WO2021195914A1 - 负极材料、负极极片、电化学装置和电子装置 - Google Patents

负极材料、负极极片、电化学装置和电子装置 Download PDF

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WO2021195914A1
WO2021195914A1 PCT/CN2020/082267 CN2020082267W WO2021195914A1 WO 2021195914 A1 WO2021195914 A1 WO 2021195914A1 CN 2020082267 W CN2020082267 W CN 2020082267W WO 2021195914 A1 WO2021195914 A1 WO 2021195914A1
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silicon
based material
pole piece
conductive agent
negative electrode
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PCT/CN2020/082267
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English (en)
French (fr)
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陈聪荣
陈志焕
崔航
谢远森
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宁德新能源科技有限公司
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Priority to CN202080030134.1A priority Critical patent/CN113728466B/zh
Priority to EP20928679.8A priority patent/EP4131486A4/en
Priority to PCT/CN2020/082267 priority patent/WO2021195914A1/zh
Publication of WO2021195914A1 publication Critical patent/WO2021195914A1/zh
Priority to US17/956,373 priority patent/US20230052928A1/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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • 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
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
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    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
    • H—ELECTRICITY
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    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • H—ELECTRICITY
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    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • 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 disclosure relates to the field of electronic technology, and in particular to a negative electrode material, a negative pole piece, an electrochemical device and an electronic device.
  • Silicon-based materials have a theoretical specific capacity as high as 4200 mAh/g, which is a promising negative electrode material for next-generation electrochemical devices (for example, lithium ion batteries).
  • silicon-based materials have a volume expansion of about 300% during charging and discharging, and have poor electrical conductivity, which hinders further large-scale applications of silicon-based materials.
  • the present disclosure uses silicon-based material particles with recesses to improve the volume expansion of the silicon-based material by designing the structure of the silicon-based material, and enhance the interface contact between different materials, thereby improving the interface Conductivity, thereby improving the cycle performance and rate performance of the electrochemical device.
  • the present disclosure provides a negative electrode material, including a silicon-based material, wherein particles of the silicon-based material have at least one concave portion, the width of the concave portion is 50 nm-20 ⁇ m, and the depth is 50 nm-10 ⁇ m.
  • the particles of the silicon-based material have a plurality of recesses, and the thickness of the connection between the plurality of recesses is 30 nm to 10 ⁇ m.
  • the particles of the silicon-based material further have at least one rounded corner structure, and the average arc length of the rounded corner structure is 1 ⁇ m-50 ⁇ m.
  • the negative electrode material further includes graphite and a conductive agent
  • at least part of the graphite is located in the concave portion of the silicon-based material, the average width of the concave portion is a, and the average particle size D50 of the graphite is b.
  • the average minimum particle width of graphite is c, where c ⁇ a, b ⁇ 3a.
  • the silicon-based material includes at least one of silicon, silicon oxide, silicon carbon, or siloxycarbon ceramic material (SiOC).
  • the negative electrode material further includes graphite and a conductive agent
  • the conductive agent includes at least one of conductive carbon black, Ketjen black, acetylene black, carbon nanotube, or graphene.
  • the negative electrode material further includes a carbon material, a conductive agent, and a binder
  • the mass ratio of the silicon-based material, the carbon material, the conductive agent, and the binder is 5 ⁇ 40:55 ⁇ 90:0.5 ⁇ 10:0.5 ⁇ 10
  • the mass of the silicon-based material accounts for the percentage of the total mass of the silicon-based material, the carbon material, the conductive agent and the binder 5% to 40%
  • the mass of the conductive agent accounts for 0.5% to 10% of the total mass of the silicon-based material, the carbon material, the conductive agent, and the binder.
  • the present disclosure also provides a negative electrode piece, which includes: a current collector; an active material layer located on the current collector; wherein the active material layer includes any of the above-mentioned negative electrode materials.
  • the present disclosure also provides an electrochemical device, including: a positive pole piece; a negative pole piece; Pole piece.
  • the present disclosure also provides an electronic device, including the electrochemical device described above.
  • the present disclosure solves the problem of large volume expansion of the silicon-based material by adopting a silicon-based material with a recessed structure (recess), which leaves a certain expansion space for the silicon-based material.
  • a silicon-based material with a recessed structure is combined with a carbon material (for example, graphite) and a conductive agent to form a negative pole piece, smaller carbon material (for example, graphite) particles and conductive agent are embedded in the recess of the silicon-based material.
  • the problem of low compaction density of the silicon-based negative electrode material of the recessed structure is solved, and the defect of the low volume energy density of the recessed structure is made up for.
  • the silicon-based material of the recessed structure can promote the diffusion and penetration of the electrolyte, improve the liquid retention capacity of the negative pole piece, and reduce the transmission impedance, thereby improving the rate performance and cycle performance of the corresponding electrochemical device.
  • FIG. 1 is an exemplary image of the negative electrode material of the present disclosure.
  • Fig. 2 is a schematic diagram of the negative pole piece of the present disclosure.
  • Fig. 3 is a scanning electron microscope image of the negative pole piece after the cycle of the present disclosure.
  • FIG. 4 is a schematic diagram of the electrode assembly of the electrochemical device of the present disclosure.
  • 5 to 7 are images of cross-sections of the negative pole piece in Example 1 of the present disclosure.
  • silicon-based materials can significantly increase the energy density of the electrode assembly, but the silicon-based materials have poor electrical conductivity and large volume expansion and contraction during the process of deintercalating lithium.
  • porous silicon-based materials can be designed, the size of silicon-based materials can be reduced, oxide coatings, polymer coatings, and carbon materials coatings can be used. Designing porous silicon-based materials and reducing the size of silicon-based materials can improve the rate performance of electrochemical devices to a certain extent, but as the cycle progresses, side reactions occur and uncontrollable solid electrolyte interface (SEI, solid electrolyte interface) The growth of the film further limits the cycle stability of the material.
  • SEI solid electrolyte interface
  • the carbon-coated silicon-based material is likely to decarburize due to repeated shearing forces, thereby affecting its Coulomb efficiency and forming SEI
  • the electrolyte is consumed when the membrane is formed.
  • the carbon layer is easily peeled off from the silicon-based material particles. With the formation of SEI, it is wrapped by the by-products, resulting in electrochemical impedance and extreme resistance. The increase in chemistry affects the cycle life.
  • the present disclosure utilizes the structural design of silicon-based material particles, and utilizes the mechanical interlocking between the depressions of the silicon-based material particles (large-area depressions and inwardly curved morphologies on the surface of the material), carbon materials (for example, graphite) and conductive agents, thereby improving
  • the conductivity between the interfaces of different materials makes the transmission of electrons and ions more convenient, and can effectively reduce the DC resistance of electrochemical devices.
  • this recessed structure leaves a certain expansion space for the silicon-based material, and the engagement with the carbon material (for example, graphite) can also buffer the volume expansion of the silicon-based material.
  • the recesses are conducive to the mutual engagement of silicon-based materials and carbon materials (for example, graphite), making the interface between the two materials closer, and when they are combined with carbon materials (for example, graphite) to make a negative pole piece, it is more Small carbon material (for example, graphite) particles are embedded in the recesses of the silicon-based material, which solves the problem of low compaction density of the silicon-based negative electrode material of the recessed structure, and makes up for the defect of low volume energy density of the recessed structure.
  • the recessed structure can promote electrolyte diffusion and penetration, improve the liquid retention capacity of the negative pole piece, reduce the transmission impedance, and thereby improve the rate performance and cycle performance of the corresponding electrochemical device.
  • the anode material includes a silicon-based material, wherein particles of the silicon-based material have at least one recess.
  • the width of the recess is 50 nm to 20 ⁇ m, and the depth is 50 nm to 10 ⁇ m.
  • the silicon-based materials with recesses By using silicon-based materials with recesses, on the one hand, space is left for volume expansion, which solves the problem of large volume expansion of silicon-based materials; on the other hand, carbon materials (for example, graphite) and conductive agents in the negative electrode material can fall into In the recesses of the silicon-based material, the problem of low compaction density caused by the silicon-based material with a recessed structure is overcome, and the volume capacity density of the negative electrode material is improved.
  • the recess has an irregular shape.
  • the recess has one or more smaller recesses inside.
  • the silicon-based material includes at least one of silicon, silicon oxide, silicon carbon, or silicon-oxy-carbon ceramic material (SiOC).
  • the silicon-based material is a silica particulate material.
  • the silicon-based material includes SiO x C y M z , where 0 ⁇ x ⁇ 2, 0 ⁇ y ⁇ 1, 0 ⁇ z ⁇ 0.5, and M represents at least one of lithium, magnesium, titanium, or aluminum .
  • the silicon-based material particles with recesses may be obtained by etching or the like, but the present disclosure is not limited to this, and any other suitable method may be used to obtain the silicon-based material particles with recesses.
  • the silicon-based material particles have multiple recesses, and the thickness of the connection between the multiple recesses is 30 nm-10 ⁇ m. As shown in FIG. 1, the thickness of the connection between the recesses refers to the shortest distance between the recesses. For example, if a certain silicon-based material particle has an upper recess and a lower recess, the thickness of the connection between the upper recess and the lower recess is the shortest distance between the two recesses.
  • a certain thickness of the connection between the recesses can be maintained to avoid a hollow structure, which is beneficial to improve the compaction density and volume energy density of the negative electrode material.
  • the silicon-based material particles further have at least one rounded corner structure, and the average arc length of the rounded corner structure is 1 ⁇ m-50 ⁇ m.
  • the rounded structure of the particles of the silicon-based material facilitates the sliding of the graphite and the conductive agent into the concave portion when mixed with the graphite and the conductive agent.
  • the negative electrode material further includes graphite and a conductive agent, and at least part of the graphite is located in the recess of the silicon-based material.
  • the average width of the recess is a
  • the average particle diameter D 50 of the graphite is b
  • the average width of the smallest particles of graphite is c, where, c ⁇ a, b ⁇ 3a .
  • the width of the recess refers to the size corresponding to the shorter side of the recess
  • the longer side corresponds to the length of the recess
  • the minimum particle width of graphite refers to the width corresponding to the shorter side of the graphite particles. The minimum value.
  • the graphite includes artificial graphite, natural graphite, or a combination thereof, wherein the artificial graphite or natural graphite includes at least one of mesophase carbon microspheres, soft carbon, or hard carbon.
  • the conductive agent is a carbon-containing conductive agent.
  • the conductive agent includes at least one of conductive carbon black, Ketjen black, acetylene black, carbon nanotubes, or graphene.
  • the negative electrode material includes a carbon material, a conductive agent, and a binder.
  • the carbon material in the negative electrode material includes graphite and/or graphene.
  • the mass ratio of the silicon-based material, the carbon material, the conductive agent, and the binder is 5-40:55-90:0.5-10:0.5-10.
  • the mass of the silicon-based material accounts for 5%-40% of the total mass of the silicon-based material, the carbon material, the conductive agent, and the binder. If the content of the silicon-based material is too small, the effect on increasing the specific capacity is limited; if the content of the silicon-based material exceeds 40%, the compaction density and liquid retention of the negative pole piece will decrease greatly.
  • the mass of the conductive agent accounts for 0.5%-10% of the total mass of the silicon-based material, the carbon material, the conductive agent, and the binder.
  • appropriately increasing the content of the conductive agent can increase the amount of conductive agent in the recesses of the silicon-based material and improve the conductivity of the negative electrode material.
  • the cycle performance of the pole piece reduces the DC resistance. However, when the content of the conductive agent is too high, the volumetric energy density of the negative electrode material will be reduced.
  • the average particle size of the silicon-based particles is 500 nm-50 ⁇ m. If the average particle size of the silicon-based material is too small, the silicon-based material is prone to agglomeration and consumes more electrolyte to form the SEI film due to the large specific surface area. If the average particle size of the silicon-based material is too large, it is not conducive to suppressing the volume expansion of the silicon-based material, and it is also easy to cause the deterioration of the conductivity of the active material layer. In addition, if the average particle size of the silicon-based material is too large, the strength of the negative pole piece will decrease.
  • the negative pole piece includes a current collector 1 and an active material layer 2.
  • the active material layer 2 is located on the current collector 1. It should be understood that although the active material layer 2 is shown as being located on one side of the current collector 1 in FIG. 2, this is only exemplary, and the active material layer 2 may be located on both sides of the current collector 1.
  • the current collector of the negative pole piece may include at least one of copper foil, aluminum foil, nickel foil, or carbon-based current collector.
  • the active material layer 2 includes any one of the above-mentioned negative electrode materials.
  • the active material layer includes a silicon-based material, a carbon material, a conductive agent, and a binder, and the mass ratio of the silicon-based material, the carbon material, the conductive agent, and the binder is 5-40:55-90:0.5 ⁇ 10: 0.5-10, the mass percentage of the silicon-based material in the active material layer is 5%-40%, and the mass percentage of the conductive agent in the active material layer is 0.5%-10%.
  • silicon-based materials, carbon materials, and conductive agents as described above can be selected.
  • the binder may include carboxymethyl cellulose (CMC), polyacrylic acid, polyvinylpyrrolidone, polyaniline, polyimide, polyamideimide, polysiloxane, polystyrene-butadiene At least one of rubber, epoxy resin, polyester resin, polyurethane resin, or polyfluorene.
  • the mass percentage of the binder in the active material layer is 0.5%-10%.
  • the thickness of the active material layer is 50 ⁇ m to 200 ⁇ m
  • the compacted density of the negative electrode material in the active material layer under a pressure of 5 t is 0.8 g/cm 3 to 5 g/cm 3 .
  • the mass content of the carbon element in the active material layer is 0-80%.
  • the specific surface area of the negative electrode material in the active material layer ranges from 1 m 2 /g to 50 m 2 /g.
  • the present disclosure starts from the topography and structure of the silicon-based material, uses a recessed structure to solve some of the problems caused by the volume expansion of the silicon-based material, and cooperates with a carbon material (for example, graphite) and a conductive agent to make a negative pole piece.
  • a carbon material for example, graphite
  • a conductive agent for example, graphite
  • It not only makes up for the low compaction density of the silicon-based material with recesses, but also improves the problem caused by the volume expansion of the silicon-based material, improves the DC resistance and liquid retention capacity of the negative pole piece, thereby improving the corresponding electrical Cycle performance of chemical equipment, etc.
  • Figure 3 a scanning electron micrograph of the negative pole piece after cycling is shown. Due to the advantages of the recessed structure of the silicon-based material, when a carbon material (for example, graphite) and a conductive agent are combined to form a negative pole piece, the structure does not change significantly after cycling.
  • the electrochemical device includes a positive pole piece 10, a negative pole piece 12, and a separator disposed between the positive pole piece 10 and the negative pole piece 12.
  • the positive electrode piece 10 may include a positive electrode current collector and a positive electrode active material layer coated on the positive electrode current collector. In some embodiments, the positive active material layer may only be coated on a partial area of the positive current collector.
  • the positive active material layer may include a positive active material, a conductive agent, and a binder. Al foil can be used as the positive electrode current collector, and similarly, other positive electrode current collectors commonly used in this field can also be used.
  • the conductive agent of the positive pole piece may include at least one of conductive carbon black, sheet graphite, graphene, or carbon nanotubes.
  • the binder in the positive pole piece may include polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, styrene-acrylate copolymer, styrene-butadiene copolymer, polyamide, polyacrylonitrile, Polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinyl acetate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene or polyhexafluoropropylene At least one of them.
  • the positive active material includes, but is not limited to, at least one of lithium cobaltate, lithium nickelate, lithium manganate, lithium nickel manganate, lithium nickel cobaltate, lithium iron phosphate, lithium nickel cobalt aluminate or lithium nickel cobalt manganate,
  • the above positive active material can be doped or coated.
  • the isolation film 11 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.
  • polyethylene and polypropylene they have a good effect on preventing short circuits, and can improve the stability of the battery through the shutdown effect.
  • the thickness of the isolation film is in the range of 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 isolation membrane, the porous layer includes inorganic particles and a binder, and the inorganic particles are selected from alumina (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), oxide Zinc (ZnO), calcium oxide (CaO), zirconium oxide (ZrO 2 ), yttrium oxide (Y 2 O 3 ), silicon carbide (SiC), boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide or sulfuric acid At least one of barium.
  • alumina Al 2 O 3
  • Silicon oxide SiO 2
  • magnesium oxide MgO
  • titanium oxide TiO 2
  • hafnium dioxide HfO 2
  • the pores of the isolation membrane have a diameter in the range of about 0.01 ⁇ m to 1 ⁇ m.
  • the binder is selected from polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyethylene pyrrole At least one of alkanone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, or polyhexafluoropropylene.
  • the porous layer on the surface of the isolation membrane can improve the heat resistance, oxidation resistance and electrolyte infiltration performance of the isolation membrane, and enhance the adhesion between the isolation membrane and the pole piece.
  • the negative pole piece 12 may be the negative pole piece as described above.
  • the electrode assembly of the electrochemical device is a wound electrode assembly or a stacked electrode assembly.
  • the electrochemical device includes a lithium ion battery, but the present disclosure is not limited thereto.
  • the electrochemical device may further include an electrolyte.
  • the electrolyte includes, but is not limited to, dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), ethylene carbonate (EC), propylene carbonate (PC), At least two of propyl propionate (PP).
  • the electrolyte may additionally include at least one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), or dinitrile compound as an additive to the electrolyte.
  • the electrolyte further includes a lithium salt.
  • the positive pole piece, the separator film, and the negative pole piece are sequentially wound or stacked to form an electrode piece, and then packed into, for example, an aluminum plastic film for packaging, and injection electrolysis Lithium-ion battery is made by liquid, formed and packaged. Then, perform performance test and cycle test on the prepared lithium-ion battery.
  • the embodiments of the present disclosure also provide an electronic device including the above-mentioned electrochemical device.
  • the electronic device of the present application is not particularly limited, and it can be used in any electronic device known in the prior art.
  • electronic devices may include, but are not limited to, notebook computers, pen-input computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, headsets, Video recorders, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, assisted bicycles, bicycles, Lighting equipment, toys, game consoles, clocks, power tools, flashlights, cameras, large household storage batteries and lithium-ion capacitors, etc.
  • the current collector adopts copper foil with a thickness of 10 ⁇ m
  • the active material adopts Si and graphite
  • the conductive agent adopts conductive carbon black
  • the binder adopts polyacrylic acid
  • After mixing the active material, conductive carbon black, and binder Disperse it in deionized water to form a slurry, stir it evenly, coat it on copper foil, and control the coating weight at 0.108kg/1540.25m 2 , dry, cold press, and slit to obtain a negative pole piece.
  • the corresponding parameters are shown in Table 1.
  • Preparation of positive pole piece After taking positive active material LiCoO 2 , conductive carbon black, and binder polyvinylidene fluoride (PVDF) at a mass ratio of 96.7:1.7:1.6 in an N-methylpyrrolidone solvent system, stir and mix well. Coating on the aluminum foil, and then drying and cold pressing to obtain a positive pole piece.
  • positive active material LiCoO 2 LiCoO 2 , conductive carbon black, and binder polyvinylidene fluoride (PVDF) at a mass ratio of 96.7:1.7:1.6 in an N-methylpyrrolidone solvent system
  • Battery preparation Polyethylene porous polymer film is used as the separator, and the positive pole piece, separator film, and negative pole piece are stacked in sequence, so that the separator is in the middle of the positive and negative pole pieces for isolation, and rolled Wind the electrode assembly. Place the electrode assembly in the outer packaging aluminum-plastic film, inject the electrolyte containing ethylene carbonate (EC), diethyl carbonate (DEC) and dimethyl carbonate (DMC) with a volume ratio of 1:1:1 and package it , After forming, degassing, trimming and other technological processes, the lithium ion battery is obtained.
  • EC ethylene carbonate
  • DEC diethyl carbonate
  • DMC dimethyl carbonate
  • Liquid retention coefficient liquid retention volume/capacity of the electrode assembly.
  • the test temperature is 25°C/45°C. It is charged to 4.4V at a constant current of 0.7C, then charged to 0.025C at a constant voltage, and discharged to 3.0V at 0.5C after standing for 5 minutes.
  • the capacity obtained in this step is the initial capacity, and the 0.7C charge/0.5C discharge is carried out for a cycle test, and the capacity at each step is used as the ratio of the initial capacity to obtain the capacity attenuation curve.
  • the number of turns from 25°C cycling to 90% of the capacity retention rate is recorded as the room temperature cycle performance of the electrode assembly, and the number of turns from 45°C cycling to 80% is recorded as the high temperature cycling performance of the electrode assembly.
  • Example 2 By comparing Example 2 and Comparative Examples 1-2, it can be seen that the silicon-based material with the recessed structure can increase the liquid retention capacity and reduce the expansion of the electrode assembly, thereby improving the cycle performance of the electrochemical device and reducing the DC resistance.
  • the silicon-based material with a recessed structure can also have a relatively high compaction density and liquid retention when the content of the conductive agent is increased, and the cycle performance and expansion performance of the electrochemical device Can also be improved.

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Abstract

本公开提供了负极材料、负极极片、电化学装置和电子装置。负极材料包括硅基材料，其中，硅基材料的颗粒具有至少一个凹部，凹部的宽度为50nm～20μm，深度为50nm～10μm。本公开通过采用具有凹陷结构的硅基材料，这种凹陷结构给硅基材料留出一定的膨胀空间，解决了硅基材料的体积膨胀大的问题。另外，凹陷结构的硅基材料在与碳材料、导电剂等复合制成负极极片时，较小的碳材料颗粒和导电剂嵌入硅基材料的凹部，解决了凹陷结构的硅基负极材料压实密度不高的问题，弥补了凹陷结构体积能量密度低的缺陷。

Description

负极材料、负极极片、电化学装置和电子装置 技术领域
本公开涉及电子技术领域，尤其涉及一种负极材料、负极极片、电化学装置和电子装置。
背景技术
硅基材料具有高达4200mAh/g的理论比容量，是具有应用前景的下一代电化学装置(例如，锂离子电池)的负极材料。然而，硅基材料在充放电过程中具有约300％的体积膨胀，并且导电性较差，阻碍了硅基材料的进一步规模化应用。
目前，通过采用氧化物包覆、聚合物包覆等手段来改善硅基材料的体积膨胀，进而改善相应的电化学装置的循环性能和倍率性能。然而，目前的改善方案并不令人满意。
发明内容
鉴于以上所述现有技术的缺点，本公开通过对硅基材料进行结构设计，采用具有凹部的硅基材料颗粒来改善硅基材料的体积膨胀，增强不同材料之间的界面接触，从而提高界面导电性，进而改善电化学装置的循环性能和倍率性能。
本公开提供一种负极材料，包括：硅基材料，其中，所述硅基材料的颗粒具有至少一个凹部，所述凹部的宽度为50nm～20μm，深度为50nm～10μm。
在上述负极材料中，其中，所述硅基材料的颗粒具有多个凹部，所述多个凹部之间的连结厚度为30nm～10μm。
在上述负极材料中，其中，所述硅基材料的颗粒还具有至少一个圆角结构，所述圆角结构的平均弧长为1μm～50μm。
在上述负极材料中，其中，所述负极材料还包括石墨和导电剂，至少部分石墨位于所述硅基材料的所述凹部中，所述凹部的平均宽度为a，石墨的平均粒径D50为b，石墨的平均最小颗粒宽度为c，其中，c<a，b<3a。
在上述负极材料中，其中，所述硅基材料包括硅、氧化亚硅、硅碳或硅氧碳陶瓷材料(SiOC)中的至少一种。
在上述负极材料中，其中，所述负极材料还包括石墨和导电剂，所述导电剂包括导电炭黑、科琴黑、乙炔黑、碳纳米管或石墨烯中的至少一种。
在上述负极材料中，其中，所述负极材料还包括碳材料、导电剂和粘结剂，所述硅基材料、所述碳材料、所述导电剂和所述粘结剂的质量比为5～40：55～90：0.5～10：0.5～10，所述硅基材料的质量占所述硅基材料、所述碳材料、所述导电剂和所述粘结剂的总质量的百分比为5％～40％，所述导电剂的质量占所述硅基材料、所述碳材料、所述导电剂和所述粘结剂的总质量的百分比为0.5％～10％。
本公开还提供了一种负极极片，包括：集流体；活性物质层，位于所述集流体上；其中，所述活性物质层包括上述任一负极材料。
本公开还提供了一种电化学装置，包括：正极极片；负极极片；隔离膜，设置于所述正极极片和所述负极极片之间；其中，所述负极极片为上述负极极片。
本公开还提供了一种电子装置，包括上述电化学装置。
本公开通过采用具有凹陷结构(凹部)的硅基材料，这种凹陷结构给硅基材料留出一定的膨胀空间，解决了硅基材料的体积膨胀大的问题。另外，凹陷结构的硅基材料在与碳材料(例如，石墨)、导电剂等复合制成负极极片时，较小的碳材料(例如，石墨)颗粒和导电剂嵌入硅基材料的凹部，解决了凹陷结构的硅基负极材料压实密度不高的问题，弥补了凹陷结构体积能量密度低的缺陷。此外，凹陷结构的硅基材料能够促进电解液扩散和渗透，提高负极极片的保液能力，降低传输阻抗，进而提高相应的电化学装置的倍率性能和循环性能。
附图说明
图1是本公开的负极材料的示例性图像。
图2是本公开的负极极片的示意图。
图3是本公开的循环后的负极极片的扫描电镜图像。
图4是本公开的电化学装置的电极组件的示意图。
图5至图7是本公开的实施例1中的负极极片的横截面的图像。
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。
硅基材料作为下一代高比容量负极材料，可以显著提升电极组件的能量密度，但是硅基材料的导电性较差，并且在脱嵌锂过程中存在较大的体积膨胀和收缩。为了改善硅基材料的体积膨胀，可以设计多孔硅基材料、降低硅基材料的尺寸、采用氧化物包覆、聚合物包覆以及碳材料包覆等。设计多孔硅基材料以及降低硅基材料的尺寸在一定程度上可以改善电化学装置的倍率性能，但是随着循环的进行，副反应的发生以及不可控的固体电解质界面(SEI，solid electrolyte interface)膜的生长进一步限制了材料的循环稳定性。此外，在硅基材料表面进行材料包覆时，在极片加工过程中，碳包覆硅基材料很可能由于反复剪切力的作用出现脱碳现象，从而影响其库伦效率，并且在形成SEI膜时消耗电解液。另一方面，在多次的循环过程中由于硅基材料的膨胀收缩和破裂，碳层很容易从硅基材料颗粒上剥落，随着SEI的生成而被副产物包裹，导致电化学阻抗和极化增大，从而影响循环寿命。
本公开通过对硅基材料颗粒进行结构设计，利用硅基材料颗粒的凹陷(材料表面大面积凹陷和向内弯曲的形貌)与碳材料(例如，石墨)和导电剂的机械咬合，从而提高不同材料界面之间的导电性能，使得电子和离子的传输更为便利，可有效降低电化学装置的直流电阻。同时，这种凹陷结构给硅基材料留出一定的膨胀空间，与碳材料(例如，石墨)的咬合也能缓冲硅基材料的体积膨胀。此外，凹部有利于硅基材料和碳材料(例如，石墨)的互相咬合，使这两种材料的界面接触更紧密，并且在与碳材料(例如，石墨)复合制作成负极极片时，较小的碳材料(例如，石墨)颗粒嵌 入硅基材料的凹部，解决凹陷结构的硅基负极材料压实密度不高的问题，弥补了凹陷结构体积能量密度低的缺陷。凹陷结构能够促进电解液扩散和渗透，提高负极极片的保液能力，降低传输阻抗，进而提高相应的电化学装置的倍率性能和循环性能。
本公开的一些实施例提供了一种负极材料，负极材料包括硅基材料，其中，硅基材料的颗粒具有至少一个凹部。在一些实施例中，凹部的宽度为50nm～20μm，深度为50nm～10μm。通过采用具有凹部的硅基材料，一方面为体积膨胀留出空间，解决了硅基材料体积膨胀大的问题；另一方面，负极材料中的碳材料(例如，石墨)和导电剂可以落入硅基材料的凹部中，克服了具有凹陷结构的硅基材料带来的压实密度不高的问题，提高了负极材料的体积能力密度。在一些实施例中，凹部具有不规则形状。在一些实施例中，凹部里面具有一个或多个更小的凹部。在一些实施例中，硅基材料包括硅、氧化亚硅、硅碳或硅氧碳陶瓷材料(SiOC)中的至少一种。在一些实施例中，硅基材料为硅氧颗粒材料。在一些实施例中，硅基材料包括SiO xC yM z，其中0≤x≤2，0≤y≤1，0≤z≤0.5，M表示锂、镁、钛或铝中的至少一种。在一些实施例中，可以通过蚀刻等获得带有凹部的硅基材料颗粒，但是本公开不限于此，可以采用任何其他合适的方法获得带有凹部的硅基材料颗粒。
在一些实施例中，硅基材料的颗粒具有多个凹部，多个凹部之间的连结厚度为30nm～10μm。如图1所示，凹部之间的连结厚度指的是凹部之间的最近的距离。例如，假如某个硅基材料颗粒具有一个上凹部和一个下凹部，则上凹部和下凹部之间的连接厚度是这两个凹部之间的最短距离。在硅基材料的颗粒具有多个凹部时，凹部之间可以保持一定的连结厚度，以避免成为中空结构，从而有利于改善负极材料的压实密度和体积能量密度。
在一些实施例中，硅基材料的颗粒还具有至少一个圆角结构，圆角结构的平均弧长为1μm～50μm。硅基材料的颗粒的圆角结构有利于在与石墨和导电剂等混合时促进石墨和导电剂等滑入凹部。
在一些实施例中，负极材料还包括石墨和导电剂，至少部分石墨位于硅基材料的凹部中。如图1所示，硅基材料的凹部内具有小的石墨颗粒(图1中的虚线框所示)。在一些实施例中，凹部的平均宽度为a，石墨的平均粒径D 50为b，石墨的平均最小颗粒宽度为c，其中，c<a，b<3a。在一些实施例中， 凹部的宽度指的是凹部的较短的边对应的尺寸，较长的边对应凹部的长度，石墨的最小颗粒宽度指的是石墨颗粒的较短的边所对应的宽度的最小值。通过使c<a并且b<3a，可以在硅基材料、石墨和导电剂等复合制备负极极片时，石墨和导电剂可以更好地咬合在或落入硅基材料颗粒的凹部中，起到增强负极材料的导电性以及提高负极材料的压实密度的作用。在一些实施例中，石墨包括人造石墨、天然石墨或其组合，其中人造石墨或天然石墨包括中间相碳微球、软碳或硬碳中的至少一种。在一些实施例中，导电剂为含碳导电剂。在一些实施例中，导电剂包括导电炭黑、科琴黑、乙炔黑、碳纳米管或石墨烯中的至少一种。
在一些实施例中，负极材料包括碳材料、导电剂和粘结剂。在一些实施例中，负极材料中的碳材料包括石墨和/或石墨烯等。在一些实施例中，硅基材料、碳材料、导电剂和粘结剂的质量比为5～40：55～90：0.5～10：0.5～10。在一些实施例中，硅基材料的质量占硅基材料、碳材料、导电剂和粘结剂的总质量的百分比为5％～40％。如果硅基材料的含量太少，则对提高比容量的作用有限；如果硅基材料的含量超过40％，负极极片的压实密度和保液量降低幅度大。这是由于具有凹陷结构的硅基材料本身具有较低的压实密度，但是和碳材料(例如，石墨)、导电剂配合使用时，碳材料和导电剂进入硅基材料的凹部，弥补了其压实密度低的缺点，同时提高了负极极片对电解液的保液量。当具有凹陷结构的硅基材料的添加量太多时，会使其本身的缺点显现，使压实密度和保液量降低。
在一些实施例中，导电剂的质量占硅基材料、碳材料、导电剂和粘结剂的总质量的百分比为0.5％～10％。在一些实施例中，适当提高导电剂的含量，可以使硅基材料的凹部内的导电剂更多，提高负极材料的导电性，不仅不会影响压实密度和保液量，也能够改善负极极片的循环性能，减小直流电阻。然而，当导电剂的含量太高时，会降低负极材料的体积能量密度。
在一些实施例中，硅基颗粒的平均粒径为500nm～50μm。如果硅基材料的平均粒径过小，硅基材料容易发生团聚，并且由于比表面积大而消耗更多的电解液来形成SEI膜。如果硅基材料的平均粒径过大，不利于抑制硅基材料的体积膨胀，也容易引起活性物质层的导电性能的恶化。另外，如果硅基材料的平均粒径太大，则会使得负极极片的强度降低。
如图2所示，本公开的一些实施例提供了一种负极极片，负极极片包括集流体1和活性物质层2。活性物质层2位于集流体1上。应该理解，虽然图2中将活性物质层2示出为位于集流体1的一侧上，但是这仅是示例性的，活性物质层2可以位于集流体1的两侧上。在一些实施例中，负极极片的集流体可以包括铜箔、铝箔、镍箔或碳基集流体中的至少一种。在一些实施例中，活性物质层2包括上述任一种负极材料。
在一些实施例中，活性物质层包括硅基材料、碳材料、导电剂和粘结剂，硅基材料、碳材料、导电剂和粘结剂的质量比为5～40：55～90：0.5～10：0.5～10，活性物质层中的硅基材料的质量百分比为5％～40％，活性物质层中的导电剂的质量百分比为0.5％～10％。在一些实施例中，可以选择如上所述的硅基材料、碳材料、导电剂。在一些实施例中，粘结剂可以包括羧甲基纤维素(CMC)、聚丙烯酸、聚乙烯基吡咯烷酮、聚苯胺、聚酰亚胺、聚酰胺酰亚胺、聚硅氧烷、聚丁苯橡胶、环氧树脂、聚酯树脂、聚氨酯树脂或聚芴中的至少一种。在一些实施例中，活性物质层中的粘结剂的质量百分比为0.5％～10％。在一些实施例中，活性物质层的厚度为50μm～200μm，活性物质层中的负极材料在5t的压力下的压实密度为0.8g/cm 3～5g/cm 3。在一些实施例中，活性物质层中的碳元素的质量含量为0～80％。在一些实施例中，活性物质层中的负极材料的比表面积为1m 2/g～50m 2/g。
在一些实施例中，本公开从硅基材料的形貌结构出发，采用凹陷结构解决硅基材料的体积膨胀带来的一些问题，配合碳材料(例如，石墨)和导电剂制成负极极片，既弥补了具有凹部的硅基材料本身压实密度低的缺点，又改善了硅基材料的体积膨胀带来的问题，提高了负极极片的直流电阻和保液能力，从而改善相应的电化学装置的循环性能等。如图3所示，示出了循环后的负极极片的扫描电镜图。由于硅基材料的凹陷结构的自身优势，在配合碳材料(例如，石墨)和导电剂做成负极极片时，经过循环后其结构并没有发生明显的改变。
如图4所示，本公开的一些实施例提供了一种电化学装置，电化学装置包括正极极片10、负极极片12以及设置于正极极片10和负极极片12之间的隔离膜11。正极极片10可以包括正极集流体和涂覆在正极集流体上的 正极活性物质层。在一些实施例中，正极活性物质层可以仅涂覆在正极集流体的部分区域上。正极活性物质层可以包括正极活性物质、导电剂和粘结剂。正极集流体可以采用Al箔，同样，也可以采用本领域常用的其他正极集流体。正极极片的导电剂可以包括导电炭黑、片层石墨、石墨烯或碳纳米管中的至少一种。正极极片中的粘结剂可以包括聚偏氟乙烯、偏氟乙烯-六氟丙烯的共聚物、苯乙烯-丙烯酸酯共聚物、苯乙烯-丁二烯共聚物、聚酰胺、聚丙烯腈、聚丙烯酸酯、聚丙烯酸、聚丙烯酸盐、羧甲基纤维素纳、聚醋酸乙烯酯、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。正极活性物质包括但不限于钴酸锂、镍酸锂、锰酸锂、镍锰酸锂、镍钴酸锂、磷酸铁锂、镍钴铝酸锂或镍钴锰酸锂中的至少一种，以上正极活性物质可以经过掺杂或包覆处理。
在一些实施例中，隔离膜11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～500μm的范围内。
在一些实施例中，隔离膜表面还可包括多孔层，多孔层设置在隔离膜的至少一个表面上，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～1μm的范围的直径。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、羧甲基纤维素纳、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接性。
在一些实施例中，负极极片12可以为如上所述的负极极片。
在本公开的一些实施例中，电化学装置的电极组件为卷绕式电极组件或堆叠式电极组件。
在一些实施例中，电化学装置包括锂离子电池，但是本公开不限于此。在一些实施例中，电化学装置还可以包括电解液。在一些实施例中，电解液包括但不限于碳酸二甲酯(DMC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、丙酸丙酯(PP)中的至少两种。此外，电解液还可以额外地包括作为电解液添加剂的碳酸亚乙烯酯(VC)、氟代碳酸乙烯酯(FEC)或二腈化合物中的至少一种。在一些实施例中，电解液还包括锂盐。
在本公开的一些实施例中，以锂离子电池为例，将正极极片、隔离膜、负极极片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及循环测试。
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。
本公开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公开进行说明，其中，采用锂离子电池作为示例。
实施例1
负极极片的制备：集流体采用铜箔，厚度为10μm；活性材料采用Si和石墨，导电剂采用导电炭黑，粘结剂采用聚丙烯酸；将活性材料、导电炭黑、粘结剂混合后分散于去离子水中形成浆料，经搅拌均匀、涂布于铜箔上，涂布重量控制在0.108kg/1540.25m 2，干燥、冷压、分条后得到负极极片。相应的参数如表1所示。
正极极片制备：取正极活性物质LiCoO 2、导电炭黑、粘结剂聚偏二氟乙烯(PVDF)按质量比96.7：1.7：1.6在N-甲基吡咯烷酮溶剂体系中充分搅拌混合均匀后，涂覆于铝箔上，再经烘干、冷压，得到正极极片。
电池制备：以聚乙烯多孔聚合薄膜作为隔离膜，将正极极片、隔离膜、负极极片按顺序依次叠好，使隔离膜处于正积极片和负极极片中间起到隔离的作用，并卷绕得到电极组件。将电极组件置于外包装铝塑膜中，注入含有体积比为1:1:1的碳酸乙烯酯(EC)、碳酸二乙酯(DEC)和碳酸二甲酯(DMC)的电解液并封装，经过化成，脱气，切边等工艺流程得到锂离子电池。
在实施例2～12与对比例1～4中，正极极片、锂离子电池制备均与实施例1相同，仅负极极片的制备有些不同，参数的差异示出于相应的表1中。
表1
Figure PCTCN2020082267-appb-000001
Figure PCTCN2020082267-appb-000002
实施例和对比例的各项性能参数的测定方法如下。
极片压实密度测试：
采用30t的压力压实，冲出面积为1540.25mm 2的圆片，用千分尺测量圆片厚度，对圆片称重，计算圆片体积，即可计算出极片的压实密度。
保液系数测试：
观察电化学装置的电极组件的外观，电极组件的密封袋(pocket)表面无明显的液泡，无明显褶皱，形状如饼干。记录电极组件内的电解液的重量。保液系数＝保液量/电极组件的容量。
循环性能测试：
测试温度为25℃/45℃，以0.7C恒流充电到4.4V，再恒压充电到0.025C，静置5分钟后以0.5C放电到3.0V。以此步得到的容量为初始容量，进行0.7C充电/0.5C放电进行循环测试，以每一步的容量与初始容量做比值，得到容量衰减曲线。以25℃循环截至到容量保持率为90％的圈数记为电极组件的室温循环性能，以45℃循环截至到80％的圈数记为电极组件的高温循环性能，通过比较上述两种情况下的循环圈数而得到材料的循环性能。
电极组件的膨胀率测试：
用螺旋千分尺测试半充时新鲜电极组件的厚度，循环至500cls时，再用螺旋千分尺测试此时电极组件的厚度，与初始半充时新鲜电极组件的厚度对比，即可得此时电极组件的膨胀率。
直流阻抗(DCR)测试：
利用Maccor机在25℃测试电极组件的实际容量(0.7C恒流充电到4.4V,恒压充电到0.025C,静置10分钟，以0.1C放电到3.0V，静置5分钟)通过 0.1C放电一定荷电状态(SOC)下，测试1s放电以5ms进行采点，计算出在不同SOC下的DCR值。
对实施例1～12以及对比实施例1～4的结果进行数据统计，统计结果见表2。
表2
Figure PCTCN2020082267-appb-000003
通过比较实施例1～12和对比例1～3可知，通过采用具有凹陷结构的硅基材料，电极组件的保液系数具有不同程度的增大，DCR也减小，电极组件的膨胀率减小，电化学装置的循环性能也得到提升。
通过比较实施例1～2和6～9可知，负极极片中随着具有凹陷结构的硅基材料的含量增加，在一定的压力下，负极极片的压实密度没有明显的差异。当硅基材料的含量增加到35％时，负极极片的压实密度有所降低，当含量增加到40％时，负极极片的压实密度和保液量降低幅度更大。这是由于具有凹陷结构的硅基材料本身具有较低的压实密度，但是和石墨、导电剂配合使用时，石墨和导电剂进入硅基材料的凹部处，弥补了其压实密度低的缺点，同 时提高了负极极片对电解液的保液量。当具有凹陷结构的硅基材料添加量太多，则会使硅基材料本身的缺点显现，使压实密度和保液量降低。图5至图7示出了本公开的实施例1中的负极极片的横截面的图像。
通过比较实施例2～5可知，采用不同种类的具有凹陷结构的硅基材料，均能改善保液量，降低DCR，改善电化学装置的膨胀和循环性能。
通过比较实施例2和10～11可知，除导电炭黑(Super P)外，使用其它种类的导电剂，凹陷结构的硅基材料也能体现出优异的负极极片压实密度和保液量，并且电化学装置的循环性能得到改善，直流电阻减小。
通过比较实施例2和12可知，适当提高导电剂含量，可以使凹部内的导电剂更多，提高负极材料的导电性，不仅不会影响压实密度和保液量，也能够改善电化学装置的循环性能，减小直流电阻。
通过比较实施例2和对比例1～2可知，采用凹陷结构的硅基材料能够提高保液量，减小电极组件的膨胀，从而提高电化学装置的循环性能，降低直流电阻。
通过比较实施例12和对比例3可知，采用凹陷结构的硅基材料，在导电剂含量提高时，也能有比较高的压实密度和保液量，并且电化学装置的循环性能和膨胀性能也能得到改善。
通过比较实施例1～2、6～7和对比例4可知，当凹陷结构的硅基材料的含量小于或等于20％时，负极极片的压实密度和保液量和不加硅基材料的负极极片相当，并且电极组件的膨胀率也相当。这表明通过凹陷结构的硅基材料和石墨、导电剂等配合，已经完全克服了凹陷结构的硅基材料的压实密度不高的缺点。
以上描述仅为本公开的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，本公开中所涉及的公开范围，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公开构思的情况下，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中公开的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. 一种负极材料，包括：
    硅基材料，
    其中，所述硅基材料的颗粒具有至少一个凹部，所述凹部的宽度为50nm～20μm，深度为50nm～10μm。
  2. 根据权利要求1所述的负极材料，其中，所述硅基材料的颗粒具有多个凹部，所述多个凹部之间的连结厚度为30nm～10μm。
  3. 根据权利要求1所述的负极材料，其中，所述硅基材料的颗粒还具有至少一个圆角结构，所述圆角结构的平均弧长为1μm～50μm。
  4. 根据权利要求1所述的负极材料，其中，所述负极材料还包括石墨和导电剂，至少部分石墨位于所述硅基材料的所述凹部中，所述凹部的平均宽度为a，石墨的平均粒径D 50为b，石墨的平均最小颗粒宽度为c，其中，c<a，b<3a。
  5. 根据权利要求1所述的负极材料，其中，所述硅基材料包括硅、氧化亚硅、硅碳或硅氧碳陶瓷材料(SiOC)中的至少一种。
  6. 根据权利要求1所述的负极材料，其中，所述负极材料还包括石墨和导电剂，所述导电剂包括导电炭黑、科琴黑、乙炔黑、碳纳米管或石墨烯中的至少一种。
  7. 根据权利要求1所述的负极材料，其中，所述负极材料还包括碳材料、导电剂和粘结剂，所述硅基材料、所述碳材料、所述导电剂和所述粘结剂的质量比为5～40：55～90：0.5～10：0.5～10，所述硅基材料的质量占所述硅基材料、所述碳材料、所述导电剂和所述粘结剂的总质量的百分比为5％～40％，所述导电剂的质量占所述硅基材料、所述碳材料、所述导电剂和所述粘结剂的总质量的百分比为0.5％～10％。
  8. 一种负极极片，包括：
    集流体；
    活性物质层，位于所述集流体上；
    其中，所述活性物质层包括根据权利要求1至7中任一项所述的负极材料。
  9. 一种电化学装置，包括：
    正极极片；
    负极极片；
    隔离膜，设置于所述正极极片和所述负极极片之间；
    其中，所述负极极片为根据权利要求8所述的负极极片。
  10. 一种电子装置，包括根据权利要求9所述的电化学装置。
PCT/CN2020/082267 2020-03-31 2020-03-31 负极材料、负极极片、电化学装置和电子装置 WO2021195914A1 (zh)

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