WO2023178470A1 - 电化学装置和电子装置 - Google Patents

电化学装置和电子装置 Download PDF

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Publication number
WO2023178470A1
WO2023178470A1 PCT/CN2022/081964 CN2022081964W WO2023178470A1 WO 2023178470 A1 WO2023178470 A1 WO 2023178470A1 CN 2022081964 W CN2022081964 W CN 2022081964W WO 2023178470 A1 WO2023178470 A1 WO 2023178470A1
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Prior art keywords
pole piece
binder
electrochemical device
thermoplastic polymer
arc
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PCT/CN2022/081964
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English (en)
French (fr)
Inventor
郭华鑫
李嘉文
石长川
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宁德新能源科技有限公司
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Application filed by 宁德新能源科技有限公司 filed Critical 宁德新能源科技有限公司
Priority to CN202280006004.3A priority Critical patent/CN116261796A/zh
Priority to PCT/CN2022/081964 priority patent/WO2023178470A1/zh
Publication of WO2023178470A1 publication Critical patent/WO2023178470A1/zh

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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
    • 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
    • H01M4/62—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

  • the present application relates to the field of electrochemical energy storage, and in particular to electrochemical devices and electronic devices.
  • the demand for arc-shaped electrochemical devices continues to increase.
  • the activity of the pole pieces The bonding performance between the material layer and the current collector under high curvature and the arc stability of the pole piece have a great impact on the cycle performance and rate performance of the electrochemical device.
  • the existing binders have high crystallinity and curing cross-linking degree, and are highly rigid and difficult to deform. The large internal stress generated during bending can easily cause the pole pieces to crack, making it difficult to adapt to the application requirements of arc-shaped batteries.
  • an electrochemical device in some embodiments of the present application, includes a pole piece.
  • the pole piece includes a current collector and an active material layer located on at least one side of the current collector; the active material layer includes an active material and a binder.
  • the binder includes bonding polymers and thermoplastic polymers, and the curvature radius R of the pole piece is 5mm to 200mm.
  • the molecular chains in the binder have good mobility.
  • the pole pieces bend into arcs with the electrochemical device. Stress concentration occurs in parts with high curvature.
  • the binder absorbs energy through plastic deformation to avoid interface loss and pole piece cracking.
  • the amount of permanent deformation produced by the adhesive can limit the arc rebound rate, thereby obtaining an arc-shaped pole piece with better curvature.
  • the adhesive in this application ensures bonding strength through the anchoring effect of bonding polymers. It uses thermoplastic polymers with good plasticity and low elasticity as plasticizers to provide the ability to undergo permanent deformation, which can change the curvature of the arc-shaped pole piece. The rebound rate is reduced, the pole piece has good processing type, and when the curvature radius of the pole piece is in the range of 5mm to 200mm, the electrochemical device has good cycle performance.
  • the radius of curvature R of the pole piece is 25 mm to 100 mm, thereby meeting the requirement for an arc-shaped pole piece and preventing desorption of the active material layer from the current collector.
  • the thermoplastic polymer includes at least one of polyethylene, polypropylene, polyvinyl chloride, polycarbonate, dendritic polyamidoamine, ethylene vinyl acetate copolymer, hyperbranched acrylic acid or hyperbranched acrylate.
  • the crystallinity of the thermoplastic polymer is less than 50% to prevent excessive stiffness.
  • the weight average molecular weight of the thermoplastic polymer is 5,000 to 80,000, thereby ensuring processing performance.
  • the thermoplastic polymer has an elongation at break of 100% to 500%, thereby preventing arc rebound of the pole piece.
  • the binding polymer includes polyvinylidene fluoride, styrene-butadiene emulsion, carboxymethylcellulose, polyaniline, polyacrylic acid, alginate, guar gum, gum arabic, xanthan gum, gelatin, shell At least one of polysaccharide, ⁇ -cyclodextrin, polyethylenimine, polyimide or water-based epoxy resin.
  • the mass percentage of the thermoplastic polymer in the binder is 0.5% to 50% based on the total mass of the binder, thereby ensuring both plasticity and adhesion.
  • the pole piece is a positive electrode, and the mass percentage of the thermoplastic polymer in the binder is 0.5% to 10%.
  • the pole piece is a negative electrode
  • the mass percentage of thermoplastic polymer in the binder is 1% to 50%, so as to be compatible with the positive electrode and ensure bonding with sufficient plasticity.
  • the adhesive force of the agent In some embodiments, the adhesive has a tensile permanent deformation of 50% to 100%, indicating good plasticity.
  • An embodiment of the present application also provides an electronic device, including the above electrochemical device.
  • the adhesive includes adhesive polymers and thermoplastic polymers. Therefore, the adhesive is a plastic adhesive.
  • the molecular chains in the adhesive have good mobility.
  • the pole pieces are bent into shape as they are bent. Stress concentration occurs in arc-shaped parts with high curvature.
  • the adhesive absorbs energy through plastic deformation to avoid problems of interface loss and pole piece cracking. At the same time, the adhesive produces permanent deformation and limits the arc rebound rate, thereby obtaining a better curvature. High arc.
  • the adhesive provided in this application ensures bonding strength through the anchoring effect of bonding polymers.
  • thermoplastic polymers with good plasticity and low elasticity are added as plasticizers to provide the ability to undergo permanent deformation and enable arc-shaped electrochemical
  • the arc rebound rate of the device is reduced, the pole piece has good processability, and the arc-shaped pole piece has a curvature radius of 5mm to 200mm and still has good cycle performance.
  • Figure 1 is a schematic diagram of an electrochemical device.
  • Figure 2 is a schematic diagram of the composition of an adhesive and a schematic diagram of the adhesive under stress.
  • the bonding performance between the active material layer of the pole piece and the current collector under high curvature and the arc stability of the pole piece have a great impact on the cycle performance and rate performance of the electrochemical device. Influence.
  • the existing binders have a high degree of crystallinity and curing cross-linking, and are highly rigid and difficult to deform. The large internal stress generated during bending can easily cause the pole pieces to crack, making it difficult to adapt to the application requirements of arc-shaped batteries.
  • the softness of the active material bonding layer is increased by reducing the crystallinity to achieve a flexible effect.
  • Arc springback has a great relationship with the mechanical properties of the pole piece material itself and the stress concentration during the bending process.
  • most methods to suppress arc rebound are to add external force constraints in the packaging stage, which is achieved through steel shells or increasing the ductility of packaging bags. This method increases manufacturing costs and is not conducive to the thinning of electrochemical devices.
  • the binder in the pole piece not only ensures the integrity of the pole piece, but also has a great impact on the stability and cycle performance of the battery.
  • an electrochemical device is proposed.
  • the electrochemical device can be, for example, a lithium-ion battery, a sodium-ion battery, etc.
  • the electrochemical device includes a pole piece.
  • the electrochemical device It can include a positive electrode 1, a separator 2 and a negative electrode 3.
  • the pole piece can be either the positive electrode 1 or the negative electrode 3.
  • the pole piece includes a current collector and an active material layer located on at least one side of the current collector; the current collector can be made of copper foil or aluminum foil, and the active material layer includes active materials and adhesives, and the adhesives include adhesive polymers and thermoplastic polymers.
  • the radius of curvature R of the pole piece is 5mm to 200mm.
  • the adhesive includes adhesive polymer 4 and thermoplastic polymer 5, so the adhesive has plasticity.
  • the adhesive is subjected to external force F When the molecular chain moves, irreversible deformation occurs, showing plasticity.
  • the molecular chains in the binder have good mobility.
  • the pole pieces are bent into arcs with the electrochemical device. Stress concentration occurs in parts with high curvature.
  • the binder absorbs energy through plastic deformation to avoid interface loss and pole piece cracking.
  • the plastic binder produces permanent deformation and limits the arc rebound rate, thereby obtaining an arc-shaped electrochemical device with better curvature.
  • the adhesive provided in this application ensures bonding strength through the anchoring effect of bonding polymers.
  • thermoplastic polymers with good plasticity and low elasticity are added as plasticizers to provide the ability to undergo permanent deformation and enable arc-shaped
  • the arc rebound rate of the electrochemical device is reduced, the pole piece has good processability, and it still has good cycle performance when the curvature radius reaches the range of 5mm to 200mm.
  • the binder in this application includes both bonding polymers and thermoplastic polymers.
  • the bonding polymers usually use polyvinylidene fluoride, styrene-butadiene rubber emulsion, carboxymethyl cellulose, etc. If only bonding polymers are used, due to the Vinylidene fluoride has high crystallinity. When the electrode is bent by external force, the crystal structure is destroyed and cracks occur, which can easily cause the active material layer to fall from the current collector.
  • Styrene-butadiene rubber emulsion has strong adhesion, but rubber-based polymers have high elasticity and can quickly recover from large deformations, making it difficult to maintain the stability of the arc.
  • Carboxymethylcellulose has a high elastic modulus and is highly brittle after curing.
  • Arc-shaped batteries using carboxymethylcellulose as a binder have large internal stress after bending, which can easily cause stress concentration and the pole pieces can easily crack, affecting the performance of the battery. performance.
  • If only thermoplastic polymers are used as binders the problem of stress concentration during processing can be improved.
  • thermoplastic polymers are mostly linear polymers with insufficient adhesion, making it difficult to ensure the integrity of the electrode.
  • the adhesive of this application uses both bonding polymers and thermoplastic polymers, which not only ensures the bonding force, but also improves the plastic deformation ability of the adhesive in the pole piece, allowing the pole piece to bend into an arc shape and pass the plastic deformation under high curvature.
  • thermoplastic polymers can increase the plastic deformation ability of the binder, allowing the electrochemical device to achieve a higher arc.
  • the radius of curvature R of the pole piece is 25 mm to 100 mm.
  • the semi-radius of curvature of the pole piece represents the arc of the pole piece. The smaller the radius of curvature, the greater the arc. If the radius of curvature is too small, it will easily cause desorption between the active material layer in the pole piece and the current collector. If the radius of curvature is too large, the arc of the pole piece will be affected. Insufficient, it may not meet the demand.
  • the curvature radius R of the pole piece is 25 mm to 100 mm, so as to meet the demand for arc-shaped pole pieces and prevent the active material layer from desorbing from the current collector.
  • the thermoplastic polymer includes at least one of polyethylene, polypropylene, polyvinyl chloride, polycarbonate, dendritic polyamidoamine, ethylene vinyl acetate copolymer, hyperbranched acrylic acid or hyperbranched acrylate. A sort of. In some embodiments, the mass percentage of vinyl acetate in the ethylene vinyl acetate copolymer is 15% to 40%.
  • the crystallinity of the thermoplastic polymer is less than 50%. In some embodiments, the crystallinity of the thermoplastic polymer will affect the stiffness of the thermoplastic polymer. If the crystallinity is too high, the stiffness will be too high, which may cause difficulty in deformation.
  • the weight average molecular weight of the thermoplastic polymer ranges from 5,000 to 80,000. In some embodiments, the weight average molecular weight is closely related to the usage performance and processing performance of the polymer material. If the relative weight average molecular weight is too low, the mechanical strength and toughness of the material will be affected. If the weight average molecular weight is too high, the melt viscosity of the polymer will increase, making processing and molding difficult.
  • the thermoplastic polymer has an elongation at break of 100% to 500%. In some embodiments, if the elongation at break of the thermoplastic polymer is too low, the pole piece may cause the thermoplastic polymer to break during the bending process, causing the flexibility of the pole piece to be affected. If the elongation at break of the thermoplastic polymer is too low, the thermoplastic polymer may break. If it is large, the energy that the thermoplastic polymer can absorb during plastic deformation may be insufficient, which is not conducive to preventing the arc rebound of the pole piece.
  • the binding polymer includes polyvinylidene fluoride, styrene-butadiene emulsion, carboxymethylcellulose, polyaniline, polyacrylic acid, alginate, guar gum, gum arabic, xanthan gum, At least one of gelatin, chitosan, ⁇ -cyclodextrin, polyethylenimine, polyimide or water-based epoxy resin.
  • the mass percentage of the thermoplastic polymer in the binder is 0.5% to 50% based on the total mass of the binder.
  • the mass percentage of thermoplastic polymers as plasticizers in the binder ranges from 0.5% to 50%.
  • Thermoplastic polymers have flexible molecular chain segments that deform and bond through molecular chain extension and slippage. Polymers can coat or entangle active materials, play a bridging role between active materials and current collectors, and take advantage of high adhesion. By adjusting the ratio of bonding polymers and thermoplastic polymers, the composite obtained binder has both plasticity and adhesiveness.
  • the pole piece material After being bent by external force, the pole piece material undergoes irreversible deformation internally, which can effectively suppress the curvature of the arc-shaped battery. rebound.
  • Adding thermoplastic polymers to the pole piece can reduce the arc rebound rate of the electrochemical device to 1% to 5%, and the pole piece has good processability and still has good cycle performance when the curvature radius reaches 5mm to 200mm. If the mass percentage of thermoplastic polymers in the binder is too low, it may not be able to provide sufficient plasticity for the binder. If the mass percentage of thermoplastic polymers in the binder is too high, it may cause adhesion. The adhesive strength of the agent is insufficient.
  • the pole piece is a positive electrode
  • the mass percentage of the thermoplastic polymer in the binder is 0.5% to 10%.
  • the mass percentage of thermoplastic polymers in the binder in the positive electrode and the negative electrode may be different. This is because the active materials and binders used in the positive electrode and the negative electrode may be different, and the plasticity exhibited by the positive electrode may be different. It is usually stronger than the negative electrode, so the mass percentage of plastic polymers in the binder of the positive electrode can be relatively higher than the mass percentage of plastic polymers in the binder of the negative electrode, so that the positive electrode and the negative electrode bend at the same degree.
  • the arc rebound shown is similar to avoid misalignment of the positive and negative electrodes due to different arc rebound.
  • the mass percentage of the thermoplastic polymer in the positive electrode in the binder is 0.5% to 10%, which can ensure the adhesive force of the binder while ensuring that the positive electrode has sufficient plasticity.
  • the pole piece is the negative electrode
  • the mass percentage of the thermoplastic polymer in the binder is 1% to 50%, so as to be compatible with the positive electrode and have sufficient plasticity. Ensure the adhesive strength of the adhesive.
  • the tensile permanent deformation of the adhesive ranges from 50% to 100%.
  • the tensile permanent deformation of the adhesive is measured as follows: the adhesive is placed on a horizontal glass plate and allowed to dry naturally for 24 hours, then dried in a constant temperature oven at 60°C to constant weight to obtain an adhesive film, and a dumbbell-shaped cutter is used. Cut it into a dumbbell-shaped standard sample, and use a universal electronic tensile testing machine for tensile testing. The film is maintained at 100% fixed elongation for 10 minutes and then immediately releases the load, allowing it to recover freely for 10 minutes. The residual deformation is measured and the tensile permanent deformation is calculated. In this embodiment, the permanent deformation of the adhesive after 100% fixed elongation reaches 50%, which indicates that the adhesive has good plasticity and small arc rebound.
  • the pole piece is a positive electrode
  • the active material layer is a positive active material layer
  • the active material is a positive electrode material.
  • the cathode material includes lithium cobalt oxide, lithium iron phosphate, lithium iron manganese phosphate, sodium iron phosphate, lithium vanadium phosphate, sodium vanadium phosphate, lithium vanadyl phosphate, sodium vanadyl phosphate, lithium vanadate, manganate At least one of lithium, lithium nickelate, lithium nickel cobalt manganate, lithium-rich manganese-based materials, or lithium nickel cobalt aluminate.
  • the positive active material layer may further include a conductive agent.
  • the conductive agent in the positive active material layer may include at least one of conductive carbon black, Ketjen black, flake graphite, graphene, carbon nanotubes or carbon fibers.
  • the mass ratio of the cathode material, the conductive agent and the binder in the cathode active material layer may be (80 to 99): (0.1 to 10): (0.1 to 10).
  • the thickness of the positive active material layer may be 10 ⁇ m to 500 ⁇ m. It should be understood that the above is only an example, and the positive active material layer of the positive electrode may adopt any other suitable materials, thicknesses and mass ratios.
  • Al foil can be used as the current collector of the positive electrode.
  • the thickness of the current collector of the positive electrode may be 1 ⁇ m to 200 ⁇ m.
  • the positive active material layer may be coated on only a partial area of the current collector of the positive electrode.
  • the active material layer is a negative active material layer.
  • the negative active material layer includes a negative electrode material, and the negative electrode material may include at least one of graphite, hard carbon, silicon, silicon oxide, or organic silicon.
  • a conductive agent may also be included in the negative active material layer.
  • the conductive agent in the negative active material layer may include at least one of conductive carbon black, Ketjen black, flake graphite, graphene, carbon nanotubes or carbon fibers.
  • the mass ratio of the negative electrode material, the conductive agent and the binder in the negative electrode active material layer may be (80 to 98): (0.1 to 10): (0.1 to 10). It should be understood that the above are only examples and any other suitable materials and mass ratios may be used.
  • the current collector of the negative electrode may be at least one of aluminum foil, copper foil, nickel foil or carbon-based current collector.
  • the release film includes at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, or aramid.
  • polyethylene includes at least one selected from high-density polyethylene, low-density polyethylene, or ultra-high molecular weight polyethylene.
  • the thickness of the isolation film ranges from about 5 ⁇ m to 500 ⁇ m.
  • the surface of the isolation membrane may further include a porous layer.
  • the porous layer is disposed on at least one surface of the base material of the isolation membrane.
  • the porous layer includes inorganic particles and a binder.
  • the inorganic particles are selected from aluminum oxide (Al 2 O 3 ), silicon oxide (SiO 2 ), magnesium oxide (MgO), titanium oxide (TiO 2 ), hafnium dioxide (HfO 2 ), tin oxide (SnO 2 ), ceria (CeO 2 ), nickel oxide (NiO) ), zinc oxide (ZnO), calcium oxide (CaO), zirconium oxide (ZrO 2 ), yttrium oxide (Y 2 O 3 ), silicon carbide (SiC), boehmite, aluminum hydroxide, magnesium hydroxide, hydroxide At least one of calcium or barium sulfate.
  • the pores of the isolation film have a diameter in the range of about 0.01 ⁇ m to 1 ⁇ m.
  • the binder of the porous layer is selected from polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethylcellulose, poly At least one of vinylpyrrolidone, polyvinyl ether, polymethylmethacrylate, polytetrafluoroethylene or polyhexafluoropropylene.
  • the porous layer on the surface of the isolation membrane can improve the heat resistance, oxidation resistance and electrolyte wetting performance of the isolation membrane, and enhance the adhesion between the isolation membrane and the pole piece.
  • the electrode assembly of the electrochemical device is a rolled electrode assembly, a stacked electrode assembly, or a folded electrode assembly.
  • the positive electrode and/or negative electrode of the electrochemical device may be a multi-layer structure formed by being rolled or stacked, or may be a single-layer structure in which a single-layer positive electrode, a separator, and a single-layer negative electrode are stacked.
  • the electrochemical device includes a lithium-ion battery, although the application is not limited thereto.
  • the electrochemical device may also include an electrolyte.
  • the electrolyte may be one or more of a gel electrolyte, a solid electrolyte, and an electrolyte solution, and the electrolyte solution includes a lithium salt and a non-aqueous solvent.
  • the lithium salt is selected from LiPF 6 , LiBF 4 , LiAsF 6 , LiClO 4 , LiB(C 6 H 5 ) 4 , LiCH 3 SO 3 , LiCF 3 SO 3 , LiN(SO 2 CF 3 ) 2 , LiC(SO 2 CF 3 ) 3 , one or more of LiSiF 6 , LiBOB or lithium difluoroborate.
  • LiPF 6 was chosen for the lithium salt because it has high ionic conductivity and improves cycling characteristics.
  • the non-aqueous solvent may be a carbonate compound, a carboxylate compound, an ether compound, other organic solvents, or a combination thereof.
  • the carbonate compound may be a chain carbonate compound, a cyclic carbonate compound, a fluorocarbonate compound, or a combination thereof.
  • chain carbonate compounds are diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methyl carbonate Ethyl ester (MEC) and its combinations.
  • chain carbonate compounds are diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methyl carbonate Ethyl ester (MEC) and its combinations.
  • Examples of the cyclic carbonate compound are ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylethylene carbonate (VEC) or combinations thereof.
  • fluorocarbonate compound are fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate.
  • carboxylate compounds are methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, ⁇ -butyrolactone, decanolactone, Valerolactone, mevalonolactone, caprolactone, methyl formate or combinations thereof.
  • ether compounds are dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxy ethane, 2-methyltetrahydrofuran, tetrahydrofuran or combinations thereof.
  • organic solvents examples include dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, methane Amides, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters or combinations thereof.
  • the positive electrode, separator, and negative electrode are wound or stacked in order to form an electrode piece, and then put into, for example, an aluminum-plastic film for packaging, and the electrolyte is injected to form, Encapsulated to make a lithium-ion battery. Then, the prepared lithium-ion battery was tested for performance.
  • electrochemical devices eg, lithium-ion batteries
  • electrochemical devices eg, lithium-ion batteries
  • Other methods commonly used in the art can be used without departing from the content disclosed in this application.
  • Embodiments of the present application also provide an electronic device including the above electrochemical device.
  • the electronic device in the embodiment of the present application is not particularly limited and may be used in any electronic device known in the prior art.
  • electronic devices may include, but are not limited to, laptop computers, pen computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headsets, Video recorders, LCD TVs, portable cleaners, 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 appliances, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries and lithium/sodium ion capacitors, etc.
  • Preparation of the positive electrode Use aluminum foil as the current collector of the positive electrode, dissolve the positive active material lithium cobalt oxide, conductive agent conductive carbon black, and binder in N-methylpyrrolidone (NMP) solution in a weight ratio of 98.2:0.5:1.3 In the process, the slurry of the positive electrode active material layer is formed, and the slurry is coated on the current collector to obtain the positive electrode active material layer. After drying, cold pressing, and cutting, the positive electrode is obtained.
  • NMP N-methylpyrrolidone
  • Preparation of negative electrode Dissolve graphite, conductive agent and binder in deionized water in a weight ratio of 97.8:0.5:1.7 to form negative electrode slurry. A 10 ⁇ m thick copper foil is used as the current collector of the negative electrode. The negative electrode slurry is coated on the current collector of the negative electrode, dried, and cut to obtain the negative electrode.
  • the isolation film base material is 8 ⁇ m thick polyethylene (PE) as the isolation film.
  • EC ethylene carbonate
  • PC propylene carbonate
  • Preparation of lithium-ion batteries The positive electrode, isolation layer, and negative electrode are in close contact in sequence, and the battery unit is obtained by rolling.
  • the battery unit and the electrolyte are sealed in a soft bag, and placed in a mold with a certain curvature to press and bend. A curved battery was produced.
  • the adhesive or thermoplastic polymer emulsion on a horizontal glass plate to dry naturally for 24 hours, and then dry it in a constant temperature oven at 60°C to a constant weight to obtain the adhesive film.
  • a dumbbell-shaped cutter to cut it into a dumbbell-shaped standard sample.
  • the tensile test is done using a universal universal Electronic tensile testing machine. The film is maintained at 100% fixed elongation for 10 minutes and then immediately releases the load, allowing it to recover freely for 10 minutes. The residual deformation is measured and the 100% tensile permanent deformation is calculated.
  • the electrode slurry is evenly applied on the current collector. After the electrode piece is dried, it is wrapped around a cylinder with a diameter of 2 cm, bent and held for 5 seconds. A CCD camera is used to observe and record the number of cracks on the surface of the electrode piece after bending.
  • the positive electrode, isolation layer, and negative electrode are rolled or stacked to form a battery unit, sealed in a soft bag together with the electrolyte, and hot-pressed and bent through a concave and convex mold.
  • the arc test uses a surface 3D profiler to record the arc shape. Calculate the change in curvature radius of the battery before and after it is left standing for 48 hours, and calculate the rebound rate.
  • the charge and discharge voltage range is 3.0V to 4.5V.
  • the binder is different.
  • the specific binder types and components are shown in the table below.
  • the negative electrode plates of Examples 1 to 13 and Comparative Examples 1 to 3 were subjected to a bending test, and the negative electrode was recorded.
  • the number of cracks after the pole piece is wound around a cylinder with a diameter of 2cm. Carry out arc rebound rate and cycle performance tests on arc-shaped batteries, and calculate the arc rebound rate and cycle capacity retention rate.
  • CMC is carboxymethylcellulose
  • PAA acrylic acid polymer
  • SBR is styrene-butadiene emulsion
  • EVA is ethylene vinyl acetate copolymer
  • Examples 1 and 2 The difference between Examples 1 and 2 is that the types of thermoplastic polymers are different. In Examples 3 to 5, the types and mass percentages of the binding polymers and thermoplastic polymers are the same. The only difference is that the crystallinity of the thermoplastic polymers is different. The mass percentage of thermoplastic polymers in Examples 6 to 8 and Comparative Examples 1 to 3 are different, and the 100% tensile permanent deformation of the binder is different. The difference between Examples 9 to 12 is only that the radius of curvature is different. Examples 13 used different binding polymers and thermoplastic polymers.
  • Comparing Examples 1 to 13 and Comparative Examples 1 to 3 it can be seen that the arc rebound rates of the lithium ion batteries in Examples 1 to 13 are all smaller than those of Comparative Examples 1 to 3, and the 400 cycle capacity retention rates are higher than those of the Comparative Example. 1 to 3.
  • the adhesive obtained by compounding the bonding polymer and the thermoplastic polymer used in the examples of this application has a large amount of permanent deformation, and the surface of the produced pole piece has no cracks after being bent.
  • the elongation rate of the binder without adding thermoplastic polymer is less than 100%, and the plasticity is insufficient.
  • the surface of the produced pole piece is cracked around the cylinder with a diameter of 2 cm, and the number of cracks is relatively large.
  • Comparative Example 3 the binder without adding thermoplastic polymer is The permanent deformation of the binder is small, causing the curvature rebound rate of the produced battery to increase. Compared with Comparative Examples 1 to 3, the curvature rebound rate of the battery in Examples 1 to 11 is reduced. Compared with Comparative Example 2, even if the battery unit is bent with a curvature radius of 50 mm, the battery in Example 12 Still has low arc rebound rate and high capacity retention rate of 94%. It can be seen from this that the amount of thermoplastic polymer added to the binder in the range of 0.5% to 50% can effectively increase the permanent deformation of the binder to 50% to 100%, thereby ensuring the use The arc rebound rate of the arc-shaped battery produced by the pole piece described in this application is less than 5%. The larger the curvature radius of the arc-shaped battery, the lower the arc rebound rate.
  • the crystallinity of the thermoplastic polymer has an impact on the arc rebound rate and cycle performance of the arc battery.
  • the crystallinity is not greater than 50%, the overall performance is better.
  • thermoplastic polymers increases the 100% tensile permanent deformation of the binder. This is because the increase in the content of thermoplastic polymers improves the binder's 100% tensile permanent deformation. The plasticity, radian rebound rate and cycle performance change little, but if the mass percentage of thermoplastic polymer is too high, it will lead to insufficient bonding force of the adhesive, so the mass percentage needs to be controlled.
  • the electrode plate described in this application can maintain the electrode integrity and cycle performance of the arc-shaped battery during high curvature bending and use.
  • the arc-shaped battery electrode plate in this application passes the definition
  • the composition of the binder improves its plastic deformation ability and can produce a greater amount of permanent deformation when the pole piece is bent, thereby effectively reducing the arc rebound of arc-shaped batteries.

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Abstract

一种电化学装置和电子装置。电化学装置包括极片，极片包括集流体以及位于集流体至少一面上的活性物质层；活性物质层包括活性材料和粘结剂，粘结剂包括粘结高分子和热塑性高分子，极片的曲率半径R为5mm至200mm。粘结剂通过粘结高分子的锚固作用保证粘结强度，通过塑性好、弹性小的热塑性高分子作为增塑剂，提供发生永久变形的能力，能够使弧形极片的弧度回弹率降低，极片具有良好的加工性能，在极片的曲率半径为5mm至200mm范围内时，电化学装置具有良好的循环性能。

Description

电化学装置和电子装置 技术领域
本申请涉及电化学储能领域，尤其涉及电化学装置和电子装置。
背景技术
随着电化学装置(例如，锂离子电池、钠离子电池等)的发展和进步，对于弧形电化学装置的需求不断增加，在弧形电化学装置的制造和使用过程中，极片的活性物质层与集流体在高曲率下的粘接性能以及极片的弧度稳定性对电化学装置的循环性能和倍率性能有较大影响。现有的粘结剂结晶度和固化交联度高，刚性强不易发生变形，折弯时产生较大内应力容易造成极片开裂，难以适应弧形电池的应用要求。
发明内容
在本申请的一些实施例中提出一种电化学装置，电化学装置包括极片，极片包括集流体以及位于集流体至少一面上的活性物质层；活性物质层包括活性材料和粘结剂，粘结剂包括粘结高分子和热塑性高分子，极片的曲率半径R为5mm至200mm。粘结剂中的分子链具有良好的移动能力，极片随电化学装置弯曲成弧形，曲率高的部位发生应力集中，粘结剂通过塑性变形吸收能量，避免界面失粘、极片开裂的问题，同时，粘结剂产生的永久变形量能够限制弧度回弹率，从而获得曲率更好的弧形极片。本申请中的粘结剂通过粘结高分子的锚固作用保证粘结强度，通过塑性好、弹性小的热塑性高分子作为增塑剂，提供发生永久变形的能力，能够使弧形极片的弧度回弹率降低，极片具有良好的加工型，在极片的曲率半径为5mm至200mm范围内时，电化学装置具有良好的循环性能。
在一些实施例中，极片的曲率半径R为25mm至100mm，从而能够满足对于弧形极片的需求并防止活性物质层与集流体脱附。在一些实施例中，热塑性高分子包括聚乙烯、聚丙烯、聚氯乙烯、聚碳酸酯、树枝状聚酰胺胺、乙烯醋酸乙烯共聚物、超支化丙烯酸或超支化丙烯酸酯中的至少一种。在一些实施例中，热塑性高分子的结晶度小于50％，从而防止刚度过大。在一些实施例中，热塑性高分子的重均分子量为5000至80000，从而保证加工性能。在一些实施例中，热塑性高分子的断裂伸长率为100％至500％，从而防止极片的弧度回弹。
在一些实施例中，粘结高分子包括聚偏氟乙烯、丁苯乳液、羧甲基纤维素、聚苯胺、聚丙烯酸、海藻酸盐、瓜尔胶、阿拉伯树胶、黄原胶、明胶、壳聚糖、β-环糊精、聚乙烯亚胺、聚酰亚胺或水性环氧树脂中的至少一种。在一些实施例中，基于粘结剂的总质量，热塑性高分子在粘结剂中的质量百分含量为0.5％至50％，从而同时保证塑性和粘结力。在一些实施例中，极片为正极，热塑性高分子在粘结剂中的质量百分含量为0.5％至10％。在一些实施例中，极片为负极，热塑性高分子在粘结剂中的质量百分含量为1％至50％，从而与正极相适配，并在具有足够的塑性的情况下保证粘结剂的粘结力。在一些实施例中，粘结剂的拉伸永久变形量为50％至100％，表明其具有良好的塑性。
本申请的实施例还提供了一种电子装置，包括上述电化学装置。
本申请的实施例中粘结剂包括粘结高分子和热塑性高分子，因此粘结剂为具有塑性的粘结剂，粘结剂中的分子链具有良好的移动能力，极片随着弯曲成弧形，曲率高的部位发生应力集中，粘结剂通过塑性变形吸收能量，避免界面失粘、极片开裂问题，同时，粘结剂产生永久变形量，限制弧度回弹率，从而获得曲率更高的弧形。本申请提供的粘结剂通过粘结高分子的锚固作用，保证粘接强度，同时添加塑性好、弹性小的热塑性高分子作为增塑剂，提供发生永久变形的能力，能够使弧形电化学装置的弧度回弹率降低，极片具有良好的加工性，弧形极片的曲率半径达到5mm至200mm仍具有良好的循环性能。
附图说明
结合附图并参考以下具体实施方式，本公开各实施例的上述和其他特征、优点及方面将变得更加明显。贯穿附图中，相同或相似的附图标记表示相同或相似的元素。应当理解附图是示意性的，原件和元素不一定按照比例绘制。
图1是一种电化学装置的示意图。
图2是一种粘结剂的组成示意图和粘结剂受力时的示意图。
具体实施方式
下面的实施例可以使本领域技术人员更全面地理解本申请，但不以任何方式限制本申请。
随着技术的不断进步，对于能够实现曲率折弯的弧形的电化学装置的需求不断增加。在弧形电化学装置的制造和使用过程中，极片的活性物质层与集流体在高曲率下的粘接性能以及极片的弧度稳定性对电化学装置的循环性能和倍率性能有很大影响。现有的粘结剂的结晶度和固化交联度高，刚性强不易发生变形，折弯时产生较大内应力容易造成极片开裂，难以适应弧形电池的应用要求。一些技术中通过降低结晶度的方式增加活性物质黏结层的柔软性，达到可挠的效果。对于弧形极片，除了对粘合层的粘接性以及柔软性进行改进，还需要进一步控制粘合层的可塑性，避免极片弯曲后的弧度回弹。
弧度回弹与极片材料本身的力学性能以及弯曲过程中的应力集中有很大关系。目前抑制弧度回弹方法多为在封装阶段增加外力约束，通过钢壳或增加包装袋的延展性来实现，这种方式增加了制造成本，而且不利于电化学装置的减薄。极片中的粘结剂作为连接极片的主要添加剂，不仅能够保证极片的完整性，而且对电池的稳定性和循环性能有很大影响。
在本申请的一些实施例中提出一种电化学装置，电化学装置例如可以是锂离子电池、钠离子电池等，电化学装置包括极片，一些实施例中，可参考图1，电化学装置可以包括正极1、隔离膜2和负极3， 极片可以是正极1也可以是负极3。极片包括集流体以及位于集流体至少一面上的活性物质层；集流体可以采用铜箔或铝箔制作，活性物质层包括活性材料和粘结剂，粘结剂包括粘结高分子和热塑性高分子，极片的曲率半径R为5mm至200mm。在申请中，如图2(a)所示，粘结剂包括粘结高分子4和热塑性高分子5，因此粘结剂具有塑性，如图2(b)所示，粘结剂受到外力F时通过分子链移动产生不可逆的变形，显示出塑性。粘结剂中的分子链具有良好的移动能力，极片随电化学装置弯曲成弧形，曲率高的部位发生应力集中，粘结剂通过塑性变形吸收能量，避免界面失粘和极片开裂的问题，同时，具有塑性的粘结剂产生永久形变量，限制弧度回弹率，从而获得曲率更好的弧形电化学装置。本申请中提供的粘结剂通过粘结高分子的锚固作用，保证粘结强度，同时添加了塑性好、弹性小的热塑性高分子作为增塑剂，提供发生永久变形的能力，能够使得弧形电化学装置的弧度回弹率降低，极片具有良好的加工性，在曲率半径达到5mm至200mm范围时仍然具有良好的循环性能。
本申请中粘结剂同时包括粘结高分子和热塑性高分子，粘结高分子通常采用聚偏氟乙烯、丁苯橡胶乳液、羧甲基纤维素等，如果只采用粘结高分子，由于聚偏氟乙烯结晶度高，电极受外力弯曲时晶体结构遭到破坏，产生裂纹，容易造成活性物质层从集流体掉落。丁苯橡胶乳液粘结力强，但是橡胶类聚合物具有高弹性，能够在大的变形下迅速恢复形变，很难保持弧度的稳定性。羧甲基纤维素的弹性模量高，固化后脆性大，以羧甲基纤维素作为粘结剂的弧形电池折弯后内应力大，容易造成应力集中，极片易开裂，影响电池的性能。如果只使用热塑性高分子作为粘结剂，加工过程中应力集中的问题能够得到改善，但是热塑性高分子多为线性聚合物，粘接力不足，难以保证电极的完整性。本申请粘结剂同时使用粘结高分子和热塑性高分子，在保证粘结力的同时提高了极片中粘结剂的塑性变形能力，使得极片弯曲成弧形，在高曲率下通过塑性变形吸收能量，阻碍微裂纹扩展，保证弧形极片的完整性，避免弧形极片开裂和掉粉的问题。通过热塑性高分子作为增塑剂使得粘结剂中的分子链具有良好的移动能力，在极片弯曲 受力时产生较大永久变形量，减少弧形极片的弧度回弹，从而提升电化学装置的循环性能。热塑性高分子作为粘结剂中的增塑剂，可以增加粘结剂的塑性变形能力，使得电化学装置的弧度能够做到更高。
在本申请的一些实施例中，极片的曲率半径R为25mm至100mm。极片的曲率半半径表征了极片的弧度，曲率半径越小弧度越大，曲率半径太小容易造成极片中活性物质层与集流体之间脱附，曲率半径太大则极片的弧度不足，可能无法满足需求，本实施例中极片的曲率半径R为25mm至100mm，从而能够满足对于弧形极片的需求并防止活性物质层与集流体脱附。
在本申请的一些实施例中，热塑性高分子包括聚乙烯、聚丙烯、聚氯乙烯、聚碳酸酯、树枝状聚酰胺胺、乙烯醋酸乙烯共聚物、超支化丙烯酸或超支化丙烯酸酯中的至少一种。一些实施例中，乙烯醋酸乙烯共聚物中醋酸乙烯的质量百分含量为15％至40％。
在本申请的一些实施例中，热塑性高分子的结晶度小于50％。一些实施例中，热塑性高分子的结晶度会影响热塑性高分子的刚度，结晶度过高则刚度过高，可能会导致不易变形。
在本申请的一些实施例中，热塑性高分子的重均分子量为5000至80000，一些实施例中，重均分子量与高分子材料的使用性能与加工性能密切相关。相对重均分子量太低，材料的机械强度和韧性会受到影响。重均分子量太高，则高分子的熔体粘度增加，给加工成型造成困难。
在本申请的一些实施例中，热塑性高分子的断裂伸长率为100％至500％。一些实施例中，热塑性高分子的断裂延伸率如果太低，极片在弯曲的过程中可能会导致热塑性高分子断裂，造成极片的柔韧性受到影响，热塑性高分子的断裂伸长率如果过大，则热塑性高分子在塑性变形时所能吸收的能量可能会不足，不利于阻止极片的弧度回弹。
在本申请的一些实施例中，粘结高分子包括聚偏氟乙烯、丁苯乳液、羧甲基纤维素、聚苯胺、聚丙烯酸、海藻酸盐、瓜尔胶、阿拉伯树胶、黄原胶、明胶、壳聚糖、β-环糊精、聚乙烯亚胺、聚酰亚胺或水性环氧树脂中的至少一种。
在本申请的一些实施例中，基于粘结剂的总质量，热塑性高分子在粘结剂中的质量百分含量为0.5％至50％。本实施例中热塑性高分子作为增塑剂在粘结剂中的质量百分比介于0.5％至50％之间，热塑性高分子具有柔性分子链段，通过分子链伸展和滑移发生变形，粘结高分子能够包覆或缠结活性材料，在活性材料和集流体之间起到桥接作用，发挥高粘结的优点。通过调整粘结高分子和热塑性高分子的配比，复合得到粘结剂同时具备了塑性和粘结性，在受到外力弯曲后，极片材料内部发生不可逆形变，能够有效抑制弧形电池的弧度回弹。热塑性高分子添加至极片中，能够使电化学装置的弧度回弹率降低至1％至5％，且极片具有良好的加工性，曲率半径达到5mm至200mm时仍具有良好的循环性能。热塑性高分子在粘结剂中的质量百分含量如果过低，可能无法为粘结剂提供足够的塑性，热塑性高分子在粘结剂中的质量百分含量如果过高，可能会导致粘结剂的粘结力不足。
在本申请的一些实施例中，极片为正极，热塑性高分子在粘结剂中的质量百分含量为0.5％至10％。一些实施例中，正极和负极中，热塑性高分子在粘结剂中的质量百分含量可以不同，这是因为正极和负极所使用的活性材料以及粘结剂可能不同，正极所表现出的塑性通常强于负极，因此正极的粘结剂中塑性高分子的质量百分含量，可以相对高于负极粘结剂中塑性高分子的质量百分含量，这样使得正极和负极在相同的弯曲程度下所表现出的弧度回弹相近，避免因为弧度回弹不同造成正极和负极错位。正极中热塑性高分子在粘结剂中的质量百分含量为0.5％至10％，这样能够在保证正极具有足够的塑性的情况下，保证粘结剂的粘结力。
在本申请的一些实施例中，极片为负极，热塑性高分子在粘结剂中的质量百分含量为1％至50％，从而与正极相适配，并在具有足够的塑性的情况下保证粘结剂的粘结力。
在本申请的一些实施例中，粘结剂的拉伸永久变形量为50％至100％。一些实施例中，粘结剂的拉伸永久变形量通过如下方式测定：将粘结剂置于水平玻璃板自然干燥24h，60℃恒温箱烘干至恒重，得到胶膜，使用哑铃型刀具裁切成哑铃状标准样，拉伸测试采用万能电 子拉力试验机。胶膜在100％固定伸长下保持10min后立即释放载荷，使其自由回复10min，测量残余变形，计算得到拉伸永久变形量。本实施例中，粘结剂在100％固定伸长后的永久变形量达到50％，这表明粘结剂已经具有较好的塑性，弧度回弹较小。
在一些实施例中，极片为正极，活性物质层为正极活性物质层，活性材料为正极材料。在一些实施例中，正极材料包括钴酸锂、磷酸铁锂、磷酸锰铁锂、磷酸铁钠、磷酸钒锂、磷酸钒钠、磷酸钒氧锂、磷酸钒氧钠、钒酸锂、锰酸锂、镍酸锂、镍钴锰酸锂、富锂锰基材料或镍钴铝酸锂中的至少一种。在一些实施例中，正极活性物质层还可以包括导电剂。在一些实施例中，正极活性物质层中的导电剂可以包括导电炭黑、科琴黑、片层石墨、石墨烯、碳纳米管或碳纤维中的至少一种。在一些实施例中，正极活性物质层中的正极材料、导电剂和粘结剂的质量比可以为(80至99)：(0.1至10)：(0.1至10)。在一些实施例中，正极活性物质层的厚度可以为10μm至500μm。应该理解，以上所述仅是示例，正极的正极活性物质层可以采用任何其他合适的材料、厚度和质量比。
在一些实施例中，正极的集流体可以采用Al箔，当然，也可以采用本领域常用的其他集流体。在一些实施例中，正极的集流体的厚度可以为1μm至200μm。在一些实施例中，正极活性物质层可以仅涂覆在正极的集流体的部分区域上。
在一些实施例中，当极片为负极时，活性物质层为负极活性物质层。在一些实施例中，负极活性物质层包括负极材料，负极材料可以包括石墨、硬碳、硅、氧化亚硅或有机硅中的至少一种。在一些实施例中，负极活性物质层中还可以包括导电剂。在一些实施例中，负极活性物质层中的导电剂可以包括导电炭黑、科琴黑、片层石墨、石墨烯、碳纳米管或碳纤维中的至少一种。在一些实施例中，负极活性物质层中的负极材料、导电剂和粘结剂的质量比可以为(80至98)：(0.1至10)：(0.1至10)。应该理解，以上所述仅是示例，可以采用任何其他合适的材料和质量比。在一些实施例中，负极的集流体可以采用铝箔、铜箔、镍箔或碳基集流体中的至少一种。
在一些实施例中，隔离膜包括聚乙烯、聚丙烯、聚偏氟乙烯、聚对苯二甲酸乙二醇酯、聚酰亚胺或芳纶中的至少一种。例如，聚乙烯包括选自高密度聚乙烯、低密度聚乙烯或超高分子量聚乙烯中的至少一种。尤其是聚乙烯和聚丙烯，它们对防止短路具有良好的作用，并可以通过关断效应改善电池的稳定性。在一些实施例中，隔离膜的厚度在约5μm至500μm的范围内。
在一些实施例中，隔离膜表面还可以包括多孔层，多孔层设置在隔离膜的基材的至少一个表面上，多孔层包括无机颗粒和粘结剂，无机颗粒选自氧化铝(Al 2O 3)、氧化硅(SiO 2)、氧化镁(MgO)、氧化钛(TiO 2)、二氧化铪(HfO 2)、氧化锡(SnO 2)、二氧化铈(CeO 2)、氧化镍(NiO)、氧化锌(ZnO)、氧化钙(CaO)、氧化锆(ZrO 2)、氧化钇(Y 2O 3)、碳化硅(SiC)、勃姆石、氢氧化铝、氢氧化镁、氢氧化钙或硫酸钡中的至少一种。在一些实施例中，隔离膜的孔具有在约0.01μm至1μm的范围的直径。多孔层的粘结剂选自聚偏氟乙烯、偏氟乙烯-六氟丙烯的共聚物、聚酰胺、聚丙烯腈、聚丙烯酸酯、聚丙烯酸、聚丙烯酸盐、羧甲基纤维素钠、聚乙烯呲咯烷酮、聚乙烯醚、聚甲基丙烯酸甲酯、聚四氟乙烯或聚六氟丙烯中的至少一种。隔离膜表面的多孔层可以提升隔离膜的耐热性能、抗氧化性能和电解质浸润性能，增强隔离膜与极片之间的粘结性。
在本申请的一些实施例中，电化学装置的电极组件为卷绕式电极组件、堆叠式电极组件或折叠式电极组件。在一些实施例中，电化学装置的正极和/或负极可以是卷绕或堆叠式形成的多层结构，也可以是单层正极、隔离膜、单层负极叠加的单层结构。
在一些实施例中，电化学装置包括锂离子电池，但是本申请不限于此。在一些实施例中，电化学装置还可以包括电解质。电解质可以是凝胶电解质、固态电解质和电解液中的一种或多种，电解液包括锂盐和非水溶剂。锂盐选自LiPF 6、LiBF 4、LiAsF 6、LiClO 4、LiB(C 6H 5) 4、LiCH 3SO 3、LiCF 3SO 3、LiN(SO 2CF 3) 2、LiC(SO 2CF 3) 3、LiSiF 6、LiBOB或者二氟硼酸锂中的一种或多种。例如，锂盐选用LiPF 6，因为它具有高的离子导电率并可以改善循环特性。
非水溶剂可为碳酸酯化合物、羧酸酯化合物、醚化合物、其它有机溶剂或它们的组合。
碳酸酯化合物可为链状碳酸酯化合物、环状碳酸酯化合物、氟代碳酸酯化合物或其组合。
链状碳酸酯化合物的实例为碳酸二乙酯(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)、碳酸甲乙酯(MEC)及其组合。所述环状碳酸酯化合物的实例为碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸亚丁酯(BC)、碳酸乙烯基亚乙酯(VEC)或者其组合。所述氟代碳酸酯化合物的实例为碳酸氟代亚乙酯(FEC)、碳酸1,2-二氟亚乙酯、碳酸1,1-二氟亚乙酯、碳酸1,1,2-三氟亚乙酯、碳酸1,1,2,2-四氟亚乙酯、碳酸1-氟-2-甲基亚乙酯、碳酸1-氟-1-甲基亚乙酯、碳酸1,2-二氟-1-甲基亚乙酯、碳酸1,1,2-三氟-2-甲基亚乙酯、碳酸三氟甲基亚乙酯或者其组合。
羧酸酯化合物的实例为乙酸甲酯、乙酸乙酯、乙酸正丙酯、乙酸叔丁酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、γ-丁内酯、癸内酯、戊内酯、甲瓦龙酸内酯、己内酯、甲酸甲酯或者其组合。
醚化合物的实例为二丁醚、四甘醇二甲醚、二甘醇二甲醚、1,2-二甲氧基乙烷、1,2-二乙氧基乙烷、乙氧基甲氧基乙烷、2-甲基四氢呋喃、四氢呋喃或者其组合。
其它有机溶剂的实例为二甲亚砜、1,2-二氧戊环、环丁砜、甲基环丁砜、1,3-二甲基-2-咪唑烷酮、N-甲基-2-吡咯烷酮、甲酰胺、二甲基甲酰胺、乙腈、磷酸三甲酯、磷酸三乙酯、磷酸三辛酯、和磷酸酯或者其组合。
在本申请的一些实施例中，以锂离子电池为例，将正极、隔离膜、负极按顺序卷绕或堆叠成电极件，之后装入例如铝塑膜中进行封装，注入电解液，化成、封装，即制成锂离子电池。然后，对制备的锂离子电池进行性能测试。
本领域的技术人员将理解，以上描述的电化学装置(例如，锂离子电池)的制备方法仅是实施例。在不背离本申请公开的内容的基础上，可以采用本领域常用的其他方法。
本申请的实施例还提供了包括上述电化学装置的电子装置。本申请实施例的电子装置没有特别限定，其可以是用于现有技术中已知的任何电子装置。在一些实施例中，电子装置可以包括，但不限于，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/钠离子电容器等。
下面列举了一些具体实施例和对比例以更好地对本申请进行说明，其中，采用锂离子电池作为示例。
正极的制备：采用铝箔作为正极的集流体，将正极活性材料钴酸锂、导电剂导电炭黑、粘结剂按重量比98.2：0.5：1.3的比例溶于N-甲基吡咯烷酮(NMP)溶液中，形成正极活性物质层的浆料，将该浆料涂覆于集流体上，得到正极活性物质层，经过干燥、冷压、裁切后得到正极。
负极的制备：将石墨、导电剂和粘结剂按重量比97.8：0.5：1.7的比例溶于去离子水中，形成负极浆料。采用10μm厚度铜箔作为负极的集流体，将负极浆料涂覆于负极的集流体上，干燥，裁切后得到负极。
隔离膜的制备：隔离膜基材为8μm厚的聚乙烯(PE)作为隔离膜。
电解液的制备：在含水量小于10ppm的环境下，将LiPF 6加入非水有机溶剂(碳酸乙烯酯(EC)：碳酸丙烯酯(PC)＝50：50，重量比)，LiPF 6的浓度为1.15mol/L，混合均匀，得到电解液。
锂离子电池的制备：正极、隔离层、负极依次紧密接触，通过卷叠方式得到电池单元，将电池单元与电解液一同密封在软包袋中，置于具有一定曲率的模具中压制进行折弯制得弧形电池。
测试方法：
胶膜拉伸测试：
将粘结剂或热塑性高分子增乳液置于水平玻璃板自然干燥24h，60℃恒温箱烘干至恒重，得到胶膜，使用哑铃型刀具裁切成哑铃状标准样，拉伸测试采用万能电子拉力试验机。胶膜在100％固定伸长下保持10min后立即释放载荷，使其自由回复10min，测量残余变形，计算得到100％拉伸永久变形量。
极片弯折测试：
将电极的浆料均匀涂敷在集流体上，极片干燥后缠绕于直径2cm的圆柱进行弯折并保持5s，使用CCD相机观察并记录弯折后极片表面裂纹数量。
弧度回弹率测试：
将正极、隔离层、负极通过卷绕或堆叠的方式做成电池单元，与电解液一同密封在软包袋中，通过凹凸模具进行热压折弯,弧度测试采用表面3D轮廓仪，记录弧形电池在静置48h前后的曲率半径变化，计算回弹率。
循环性能测试：
将激活状态的弧形电池放置在测试夹具中夹持，在25℃恒温箱中进行充放电循环测试，充放电电压范围为3.0V至4.5V，以1.2C的倍率充电至4.5V，然后以4.5V恒压充电至0.02C并静置10分钟，再以0.5C的倍率放电至3V，循环上述充放电过程400圈，记录初始容量和第400次循环后的容量，用第400次循环后的容量与初始容量的比值作为容量保持率。
各个实施例的区别在于粘结剂不同，具体的粘结剂种类和组分见下表，按照上述测试方法对实施例1至13及对比例1至3负极极片进行弯折测试，记录负极极片绕直径2cm圆柱后裂纹数量。对弧形电池进行弧度回弹率以及循环性能测试，计算弧度回弹率以及循环容量保持率。
表1
Figure PCTCN2022081964-appb-000001
Figure PCTCN2022081964-appb-000002
其中，“/”表示无，CMC为羧甲基纤维素、PAA为丙烯酸聚合物、SBR为丁苯乳液、EVA为乙烯醋酸乙烯共聚物。
实施例1和2的区别在于热塑性高分子中的种类不同，实施例3至5中粘结高分子和热塑性高分子的种类和质量百分含量相同，区别仅在于热塑性高分子的结晶度不同，实施例6至8、对比例1至3中热塑性高分子的质量百分含量不同，粘结剂的100％拉伸永久变形量不同，实施例9至12的区别仅在于曲率半径不同，实施例13中使用了不同的粘结高分子和热塑性高分子。
对比实施例1至13和对比例1至3可以看出，实施例1至13中锂离子电池的弧度回弹率均小于对比例1至3，且400圈循环容量保 持率均高于对比例1至3。本申请实施例中的使用的粘结高分子及热塑性高分子复合得到的粘结剂具有较大的永久变形量，制成的极片经过弯折之后表面无裂纹，而对比例1和2中未添加热塑性高分子的粘结剂的伸长率低于100％，塑性不足，所制得的极片绕直径2cm圆柱后表面开裂，裂纹数量较多，对比例3中未添加热塑性高分子的粘结剂的永久变形量小，造成制得的电池弧度回弹率升高。与对比例1至3相比，实施例1至11中的电池的弧度回弹率降低，与对比例2相比，即使以50mm的曲率半径对电池单元进行折弯，实施例12中的电池仍具有低的弧度回弹率和94％的高容量保持率。由此可以看出，采用的热塑性高分子在粘结剂中的添加量在0.5％至50％的范围内都能有效的提高粘结剂的永久变形量至50％至100％，从而保证使用本申请所述极片制得的弧形电池的弧度回弹率在5％以下，而弧形电池的曲率半径越大则能够使其弧度回弹率随之降低。
从实施例3至5可以看出，热塑性高分子的结晶度对弧形电池的弧度回弹率和循环性能有影响，当结晶度不大于50％时整体性能较好。
从实施例6至8可以看出，热塑性高分子的质量百分含量的增加，提高了粘结剂的100％拉伸永久变形量，这是因为热塑性高分子的含量的增加改善了粘结剂的塑性，弧度回弹率和循环性能变化较小，但如果热塑性高分子的质量百分含量过高，会导致粘结剂的粘结力不足，因此需要控制器质量百分含量。
从实施例9至12可以看出，当极片的曲率半径在25mm至200mm范围内时，本申请提出的电池均能具有较好的性能，从实施例13可以看出，当曲率半径为5mm时，弧形电池弧度回弹率也仅为2.6％，并且400圈循环容量保持率仍然达到92.8％，表现出良好的循环性能，可见采用本申请提出的实施例可以在保证循环性能的同时，满足对弧形电池的需求。
通过上述实施例和对比例可以看出，本申请所述的极片能够维持弧形电池在高曲率折弯和使用过程中的电极完整性和循环性能，本申请的弧形电池极片通过限定粘结剂的组成，提升其塑性变形能力，能够在极片折弯时产生更大的永久变形量，进而有效降低弧形电池的弧 度回弹。
以上描述仅为本公开的一些较佳实施例以及对所运用技术原理的说明。本领域技术人员应当理解，本公开的实施例中所涉及的发明范围，并不限于上述技术特征的特定组合而成的技术方案，同时也应涵盖在不脱离上述发明构思的情况下，由上述技术特征或其等同特征进行任意组合而形成的其它技术方案。例如上述特征与本公开的实施例中公开的(但不限于)具有类似功能的技术特征进行互相替换而形成的技术方案。

Claims (10)

  1. 一种电化学装置，包括极片，所述极片包括集流体以及位于所述集流体至少一面上的活性物质层；所述活性物质层包括活性材料和粘结剂，其特征在于，所述粘结剂包括粘结高分子和热塑性高分子，所述极片的曲率半径R为5mm至200mm。
  2. 根据权利要求1所述的电化学装置，其特征在于，所述极片的曲率半径R为25mm至100mm。
  3. 根据权利要求1所述的电化学装置，其特征在于，所述热塑性高分子包括聚乙烯、聚丙烯、聚氯乙烯、聚碳酸酯、树枝状聚酰胺胺、乙烯醋酸乙烯共聚物、超支化丙烯酸或超支化丙烯酸酯中的至少一种。
  4. 根据权利要求3所述的电化学装置，其特征在于，所述热塑性高分子满足以下条件中的至少一者：
    所述热塑性高分子的结晶度小于50％；
    所述热塑性高分子的重均分子量为5000至80000；
    所述热塑性高分子的断裂伸长率为100％至500％。
  5. 根据权利要求1所述的电化学装置，其特征在于，所述粘结高分子包括聚偏氟乙烯、丁苯乳液、羧甲基纤维素、聚苯胺、聚丙烯酸、海藻酸盐、瓜尔胶、阿拉伯树胶、黄原胶、明胶、壳聚糖、β-环糊精、聚乙烯亚胺、聚酰亚胺或水性环氧树脂中的至少一种。
  6. 根据权利要求1所述的电化学装置，其特征在于，基于所述粘结剂的总质量，所述热塑性高分子在所述粘结剂中的质量百分含量为0.5％至50％。
  7. 根据权利要求6所述的电化学装置，其特征在于，
    所述极片为正极，所述热塑性高分子在所述粘结剂中的质量百分含量为0.5％至10％。
  8. 根据权利要求6所述的电化学装置，其特征在于，
    所述极片为负极，所述热塑性高分子在所述粘结剂中的质量百分含量为1％至50％。
  9. 根据权利要求1所述的电化学装置，其特征在于，
    所述粘结剂的拉伸永久变形量为50％至100％。
  10. 一种电子装置，包括根据权利要求1至9中任一项所述的电化学装置。
PCT/CN2022/081964 2022-03-21 2022-03-21 电化学装置和电子装置 WO2023178470A1 (zh)

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CN116544347B (zh) * 2023-07-05 2024-05-03 宁德新能源科技有限公司 一种电化学装置和用电装置
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