WO2023142308A1 - 负极极片、二次电池、电池模块、电池包及用电装置 - Google Patents

负极极片、二次电池、电池模块、电池包及用电装置 Download PDF

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WO2023142308A1
WO2023142308A1 PCT/CN2022/093124 CN2022093124W WO2023142308A1 WO 2023142308 A1 WO2023142308 A1 WO 2023142308A1 CN 2022093124 W CN2022093124 W CN 2022093124W WO 2023142308 A1 WO2023142308 A1 WO 2023142308A1
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negative electrode
fibers
electrode sheet
active material
battery
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PCT/CN2022/093124
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English (en)
French (fr)
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邓凯明
陆雷
王亚龙
贾海
戴顺浩
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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 EP22923123.8A priority Critical patent/EP4293755A1/en
Publication of WO2023142308A1 publication Critical patent/WO2023142308A1/zh
Priority to US18/371,479 priority patent/US20240021827A1/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
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/02—Details
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • 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
    • 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
    • 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
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • 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 relates to the technical field of secondary batteries, in particular to a negative pole piece, a secondary battery, a battery module, a battery pack and an electrical device.
  • the batteries in secondary batteries are mainly made by lamination and winding processes.
  • the above-mentioned processes require the pole pieces of the batteries to have good flexibility. If the pole pieces are easily cracked when bent, it will cause the battery invalidated. Therefore, while improving the energy density of the secondary battery, it is urgent to improve the flexibility of the electrode sheet of the battery.
  • the present application provides a negative pole piece, a secondary battery, a battery module, a battery pack and an electrical device.
  • the negative pole piece has good flexibility and can also increase the energy density of the secondary battery.
  • a negative electrode sheet comprising:
  • the negative electrode active material layer is arranged on at least one surface of the negative electrode current collector, based on the total weight of the negative electrode active material layer, the negative electrode active material layer comprises components in the following weight ratio:
  • Negative active material 90.0%-98.6%
  • Polymer binder 1.0%-5.0%;
  • Toughening fibers 0.2%-4.0%.
  • an appropriate amount of polymer binder contained in the negative electrode active material layer has good binding properties, and can effectively lock the negative electrode active material to improve the strength of the negative electrode sheet.
  • an appropriate amount of polymer binder and an appropriate amount of toughening fibers contained in the negative electrode active material layer cooperate with each other to reduce the cracking of the negative electrode sheet, thereby achieving the effect of improving the flexibility of the negative electrode sheet.
  • the negative electrode active material layer of the negative electrode sheet contains an appropriate amount of toughening fibers and an appropriate amount of polymer binder, which can make the secondary battery have a lower battery impedance and achieve the effect of increasing the energy density of the secondary battery.
  • the polymer binder has a three-dimensional cross-linked network structure.
  • the polymer binder with a three-dimensional cross-network structure has better cohesiveness, which makes it more effective to lock the negative electrode active material, so as to improve the strength of the negative electrode sheet.
  • the three-dimensional cross-network structure of the polymer binder can better cooperate with the toughening fibers to further reduce the cracking of the negative electrode sheet, so that the negative electrode sheet has good flexibility.
  • the polymer binder is a copolymer containing multiple polar functional groups.
  • Polar functional groups can interact to form hydrogen bonds, so that a three-dimensional cross-linked network structure is formed in the polymer binder. And the formation of hydrogen bonds can help the polymer binder reduce the cracking of the negative electrode sheet, thereby improving the flexibility of the negative electrode sheet.
  • the polar functional group includes at least one of carboxyl, cyano, amide, amino and hydroxyl.
  • the above-mentioned polar functional groups are easy to form hydrogen bonds, and then it is easier to form a three-dimensional cross-linked network structure in the polymer binder, so as to reduce the cracking of the negative electrode sheet and improve the flexibility of the negative electrode sheet.
  • the weight average molecular weight of the copolymer is greater than or equal to 300,000.
  • the weight average molecular weight of the copolymer within the above range can help to improve the performance of the polymer binder, such as the strength, tensile strength and cohesive force of the three-dimensional cross-linked network structure.
  • the copolymer is selected from at least one of polyacrylic acid-acrylonitrile copolymer and its derivatives, acrylic acid-acrylamide and its derivatives, and acrylic acid-acrylate copolymer. Hydrogen bonds can be formed between carboxyl groups and cyano groups in polyacrylic acid-acrylonitrile copolymers and carboxyl groups in acrylic acid-acrylate copolymers. The strong intermolecular forces formed by them can effectively improve the cracking of negative electrode sheets and achieve improved negative electrode performance. The effect of pole piece flexibility.
  • the diameter of the toughening fiber is in the range of 0.1 ⁇ m-50 ⁇ m, and the aspect ratio of the toughening fiber is greater than or equal to 20.
  • the diameter of the toughening fiber is within the above range, which is beneficial to improve the flexibility of the negative electrode sheet.
  • the aspect ratio of the toughening fiber is greater than or equal to 20, which can further improve the flexibility of the negative electrode sheet.
  • the toughening fiber is selected from at least one of aramid fiber, plastic fiber and carbon fiber.
  • the above-mentioned fibers can better play a synergistic effect with the polymer binder to reduce the cracking of the negative electrode sheet and make the negative electrode sheet have good flexibility.
  • the plastic fiber is selected from one or more of polyimide fiber, polyphenylene sulfide fiber, polyparaphenylene benzobisoxazole fiber and ultra-high molecular weight polyethylene fiber A combination;
  • the carbon fibers are selected from one or more combinations of polyacrylonitrile-based carbon fibers, pitch-based carbon fibers and viscose-based carbon fibers.
  • the above-mentioned fibers can better play a synergistic effect with the polymer binder to reduce the cracking of the negative electrode sheet and make the negative electrode sheet have good flexibility.
  • the present application provides a secondary battery, including:
  • a negative pole piece, the negative pole piece is the negative pole piece described in any one of the above embodiments;
  • the secondary battery includes the negative electrode sheet in the above embodiment, and the negative electrode sheet can not only improve the flexibility of the negative electrode sheet by rationally selecting the components and their contents in the negative electrode active material layer, Moreover, the energy density of the secondary battery can be improved. Therefore, the secondary battery has better strength and higher energy density.
  • the present application further provides a battery module, the battery module including the secondary battery described in the above embodiments.
  • the battery module since the battery module includes the secondary battery in the above embodiments, the battery module has higher energy density.
  • the present application further provides a battery pack, the battery pack includes the battery module described in the foregoing embodiments.
  • the battery pack since the battery pack includes the battery module in the above embodiment, the battery pack has a higher energy density.
  • the present application also provides an electric device, which includes the secondary battery described in any one of the above embodiments, the battery module described in the above embodiments, or the battery module described in the above embodiments. battery pack.
  • the electric device includes the secondary battery in the above embodiments, the battery module in the above embodiments, or the battery pack in the above embodiments, therefore, the electric device has a relatively long battery life.
  • Fig. 1 is the schematic structural view of the negative pole sheet of some embodiments of the present application.
  • FIG. 2 is a schematic structural view of a negative pole piece according to another embodiment of the present application.
  • Figure 3 is a diagram of the mechanism of action between the carboxyl group and the cyano group in the polyacrylic acid-acrylonitrile copolymer contained in the negative electrode active material layer of some embodiments of the present application;
  • Figure 4 is a diagram of the mechanism of action between the carboxyl groups in the acrylic acid-acrylate copolymer contained in the negative electrode active material layer of some embodiments of the present application;
  • Fig. 5 is a schematic diagram of some embodiments of the present application where the negative pole piece is wound and attached to the needle;
  • Fig. 6 is a schematic diagram of some embodiments of the present application where the negative pole piece is wound and pasted on the needle;
  • Fig. 7 is a schematic diagram of folding in half the diaphragm formed by the negative electrode active material layer in some embodiments of the present application.
  • Fig. 8 is a schematic diagram of a secondary battery in some embodiments of the present application.
  • Fig. 9 is an exploded view of the secondary battery of some embodiments of the present application shown in Fig. 5;
  • FIG. 10 is a schematic diagram of a battery module according to some embodiments of the present application.
  • Fig. 11 is a schematic diagram of a battery pack according to some embodiments of the present application.
  • Fig. 12 is an exploded view of the battery pack of some embodiments of the present application shown in Fig. 11;
  • Fig. 13 is a schematic diagram of an electrical device in which a secondary battery is used as a power source in some embodiments of the present application.
  • the term “multiple” refers to more than two (including two).
  • the present application provides a secondary battery, which includes a positive pole piece, a negative pole piece, an electrolyte and a separator.
  • a secondary battery which includes a positive pole piece, a negative pole piece, an electrolyte and a separator.
  • active ions are intercalated and extracted back and forth between the positive electrode and the negative electrode.
  • the electrolyte plays the role of conducting ions between the positive pole piece and the negative pole piece.
  • the separator is arranged between the positive pole piece and the negative pole piece, which mainly plays a role in preventing the short circuit of the positive and negative poles, and at the same time allows ions to pass through.
  • the positive pole piece includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector.
  • the positive electrode current collector has two opposing surfaces in its own thickness direction, and the positive electrode active material layer is disposed on any one or both of the two opposing surfaces of the positive electrode current collector.
  • a metal foil or a composite current collector can be used as the positive electrode current collector.
  • aluminum foil can be used as the metal foil.
  • the composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • the composite current collector can be formed by forming metal materials (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalic acid It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene glycol ester
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • positive electrode active materials known in the art for batteries may be used as the positive electrode active material.
  • the positive active material may include at least one of the following materials: olivine-structured lithium-containing phosphate, lithium transition metal oxide, and their respective modified compounds.
  • the present application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials of batteries can also be used. These positive electrode active materials may be used alone or in combination of two or more.
  • lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO 2 ), lithium nickel oxides (such as LiNiO 2 ), lithium manganese oxides (such as LiMnO 2 , LiMn 2 O 4 ), lithium Nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi1/ 3 Co 1/3 Mn 1/3 O 2 (also referred to as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (also abbreviated as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (also abbreviated as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (also abbreviated as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 At least one of O 2 (also abbreviated as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15), lithium nickel cobal
  • lithium-containing phosphate of olivine structure can be Including but not limited to lithium iron phosphate (such as LiFePO 4 (also referred to as LFP)), composite materials of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), composite materials of lithium manganese phosphate and carbon, ferromanganese phosphate At least one of lithium, lithium manganese iron phosphate and carbon composite materials.
  • lithium iron phosphate such as LiFePO 4 (also referred to as LFP)
  • LiMnPO 4 lithium manganese phosphate
  • LiMnPO 4 lithium manganese phosphate
  • ferromanganese phosphate At least one of lithium, lithium manganese iron phosphate and carbon composite materials.
  • 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 meta-copolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • the positive electrode active material layer may further optionally include 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 sheet can be prepared in the following manner: the above-mentioned components used to prepare the positive electrode sheet, such as positive active material, conductive agent, binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.
  • a solvent such as N-methylpyrrolidone
  • Negative electrode sheet 10 The negative electrode sheet 10 provided in this application includes a negative electrode current collector 11 and a negative electrode active material layer 12, wherein the negative electrode active material layer 12 is arranged on at least one surface of the negative electrode current collector 11, based on the negative electrode active material layer 12 Gross weight, the negative electrode active material layer 12 comprises the components of the following weight ratio:
  • Negative active material 90.0%-98.6%
  • Polymer binder 1.0%-5.0%;
  • Toughening fibers 0.2%-4.0%.
  • the negative electrode active material layer 12 contains an appropriate amount of polymer binder and an appropriate amount of toughening fibers, and the two cooperate with each other to reduce the cracking of the negative electrode sheet 10, thereby achieving the improvement of the flexibility of the negative electrode sheet 10 Effect.
  • an appropriate amount of toughening fibers and an appropriate amount of polymer binder can make the secondary battery have lower battery impedance, thereby achieving the effect of increasing the energy density of the secondary battery.
  • the negative electrode current collector 11 may use a metal foil or a composite current collector.
  • copper foil can be used as the metal foil.
  • the composite current collector may include a base layer of polymer material and a metal layer formed on at least one surface of the base material of polymer material.
  • Composite current collectors can be formed by metal materials (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyethylene terephthalic acid It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • the negative electrode current collector 11 has two opposite surfaces in the thickness direction, and the negative electrode active material layer 12 is disposed on any one or both of the two surfaces of the negative electrode current collector 11 .
  • FIG. 1 schematically shows a negative electrode sheet 10, please refer to FIG. 1, the negative electrode sheet 10 includes a negative electrode current collector 11 and a negative electrode active material layer 12, wherein the negative electrode current collector 11 is Having opposite first surface 111 and second surface 112 , the negative electrode active material layer 12 is disposed on the first surface 111 and the second surface 112 of the negative electrode current collector 11 .
  • FIG. 2 schematically shows another negative electrode sheet 10.
  • the negative electrode active material layer 12 is disposed on the first surface 111 of the negative electrode current collector 11 .
  • the negative electrode active material layer 12 may also be disposed on the second surface 112 of the negative electrode current collector 11 .
  • the above-mentioned negative electrode active material layer 12 is formed by coating the negative electrode slurry on the surface of the negative electrode current collector 11, and the content of the negative electrode active material in the negative electrode active material layer 12 is set in the range of 90.0% to 98.6%, and the application of the negative electrode active material
  • the type is not specifically limited, and can be selected according to actual needs.
  • the negative electrode 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, and lithium titanate.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon-oxygen compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys.
  • the tin-based material can be selected from at least one of simple tin, tin oxide and tin alloy.
  • the present application is not limited to these materials, and other conventional materials that can be used as the active material of the negative electrode of the battery can also be used. These negative electrode active materials may be used alone or in combination of two or more.
  • the content of the polymer binder is set in the range of 1.0%-5.0%, which can reduce the cracking of the negative electrode sheet 10 and reduce the impedance of the secondary battery, thereby improving the flexibility of the negative electrode sheet 10 performance and increase the energy density of secondary batteries. If the content of the polymer binder is lower than 1.0%, the binding effect of the polymer binder will be reduced, and the bond between the negative electrode active material layer 12 and the surface of the negative electrode current collector 11 is not firm enough, that is to say, the negative electrode The active material layer 12 is easy to fall off from the surface of the negative electrode current collector 11 , which cannot improve the flexibility of the negative electrode sheet 10 .
  • the content of the polymer binder is higher than 5.0%, it will hinder the transmission of lithium ions between the negative electrode active materials, making it difficult for lithium ions to detach or intercalate therefrom, thereby increasing the impedance of the secondary battery and affecting the rate performance of the secondary battery .
  • the content of the polymer binder can be, but not limited to, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.0%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7% , 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5.0%.
  • the polymeric binder has a three-dimensional cross-linked network structure.
  • the three-dimensional cross-network structure of the polymer binder makes it have better cohesiveness, and can effectively lock the negative active material to improve the strength of the negative active material layer 12, so that the negative active material layer 12 can be processed and used It is not easy to crack during the process.
  • the toughening fiber can pass through the gap of the negative electrode active material and intertwine with the solid components such as the negative electrode active material and the polymer binder, so that the polymer binder can better play a synergistic role with the toughening fiber, further reducing the The cracking of the negative electrode sheet 10 makes the negative electrode sheet 10 have good flexibility.
  • the three-dimensional cross-network structure of the above-mentioned polymer binder can be formed through the interaction of the functional groups of the polymers in the binder.
  • the polymeric binder is a copolymer containing multiple polar functional groups. These polar functional groups can interact to form hydrogen bonds, so that a three-dimensional cross-linked network structure is formed in the polymer binder. Moreover, the formation of hydrogen bonds can enhance the strength of the negative electrode active material layer, thereby making the negative electrode sheet 10 less likely to crack, thereby improving the flexibility of the negative electrode sheet 10 .
  • the polar functional group of the copolymer in the polymer binder may contain at least one of carboxyl, cyano, amide, amino and hydroxyl. These polar functional groups are easy to form hydrogen bonds, thereby making it easier to form a three-dimensional cross-linked network structure in the polymer binder, so as to reduce the cracking of the negative electrode sheet 10 and improve the flexibility of the negative electrode sheet 10 .
  • the copolymer in the polymer binder can further improve the flexibility of the negative electrode sheet 10 by adjusting the weight average molecular weight to improve the performance of the polymer.
  • the weight-average molecular weight of the copolymer is greater than or equal to 300,000, and the weight-average molecular weight of the copolymer can be determined by methods such as light scattering method, ultracentrifugation sedimentation velocity method, and gel chromatography. Setting the weight-average molecular weight of the copolymer within this range can help to improve the performance of the polymer binder, such as the strength, tensile strength and cohesive force of the three-dimensional cross-linked network structure.
  • the copolymer in the polymer binder may be selected from polyacrylic acid-acrylonitrile copolymer and its derivatives, acrylic acid-acrylamide copolymer and its derivatives, and acrylic acid-acrylate copolymer at least one of the Among them, the carboxyl group in the polyacrylic acid-acrylonitrile copolymer and the cyano group (shown in Figure 3) and the carboxyl group in the acrylic acid-acrylate copolymer (shown in Figure 4) can form hydrogen bonds, and the strong intermolecular bonds formed by them The force can enhance the strength of the negative electrode active material layer, so that the negative electrode sheet 10 is not easy to crack, so as to achieve the effect of improving the flexibility of the negative electrode sheet 10 .
  • the content of the toughening fiber in the negative electrode active material layer 12 is set in the range of 0.2%-4.0%, which can improve the flexibility of the negative electrode sheet 10 and increase its energy by reducing the impedance of the secondary battery. density. If the content of the toughening fiber is lower than 0.2%, the toughening fiber cannot be intertwined with other solid components, thus the effect of improving the flexibility of the negative pole sheet 10 cannot be achieved; if the content of the toughening fiber is higher than 4.0%, it will hinder The transmission of lithium ions between the negative electrode active materials makes it difficult for lithium ions to deintercalate/intercalate, thereby increasing the impedance of the secondary battery and resulting in a decrease in the energy density of the secondary battery.
  • the content of toughening fiber can be but not limited to 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3% , 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0 %, 3.0%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%.
  • one or both of natural fibers and synthetic fibers can be used as the toughening fibers, as long as the flexibility of the negative electrode sheet 10 can be improved.
  • synthetic fibers are used as toughening fibers.
  • the synthetic fiber may be selected from at least one of aramid fiber, plastic fiber and carbon fiber.
  • the above-mentioned synthetic fibers can better play a synergistic effect with the polymer binder to reduce the cracking of the negative electrode sheet 10 and make the negative electrode sheet 10 have good flexibility.
  • the aramid fiber can be any one of para-aramid fiber and meta-aramid fiber or a mixture of both;
  • the plastic fiber can be polyimide fiber, polyphenylene sulfide fiber, polypara-aramid fiber A mixture of any one or more of phenylene benzobisoxazole fibers and ultra-high molecular weight polyethylene fibers.
  • the ultra-high molecular weight polyethylene fibers here refer to polyethylene with a molecular weight of 1 million to 5 million.
  • the carbon fiber can be any one or a mixture of polyacrylonitrile-based carbon fibers, pitch-based carbon fibers and viscose-based carbon fibers, and can also be carbon nanofibers or carbon nanotubes.
  • the diameter of the toughening fiber is in the range of 0.1 ⁇ m-50 ⁇ m, and setting the diameter of the toughening fiber within this range is beneficial to further improve the flexibility of the negative electrode sheet 10 .
  • the diameter of the toughening fiber may be, but not limited to, 0.1 ⁇ m, 0.2 ⁇ m, 0.3 ⁇ m, 0.4 ⁇ m, 0.5 ⁇ m, 0.6 ⁇ m, 0.7 ⁇ m, 0.8 ⁇ m, 0.9 ⁇ m, 1 ⁇ m, 2 ⁇ m, 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, 6 ⁇ m, 7 ⁇ m, 8 ⁇ m, 9 ⁇ m, 10 ⁇ m, 11 ⁇ m, 12 ⁇ m, 13 ⁇ m, 14 ⁇ m, 15 ⁇ m, 16 ⁇ m, 17 ⁇ m, 18 ⁇ m, 19 ⁇ m, 20 ⁇ m, 21 ⁇ m, 22 ⁇ m, 23 ⁇ m, 24 ⁇ m, 25 ⁇ m, 26 ⁇ m, 27 ⁇ m, 28 ⁇ m, 29 ⁇ m, 30 ⁇ m, 31 ⁇ m, 32 ⁇ m, 33 ⁇ m, 34 ⁇ m, 35 ⁇ m, 37 ⁇ m, 38 ⁇ m, 39 ⁇ m, 40 ⁇ m, 41 ⁇ m, 42 ⁇ m, 43 ⁇ m, 44 ⁇ m, 45 ⁇ m, 46 ⁇
  • the aspect ratio of the toughening fiber is greater than or equal to 20, where the aspect ratio refers to the ratio of the length to the diameter of the toughening fiber, and the length, diameter and aspect ratio of the toughening fiber are determined by an electron microscope.
  • the aspect ratio of the toughening fiber is greater than or equal to 20, which can further improve the flexibility of the negative electrode sheet 10 .
  • the aspect ratio of the toughening fiber can be, but not limited to, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36 , 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50 or more than 50.
  • the negative electrode active material layer further includes a conductive agent, and the weight ratio of the conductive agent in the negative electrode active material layer is 0.2% ⁇ 1.0%.
  • the conductive agent is one or more of graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the present application also provides a method for manufacturing the negative electrode sheet 10, the method includes the following steps:
  • the negative electrode slurry After mixing the negative electrode active material, conductive agent, polymer binder, toughening fiber and solvent according to the above ratio, the negative electrode slurry is obtained;
  • the negative electrode active material layer is combined with the negative electrode current collector, and the negative electrode sheet is obtained through processes such as drying and cutting.
  • the preparation of negative electrode slurry specifically includes the following steps:
  • a polymer binder and a solvent are added to the above mixed solids for mixing to obtain negative electrode slurry.
  • this application provides a secondary battery, including:
  • a negative pole piece, the negative pole piece is the negative pole piece described in any one of the above embodiments;
  • the secondary battery includes the negative electrode sheet in the above embodiment, and the negative electrode sheet can not only improve the flexibility of the negative electrode sheet by rationally selecting the components and their contents in the negative electrode active material layer, Moreover, the energy density of the secondary battery can be improved. Therefore, the secondary battery has better strength and higher energy density.
  • the present application has no particular limitation on the type of the isolation membrane, and any known porous structure isolation membrane with good chemical stability and mechanical stability can be selected.
  • the material of the isolation film may be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the separator can be a single-layer film or a multi-layer composite film, without any particular limitation. When the separator is a multilayer composite film, the materials of each layer may be the same or different, and there is no particular limitation.
  • the electrolyte plays the role of conducting ions between the positive pole piece and the negative pole piece.
  • the present application has no specific limitation on the type of electrolyte, which can be selected according to requirements.
  • electrolytes can be liquid, gel or all solid.
  • the electrolyte includes an electrolyte salt and a solvent.
  • the electrolyte salt may be selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, At least one of lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium difluorooxalate borate, lithium difluorodifluorooxalatephosphate, and lithium tetrafluorooxalatephosphate.
  • the solvent can be selected from ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethylene carbonate Propyl ester, Butylene carbonate, Fluoroethylene carbonate, Methyl formate, Methyl acetate, Ethyl acetate, Propyl acetate, Methyl propionate, Ethyl propionate, Propyl propionate, Methyl butyrate, At least one of ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • the electrolyte also optionally includes additives.
  • additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain performances of the battery, such as additives that improve battery overcharge performance, additives that improve high-temperature or low-temperature performance of batteries, and the like.
  • the positive pole piece, the negative pole piece and the separator can be made into an electrode assembly through a winding process or a lamination process.
  • the above-mentioned positive pole piece, separator, and negative pole piece are stacked in order, so that the separator is placed between the positive pole piece and the negative pole piece to play the role of isolation, and a bare cell is obtained, which can also be wound Finally, the bare cell is obtained; the tabs are connected to the bare cell, and the cell is placed in the packaging shell, and then the excess water is removed by heating, and then the electrolyte is injected and sealed; finally, after standing, hot and cold pressing, formation, Shaping, capacity testing and other processes to obtain the secondary battery of the present application.
  • the secondary battery may include an outer package.
  • the outer package can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer package of the secondary battery may be a hard shell, such as a hard plastic shell, aluminum shell, steel shell, and the like.
  • 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 case may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
  • FIG. 8 shows a secondary battery 1 having a square structure as an example.
  • the outer package may include a casing 21 and a cover plate 23 .
  • the housing 21 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plates enclose to form an accommodating cavity.
  • the housing 21 has an opening communicating with the receiving cavity, and the cover plate 23 can cover the opening to close the receiving cavity.
  • the positive pole piece, the negative pole piece and the separator can be formed into the electrode assembly 22 through a winding process or a lamination process.
  • the electrode assembly 22 is packaged in the accommodating chamber.
  • the electrolyte is infiltrated in the electrode assembly 22 .
  • the number of electrode assemblies 22 contained in the secondary battery 8 can be one or more, and those skilled in the art can select according to specific actual needs.
  • the secondary battery can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module .
  • FIG. 10 is a battery module 2 as an example.
  • a plurality of secondary batteries 1 may be arranged in sequence along the length direction of the battery module 2 .
  • the plurality of secondary batteries 1 may be fixed by fasteners.
  • the battery module 2 may further include a casing having a housing space in which a plurality of secondary batteries 1 are accommodated.
  • 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 one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack .
  • the battery pack 3 may include a battery box and a plurality of battery modules 2 disposed in the battery box.
  • the battery box includes an upper box body 31 and a lower box body 32 , the upper box body 31 can cover the lower box body 32 and form a closed space for accommodating the battery module 2 .
  • Multiple battery modules 2 can be arranged in the battery box in any manner.
  • the present application also provides an electric device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application.
  • a secondary battery, a battery module, or a battery pack can be used as a power source of a power consumption device, and can also be used as an energy storage unit of the power consumption device.
  • Electric devices can include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but not limited thereto.
  • secondary batteries, battery modules, or battery packs can be selected according to their usage requirements.
  • FIG. 13 is an example of an electrical device.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • a battery pack or a battery module may be used.
  • a device may be a cell phone, tablet, laptop, or the like.
  • the device is generally required to be light and thin, and a secondary battery can be used as a power source.
  • the raw material components in the negative electrode slurry are artificial graphite, carbon black, acrylic acid-acrylonitrile copolymer and para-aramid fiber, wherein the diameter of the para-aramid fiber is 0.5 ⁇ m, and the aspect ratio of the para-aramid fiber is 0.5 ⁇ m. for 40.
  • the specific preparation steps of negative electrode slurry are as follows:
  • the negative electrode slurry is rolled by a roller press to obtain a negative electrode active material layer, wherein, based on the total weight of the negative electrode active material layer, the weight ratio of each component in the negative electrode active material layer is 96.6:0.4:2:1,
  • the negative electrode active material layer is composited with copper foil, dried in an oven at 100° C., and then cut to obtain negative electrode sheets.
  • a polypropylene film is used as the separator.
  • Example 1 The difference from Example 1 is that the weight ratio of artificial graphite in the negative electrode active material layer: carbon black: acrylic acid-acrylonitrile copolymer: para-aramid fiber is 98.6:0.2:1:0.2.
  • Example 1 The difference from Example 1 is that the weight ratio of artificial graphite in the negative electrode active material layer: carbon black: acrylic acid-acrylonitrile copolymer: para-aramid fiber is 90:1:5:4.
  • Example 1 The difference from Example 1 is that the weight ratio of artificial graphite in the negative electrode active material layer: carbon black: acrylic acid-acrylonitrile copolymer: para-aramid fiber is 96.1:0.4:1.5:2.
  • Example 1 The difference from Example 1 is that the weight ratio of artificial graphite in the negative active material layer: carbon black: acrylic acid-acrylonitrile copolymer: para-aramid fiber is 96:0.4:3:0.6.
  • Example 1 The difference from Example 1 is that the weight ratio of artificial graphite in the negative electrode active material layer: carbon black: acrylic acid-acrylamide copolymer: para-aramid fiber is 96.6:0.4:2:1.
  • Example 1 The difference from Example 1 is that the weight ratio of artificial graphite in the negative active material layer: carbon black: acrylic acid-acrylate copolymer: para-aramid fiber is 96.6:0.4:2:1.
  • Example 1 The difference from Example 1 is that the weight ratio of artificial graphite in the negative electrode active material layer: carbon black: acrylic acid-acrylonitrile copolymer: polyacrylonitrile-based carbon fiber is 96.6:0.4:2:1.
  • Example 1 The difference from Example 1 is that the weight ratio of artificial graphite in the negative electrode active material layer: carbon black: acrylic acid-acrylonitrile copolymer: pitch-based carbon fiber is 96.6:0.4:2:1.
  • Example 1 The difference from Example 1 is that the weight ratio of artificial graphite in the negative active material layer: carbon black: acrylic acid-acrylonitrile copolymer: viscose-based carbon fiber is 96.6:0.4:2:1.
  • Example 1 The difference from Example 1 is that the weight ratio of artificial graphite in the negative active material layer: carbon black: acrylic acid-acrylonitrile copolymer: polyimide fiber is 96.6:0.4:2:1.
  • Example 1 The difference from Example 1 is that the weight ratio of artificial graphite in the negative active material layer: carbon black: acrylic acid-acrylonitrile copolymer: polyphenylene sulfide fiber is 96.6:0.4:2:1.
  • Example 1 The difference from Example 1 is that the weight ratio of artificial graphite in the negative electrode active material layer: carbon black: acrylic acid-acrylonitrile copolymer: poly-p-phenylenebenzobisoxazole fiber is 96.6:0.4:2:1.
  • Example 1 The difference from Example 1 is that the weight ratio of artificial graphite in the negative active material layer: carbon black: acrylic acid-acrylonitrile copolymer: ultra-high molecular weight polyethylene fiber is 96.6:0.4:2:1.
  • artificial graphite, carbon black, styrene-butadiene rubber (bonding agent), sodium hydroxymethyl cellulose (thickener) and para-aramid fibers in the negative electrode active material layer are 96.6: 0.4:0.8:1.2:1 Dissolved in deionized water, mixed evenly to prepare negative electrode slurry; evenly coated negative electrode slurry on copper foil, after drying, cold pressing, slitting and other processes, the negative electrode was obtained pole piece.
  • Example 2 The difference from Example 1 is that the weight ratio of artificial graphite: carbon black: acrylic acid-acrylonitrile copolymer in the negative electrode active material layer is 97.6:0.4:2.
  • Example 1 The difference from Example 1 is that the weight ratio of artificial graphite in the negative active material layer: carbon black: acrylic acid-acrylonitrile copolymer: para-aramid fiber is 98.1:0.4:0.5:1.
  • Example 1 The difference from Example 1 is that the weight ratio of artificial graphite in the negative electrode active material layer: carbon black: acrylic acid-acrylonitrile copolymer: para-aramid fiber is 97.5:0.4:2:0.1.
  • Example 1 The difference from Example 1 is that the weight ratio of artificial graphite in the negative electrode active material layer: carbon black: acrylic acid-acrylonitrile copolymer: para-aramid fiber is 87.6:0.4:2:10.
  • Example 1 The difference from Example 1 is that the weight ratio of artificial graphite in the negative electrode active material layer: carbon black: acrylic acid-acrylonitrile copolymer: para-aramid fiber is 88.6:0.4:10:1.
  • the Instron metal tensile testing machine is used for testing.
  • the specific steps include: take the negative electrode slurry to be tested and roll it to form a negative electrode active material layer, and then cut it into a test sample with a length of 100 mm, a width of 20 mm, and a thickness of 1 mm.
  • the tensile strength (Rm) of the sample is tested by the machine at 2mm/min, and the test result is shown in icon 2.
  • Rm The unit of Rm is MPa
  • the unit of DCR is m ⁇ .
  • the negative electrode sheets prepared in Examples 1-14 not only have good flexibility, but also can reduce the DC resistance of the secondary battery to increase its energy density.
  • the negative electrode slurry in the negative electrode active material layer contains an appropriate amount of polymer binder and an appropriate amount of toughening fibers, and the two cooperate with each other to reduce the cracking of the negative electrode sheet, thereby achieving the improvement The effect of the flexibility of the negative electrode sheet.
  • the negative electrode slurry in the negative electrode active material layer contains an appropriate amount of toughening fibers and an appropriate amount of polymer binder, which can make the secondary battery have a lower battery impedance and improve the secondary battery.
  • the effect of secondary battery energy density is not limited to

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Abstract

本申请实施例提供一种负极极片、二次电池、电池模块、电池包及用电装置，该负极极片包括负极集流体和负极活性物质层，其中，负极活性物质层设置在负极集流体的至少一个表面，基于负极活性物质层的总重量，负极活性物质层中包含如下重量比的组分:负极活性物质，90.0％-98.6％；聚合物粘结剂，1.0％-5.0％；增韧纤维，0.2％-4.0％。该负极极片在具有较好柔韧性的同时，还能够提升二次电池的能量密度。

Description

负极极片、二次电池、电池模块、电池包及用电装置
相关申请的交叉引用
本申请要求享有于2022年01月27日提交的名称为“负极极片、二次电池、电池模块、电池包及用电装置”的中国专利申请202210099624.8的优先权，该申请的全部内容通过引用并入本文中。
技术领域
本申请涉及二次电池技术领域，具体涉及一种负极极片、二次电池、电池模块、电池包及用电装置。
背景技术
近些年来，随着新能源汽车、储能、通信等领域的快速发展，推动了大容量二次电池的需求，并且这些领域对二次电池的能量密度提出了更高的要求。
目前，二次电池中的电芯主要通过叠片和卷绕工艺制作而成，上述工艺需要电芯的极片具有较好的柔韧性，若极片弯曲时极易开裂，则会导致电芯失效。因此，在提升二次电池能量密度的同时，亟需提升电芯极片的柔韧性。
发明内容
本申请提供了一种负极极片、二次电池、电池模块、电池包及用电装置，该负极极片在具有较好柔韧性的同时，还能够提升二次电池的能量密度。
第一方面，本申请提供了一种负极极片，包括：
负极集流体；
负极活性物质层，设置在所述负极集流体的至少一个表面，基于所述负极活性物质层的总重量,所述负极活性物质层中包含如下重量比的组分:
负极活性物质，90.0％-98.6％；
聚合物粘结剂，1.0％-5.0％；
增韧纤维，0.2％-4.0％。
在上述实施例中，一方面，负极活性物质层中所包含适量的聚合物粘结剂具有良好的粘结性，能够有效的锁住负极活性物质来提升负极极片的强度。另一方面，负极活性物质层中所含有适量的聚合物粘结剂和适量的增韧纤维，两者相互协同以减少负极极片的开裂，从而达到提升负极极片的柔韧性的效果。同时，负极极片的负极活性物质层中含有适量的增韧纤维和适量的聚合物粘结剂，可使二次电池具有较低的电池阻抗，达到提升二次电池能量密度的效果。
在本申请的一些实施例中，所述聚合物粘结剂具有三维交联网状结构。具有三维交联网状结构的聚合物粘结剂具有更好的粘结性，使其更有效的锁住负极活性物质，以提升负极极片的强度。此外，聚合物粘结剂的三维交联网状结构能够更好地与增韧纤维发挥协同作用，进一步减少负极极片的开裂，从而使负极极片具有良好的柔韧性。
在本申请的一些实施例中，所述聚合物粘结剂为含有多个极性官能团的共聚物。极性官能团间可相互作用形成氢键，使聚合物粘结剂内形 成三维交联网状结构。并且氢键的形成可有助于聚合物粘结剂减少负极极片的开裂，从而提升负极极片的柔韧性。
在本申请的一些实施例中，所述极性官能团包含羧基、氰基、酰胺、氨基和羟基中的至少一种。上述极性官能团间容易形成氢键，进而使聚合物粘结剂内更容易形成三维交联网状结构，以减少负极极片的开裂来提升负极极片的柔韧性。
在本申请的一些实施例中，所述共聚物的重均分子量大于或等于300000。共聚物的重均分子量在上述范围内，可以有助于提升聚合物粘结剂的性能，例如三维交联网状结构的强度、拉伸强度和粘结力等。
在本申请的一些实施例中，所述共聚物选自聚丙烯酸-丙烯腈共聚物及其衍生物、丙烯酸-丙烯酰胺及其衍生物和丙烯酸-丙烯酸酯共聚物中的至少一种。聚丙烯酸-丙烯腈共聚物中的羧基与氰基以及丙烯酸-丙烯酸酯共聚物中的羧基间可形成氢键，它们所形成的强分子间力可有效的改善负极极片的开裂，达到提升负极极片柔韧性的效果。
在本申请的一些实施例中，所述增韧纤维的直径在0.1μm-50μm范围内，所述增韧纤维的长径比大于或等于20。增韧纤维的直径在上述范围内，有利于提升负极极片的柔韧性。同时，增韧纤维的长径比大于或等于20，也可进一步提升负极极片的柔韧性。
在本申请的一些实施例中，所述增韧纤维选自芳纶纤维、塑料纤维和碳纤维中的至少一种。上述这些纤维能够与聚合物粘结剂更好地发挥协同作用，以减少负极极片的开裂来使负极极片具有良好的柔韧性。
在本申请的一些实施例中，所述塑料纤维选自聚酰亚胺纤维、聚苯硫醚纤维、聚对苯撑苯并双噁唑纤维和超高分子量聚乙烯纤维中的一种或多种组合；所述碳纤维选自聚丙烯腈基碳纤维、沥青基碳纤维和粘胶基 碳纤维一种或多种组合。上述这些纤维能够与聚合物粘结剂更好地发挥协同作用，以减少负极极片的开裂来使负极极片具有良好的柔韧性。
第二方面，本申请提供了一种二次电池，包括：
正极极片；
负极极片，所述负极极片为上述任一项实施例中所述的负极极片；
隔离膜，设置在所述正极极片和所述负极极片之间；
电解质。
在上述实施例中，二次电池包括上述实施例中的负极极片，该负极极片通过合理选择负极活性物质层中的组分及其含量，使其不仅能够提升负极极片的柔韧性，而且还能够提升二次电池的能量密度。因此，该二次电池具有较好的强度以及较高的能量密度。
第三方面，本申请还提供了一种电池模块，所述电池模块包括上述实施例中所述的二次电池。
在上述实施例中，由于电池模块包括上述实施例中的二次电池，因此，该电池模块具有较高的能量密度。
第四方面，本申请还提供了一种电池包，所述电池包包括上述实施例中所述的电池模块。
在上述实施例中，由于电池包包括上述实施例中的电池模块，因此，该电池包具有较高的能量密度。
第五方面，本申请还提供了一种用电装置，所述用电装置包括上述任一项实施例所述的二次电池、上述实施例中所述的电池模块或上述实施例中所述的电池包。
在上述实施例中，用电装置包括上述实施例的二次电池、上述实施例中的电池模块或上述实施例中的电池包，因此，该用电装置具有较长的续航能力。
附图说明
为了更清楚地说明本申请的实施例，下面将对本申请实施例中所需要使用的附图作简单地介绍，显而易见地，下面所描述的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据附图获得其他的附图。
图1为本申请一些实施例的负极极片的结构示意图；
图2为本申请另一项实施例的负极极片的结构示意图；
图3为本申请一些实施例的负极活性物质层含有的聚丙烯酸-丙烯腈共聚物中的羧基与氰基之间的作用机理图；
图4为本申请一些实施例的负极活性物质层含有的丙烯酸-丙烯酸酯共聚物中的羧基之间的作用机理图；
图5为本申请一些实施例的负极极片缠绕贴合在卷针的示意图；
图6为本申请一些实施例的负极极片缠绕贴合在卷针的示意图；
图7为本申请一些实施例的负极活性物质层所形成的膜片进行对折的示意图；
图8是本申请一些实施实施例的二次电池的示意图；
图9是图5所示的本申请一些实施例的二次电池的分解图；
图10是本申请一些实施例的电池模块的示意图；
图11是本申请一些实施例的电池包的示意图；
图12是图11所示的本申请一些实施例的电池包的分解图；
图13是本申请一些实施例的二次电池用作电源的用电装置的示意图。
在附图中，附图并未按照实际的比例绘制。
标记说明：
1-二次电池；
10-负极极片；
11-负极集流体；
111-第一表面；
112-第二表面；
12-负极活性物质层；
21-壳体；
22-电极组件；
23-盖板；
2-电池模块；
3-电池包；
31-上箱体；
32-下箱体。
具体实施方式
下面将结合附图对本申请的实施例进行详细的描述。以下实施例仅用于更加清楚地说明本申请的实施例，因此只作为示例，而不能以此来限制本申请的保护范围。
除非另有定义，本文所使用的所有的技术和科学术语与属于本申请的技术领域的技术人员通常理解的含义相同；本文中所使用的术语只是为了描述具体的实施例的目的，不是旨在于限制本申请；本申请的说明书和权利要求书及上述附图说明中的术语“包括”和“具有”以及它们的任何 变形，意图在于覆盖不排他的包含。
在本申请实施例的描述中，技术术语“第一”“第二”等仅用于区别不同对象，而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特征的数量、特定顺序或主次关系。在本申请实施例的描述中，“多个”的含义是两个以上，除非另有明确具体的限定。
在本文中提及“实施例”意味着，结合实施例描述的特定特征、结构或特性可以包含在本申请的至少一个实施例中。在说明书中的各个位置出现该短语并不一定均是指相同的实施例，也不是与其它实施例互斥的独立的或备选的实施例。本领域技术人员显式地和隐式地理解的是，本文所描述的实施例可以与其它实施例相结合。
在本申请实施例的描述中，术语“和/或”仅仅是一种描述关联对象的关联关系，表示可以存在三种关系，例如A和/或B，可以表示：单独存在A，同时存在A和B，单独存在B这三种情况。另外，本文中字符“/”，一般表示前后关联对象是一种“或”的关系。
在本申请实施例的描述中，术语“多个”指的是两个以上(包括两个)。
本申请提供了一种二次电池，该二次电池包括正极极片、负极极片、电解质和隔离膜。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。
正极极片
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。
在本申请的一些实施例中，正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，可采用铝箔。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层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、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。
在本申请的一些实施例中，正极活性物质可采用本领域公知的用于电池的正极活性物质。作为示例，正极活性物质可包括以下材料中的至少一种：橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。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正极活性物质的传统材料。这些正极活性物质可以仅单独使用一种，也可以将两种以上组合使用。其中，锂过渡金属氧化物的示例可包括但不限于锂钴氧化物(如LiCoO 2)、锂镍氧化物(如LiNiO 2)、锂锰氧化物(如LiMnO 2、LiMn 2O 4)、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(如LiNi1/ 3Co 1/3Mn 1/3O 2(也可以简称为NCM333)、LiNi 0.5Co 0.2Mn 0.3O 2(也可以简称为NCM523)、LiNi 0.5Co 0.25Mn 0.25O 2(也可以简称为NCM211)、LiNi 0.6Co 0.2Mn 0.2O 2(也可以简称为NCM622)、LiNi 0.8Co 0.1Mn 0.1O 2(也可以简称为NCM811)、锂镍钴铝氧化物(如LiNi 0.85Co 0.15Al 0.05O 2)及其改性化合物等中的至少一种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂(如LiFePO 4(也可以简称为LFP))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO 4)、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中的至少一种。
在本申请的一些实施例中，正极活性物质层还可选地包括粘结剂。作为示例，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。
在本申请的一些实施例中，正极活性物质层还可选地包括导电剂。作为示例，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。
在本申请的一些实施例中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极活性物质、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
负极极片本申请所提供的负极极片10包括负极集流体11和负极活性物质层12，其中，负极活性物质层12设置在负极集流体11的至少一个表面，基于该负极活性物质层12的总重量,负极活性物质层12中包含如下重量比的组分:
负极活性物质，90.0％-98.6％；
聚合物粘结剂，1.0％-5.0％；
增韧纤维，0.2％-4.0％。
在上述实施例中，负极活性物质层12中含有适量的聚合物粘结剂和适量的增韧纤维，两者相互协同以减少负极极片10的开裂，从而达到提升负极极片10的柔韧性的效果。同时，适量的增韧纤维和适量的聚合物粘结剂，可使二次电池具有较低的电池阻抗，达到提升二次电池能量密度的效果。
在本申请的实施例中，负极集流体11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。此外，负极集流体11在厚度方向具有相对的两个表面，负极活性物质层12设置于负极集流体11的两个表面中的任意一者或两者上。
作为一个示例，图1示意性地示出了一种负极极片10，请参照图1，负极极片10包括负极集流体11和负极活性物质层12，其中，负极集流体11在厚度方向上具有相对的第一表面111和第二表面112，负极活性物质层12设置于负极集流体11的第一表面111及第二表面112上。
作为另一个示例，图2示意性地示出了另一种负极极片10，请参照图2，负极极片10包括负极集流体11和负极活性物质层12，其中，负极集流体11在厚度方向上具有相对的第一表面111和第二表面112，负极活性物质层12设置于负极集流体11的第一表面111上。当然，负极活性物质层12也可以是设置于负极集流体11的第二表面112上。
上述负极活性物质层12通过负极浆料涂覆于负极集流体11表面而形成，该负极活性物质层12中负极活性物质的含量设置90.0％～98.6％范围内，并且本申请对负极活性物质的种类不做具体限制，可以根据实际需求进行选择。
在本申请的一些实施例中，负极活性物质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。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。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物质的传统材料。这些负极活性物质可以仅单独使用一种，也可以将两种以上组合使用。
在本申请的实施例中，聚合物粘结剂的含量设置在1.0％-5.0％范围内，可减少负极极片10的开裂及降低二次电池的阻抗，从而实现提升负极极片10的柔韧性及提升二次电池的能量密度。若聚合物粘结剂的含量低于1.0％，则会导致聚合物粘结剂的粘结效果降低，使负极活性物质层12与负极集流体11表面的粘结不够牢固，也就是说，负极活性物质层12易从负极集流体11表面脱落，无法提升负极极片10的柔韧性。若聚合物粘结剂的含量高于5.0％，则会阻碍锂离子在负极活性物质间的传输，使得锂离子不易从中脱离或嵌入，从而增加二次电池的阻抗，影响二次电池的倍率性能。
示例性的，聚合物粘结剂的含量可以但不局限于为1.0％、1.1％、1.2％、1.3％、1.4％、1.5％、1.6％、1.7％、1.8％、1.9％、2.0％、2.1％、2.2％、2.3％、2.4％、2.5％、2.6％、2.7％、2.8％、2.9％、3.0％、3.0％、3.2％、3.3％、3.4％、3.5％、3.6％、3.7％、3.8％、3.9％、4.0％、4.1％、4.2％、4.3％、4.4％、4.5％、4.6％、4.7％、4.8％、4.9％、5.0％。
在本申请的一些实施例中，聚合物粘结剂具有三维交联网状结构。聚合物粘结剂的三维交联网状结构使其具有更好的粘结性，能够有效地锁住负极活性物质来提高负极活性物质层12的强度，从而使负极活性物质层12在加工和使用过程中不易开裂。并且增韧纤维可穿过负极活性物质的间隙与负极活性物质及聚合物粘结剂等固体组分交缠在一起，使聚合物粘结剂更好地与增韧纤维发挥协同作用，进一步减少负极极片10的开裂，从而使负极极片10具有良好的柔韧性。
上述聚合物粘结剂的三维交联网状结构可通过粘结剂内聚合物的官能团相互作用形成。在本申请的一些实施例中，聚合物粘结剂为含有多个极性官能团的共聚物。这些极性官能团间可相互作用形成氢键，使聚合物粘结剂内形成三维交联网状结构。并且氢键的形成可增强负极活性物质层的强度，进而使得负极极片10不易开裂，从而提升负极极片10的柔韧性。
进一步地，在本申请的一些实施例中，聚合物粘结剂中共聚物的极性官能团可包含羧基、氰基、酰胺、氨基和羟基中的至少一种。这些极性官能团间容易形成氢键，进而使聚合物粘结剂内更容易形成三维交联网状结构，以减少负极极片10的开裂来提升负极极片10的柔韧性。
此外，聚合物粘结剂中共聚物还可通过调整重均分子量来提升聚合物的性能来进一步改善负极极片10的柔韧性。在本申请的一些实施例中，共聚物的重均分子量大于或等于300000，共聚物的重均分子量可通过光散射法、超速离心沉降速度法以及凝胶色谱法等方法测定。共聚物的重均分子量设置在该范围内，可以有助于提升聚合物粘结剂的性能，例如三维交联网状结构的强度、拉伸强度和粘结力等。
在本申请的一些实施例中，聚合物粘结剂中的共聚物可选自聚丙烯酸-丙烯腈共聚物及其衍生物、丙烯酸-丙烯酰胺共聚物及其衍生物和丙烯酸-丙烯酸酯共聚物中的至少一种。其中，聚丙烯酸-丙烯腈共聚物中的羧基与氰基(图3所示)以及丙烯酸-丙烯酸酯共聚物中的羧基(图4所示)间可形成氢键，它们所形成的强分子间力可增强负极活性物质层的强度，使得负极极片10不易开裂，达到提升负极极片10柔韧性的效果。
在本申请的实施例中，负极活性物质层12中增韧纤维的含量设置在0.2％-4.0％范围内，可以提升负极极片10的柔韧性以及通过降低二次电池的阻抗来提升其能量密度。若增韧纤维的含量低于0.2％，增韧纤维无法与其它固体组分交缠，从而不能达到改善负极极片10柔韧性的效果；若增韧纤维的含量高于4.0％，则会阻碍锂离子在负极活性物质间的传输，使得锂离子不易从中脱嵌/嵌入，从而增加二次电池的阻抗，导致二次电池的能量密度降低。
示例性的，增韧纤维的含量可以但不局限于为0.2％、0.3％、0.4％、0.5％、0.6％、0.7％、0.8％、0.9％、1.0％、1.1％、1.2％、1.3％、1.4％、1.5％、1.6％、1.7％、1.8％、1.9％、2.0％、2.1％、2.2％、2.3％、2.4％、2.5％、2.6％、2.7％、2.8％、2.9％、3.0％、3.0％、3.2％、3.3％、3.4％、3.5％、3.6％、3.7％、3.8％、3.9％、4.0％。
在本申请的一些实施例中，增韧纤维可采用天然纤维或合成纤维中的一种或两种，只要能够提升负极极片10的柔韧性即可。
在本申请的一些实施例中，增韧纤维采用合成纤维。示例性的，合成纤维可选自芳纶纤维、塑料纤维和碳纤维中的至少一种。上述这些合成纤维能够与聚合物粘结剂更好地发挥协同作用，以减少负极极片10的开裂来使负极极片10具有良好的柔韧性。
示例性的，芳纶纤维可为对位芳纶纤维和间位芳纶纤维中的任一种或两种混合的混合物；塑料纤维可为聚酰亚胺纤维、聚苯硫醚纤维、聚对苯撑苯并双噁唑纤维和超高分子量聚乙烯纤维中的任一种或多种混合的混合物，此处的超高分子量聚乙烯纤维是指分子量在100万-500万的聚乙 烯所纺出的纤维；碳纤维可为聚丙烯腈基碳纤维、沥青基碳纤维和粘胶基碳纤维中的任一种或多种混合的混合物，还可为碳纳米纤维或碳纳米管。
进一步地，在本申请的一些实施例中，增韧纤维的直径在0.1μm-50μm范围内，增韧纤维的直径设置在该范围内，有利于进一步提升负极极片10的柔韧性。
示例性的，增韧纤维的直径可以但不局限于为0.1μm、0.2μm、0.3μm、0.4μm、0.5μm、0.6μm、0.7μm、0.8μm、0.9μm、1μm、2μm、3μm、4μm、5μm、6μm、7μm、8μm、9μm、10μm、11μm、12μm、13μm、14μm、15μm、16μm、17μm、18μm、19μm、20μm、21μm、22μm、23μm、24μm、25μm、26μm、27μm、28μm、29μm、30μm、31μm、32μm、33μm、34μm、35μm、37μm、38μm、39μm、40μm、41μm、42μm、43μm、44μm、45μm、46μm、47μm、48μm、49μm、50μm。
此外，增韧纤维的长径比大于或等于20，此处的长径比是指增韧纤维的长度与直径的比值，并通过电子显微镜来确定增韧纤维的长度、直径和长径比。增韧纤维的长径比大于或等于20，也可进一步提升负极极片10的柔韧性。
示例性的，增韧纤维的长径比可以但不局限于为20、21、22、23、24、25、26、27、28、29、30、31、32、33、34、35、36、37、38、39、40、41、42、43、44、45、46、47、48、49、50或超过50。
在本申请的一些实施例中，负极活性物质层中还包括导电剂，该导电剂在该负极活性物质层内的重量比为0.2％～1.0％。示例性的，导电剂为石墨、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一种或多种。
另外，本申请还提供了一种负极极片10的制造方法，该制造方法包括如下步骤：
将负极活性物质、导电剂、聚合物粘结剂、增韧纤维和溶剂按照上述比例混合后，得到负极浆料；
将上述负极浆料经过辊压形成负极活性物质层；
将负极活性物质层和负极集流体复合，经烘干和分切等工序，得到负极极片。
在本申请的一些实施例中，负极浆料的制备具体包括如下步骤：
将增韧纤维打碎，打碎后的增韧纤维与负极活性物质和导电剂搅拌混合均匀，得到混合固体；
向上述混合固体内添加聚合物粘结剂和溶剂进行混合，得到负极浆料。
基于同一个技术构思，本申请提供了一种二次电池，包括：
正极极片；
负极极片，所述负极极片为上述任一项实施例中所述的负极极片；
隔离膜，设置在所述正极极片和所述负极极片之间；
电解质。
在上述实施例中，二次电池包括上述实施例中的负极极片，该负极极片通过合理选择负极活性物质层中的组分及其含量，使其不仅能够提升负极极片的柔韧性，而且还能够提升二次电池的能量密度。因此，该二次电池具有较好的强度以及较高的能量密度。
隔离膜
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。
在本申请的一些实施例中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
电解质
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的或全固态的。
在本申请的一些实施例中，电解质包括电解质盐和溶剂。
在本申请的一些实施例中，电解质盐可选自六氟磷酸锂、四氟硼酸锂、高氯酸锂、六氟砷酸锂、双氟磺酰亚胺锂、双三氟甲磺酰亚胺锂、三氟甲磺酸锂、二氟磷酸锂、二氟草酸硼酸锂、二草酸硼酸锂、二氟二草酸磷酸锂及四氟草酸磷酸锂中的至少一种。
在本申请的一些实施例中，溶剂可选自碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的至少一种。
在本申请的一些实施例中，电解质还可选地包括添加剂。例如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。
在本申请的一些实施例中，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。具体的，将上述正极极片、隔离膜、负极极片按顺序堆叠好，使隔离膜处于正极极片、负极极片之间起到隔离的作用，得到裸电芯，也可以是经卷绕后得到裸电芯；在裸电芯上连接极耳，并将电芯置于包装外壳中，再经过加热去除多余的水，然后注入电解质并封口；最后经过静置、热冷压、化成、整形、容量测试等工序，得到本申请的二次电池。
在本申请的一些实施例中，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。
在本申请的一些实施例中，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，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
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。例如，图8是作为一个示例的方形结构的二次电池1。
在本申请的一些实施例中，参照图9，外包装可包括壳体21和盖板23。其中，壳体21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21具有与容纳腔连通的开口，盖板23能够盖设于开口，以封闭容纳腔。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22。电极组件22封装于所述容纳腔内。电解质浸润于电极组件22中。二次电池8所含电极组件22的数量可以为一个或多个，本领域技术人员可根据具体实际需求进行选择。
在本申请的一些实施例中，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一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。
图10是作为一个示例的电池模块2。参照图10，在电池模块2中，多个二次电池1可以是沿电池模块2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1进行固定。
可选地，电池模块2还可以包括具有容纳空间的外壳，多个二次电池1容纳于该容纳空间。
在本申请的一些实施例中，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为一个或多个，具体数量本领域技术人员可根据电池包的应用和容量进行选择。
图11和图12是作为一个示例的电池包3。参照图11和图12，在电池包3中可以包括电池箱和设置于电池箱中的多个电池模块2。电池箱包括上箱体31和下箱体32，上箱体31能够盖设于下箱体32，并形成用于容纳电池模块2的封闭空间。多个电池模块2可以按照任意的方式排布于电池箱中。
另外，本申请还提供一种用电装置，该用电装置包括本申请提供的二次电池、电池模块、或电池包中的至少一种。二次电池、电池模块、或电池包可以用作用电装置的电源，也可以用作用电装置的能量存储单元。用电装置可以包括移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行 车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能***等，但不限于此。
作为用电装置，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13是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用二次电池作为电源。
下述实施例更具体地描述了本申请公开的内容，这些实施例仅仅用于阐述性说明，因为在本申请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重量计，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
负极浆料制备
负极浆料中原料组分分别为人造石墨、炭黑、丙烯酸-丙烯腈共聚物和对位芳纶纤维，其中，对位芳纶纤维的直径为0.5μm，对位芳纶纤维的长径比为40。负极浆料的具体制备步骤如下：
(1)将对位芳纶纤维用高速剪切机分散打碎；
(2)将人造石墨、炭黑和对位芳纶纤维以1000rpm/min的速率搅拌30min，待混合均匀后，得到混合固体；
(3)将丙烯酸-丙烯腈共聚物和去离子水添加至上述混合固体中，捏合30min后，得到负极浆料，其中，负极浆料中的固含量为70％。
负极极片的制备
将负极浆料料经辊压机辊压得到负极活性物质层，其中，基于所述负极活性物质层的总重量，负极活性物质层中各组分的重量比为 96.6:0.4:2:1，该负极活性物质层与铜箔复合，经过烘箱100℃烘干后分切，得到负极极片。
正极极片的制备
将镍钴锰三元材料、炭黑、聚偏二氟乙烯、N-甲基吡咯烷酮按重量比为67.34:28.86:2.7:1.1搅拌混合均匀，得到正极浆料；然后将正极浆料均匀涂覆于正极集流体上，之后经过烘干、冷压、分切，得到正极极片。
电解质的制备
在氩气气氛手套箱中(H 2O<0.1ppm，O 2<0.1ppm)，将有机溶剂EC和EMC按照体积比3:7混合均匀，再加入12.5％LiPF 6锂盐溶解于有机溶剂中，搅拌均匀，得到电解质。
隔离膜
以聚丙烯膜作为隔离膜。
二次电池的制备
将上述正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正、负极片之间起到隔离的作用；然后卷绕得到裸电芯，给裸电芯焊接极耳，并将裸电芯装入铝壳中，并在80℃下烘烤去除水分，随即注入上述电解质并封口；最后经过静置、热冷压、化成、整形等工序，得到本实施例的二次电池。
实施例2
与实施例1不同的是，负极活性物质层中的人造石墨：炭黑：丙烯酸-丙烯腈共聚物：对位芳纶纤维的重量比为98.6:0.2:1:0.2。
实施例3
与实施例1不同的是，负极活性物质层中的人造石墨：炭黑：丙烯酸-丙烯腈共聚物：对位芳纶纤维的重量比为90:1:5:4。
实施例4
与实施例1不同的是，负极活性物质层中的人造石墨：炭黑：丙烯酸-丙烯腈共聚物：对位芳纶纤维的重量比为96.1:0.4:1.5:2。
实施例5
与实施例1不同的是，负极活性物质层中的人造石墨：炭黑：丙烯酸-丙烯腈共聚物：对位芳纶纤维的重量比为96:0.4:3:0.6。
实施例6
与实施例1不同的是，负极活性物质层中的人造石墨：炭黑：丙烯酸-丙烯酰胺共聚物：对位芳纶纤维的重量比为96.6:0.4:2:1。
实施例7
与实施例1不同的是，负极活性物质层中的人造石墨：炭黑：丙烯酸-丙烯酸酯共聚物：对位芳纶纤维的重量比为96.6:0.4:2:1。
实施例8
与实施例1不同的是，负极活性物质层中的人造石墨：炭黑：丙烯酸-丙烯腈共聚物：聚丙烯腈基碳纤维的重量比为96.6:0.4:2:1。
实施例9
与实施例1不同的是，负极活性物质层中的人造石墨：炭黑：丙烯酸-丙烯腈共聚物：沥青基碳纤维的重量比为96.6:0.4:2:1。
实施例10
与实施例1不同的是，负极活性物质层中的人造石墨：炭黑：丙烯酸-丙烯腈共聚物：粘胶基碳纤维的重量比为96.6:0.4:2:1。
实施例11
与实施例1不同的是，负极活性物质层中的人造石墨：炭黑：丙烯酸-丙烯腈共聚物：聚酰亚胺纤维的重量比为96.6:0.4:2:1。
实施例12
与实施例1不同的是，负极活性物质层中的人造石墨：炭黑：丙烯酸-丙烯腈共聚物：聚苯硫醚纤维的重量比为96.6:0.4:2:1。
实施例13
与实施例1不同的是，负极活性物质层中的人造石墨：炭黑：丙烯酸-丙烯腈共聚物：聚对苯撑苯并双噁唑纤维的重量比为96.6:0.4:2:1。
实施例14
与实施例1不同的是，负极活性物质层中的人造石墨：炭黑：丙烯酸-丙烯腈共聚物：超高分子量聚乙烯纤维的重量比为96.6:0.4:2:1。
对比例1
与实施例1不同的是，负极活性物质层中的人造石墨、碳黑、丁苯橡胶(粘结剂)、羟甲基纤维素钠(增稠剂)和对位芳纶纤维按照重量比为96.6：0.4:0.8:1.2:1溶于去离子水中，混合均匀后制备成负极浆料；将负极浆料均匀涂覆在铜箔上，经过烘干、冷压、分切等工序，得到负极极片。
对比例2
与实施例1不同的是，负极活性物质层中的人造石墨：炭黑：丙烯酸-丙烯腈共聚物的重量比为97.6:0.4:2。
对比例3
与实施例1不同的是，负极活性物质层中的人造石墨：炭黑：丙烯酸-丙烯腈共聚物：对位芳纶纤维的重量比为98.1:0.4:0.5:1。
对比例4
与实施例1不同的是，负极活性物质层中的人造石墨：炭黑：丙烯酸-丙烯腈共聚物：对位芳纶纤维的重量比为97.5:0.4:2:0.1。
对比例5
与实施例1不同的是，负极活性物质层中的人造石墨：炭黑：丙烯酸-丙烯腈共聚物：对位芳纶纤维的重量比为87.6:0.4:2:10。
对比例6
与实施例1不同的是，负极活性物质层中的人造石墨：炭黑：丙烯酸-丙烯腈共聚物：对位芳纶纤维的重量比为88.6:0.4:10:1。
测试部分
(1)负极极片的柔韧性测试
将(230mg/1540mm2)的负极片缠绕贴合在不同直径的卷针上，观测其是否有裂纹，可参照图5和图6，测试结果如表2所示。
(2)负极活性物质层的拉伸测试
采用Instron金属拉力试验机进行测试，具体步骤包括：取待测负极浆料经辊压形成负极活性物质层，然后将其裁成长为100mm、宽为 20mm、厚度为1mm的测试样品，用拉力试验机以2mm/min拉伸测试样品的拉伸强度(Rm)，测试结果图标2所示。
(3)二次电池的直流阻抗测试
在25℃下，将二次电池以1/3C恒流充电至4.3V，再以4.3V恒定电压充电至电流为0.05C，搁置5min后，然后以1/3C放电25s，将二次电池的荷电状态(SOC)调整为90％；
将90％SOC的二次电池静置60min后，3C放电30s，完成90％SOC下30s放电直流内阻测试。控制1/3C放电时间，可以得到50％SOC下放电时间为30s的二次电池的直流内阻(DCR)，测试结果如表2所示。
实施例1-14和对比例1-6的负极活性物质层中的各组分重量比如表1所示，并且实施例1-14和对比例1-6中负极极片及二次电池的测试结果示于表2。
表1
Figure PCTCN2022093124-appb-000001
Figure PCTCN2022093124-appb-000002
Figure PCTCN2022093124-appb-000003
另注：在表1中，基于负极活性物质层的总重量，各组分在负极活性物质层中比例，单位为％。
表2
Figure PCTCN2022093124-appb-000004
注：Rm的单位为MPa；
DCR的单位为mΩ。
根据表2的测试结果看出，实施例1-14所制备得到的负极极片在具有良好的柔韧性的同时，还可以降低二次电池的直流阻抗来提升其能量密度。
通过实施例1和对比例1-4可知，负极活性物质层中负极浆料含有适量的聚合物粘结剂和适量的增韧纤维，两者相互协同以减少负极极片的开裂，从而达到提升负极极片的柔韧性的效果。
通过实施例1和对比例5-6可知，负极活性物质层中负极浆料含有适量的增韧纤维和适量的聚合物粘结剂，可使二次电池具有较低的电池阻抗，达到提升二次电池能量密度的效果。
虽然已经参考优选实施例对本申请进行了描述，但在不脱离本申请的范围的情况下，可以对其进行各种改进并且可以用等效物替换其中的部件。尤其是，只要不存在结构冲突，各个实施例中所提到的各项技术特征均可以任意方式组合起来。本申请并不局限于文中公开的特定实施例，而是包括落入权利要求的范围内的所有实施例。

Claims (13)

  1. 一种负极极片，包括：
    负极集流体；
    负极活性物质层，设置在所述负极集流体的至少一个表面，基于所述负极活性物质层的总重量,所述负极活性物质层中包含如下重量比的组分:
    负极活性物质，90.0％-98.6％；
    聚合物粘结剂，1.0％-5.0％；
    增韧纤维，0.2％-4.0％。
  2. 根据权利要求1所述的负极极片，其中，所述聚合物粘结剂具有三维交联网状结构。
  3. 根据权利要求1或2所述的负极极片，其中，所述聚合物粘结剂为含有多个极性官能团的共聚物。
  4. 根据权利要求3所述的负极极片，其中，所述极性官能团包含羧基、氰基、酰胺、氨基和羟基中的至少一种。
  5. 根据权利要求3或4所述的负极极片，其中，所述共聚物的重均分子量大于或等于300000。
  6. 根据权利要求3-5中任一项所述的负极极片，其中，所述共聚物选自聚丙烯酸-丙烯腈共聚物及其衍生物、丙烯酸-丙烯酰胺及其衍生物和丙烯酸-丙烯酸酯共聚物及其衍生物中的至少一种。
  7. 根据权利要求1-6中任一项所述的负极极片，其中，所述增韧纤维的直径在0.1μm-50μm范围内，所述增韧纤维的长径比大于或等于20。
  8. 根据权利要求1-7中任一项所述的负极极片，其中，所述增韧纤维选自芳纶纤维、塑料纤维和碳纤维中的至少一种。
  9. 根据权利要求8所述的负极极片，其中，所述塑料纤维选自聚酰亚胺纤维、聚苯硫醚纤维、聚对苯撑苯并双噁唑纤维和超高分子量聚乙烯纤维中的一种或多种组合；
    所述碳纤维选自聚丙烯腈基碳纤维、沥青基碳纤维和粘胶基碳纤维一种或多种组合。
  10. 一种二次电池，包括：
    正极极片；
    负极极片，所述负极极片为权利要求1-9中任一项所述的负极极片；
    隔离膜，设置在所述正极极片和所述负极极片之间；
    电解质。
  11. 一种电池模块，所述电池模块包括权利要求10中所述的二次电池。
  12. 一种电池包，所述电池包包括权利要求11中所述的电池模块。
  13. 一种用电装置，包括权利要求10中所述的二次电池、权利要求11中所述的电池模块或权利要求12中所述的电池包。
PCT/CN2022/093124 2022-01-27 2022-05-16 负极极片、二次电池、电池模块、电池包及用电装置 WO2023142308A1 (zh)

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