WO2021226842A1 - Matériau d'électrode négative, plaque d'électrode négative, dispositif électrochimique et dispositif électronique - Google Patents

Matériau d'électrode négative, plaque d'électrode négative, dispositif électrochimique et dispositif électronique Download PDF

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WO2021226842A1
WO2021226842A1 PCT/CN2020/089842 CN2020089842W WO2021226842A1 WO 2021226842 A1 WO2021226842 A1 WO 2021226842A1 CN 2020089842 W CN2020089842 W CN 2020089842W WO 2021226842 A1 WO2021226842 A1 WO 2021226842A1
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silicon
negative electrode
based material
carbon
sheet
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PCT/CN2020/089842
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English (en)
Chinese (zh)
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张成波
谢远森
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宁德新能源科技有限公司
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Publication of WO2021226842A1 publication Critical patent/WO2021226842A1/fr

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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
    • 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
    • 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
    • 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.
  • the compacted density of the negative pole piece directly made of silicon-based negative electrode material is only 1.2g/cm 3 , which is far lower than the compacted density of graphite-based negative pole piece of 1.8g/cm 3 , and also far lower than that of silicon-based materials
  • the theoretical true density is 2.3g/cm 3 , and the compact density is too low will cause more gaps between the negative electrode materials, affect the conductivity of the negative electrode material, and cause the reduction of the volume energy density of the electrochemical device and the deterioration of the cycle performance.
  • the anode materials containing silicon-based materials in the present disclosure include sheet-like carbon-based materials with a diameter-to-thickness ratio greater than 2, thereby greatly increasing the compaction density of the anode materials, thereby improving the electrical conductivity.
  • the volumetric energy density and cycle performance of chemical devices include sheet-like carbon-based materials with a diameter-to-thickness ratio greater than 2, thereby greatly increasing the compaction density of the anode materials, thereby improving the electrical conductivity.
  • the present disclosure provides a negative electrode material, including: a silicon-based material and a sheet-shaped carbon-based material; wherein the diameter-to-thickness ratio of the sheet-shaped carbon-based material is greater than 2.
  • the sheet-shaped carbon-based material includes graphite
  • the graphitization degree of the graphite is above 90%.
  • the silicon-based material includes at least one of silicon oxide, silicon, silicon-carbon composite material, or silicon alloy.
  • the silicon-based material satisfies at least one of the following: the surface of the silicon oxide has the flaky carbon-based material; the particle size range of the silicon oxide satisfies 1 ⁇ m ⁇ Dv50 ⁇ 10 ⁇ m The specific surface area of the silicon oxide is less than 10m 2 /g; the general formula of the silicon oxide is SiO x , where 0 ⁇ x ⁇ 2; the silicon includes silicon microparticles, silicon nanoparticles, and silicon nanowires Or at least one of silicon nano-film; the silicon alloy includes at least one of silicon-iron alloy, silicon-aluminum alloy, silicon-nickel alloy, or silicon-iron-aluminum alloy.
  • the sheet-like carbon-based material includes at least one of graphite, graphene, soft carbon or hard carbon, and the particle size range of the sheet-like carbon-based material satisfies Dv50 ⁇ 10 ⁇ m.
  • 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; a separator, arranged between the positive pole piece and the negative pole piece; wherein the negative pole piece is the above-mentioned negative Pole piece.
  • the present disclosure also provides an electronic device, including the electrochemical device described above.
  • the present disclosure significantly increases the compaction density of the negative electrode material and improves the volume energy density and cycle performance of the electrochemical device by adding a sheet-like carbon-based material with a diameter-to-thickness ratio greater than 2 to the negative electrode material containing the silicon-based material.
  • Fig. 1 is a scanning electron image of flake graphite in a negative electrode material according to an embodiment of the present disclosure.
  • Fig. 2 is a cross-sectional scanning electron microscope view of flake graphite in a negative electrode material in an embodiment of the present disclosure.
  • Fig. 3 is an exemplary image of a negative pole piece of the present disclosure.
  • Fig. 4 is a schematic diagram of an electrode assembly of an electrochemical device of the present disclosure.
  • Example 5 is a schematic diagram of the compaction density of the negative electrode materials in Example 3 and Comparative Example 1 of the present disclosure under different pressures.
  • FIG. 6 is a schematic diagram of the volume energy density under different flake graphite contents in Examples 1 to 5 and Comparative Example 1 of the present disclosure.
  • Example 7 is a schematic diagram of the discharge capacity retention rate under different cycle cycles in Examples 2 and 3 and Comparative Example 1 of the present disclosure.
  • Silicon-based materials as the next-generation high-capacity anode materials, can significantly increase the energy density of the electrode assembly.
  • the compaction density of the anode pole piece prepared with silicon-based materials as the anode material is much lower than that of the anode prepared with graphite as the anode material.
  • the compaction density of the pole piece When the compaction density of the silicon-based material is low, poor contact between the silicon-based materials will cause the conductivity to deteriorate and affect the cycle performance.
  • a carbon-based material with a diameter-to-thickness ratio greater than 2 is added to the negative electrode material containing silicon-based material, thereby increasing the compaction density of the negative electrode plate prepared by the negative electrode material, increasing the electrical contact between the silicon-based materials, and at the same time
  • the sheet-shaped carbon-based material also enhances the conductivity of the negative electrode material, thereby improving the cycle performance of the electrochemical device, and can also increase the volume energy density of the electrochemical device.
  • the negative electrode material includes a silicon-based material and a sheet-shaped carbon-based material; wherein the diameter-to-thickness ratio of the sheet-shaped carbon-based material is greater than 2.
  • the flake carbon-based material in some embodiments of the present disclosure may be flake graphite as shown in FIGS. 1 and 2.
  • the diameter-to-thickness ratio of the sheet-shaped carbon-based material refers to the ratio L/H of the diameter L of the circumscribed circle projected by the sheet-shaped carbon-based material and the thickness H of the sheet-shaped carbon-based material.
  • the cross-sectional view of the flaky carbon-based material was photographed by electron microscopy to measure and calculate the diameter-to-thickness ratio of the flaky carbon-based material.
  • a sheet-shaped carbon-based material with a diameter-to-thickness ratio greater than 2 to a negative electrode material containing a silicon-based material, it can improve The compaction density of the negative electrode material reduces the gap between the silicon-based materials in the negative electrode material and enhances the electrical contact between the silicon-based materials.
  • the sheet-shaped carbon-based material can increase the conductivity of the negative electrode material, thereby improving the negative electrode material Cycle performance.
  • the diameter-to-thickness ratio of the sheet-like carbon-based material is set to be greater than 2. This is because when the diameter-to-thickness ratio is greater than 2, the sheet-like carbon-based material easily slips along the direction of the sheet. Carbon-based materials are more likely to have a lubricating effect, so as to fully fill the gaps between silicon-based materials, improve compaction density and cycle performance, and help increase the volume energy density of electrochemical devices.
  • the sheet-shaped carbon-based material is difficult to play a lubricating effect, and the gap between the silicon-based materials cannot be fully filled, so the compaction density of the negative electrode plate prepared by the negative electrode material cannot be significantly improved, and the It is beneficial to improve the volumetric energy density and cycle performance of the electrochemical device.
  • the powder compaction density of the negative electrode material at a pressure of 150 MPa is above 1.4 g/cm 3.
  • the ratio of the Dv50 of the sheet-shaped carbon-based material to the Dv50 of the silicon-based material is greater than 1
  • the size of the sheet-shaped carbon-based material is too large compared to the size of the silicon-based material.
  • the size of the gap is significantly smaller than the size of the sheet-shaped carbon-based material. Therefore, the sheet-shaped carbon-based material cannot effectively fill the gap between the silicon-based materials.
  • the conductivity between the silicon-based materials is reduced, which is not conducive to the improvement of cycle performance. Therefore, in some embodiments of the present disclosure, the ratio of the Dv50 of the sheet-shaped carbon-based material to the Dv50 of the silicon-based material is controlled to be less than 1.
  • the mass of the flaky carbon-based material accounts for 0.5%-40% of the total mass of the silicon-based material and the flaky carbon-based material. In some embodiments, when the ratio of the flaky carbon-based material to the total mass of the silicon-based material and the flaky carbon-based material is less than 0.5%, since the content of the flaky carbon-based material is too low, the compaction of the negative electrode material cannot be significantly improved. Density, conductivity and cycle performance, and when the mass of the flaky carbon-based material accounts for more than 40% of the total mass of the silicon-based material and the flaky carbon-based material, the specific capacity of the flaky carbon-based material is much smaller than that of the silicon-based material. The specific capacity of the material, too high content of the flake carbon-based material will cause the specific capacity and volume energy density of the negative electrode material to decrease.
  • the sheet-shaped carbon-based material includes graphite, and the graphitization degree of the graphite is above 90%.
  • graphite is prone to slip along the direction of the sheet to play a lubricating effect to fill the gaps between silicon-based materials.
  • the graphitization degree of graphite is less than 90%, the defects in the graphite are relatively large. Many defects will prevent graphite from sliding along the direction of the sheet.
  • Graphite is difficult to lubricate and can not effectively fill the gaps between silicon-based materials, which is not conducive to improving the compaction density, conductivity and cycle performance of the negative electrode material.
  • the silicon-based material includes at least one of silicon oxide, silicon, silicon-carbon composite material, or silicon alloy.
  • the silicon-based material at least satisfies one of the following (a) to (f): (a) the surface of the silicon oxide has a sheet-like carbon-based material.
  • the conductivity of silicon oxide is poor, so when (a) is satisfied, the conductivity of silicon oxide can be increased to improve cycle performance.
  • the particle size range of silicon oxide satisfies 1 ⁇ m ⁇ Dv50 ⁇ 10 ⁇ m. If the particle size of silicon oxide is too small, it will increase the consumption of electrolyte and is not conducive to cycle performance. When the particle size of silicon oxide is too large, it will cause degradation of rate performance. Therefore, in some embodiments, it is necessary to meet (b) control The particle size range of the silicon oxide compound.
  • the specific surface area of silicon oxide is less than 10 m 2 /g. In some embodiments, when the specific surface area of silicon oxide is not less than 10m 2 /g, more electrolyte will be consumed to form an SEI (solid electrolyte interface) film, resulting in excessive loss of first charge capacity and increased adhesion. Therefore, the specific surface area of silicon oxide is set to be less than 10 m 2 /g.
  • the general formula of silicon oxide is SiO x , where 0 ⁇ x ⁇ 2.
  • certain point defects such as holes, are introduced into silicon oxide. By introducing point defects, the conductivity of silicon oxide can be improved, thereby improving cycle performance. .
  • Silicon includes at least one of silicon microparticles, silicon nanoparticles, silicon nanowires, or silicon nanofilms.
  • the silicon alloy includes at least one of silicon-iron alloy, silicon-aluminum alloy, silicon-nickel alloy, or silicon-iron-aluminum alloy.
  • the flaky carbon-based material includes at least one of graphite, graphene, soft carbon, or hard carbon, and the particle size range of the flaky carbon-based material satisfies Dv50 ⁇ 10 ⁇ m.
  • 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 silicon-based material and the sheet-shaped carbon-based material in the negative electrode material are composited through at least one of physical mixing and mechanical nodular ink.
  • the flaky carbon-based material when preparing the negative electrode material, can be mixed with the silicon-based material according to a certain mass percentage. At least one of the airflow mixer or the horizontal mixer is mixed, and then the mixed silicon-based material and the flake carbon-based material can be further subjected to a ball milling mechanical reaction, so that at least a part of the outer surface of the silicon-based material is covered by the flake carbon-based material. The material adheres to the coating, that is, makes the surface of the silicon-based material have a sheet-like carbon-based material.
  • the silicon-based material may be at least one of silicon oxide, pure silicon, silicon carbon, or silicon alloy. In some embodiments, pure silicon may be microparticles, nanoparticles, nanowires, nanofilms, or nanospheres. At least one.
  • 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 further includes a silicon-based material conductive agent and/or a binder.
  • 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, and 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 conductive agent may include at least one of conductive carbon black, Ketjen black, acetylene black, carbon nanotubes, VGCF (Vapor Grown Carbon Fiber), or graphene.
  • 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. 11.
  • the positive pole piece 10 may include a positive current collector and a positive active material layer coated on the positive 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 electrode active material includes 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 substance 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 also 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 wound or stacked in order to form electrode parts, and then packed into, for example, aluminum-plastic film for packaging, and electrolysis is carried out.
  • 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.
  • Anode material preparation SiO x (0 ⁇ x ⁇ 2, Dv50: 6 ⁇ m, specific surface area: 2m 2 /g) and flake graphite (diameter-thickness ratio: 5, graphitization degree: 97%, Dv50: 4.2 ⁇ m) After mixing with a mass ratio of 95:5, it is placed in a planetary ball mill for further surface adhesion treatment.
  • the particle size ratio of flake graphite to SiO x is 0.7 (that is, the ratio of Dv50 of flake graphite to Dv50 of SiO x is 0.7).
  • the sample after the ball milling treatment was used as the negative electrode material.
  • the negative electrode piece the negative electrode material, conductive agent conductive acetylene black, binder polyacrylic resin (PAA), according to the weight ratio of 80:10:10 in deionized water, fully stirred and mixed uniformly to make a negative electrode slurry, and then The negative electrode slurry is evenly coated on the front and back sides of the negative electrode current collector copper foil, and then dried at 85°C to form the negative electrode active material layer, and then cold press, slitting, cutting, and welding the negative electrode tabs to obtain Negative pole piece.
  • PAA binder polyacrylic resin
  • positive electrode material lithium cobalt oxide (molecular formula is LiCoO 2 ), conductive agent (acetylene black), binder (polyvinylidene fluoride, PVDF) in N-form at a mass ratio of 96:2:2 Stir and mix the base pyrrolidone thoroughly to make a positive electrode slurry. Then, the obtained positive electrode slurry is evenly coated on the positive and negative sides of the positive electrode collector aluminum foil, and then dried at 85°C and then cold pressed, slitted, and cut. Sheet and weld the positive electrode tab to obtain the positive electrode tab.
  • LiCoO 2 LiCoO 2
  • conductive agent acetylene black
  • binder polyvinylidene fluoride, PVDF
  • the solution prepared by mass ratio 8:92 is used as the electrolyte of the lithium ion battery.
  • the isolation membrane adopts a ceramic-coated polyethylene (PE) material isolation membrane.
  • PE polyethylene
  • the positive pole piece, the isolation film, and the negative pole piece are stacked in order to obtain an electrode assembly, and the isolation film is placed between the positive and negative electrodes to play a role of isolation.
  • the electrode assembly is placed in a packaging case, electrolyte is injected and packaged, and the final lithium-ion battery is formed after chemical formation.
  • Examples 2 to 10 and Comparative Examples 1 to 2 the methods for preparing the negative pole piece, the positive pole piece and the battery are the same as that of Embodiment 1, and the difference from Embodiment 1 is only in the preparation of the negative electrode material.
  • Example 2 The difference between Example 2 and Example 1 is that the mass of flake graphite in Example 2 accounts for 10% of the total mass of SiO x and flake graphite.
  • Example 3 The difference between Example 3 and Example 1 is that the mass of flake graphite in Example 3 accounts for 20% of the total mass of SiO x and flake graphite.
  • Example 4 The difference between Example 4 and Example 1 is that the mass of flake graphite in Example 4 accounts for 30% of the total mass of SiO x and flake graphite.
  • Example 5 The difference between Example 5 and Example 1 is that the mass of flake graphite in Example 5 accounts for 40% of the total mass of SiO x and flake graphite.
  • Example 6 The difference between Example 6 and Example 1 is that the mass of flake graphite in Example 6 accounts for 20% of the total mass of SiO x and flake graphite, and the diameter-to-thickness ratio of flake graphite in Example 6 is 2.
  • Example 7 The difference between Example 7 and Example 1 is that the mass of flake graphite in Example 7 accounts for 20% of the total mass of SiO x and flake graphite, and the ratio of Dv50 of flake graphite to Dv50 of SiO x in Example 7 Is 1.
  • Example 8 The difference between Example 8 and Example 1 is that the mass of flake graphite in Example 8 accounts for 20% of the total mass of SiO x and flake graphite, and the ratio of Dv50 of flake graphite to Dv50 of SiO x in Example 8 Is 2.
  • Example 9 The difference between Example 9 and Example 1 is that the mass of flake graphite in Example 9 accounts for 20% of the total mass of SiO x and flake graphite, and the graphitization degree of flake graphite in Example 9 is 94%.
  • Example 10 The difference between Example 10 and Example 1 is that the mass of flake graphite in Example 10 accounts for 20% of the total mass of SiO x and flake graphite, and the graphitization degree of flake graphite in Example 10 is 92%.
  • Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that in Comparative Example 1, SiO x (0 ⁇ x ⁇ 2, Dv50: 6 ⁇ m, specific surface area: 2 m 2 /g) is directly used as a negative electrode material without any treatment.
  • Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that: in Comparative Example 2, non-flaky graphite with a diameter-to-thickness ratio of 1 is used, and the mass of non-flaky graphite in Comparative Example 2 accounts for the total mass of SiO x and non-flaky graphite. 20%.
  • the powder compaction density meter is used to put a specific weight of powder in the standard module, and the compression height of the powder in the standard module is measured under different pressures of MPa, so that the compression height and the cross-sectional area of the standard module can be calculated The volume of the powder under different pressures is then combined with the weight of the powder to calculate the compacted density of the powder.
  • the flake graphite content in Table 1 is the ratio of the mass of flake graphite in the negative electrode material to the total mass of flake graphite and SiO x
  • the diameter-to-thickness ratio is the diameter-to-thickness ratio of the flake graphite in the negative electrode material
  • the Dv50 ratio is the flake graphite Dv50 and Dv50 ratio of SiO x
  • the tap density ⁇ specific capacity negative electrode material volume energy density of negative electrode material.
  • Comparative Example 1 Comparative Example 1, when only silicon-based materials are used as the negative electrode material without adding flake graphite, the compaction density of the negative electrode material is It is only 1.35 g/cc and the 200-week cycle capacity retention rate is only 88.6%. In Examples 1-10 and Comparative Example 2 where flake graphite is added, the compaction density and the 200-week cycle capacity retention rate are higher than those of Comparative Example 1.
  • the gap between the silicon-based materials in the negative electrode material is large, resulting in a lower compaction density, and the lower compaction density causes the silicon-based materials to be ineffective in electrical contact with each other, and The silicon-based material itself has poor conductivity, so the cycle performance of the battery is poor.
  • the added flake graphite can fill the gaps of the silicon-based materials to increase the compaction density and achieve effective electrical contact between the silicon-based materials, thereby improving the negative electrode
  • the overall conductivity of the material further improves the cycle performance. Therefore, in some embodiments of the present disclosure, a sheet-shaped carbon-based material is added to the negative electrode material containing a silicon-based material to improve the compaction density and cycle performance.
  • the diameter-to-thickness ratio of the sheet-shaped carbon-based material is greater than 2 to ensure the volumetric energy density and cycle performance.
  • volume energy density As the content of flake graphite increases, it decreases, so the volume energy density first increases and then decreases with the increase of the content of flake graphite (refer to Figure 6). The volume energy density reaches its maximum value near 10% of the flake graphite content.
  • flake graphite has improved the conductive network of the negative electrode material containing silicon-based materials, thereby improving the cycle performance.
  • flake graphite due to the higher orientation of the flake structure of flake graphite, it has High anisotropy will lead to poor ionic conductivity, so when the content of flake graphite is too high, it will cause poor lithium ion conductivity of the composite silicon substrate, which will worsen the cycle performance.
  • the mass of the flake carbon-based material accounts for 0.5% to 40% of the total mass of the flake carbon-based material and the silicon-based material, thereby improving the cycle performance of the negative electrode material. Ensure the volumetric energy density of the negative electrode material.

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  • Battery Electrode And Active Subsutance (AREA)

Abstract

L'invention concerne un matériau d'électrode négative, une plaque d'électrode négative, un dispositif électrochimique et un dispositif électronique. Le matériau d'électrode négative comprend un matériau à base de silicium et un matériau à base de carbone en flocons. Le rapport diamètre/épaisseur du matériau à base de carbone en flocons est supérieur à 2. Le matériau à base de carbone ayant un rapport diamètre/épaisseur supérieur à 2 est ajouté au matériau d'électrode négative contenant le matériau à base de silicium, de telle sorte que la densité compacte du matériau d'électrode négative est améliorée, et le contact électrique entre les matériaux à base de silicium est augmenté. En même temps, le matériau à base de carbone en flocons améliore également la conductivité du matériau d'électrode négative, et améliore ainsi les performances de cycle du dispositif électrochimique.
PCT/CN2020/089842 2020-05-12 2020-05-12 Matériau d'électrode négative, plaque d'électrode négative, dispositif électrochimique et dispositif électronique WO2021226842A1 (fr)

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CN115832277A (zh) * 2022-01-05 2023-03-21 宁德时代新能源科技股份有限公司 正极浆料、正极极片、电芯、电池单体、电池及用电装置
EP4207385A3 (fr) * 2021-12-28 2023-09-13 Ningde Amperex Technology Ltd. Appareil électrochimique et appareil électronique le comprenant
EP4254534A1 (fr) * 2022-03-03 2023-10-04 Envision AESC Japan Ltd. Électrode négative pour batteries secondaires à électrolyte non aqueux et batterie secondaire à électrolyte non aqueux la comprenant

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EP4207385A3 (fr) * 2021-12-28 2023-09-13 Ningde Amperex Technology Ltd. Appareil électrochimique et appareil électronique le comprenant
CN115832277A (zh) * 2022-01-05 2023-03-21 宁德时代新能源科技股份有限公司 正极浆料、正极极片、电芯、电池单体、电池及用电装置
EP4254534A1 (fr) * 2022-03-03 2023-10-04 Envision AESC Japan Ltd. Électrode négative pour batteries secondaires à électrolyte non aqueux et batterie secondaire à électrolyte non aqueux la comprenant

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