lithium metal layer.
- the film layer is located on the side of the composite protective film close to the lithium metal layer.
- the composite protective film is mainly combined with the lithium metal layer through chemical bonds. The bonding effect is strong and the mechanical strength is high, and it can play a greater role in protecting the lithium metal layer.
- the strong protective effect enables it to effectively isolate the electrolyte during long-term charge and discharge cycles and reduce the SEI film generated by its reaction with the electrolyte, thus reducing the interface impedance and improving the ion conduction capacity and cycle performance of the secondary battery.
- the precipitated salt film layer includes (M 1 ) x1 (PO 4 ) y1 , (M 1 ) x2 (CO 3 ) y2 , or a combination thereof, where M 1 is Li, Mn, Mg, Ba At least one of , Ca and Sr, x 1 , y 1 and x 2 , y 2 make the net charge of the compound zero.
- the precipitated salt film layer can be Li 3 PO 4 , LiCO 3 , Mn 3 (PO 4 ) 2 , MnCO 3 , Mg 3 (PO 4 ) 2 , MgCO 3 , Ba 3 (PO 4 ) 2 , BaCO 3 , Ca 3 (PO 4 ) 2 , CaCO 3 , Sr 3 (PO 4 ) 2 , SrCO 3 or combinations thereof.
- the precipitated salt film layer is mainly composed of inorganic phosphates and carbonates. It has good lithium ion conductivity and can isolate electrons, so it can provide a migration channel for lithium ions to induce uniform lithium ion dispersion. deposition, thereby reducing the generation of lithium dendrites and improving the safety performance of secondary batteries.
- the oxide film layer includes (M 1 ) m On , where M 1 is Li, Mn, Mg, Ba, Ca, Sr or a combination thereof, and m and n are such that the metal oxide The net charge is zero.
- the oxide film layer may be Li 2 O, MnO, MgO, BaO, CaO, SrO or a combination thereof.
- the oxide film layer and the precipitated salt film layer in this application are compounded/mixed together to form a composite protective film of the lithium metal layer.
- the composite protective film is a solid electrolyte layer, has high mechanical strength, and can act on the lithium metal layer. It has a strong isolation and protection effect, and can also induce uniform deposition of lithium metal during charge and discharge cycles, inhibit the growth of lithium dendrites, and improve the cycle performance and safety performance of secondary batteries.
- the composite protective film has a thickness of 1 ⁇ m to 25 ⁇ m.
- the thickness of the composite protective film is 3 ⁇ m, 5 ⁇ m, 7 ⁇ m, 9 ⁇ m, 11 ⁇ m, 13 ⁇ m, 15 ⁇ m, 17 ⁇ m, 19 ⁇ m, 21 ⁇ m, 23 ⁇ m or within the range of any of the above values.
- the thickness of the composite protective film is 3 ⁇ m to 20 ⁇ m.
- the thickness of the oxide film layer is 50 nm to 200 nm.
- the thickness of the oxide film layer is 70nm, 90nm, 110nm, 130nm, 150nm, 170nm, 190nm or within the range of any of the above values.
- the thickness of the oxide film layer is 70 nm to 160 nm.
- the thickness of the oxide film layer and the composite protective film have well-known meanings 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 oxide film layer and the composite protective film is within an appropriate range, which can not only provide a good migration channel for lithium ions, but also enable the lithium ions to have better conductivity in the composite protective film, thereby reducing the interface impedance and It induces the uniform deposition of lithium metal and reduces or avoids the growth of lithium dendrites; it can also effectively isolate the contact between organic solvents and lithium salt anions in the electrolyte and lithium metal, reducing the irreversible loss of the electrolyte, thereby achieving the best performance during the charge and discharge cycle.
- the purpose of protecting lithium metal is within an appropriate range, which can not only provide a good migration channel for lithium ions, but also enable the lithium ions to have better conductivity in the composite protective film, thereby reducing the interface impedance and It induces the uniform deposition of lithium metal and reduces or avoids the growth of lithium dendrites; it can also effectively isolate the contact between organic solvents and lithium salt anions in the electrolyte and lithium metal, reducing the irreversible
- the passivation interval of the composite protective film is 110 mV to 420 mV.
- the passivation interval of the composite protective film can be 130mV to 400mV, 150mV to 380mV, 170mV to 360mV, 190mV to 340mV, 210mV to 320mV, 230mV to 300mV or 250mV to 280mV.
- the passivation interval of the composite protective film in this application has a well-known meaning in the art, and can be tested using methods known in the art. For example, a three-electrode system can be used to measure the electrochemical polarization curve, and the composite protective film can be obtained through the electrochemical polarization curve. Passivation interval of protective film.
- the passivation interval of the composite protective film is within the above range, indicating that the composite protective film in this application has good high voltage resistance and will not be easily decomposed even under high voltage, because it can play a long-lasting role in protecting the lithium metal layer.
- the protective effect is beneficial to improving the cycle performance of secondary batteries.
- a second aspect of the embodiment of the present application provides a method for preparing a negative electrode sheet, including:
- the film forming treatment step includes reacting the lithium metal layer with the film forming liquid to form a composite protective film to obtain the negative electrode piece, wherein the composite protective film includes a precipitated salt film layer and an oxide film layer, and the oxide film layer At least a portion of is distributed in the precipitated salt film layer.
- This application adopts an aqueous solvent that easily reacts with lithium metal, and configures a film-forming liquid according to the reaction mechanism of the deposited film. Then through the reaction of the film-forming liquid and the lithium metal layer, a controllable, thickness-controllable, and scalable film-forming liquid can be formed on the surface of the lithium metal layer.
- a high-voltage resistant inorganic salt composite protective film can effectively isolate the organic solvent in the electrolyte and the contact between lithium salt anions and lithium metal, reduce the irreversible loss of the electrolyte, thereby protecting the lithium metal layer during the charge and discharge cycle. the goal of.
- the film-forming fluid includes precipitating salt cations, precipitating salt anions, oxidizing oxyacid salts, complexing agents, and catalysts dissolved in an inert solvent.
- the preparation method further includes a step of providing a film-forming liquid, and the step of providing a film-forming liquid includes:
- the concentration of the first film-forming salt, the second film-forming salt, the complexing agent and the oxidizing oxygen acid salt is 10 g/L to 50g/L, for example, it can be 10g/L, 15g/L, 20g/L, 25g/L, 30g/L, 35g/L, 40g/L, 45g/L, 50g/L or any of the above values. within the composition range.
- the concentration of the catalyst is 10g/L to 30g/L, for example, it can be 10g/L, 15g/L, 20g/L, 25g/L, 30g/L or within the range of any of the above values.
- this application can convert in situ on the lithium metal surface to generate a dense solid-state electrolyte composite protection that can conduct lithium ions but not electrons.
- the composite protective film has low interfacial resistance, strong interfacial bonding force, and high mechanical strength. It can isolate the reaction between the electrolyte and lithium metal, weaken or avoid the irreversible loss of the electrolyte, and can induce uniform deposition of lithium metal during the cycle. , inhibiting the growth of lithium dendrites and improving the cycle performance and safety performance of secondary batteries.
- the film-forming liquid can react with the lithium metal layer by spraying to form the composite protective film.
- the thickness of the composite protective film formed on the lithium metal layer can be controlled by controlling the spraying rate.
- the film-forming liquid can be sprayed on the lithium metal layer through an atomizer, and the thickness of the formed composite protective film can be controlled within the appropriate range described above in this application by controlling the spray volume of the atomizer.
- the first film-forming salt includes MnCl 2 , Mn(NO 3 ) 2 , MnSO 4 ⁇ H 2 O, MgSO 4 , Ca(NO 3 ) 2 , Ba(NO 3 ) 2 , Sr( NO 3 ) 2 or combinations thereof.
- the second film-forming salt includes carbonate, phosphate or a combination thereof, optionally (M 2 ) 2 CO 3 , (M 2 ) x3 H y3 (PO4) z3 , (M 2 ) x4 H y4 (P 2 O 7 ) z4 or a combination thereof, where M 2 is Li, Na, K or a combination thereof, x 3 , y 3 , z 3 and x 4 , y 4 , z 4 make the The net charge of the two film-forming salts is zero.
- the second film-forming salt can be Li 2 CO 3 , Na 2 CO 3 , K 2 CO 3 , Li 2 HPO 4 , LiH 2 PO 4 , Na 2 HPO 4 , NaH 2 PO 4 , K 2 HPO 4 , KH 2 PO 4 , Li 3 HP 2 O 7 , Li 2 H 2 P 2 O 7 , LiH 3 P 2 O 7 , Na 3 HP 2 O 7 , Na 2 H 2 P 2 O 7 , NaH 3 P 2 O 7 , K 3 HP 2 O 7 , K 2 H 2 P 2 O 7 , KH 3 P 2 O 7 or combinations thereof.
- the complexing agent includes ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, ethanolamine, or combinations thereof.
- the oxidizing oxygen acid salt includes nitrate, inorganic salt (M 2 ) x5 (M 3 ) y5 O z5 or a combination thereof, optionally NaNO 3 , KNO 3 , Ca(NO 3 ) 2.
- the catalyst includes an ammonium salt, optionally NH 4 NO 3 , (NH 4 ) 2 SO 4 , NH 4 Cl, or a combination thereof.
- Each component of the film-forming liquid provided in this application exists stably in the solution.
- the interface pH increases.
- the insoluble inorganic salts in the solution reach critical supersaturation and induce deposition.
- it is converted into a dense (inorganic salt) solid electrolyte composite protective film on the surface of lithium metal.
- This composite protective film is combined with lithium metal through chemical bonds. The binding effect is strong and can play a lasting role in protecting the lithium metal layer under high voltage. Protective effects.
- reaction process between the film-forming liquid and lithium metal in this application can be as follows:
- lithium metal reacts with soluble hydrogen phosphate to consume hydrogen ions and form an insoluble phosphate precipitation film with strong protective effect.
- the conversion and precipitation efficiency can be controlled by adjusting the solution composition and the amount of spray liquid can be controlled. Reaction rate and precipitation thickness of composite protective film.
- a part of Mn 2+ can be complexed by introducing a complexing agent (represented by A) into the film-forming liquid to maintain the concentration of free Mn 2+ in the solution, so that during the reaction During the process, the Mn 2+ consumed at the interface can be replenished in time, while reducing the concentration of free Mn 2+ in the solution, promoting the ionization of H 2 PO 4- , increasing the concentration of PO 4 3- in the solution, and making the H in the solution react with the interface
- the concentration difference of 2 PO 4- is reduced, which reduces the dependence on the ionization and diffusion processes to supplement the H 2 PO 4- consumed during the film formation process, and improves the stability of the solution; in addition, after the complexing agent is introduced, the complexation in the solution
- the mixture can complex a part of Mn 2+ and release H + at the same time, promoting the dissolution of Li and increasing the precipitation rate.
- the reaction formula is as follows (B represents the intermediate product):
- NH 4+ in the catalyst in the solution can be hydrolyzed to generate NH 3 ⁇ H 2 O and release H + , and Mn 2+ can be combined to reduce free Mn 2+ concentration to maintain solution stability; when Mn 2+ is consumed by the interface reaction, it can be released and replenished in time.
- the ligand NH 3 combines with H + to generate NH 4+ .
- NH 4+ combines with H + at the interface to promote the ionization of H 2 PO 4- and accelerate the precipitation rate, thus playing a catalytic role.
- a Mn 2+ buffer pair can be established by introducing a complexing agent to avoid the reduction of the effective components of the film-forming solution; an appropriate amount of catalyst can increase the nucleation density of MnHPO 4 and improve MnHPO The precipitation rate is 4 , which improves the corrosion resistance of the formed composite protective film; an appropriate amount of oxidizing oxygen acid salt can promote the formation of a dense passivating Li 2 O film layer from lithium, thereby increasing the precipitation rate.
- the pH value of the film-forming liquid is 5 to 7.
- the acidity of the film-forming liquid can be reduced and its alkalinity can be increased, thereby increasing the number of basic acid radicals in the solution. , which is conducive to promoting the formation of precipitated salt film layer.
- the negative electrode sheet further includes a negative electrode current collector, wherein the lithium metal layer is laminated on at least one side of the negative electrode current collector using a calendering process.
- the negative electrode current collector has two surfaces opposite in its thickness direction, and the lithium metal layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
- a metal foil or porous metal plate can be used as the negative electrode current collector.
- the negative electrode current collector is copper foil.
- the negative electrode sheet can be prepared according to conventional methods in the art. For example, a lithium metal sheet is bonded to the surface of a copper foil to obtain a negative electrode sheet.
- the lamination can be achieved by, but is not limited to, roller pressing.
- 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.
- 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 prepared by the preparation 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 active material 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 active material layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
- the positive active material layer includes a positive active material.
- the specific type of the positive 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 active material 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 active material 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 active material 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 active material 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 active material 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 active material 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 piece, the negative electrode piece and the separator film can be made into an electrode assembly through 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 players, mini-discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, lighting fixtures, 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.
- Pretreatment In a drying room with a temperature of 25°C and a humidity of less than 2%, place a lithium foil with a thickness of 25 ⁇ m in absolute ethanol. Preprocess for 10 seconds to react with hydrogen to remove the surface impurity layer. Soak and clean in DOL/DME, wash away the reaction product with ethanol, blow dry, and place in a drying dish for later use;
- Film-forming liquid configuration 35g/L manganese sulfate monohydrate, 24g/L EDTA 4 Na and 1g/L ammonium sulfate are prepared together, 35g/L sodium dihydrogen phosphate, 10g/L NaNO 3 and 10mL 0.001mol/L Prepare NaOH together, dissolve them separately, mix and adjust the volume to obtain a film-forming liquid;
- 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 metal secondary battery is obtained through processes such as formation, degassing, and trimming.
- the preparation method of the lithium metal secondary battery is similar to Example 1. The difference is that the negative electrode plate and related parameters in the preparation process are adjusted. The specific parameters are shown in Table 1. Comparative Example 1 does not contain a composite protective film. , Comparative Example 2 uses an ordinary polymer protective film instead of the composite protective film in Comparative Example 1. The thickness of the composite protective film in Comparative Example 3 is not within the protection scope of this application, and "/" means that it does not contain corresponding substances.
- a three-electrode system was used to measure the electrochemical polarization curve of a square sample (surface area: 1cm 2 ), scanning separately from OCP toward both sides, with a scanning rate of 0.333mV/s, a cathodic polarization curve cutoff potential of -300mV, and an anode polarization curve cutoff potential of 1.6 V, the cut-off current is 10mA, and the passivation interval of the composite protective film is analyzed after fitting.
- the cycle test temperature is 25°C. Charge the battery to 4.3V at a constant current of 0.33C and charge to 0.025C at a constant voltage. After standing for 5 minutes, discharge it to 2.8V at 0.33C. The capacity obtained in this step is the initial capacity. 0.33C charging/0.33C discharging cycle test until the secondary battery cycle capacity retention rate is 80%, and the corresponding cycle life is recorded.
- Table 2 gives the performance test results of Examples 1 to 14 and Comparative Examples 1 to 3.
- Comparing Examples 1 to 14 and Comparative Examples 1 to 2 it can be seen that the passivation interval of the composite protective film in the negative electrode sheet of the present application is significantly higher than that of Comparative Examples 1 and 2, indicating that the composite protective film can play a role in protecting the lithium metal layer. Very good protective effect; in addition, the number of cycles at which the capacity retention rate of the secondary batteries in Comparative Examples 1 and 2 is 80% is significantly lower than that in Examples 1 to 14, and the lithium metal secondary batteries in Comparative Examples 1 and 2 have The high temperature cycle performance is also poor, which shows that the composite protective film can effectively improve the cycle performance and safety performance of the secondary battery.
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Abstract
本申请提供一种负极极片、负极极片的制备方法、二次电池、电池模块、电池包及用电装置。所述负极极片包括:锂金属层,和位于所述锂金属层至少一个表面上的复合保护膜,其中,所述复合保护膜包括沉淀盐膜层和氧化物膜层,所述氧化物膜层的至少一部分分布于所述沉淀盐膜层中。本申请提供的负极极片中的复合保护膜能够达到充放电循环过程中保护锂金属的目的,同时能够诱导充放电循环过程中锂金属的均匀沉积,减少锂枝晶的生长以及死锂的产生,由此有利于提升二次电池的容量、循环性能及安全性能。
Description
本申请属于电化学技术领域,具体涉及一种负极极片、负极极片的制备方法、二次电池、电池模块、电池包及用电装置。
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。在二次电池现有的负极材料中,锂金属负极因具备较高的理论比容量(3860mAh/g)而成为下一代高比能二次电池负极材料的最佳选择。然而,锂金属负极由于活性较高,在二次电池中极易与环境介质发生反应而导致二次电池的循环性能变差,由此极大限制了其二次电池中的大规模应用。
发明内容
本申请的目的在于提供一种负极极片、用于二次电池中的负极极片、二次电池及用电装置,旨在提升二次电池的循环性能及安全性能。
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:锂金属层,和位于所述锂金属层至少一个表面上的复合保护膜,其中,所述复合保护膜包括沉淀盐膜层和氧化物膜层,所述氧化物膜层的至少一部分分布于所述沉淀盐膜层中。
本申请中由沉淀盐膜层和氧化物膜层形成的复合保护膜非常致密,在二次电池中能够隔绝电解液中有机溶剂以及锂盐阴离子与锂金属的接触,减轻电解液的不可逆损耗,从而能够达到充放电循环过程中保护锂金属的目的。
在本申请任意实施方式中,所述沉淀盐膜层包括(M
1)
x1(PO
4)
y1、(M
1)
x2(CO
3)
y2或其组合,其中,M
1为Li、Mn、Mg、Ba、Ca和Sr中的至少一种,x
1、y
1以及x
2、y
2使得所述化合物的净电荷为零。
沉淀盐膜层主要以无机磷酸盐和碳酸盐成分为主,其具备良好的锂离子导通能力,并且能够对电子产生隔绝作用,因而可以提供锂离子的迁移通道,以诱导锂离子的均匀沉积,从而可减少锂枝晶的产生,提升二次电池的安全性能。
在本申请任意实施方式中,所述氧化物膜层包括(M
1)
mO
n,其中,M
1为Li、Mn、Mg、Ba、Ca、Sr或其组合,m、n使得所述金属氧化物的净电荷为零。
本申请中的氧化物膜层与沉淀盐膜层复合/混合在一起共同构成锂金属层的复合保护膜,该复合保护膜为固体电解质层,具备较高的机械强度,能够对锂金属层起到较强的隔绝保护作用,同时还能够诱导充放电循环过程中锂金属的均匀沉积,抑制锂枝晶的生长,提升二次电池的循环性能及安全性能。
在本申请任意实施方式中,所述氧化物膜层位于所述复合保护膜中靠近所述锂金属层的一侧,所述沉淀盐膜层位于所述复合保护膜中远离所述锂金属层的一侧。
在本申请任意实施方式中,所述复合保护膜的厚度为1μm至25μm,可选为3μm至20μm。
在本申请任意实施方式中,所述氧化物膜层的厚度为50nm至200nm,可选为70nm至160nm。
氧化物膜层及复合保护膜的厚度在合适范围内,既可以为锂离子提供良好的迁移通道,使锂离子在复合保护膜中具备较好的导通能力,以降低界面阻抗并诱导锂金属的均匀沉积,减少或避免锂枝晶的生长;又可以有效隔绝电解液中有机溶剂以及锂盐阴离子与锂金属的接触,减轻电解液的不可逆损耗,从而能够达到充放电循环过程中保护锂金属的目的。
在本申请任意实施方式中,所述复合保护膜的钝化区间为110mV至420mV。
复合保护膜的钝化区间在上述范围内,说明本申请中的复合保护膜具备较好的耐高电压性,即使在高电压下也不会轻易分解,因为能够对锂金属层起到较持久的保护作用,有利于提升二次电池的循环性能。
本申请第二方面提供一种负极极片的制备方法,包括:成膜处理步骤,包括使锂金属层与成膜液反应形成复合保护膜,以得到负极极片,其中,所述复合保护膜包括沉淀盐膜层和氧化物膜层,所述氧化物膜层的至少一部分分布于所述沉淀盐膜层中;所述成膜液包括溶解在惰性溶剂中的沉淀盐阳离子、沉淀盐阴离子、氧化性含氧酸盐、络合剂和催化剂。
通过采用极易与锂金属发生反应的水系溶剂,并依据沉积膜反应机理配置成膜液,然后通过成膜液与锂金属层的反应,可在锂金属层表面形成厚度可控、可耐高电压的无机盐复合保护膜,该复合保护膜能够有效隔绝电解液中有机溶剂以及锂盐阴离子与锂金属的接触,减轻电解液的不可逆损耗,从而达到充放电循环过程中保护锂金属层的目的。
在本申请任意实施方式中,所述制备方法还包括成膜液提供步骤,所述成膜液提供步骤包括:将包含所述沉淀盐阳离子的第一成膜盐、所述络合剂及所述催化剂溶解在第一惰性溶剂中,得到第一溶液;将包含所述沉淀盐阴离子的第二成膜盐和所述氧化性含氧酸盐溶解在第二惰性溶剂中,得到第二溶液;将所述第一溶液与所述第二溶液混匀,得到所述成膜液。
在本申请任意实施方式中,所述第一成膜盐包括MnCl
2、Mn(NO
3)
2、MnSO
4·H
2O、MgSO
4、Ca(NO
3)
2、Ba(NO
3)
2、Sr(NO
3)
2或其组合。
在本申请任意实施方式中,所述第二成膜盐包括碳酸盐、磷酸盐或其组合,可选为(M
2)
2CO
3、(M
2)
x3H
y3(PO4)
z3、(M
2)
x4H
y4(P
2O
7)
z4或其组合,其中,M
2为Li、Na、K或其组合,x
3、y
3、z
3以及x
4、y
4、z
4使得所述第二成膜盐的净电荷为零。
在本申请任意实施方式中,所述络合剂包括乙二胺四乙酸、乙二胺四乙酸二钠、乙二胺四乙酸四钠、乙醇胺或其组合。
在本申请任意实施方式中,所述氧化性含氧酸盐包括硝酸盐、无机盐(M
2)
x5(M
3)
y5O
z5或其组合,可选为NaNO
3、KNO
3、Ca(NO
3)
2、KMnO
4、Na
2FeO
4、K
2Cr
2O
7、NaCoO
2、NaVO
2或其组合,其中,M
2为Li、Na、K或其组合,M
3为V、Cr、Mn、Fe、Co、Ni或其组合,z
5为1至7,x
5、y
5、z
5使得所述氧化性含氧酸盐的净电荷为零。
在本申请任意实施方式中,所述催化剂包括铵盐,可选为NH
4NO
3、(NH
4)
2SO
4、NH
4Cl或其组合。
在本申请任意实施方式中,在所述成膜液中,所述第一成膜盐、所述第二成膜盐、所述络合剂及所述氧化性含氧酸盐的浓度为10g/L至50g/L,所述催化剂的浓度为10g/L至30g/L。
通过调节成膜液的组分,并将相应组分的浓度控制在合适范围内,可在锂金属表面原位转化生成一种致密的可导锂离子而不导电子的固态电解质复合保护膜,该复合保护膜的界面阻抗低,界面结合力强,机械强度高,能够隔绝电解液与锂金属的反应,减弱或避免电解液的不可逆损耗,同时可诱导循环过程中锂金属的均匀沉积,抑制锂枝晶的生长,提升二次电池的循环性能及安全性能。
在本申请任意实施方式中,所述成膜液的PH值为5至7。通过调节成膜液的PH值,可降低成膜液的酸性并提高其碱性,从而提升溶液中碱式酸根的数量,有利于促进沉淀盐膜层的形成。
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制备方法制得的负极极片。
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。
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。
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。
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。
图1是本申请的负极极片中复合保护膜的一实施例的表面形貌图。
图2是本申请的二次电池的一实施方式的示意图。
图3是本申请的二次电池的一实施方式的分解示意图。
图4是本申请的电池模块的一实施方式的示意图。
图5是本申请的电池包的一实施方式的示意图。
图6是图5的分解图。
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。
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。
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。
在本文的描述中,除非另有说明,“以上”、“以下”包含本数。
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)。
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。
锂金属负极的理论比容量(3860mAh/g)极高,成为下一代高比能二次电池负极材料的最佳选择。然而,发明人在研究过程中发现锂金属的活性极高,一方面在储运过程中极易与环境介质发生氧化还原反应而失效,更易与水溶液发生剧烈反应,因而限制了二次电池制备过程中很多无机盐成膜液的使用;另一方面,在二次电池充放电过程中极易与电解液反应生成SEI膜,随着循环时间的增加,SEI膜会逐渐增厚,由此导致界面阻抗增大,并导致死锂的产生,进而引起容量损失,对二次电池的循环性能产生影响;同时,在二次电池充放电过程中,不均匀的锂沉积会导致锂枝晶的产生,锂枝晶的生长可能会刺穿隔膜而导致电池短路甚至***。
目前,为了解决储运问题,现有技术中多采用在锂金属表面涂覆一层聚合物的方式,但这种方式的工艺复杂、成本较高,而且聚合物与锂金属之间主要以有机-无机键的方式结合,结合力较差;另外,聚合物保护膜缺陷较多,对锂金属负极的保护能力较差,而且聚合物膜层不耐高电压,在高电压下易分解,因而对锂金属的保护能力有限。
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,通过采用极易与锂金属发生反应的水系溶剂,依据沉积膜反应机理配置成膜液,并通过喷涂的方式控制锂金属与成膜液的反应速度,在锂金属表面沉积一层厚度可控、可耐高电压的复合保护膜,该复合保护膜能够达到在二次电池充放电循环过程中保护锂金属的目的,并能够促进锂金属的均匀沉积,进而有利于提升二次电池的循环性能及安全性能。
负极极片
本申请实施方式的第一方面提供了一种负极极片,包括:锂金属层,和位于所述锂金属层至少一个表面上的复合保护膜,其中,所述复合保护膜包括沉淀盐膜层和氧化物膜层,所述氧化物膜层的至少一部分分布于所述沉淀盐膜层中。
并非意在受限于任何理论,发明人发现本申请中由沉淀盐膜层和氧化物膜层形成的复合保护膜非常致密,在二次电池中能够隔绝电解液中有机溶剂以及锂盐阴离子与锂金属的接触,减轻电解液的不可逆损耗,从而能够达到充放电循环过程中保护锂金属的目的;同时该复合保护膜能够诱导充放电循环过程中锂金属的均匀沉积,减少锂枝晶的生长以及死锂的产生,由此有利于提升二次电池的容量、循环性能及安全性能。
在一些实施方式中,参见图1,所述复合保护膜中的沉淀盐膜层和氧化物膜层混合分布,其中,沉淀盐膜层位于复合保护膜中远离锂金属层的一侧,氧化物膜层位于复合保护膜中靠近锂金属层的一侧,所述复合保护膜主要通过化学键的作用与锂金属层结合,结合作用较强,且机械强度较高,能够对锂金属层起到较强的保护作用,使其在长期的充放电循环过程中能够有效隔绝电解液,减少其与电解液反应而生成的SEI膜,从而降低界面阻抗,提升二次电池离子导通能力及循环性能。
在一些实施方式中,所述沉淀盐膜层包括(M
1)
x1(PO
4)
y1、(M
1)
x2(CO
3)
y2或其组合,其中,M
1为Li、Mn、Mg、Ba、Ca和Sr中的至少一种,x
1、y
1以及x
2、y
2使得所述化合物的净电荷为零。例如,所述沉淀盐膜层可以为Li
3PO
4、LiCO
3、Mn
3(PO
4)
2、MnCO
3、Mg
3(PO
4)
2、MgCO
3、Ba
3(PO
4)
2、BaCO
3、Ca
3(PO
4)
2、CaCO
3、Sr
3(PO
4)
2、SrCO
3或其组合。
沉淀盐膜层主要以无机磷酸盐和碳酸盐成分为主,其具备良好的锂离子导通能力,并且能够对电子产生隔绝作用,因而可以提供锂离子的迁移通道,以诱导锂离子的均匀沉积,从而可减少锂枝晶的产生,提升二次电池的安全性能。
在一些实施方式中,所述氧化物膜层包括(M
1)
mO
n,其中,M
1为Li、Mn、Mg、Ba、Ca、Sr或其组合,m、n使得所述金属氧化物的净电荷为零。例如,所述氧化物膜层可以为Li
2O、MnO、MgO、BaO、CaO、SrO或其组合。
本申请中的氧化物膜层与沉淀盐膜层复合/混合在一起共同构成锂金属层的复合保护膜,该复合保护膜为固体电解质层,具备较高的机械强度,能够对锂金属层起到较强的隔绝保护作用,同时还能够诱导充放电循环过程中锂金属的均匀沉积,抑制锂枝晶的生长,提升二次电池的循环性能及安全性能。
在一些实施方式中,所述复合保护膜的厚度为1μm至25μm。例如,所述复合保护膜的厚度为3μm,5μm,7μm,9μm,11μm,13μm,15μm,17μm,19μm,21μm,23μm或处于以上任何数值所组成的范围内。可选的,所述复合保护膜的厚度为3μm至20μm。
在一些实施方式中,所述氧化物膜层的厚度为50nm至200nm。例如,所述氧化物膜层的厚度为70nm,90nm,110nm,130nm,150nm,170nm,190nm或处于以上任何数值所组成的范围捏。可选的,所述氧化物膜层的厚度为70nm至160nm。
本申请中氧化物膜层及复合保护膜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。
本申请中氧化物膜层及复合保护膜的厚度在合适范围内,既可以为锂离子提供良好的迁移通道,使锂离子在复合保护膜中具备较好的导通能力,以降低界面阻抗并诱导锂金属的均匀沉积,减少或避免锂枝晶的生长;又可以有效隔绝电解液中有机溶剂以及锂盐阴离子与锂金属的接触,减轻电解液的不可逆损耗,从而能够达到充放电循环过程中保护锂金属的目的。
在一些实施方式中,所述复合保护膜的钝化区间为110mV至420mV。例如,所述复合保护膜的钝化区间可以为130mV至400mV,150mV至380mV,170mV至360mV,190mV至340mV,210mV至320mV,230mV至300mV或250mV至280mV。
本申请中复合保护膜的钝化区间为本领域公知的含义,可采用本领域已知的方法测试,例如可采用三电极体系测量电化学极化曲线,通过电化学极化曲线可得出复合保护膜的钝化区间。复合保护膜的钝化区间在上述范围内,说明本申请中的复合保护膜具备较好的耐高电压性,即使在高电压下也不会轻易分解,因为能够对锂金属层起到较持久的保护作用,有利于提升二次电池的循环性能。
本申请实施方式的第二方面提供了一种负极极片的制备方法,包括:
成膜处理步骤,包括使锂金属层与成膜液反应形成复合保护膜,以得到负极极片,其中,所述复合保护膜包括沉淀盐膜层和氧化物膜层,所述氧化物膜层的至少一部分分布于所述沉淀盐膜层中。
本申请通过采用极易与锂金属发生反应的水系溶剂,并依据沉积膜反应机理配置成膜液,然后通过成膜液与锂金属层的反应,可在锂金属层表面形成厚度可控、可耐高电压的无机盐复合保护膜,该复合保护膜能够有效隔绝电解液中有机溶剂以及锂盐阴离子与锂金属的接触,减轻电解液的不可逆损耗,从而达到充放电循环过程中保护锂金属层的目的。
在一些实施方式中,所述成膜液包括溶解在惰性溶剂中的沉淀盐阳离子、沉淀盐阴离子、氧化性含氧酸盐、络合剂和催化剂。
在一些实施方式中,所述制备方法还包括成膜液提供步骤,所述成膜液提供步骤包括:
S10、将包含所述沉淀盐阳离子的第一成膜盐、所述络合剂及所述催化剂溶解在第一惰性溶剂中,得到第一溶液;
S20、将包含所述沉淀盐阴离子的第二成膜盐和所述氧化性含氧酸盐溶解在第二惰性溶剂中,得到第二溶液;
S30、将所述第一溶液与所述第二溶液混匀,得到所述成膜液。
在一些实施方式中,在所述成膜液中,所述第一成膜盐、所述第二成膜盐、所述络合剂及所述氧化性含氧酸盐的浓度为10g/L至50g/L,例如,可以为10g/L,15g/L,20g/L,25g/L,30g/L,35g/L,40g/L,45g/L,50g/L或处于以上任何数值所组成的范围内。所述催化剂的浓度为10g/L至30g/L,例如可以为10g/L,15g/L,20g/L,25g/L,30g/L或处于以上任何数值所组成的范围内。
本申请通过调节成膜液的组分,并将相应组分的浓度控制在合适范围内,可在锂金属表面原位转化生成一种致密的可导锂离子而不导电子的固态电解质复合保护膜,该复合保护膜的界面阻抗低,界面结合力强,机械强度高,能够隔绝电解液与锂金属的反应,减弱或避免电解液的不可逆损耗,同时可诱导循环过程中锂金属的均匀沉积,抑制锂枝晶的生长,提升二次电池的循环性能及安全性能。
在一些实施方式中,成膜液可通过喷涂的方式与锂金属层接触反应,生成所述复合保护膜。其中,通过控制喷涂的速率能够控制复合保护膜在锂金属层上的形成厚度。具体的,可通过雾化器将成膜液喷涂在锂金属层上,通过控制雾化器的喷液量而将形成的复合保护膜的厚度控制在本申请上述的合适范围内。
在一些实施方式中,所述第一成膜盐包括MnCl
2、Mn(NO
3)
2、MnSO
4·H
2O、MgSO
4、Ca(NO
3)
2、Ba(NO
3)
2、Sr(NO
3)
2或其组合。
在一些实施方式中,所述第二成膜盐包括碳酸盐、磷酸盐或其组合,可选为(M
2)
2CO
3、(M
2)
x3H
y3(PO4)
z3、(M
2)
x4H
y4(P
2O
7)
z4或其组合,其中,M
2为Li、Na、K或其组合,x
3、y
3、z
3以及x
4、y
4、z
4使得所述第二成膜盐的净电荷为零。例如,所述第二成膜盐可以为Li
2CO
3、Na
2CO
3、K
2CO
3、Li
2HPO
4、LiH
2PO
4、Na
2HPO
4、NaH
2PO
4、K
2HPO
4、KH
2PO
4、Li
3HP
2O
7、Li
2H
2P
2O
7、LiH
3P
2O
7、Na
3HP
2O
7、Na
2H
2P
2O
7、NaH
3P
2O
7、K
3HP
2O
7、K
2H
2P
2O
7、KH
3P
2O
7或其组合。
在一些实施方式中,所述络合剂包括乙二胺四乙酸、乙二胺四乙酸二钠、乙二胺四乙酸四钠、乙醇胺或其组合。
在一些实施方式中,所述氧化性含氧酸盐包括硝酸盐、无机盐(M
2)
x5(M
3)
y5O
z5或其组合,可选为NaNO
3、KNO
3、Ca(NO
3)
2、KMnO
4、Na
2FeO
4、K
2Cr
2O
7、NaCoO
2、NaVO
2 或其组合,其中,M
2为Li、Na、K或其组合,M
3为V、Cr、Mn、Fe、Co、Ni或其组合,z
5为1至7,x
5、y
5、z
5使得所述氧化性含氧酸盐的净电荷为零。
在一些实施方式中,所述催化剂包括铵盐,可选为NH
4NO
3、(NH
4)
2SO
4、NH
4Cl或其组合。
本申请中提供的成膜液在溶液中时各组分稳定存在,当与锂金属接触并发生反应时导致界面pH升高,此时溶液中的难溶无机盐到达临界过饱和度而诱发沉积,在锂金属表面转化生成致密的(无机盐)固态电解质复合保护膜,该复合保护膜通过化学键的作用与锂金属结合,结合作用较强,在高电压下能够对锂金属层起到持久的保护作用。
作为具体的示例,本申请中成膜液与锂金属的反应过程可为如下反应式:
Li-e→Li
+ (1)
2Li+VO
3
-→VO
2+Li
2O (2)
2H
++e→H
2 (3)
H
2PO
4
-→HPO
4
2-+H
+ (4)
HPO
4
2-→PO
4
3-+H
+ (5)
H
2O→H
++OH
- (6)
Li
++OH
-→LiOH (7)
3Li
++PO
4
3-→Li
3PO
4 (8)
Mn
2++HPO
4
2-→MnHPO
4 (9)
其中,通过锂金属与可溶性的磷酸氢盐发生反应,消耗氢离子,生成难溶的具有较强防护作用的磷酸盐沉淀膜,并可通过调节溶液成分控制转化沉淀效率,通过控制喷涂液体量控制反应速率及复合保护膜的沉淀厚度。
如下式(9)至(11)所示,成膜液中通过引入络合剂(用A表示)可将一部分Mn
2+络合起来,以维持溶液中游离Mn
2+的浓度,使得在反应过程中界面处消耗掉的Mn
2+得以及时补充,同时降低溶液中游离Mn
2+的浓度,促进H
2PO
4-电离,增加溶液中PO
4
3-浓度,使溶液中与界面反应的H
2PO
4-的浓度差减小,降低对电离以及扩散过程补充成膜过程中消耗的H
2PO
4-的依赖性,提高溶液的稳定性;另外,引入络合剂后,在溶液中络合剂可以将一部分Mn
2+络合,同时释放出H
+,促进Li的溶解,提高沉淀速率,反应式如下(B表示中间产物):
A+Mn
2+→Mn(B)
2++H
+ (10)
在界面处发生沉淀反应如下:
Mn(B)
2++HPO
4
2-→MnHPO
4+B (11)
B+H
+→A (12)
如下式(12)至(14)所示,成膜液中通过引入催化剂可以降低反应所需的活化能以促进反应的进行,提高化学反应速率并且反应前后催化剂本身不发生改变,反应方程式如下:
6NH
4
++Mn
2+→Mn(NH
3)
6
2++H
+ (13)
Mn(NH
3)
6
2++HPO
4
2-→MnHPO
4+6NH
3 (14)
NH
3+H
+→NH
4
+ (15)
由上式(12)至(14)可知,在溶液中催化剂中的NH
4+可水解生成NH
3·H
2O而释放出H
+,可以将Mn
2+配合起来,从而降低游离Mn
2+的浓度,保持溶液稳定性;界面反应消耗掉Mn
2+时,可以及时释放补充。配体NH
3与H
+结合生成NH
4+,NH
4+在界面处与H
+结合促进了H
2PO
4-的电离,又可加快沉淀速率,从而起到催化作用。
上述成膜液与锂金属的反应过程中,通过引入络合剂可建立Mn
2+缓冲对,避免了溶液中成膜的有效成分的降低;适量催化剂可增加MnHPO
4的形核密度,提高MnHPO
4的沉淀速率,提高形成的复合保护膜的耐蚀性;适量氧化性含氧酸盐可促进锂生成致密的钝化性Li
2O膜层,从而提高沉淀速率。
在一些实施方式中,所述成膜液的PH值为5至7,通过调节成膜液的PH值,可降低成膜液的酸性并提高其碱性,从而提升溶液中碱式酸根的数量,有利于促进沉淀盐膜层的形成。
在一些实施方式中,所述负极极片还包括负极集流体,其中,所述锂金属层采用压延工艺覆合在所述负极集流体的至少一侧上。
在一些实施方式中,所述负极集流体具有在自身厚度方向相对的两个表面,锂金属层设置于负极集流体所述两个相对表面中的任意一者或两者上。
负极集流体可以使用金属箔材或多孔金属板,例如使用铜、镍、钛、铁等金属或它们的合金的箔材或多孔板。作为示例,负极集流体为铜箔。
可以按照本领域常规方法制备负极极片。例如将锂金属片贴合于铜箔的表面,得到负极极片。所述贴合可以但不限于采用辊压实现。
二次电池
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。
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。
[负极极片]
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制备方法制得的负极极片。
[正极极片]
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。
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活性物质层。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,正极活性物质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。
在一些实施方式中,正极活性物质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。
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。
在一些实施方式中,正极活性物质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。
在一些实施方式中,正极活性物质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。
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。
本申请中正极极片可以按照本领域常规方法制备。例如,正极活性物质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。
本申请的正极极片并不排除除了正极活性物质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活性物质层之间、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活性物质层表面的保护层。
[电解液]
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。
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。
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。
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。
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。
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。
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。
[隔离膜]
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。
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。
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。
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。
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。
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。
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。
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。
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。
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。
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。
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。
用电装置
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。
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。
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。
实施例
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。
实施例1
负极极片的制备
1)前处理:在温度为25℃、湿度低于2%的干燥房内,将厚度为25μm的锂箔置于无水乙醇中,前处理10s,反应析氢以除去表层污杂层,再经DOL/DME浸泡清洗,洗去与乙醇的反应产物,吹干,置于干燥皿中备用;
2)成膜液配置:将35g/L一水合硫酸锰、24g/L EDTA
4Na和1g/L硫酸铵一同配置,35g/L磷酸二氢钠、10g/L NaNO
3和10mL 0.001mol/L NaOH一同配置,分别溶解后,混匀、定容,得到成膜液;
3)复合保护膜的制备:通过雾化器喷在步骤1)处理后的锂箔上,通过控制喷液量控制膜层沉淀厚度,温度维持在10℃,喷淋速率5mL/min,雾化器与锂箔相距10cm,锂箔带速为1m/s,锂带传输过程喷淋3次,再用无水乙醇将制备的样品洗净、吹干。可通过控制锂箔的传输速度以及喷淋量控制复合保护膜的厚度,记录为H。通过化学转化处理后形成表面玻璃状、均匀致密的晶态膜,处理获得具有复合保护膜的锂箔,先后经乙醇、DOL/DME清洗,干燥;
4)负极极片的制备:将具有复合保护膜的锂箔通过辊压的方式贴合于铜箔的表面,得到负极极片。
正极极片的制备
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。
电解液的制备
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。
隔离膜的制备
采用PE多孔薄膜作为隔离膜。
锂金属二次电池的制备
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金属二次电池。
实施例2至14和对比例1至3
锂金属二次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,其中,对比例1不含有复合保护膜,对比例2用普通的聚合物保护膜代替对比例1中的复合保护膜,对比例3中复合保护膜的厚度不在本申请保护范围内,“/”表示不包含相应物质。
表1
测试部分
(1)复合保护膜的厚度测试
采用赛成CHY-CA台式测厚仪,对样品表面五个均匀分布的点进行测量,观察复合保护膜是否制备均匀,并记录平均厚度。
(2)复合保护膜钝化区间的测试
采用三电极体系测正方形样品(表面积为1cm
2)电化学极化曲线,从OCP朝向两侧分开扫描,扫描速率0.333mV/s,阴极极化曲线截止电位-300mV、阳极极化曲线截止电位1.6V,截止电流为10mA,进行拟合后分析复合保护膜的钝化区间。
(3)锂金属二次电池循环性能测试
循环测试温度为25℃,将电池以0.33C恒流充电到4.3V,恒压充电到0.025C,静置5分钟后以0.33C放电到2.8V;以此步得到的容量为初始容量,进行0.33C充电/0.33C放电循环测试直至二次电池循环容量保持率为80%,记录对应循环寿命。
(4)锂金属二次电池安全性能测试
将电芯放置于有刻度的量杯中进行循环,将电池置于60℃的导热硅油浴中,浸没电芯。将电池以0.33C恒流充电到4.3V,恒压充电到0.025C,静置5分钟后以0.33C放电到2.8V;以此步得到的容量为初始容量,进行0.33C充电/0.33C放电循环测试直至二次电池循环容量保持率为10%,循环完成后进行读数确定,电芯产气体积,记录对应电芯状态。产气体积10%以下为轻度产气,体积10%-50%为中度产气,体积50%以上为重度产气。
表2给出实施例1至14和对比例1至3的性能测试结果。
表2
复合保护膜钝化区间(mV) | 容量保持率80%的循环圈数 | 高温循环性能安全测试 | |
实施例1 | 240 | 330 | 无异常 |
实施例2 | 160 | 200 | 无异常 |
实施例3 | 320 | 460 | 无异常 |
实施例4 | 210 | 240 | 无异常 |
实施例5 | 280 | 360 | 无异常 |
实施例6 | 220 | 300 | 无异常 |
实施例7 | 290 | 485 | 无异常 |
实施例8 | 110 | 135 | 中度产气 |
实施例9 | 120 | 140 | 中度产气 |
实施例10 | 135 | 150 | 轻度产气 |
实施例11 | 260 | 310 | 无异常 |
实施例12 | 270 | 336 | 无异常 |
实施例13 | 280 | 360 | 无异常 |
实施例14 | 420 | 极化太大无法循环 | 极化太大无法循环 |
对比例1 | 0 | 80 | 冒烟起火 |
对比例2 | 90 | 110 | 严重产气 |
对比例3 | 100 | 120 | 严重产气 |
对比实施例1至14和对比例1至2可以看到,本申请负极极片中复合保护膜的钝 化区间明显高于对比例1和2,说明该复合保护膜能够对锂金属层起到很好的保护作用;另外,对比例1和2中的二次电池的容量保持率80%的循环圈数明显低于实施例1至14,且对比例1和2中锂金属二次电池的高温循环性能也较差,由此说明复合保护膜能够有效提升二次电池的循环性能和安全性能;对比实施例1至14和对比例3可以看到,当复合保护膜的厚度不在本申请所选取的范围内时,复合保护膜的钝化区间以及二次电池的循环性能均明显降低,说明需将复合保护膜的厚度控制在本申请所选取的范围内。
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。
Claims (14)
- 一种负极极片,包括:锂金属层,和位于所述锂金属层至少一个表面上的复合保护膜,其中,所述复合保护膜包括沉淀盐膜层和氧化物膜层,所述氧化物膜层的至少一部分分布于所述沉淀盐膜层中。
- 根据权利要求1所述的负极极片,其中,所述沉淀盐膜层包括(M 1) x1(PO 4) y1、(M 1) x2(CO 3) y2或其组合,其中,M 1为Li、Mn、Mg、Ba、Ca和Sr中的至少一种,x 1、y 1以及x 2、y 2使得所述化合物的净电荷为零。
- 根据权利要求1或2所述的负极极片,其中,所述氧化物膜层包括(M 1) mO n,其中,M 1为Li、Mn、Mg、Ba、Ca、Sr或其组合,m、n使得所述金属氧化物的净电荷为零。
- 根据权利要求1-3中任一项所述的负极极片,其中,所述氧化物膜层位于所述复合保护膜中靠近所述锂金属层的一侧,所述沉淀盐膜层位于所述复合保护膜中远离所述锂金属层的一侧。
- 根据权利要求1-4中任一项所述的负极极片,满足如下条件中的至少一者:所述复合保护膜的厚度为1μm至25μm,可选为3μm至20μm;所述氧化物膜层的厚度为50nm至200nm,可选为70nm至160nm;所述复合保护膜的钝化区间为110mV至420mV。
- 一种负极极片的制备方法,包括:成膜处理步骤,包括使锂金属层与成膜液反应形成复合保护膜,以得到负极极片,其中,所述复合保护膜包括沉淀盐膜层和氧化物膜层,所述氧化物膜层的至少一部分分布于所述沉淀盐膜层中;所述成膜液包括溶解在惰性溶剂中的沉淀盐阳离子、沉淀盐阴离子、氧化性含氧酸盐、络合剂和催化剂。
- 根据权利要求6所述的方法,还包括成膜液提供步骤,所述成膜液提供步骤包括:将包含所述沉淀盐阳离子的第一成膜盐、所述络合剂及所述催化剂溶解在第一惰性溶剂中,得到第一溶液;将包含所述沉淀盐阴离子的第二成膜盐和所述氧化性含氧酸盐溶解在第二惰性溶剂中,得到第二溶液;将所述第一溶液与所述第二溶液混匀,得到所述成膜液。
- 根据权利要求7所述的制备方法,满足如下条件中的至少一者:所述第一成膜盐包括MnCl 2、Mn(NO 3) 2、MnSO 4·H 2O、MgSO 4、Ca(NO 3) 2、Ba(NO 3) 2、Sr(NO 3) 2或其组合;所述第二成膜盐包括碳酸盐、磷酸盐或其组合,可选为(M 2) 2CO 3、(M 2) x3H y3(PO4) z3、(M 2) x4H y4(P 2O 7) z4或其组合,其中,M 2为Li、Na、K或其组合,x 3、y 3、z 3以及x 4、y 4、z 4使得所述第二成膜盐的净电荷为零;所述络合剂包括乙二胺四乙酸、乙二胺四乙酸二钠、乙二胺四乙酸四钠、乙醇胺或其组合;所述氧化性含氧酸盐包括硝酸盐、无机盐(M 2) x5(M 3) y5O z5或其组合,可选为NaNO 3、KNO 3、Ca(NO 3) 2、KMnO 4、Na 2FeO 4、K 2Cr 2O 7、NaCoO 2、NaVO 2或其组合,其中,M 2为Li、Na、K或其组合,M 3为V、Cr、Mn、Fe、Co、Ni或其组合,z 5为1至7,x 5、y 5、z 5使得所述氧化性含氧酸盐的净电荷为零;所述催化剂包括铵盐,可选为NH 4NO 3、(NH 4) 2SO 4、NH 4Cl或其组合。
- 根据权利要求8所述的方法,其中,在所述成膜液中,所述第一成膜盐、所述第二成膜盐、所述络合剂及所述氧化性含氧酸盐的浓度为10g/L至50g/L,所述催化剂的浓度为10g/L至30g/L。
- 根据权利要求6-9中任一项所述的方法,还包括所述成膜液的PH值为5至7。
- 一种二次电池,包括权利要求1-5中任一项所述的负极极片或通过权利要求6-10中任一项所述的方法制得的负极极片。
- 一种电池模块,包括权利要求11所述的二次电池。
- 一种电池包,包括权利要求12所述的电池模块。
- 一种用电装置,包括选自权利要求11所述的二次电池、权利要求12所述的电池模块或权利要求13所述的电池包中的至少一种。
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