WO2022000226A1 - Electrochemical device and electronic device - Google Patents

Electrochemical device and electronic device Download PDF

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Publication number
WO2022000226A1
WO2022000226A1 PCT/CN2020/099112 CN2020099112W WO2022000226A1 WO 2022000226 A1 WO2022000226 A1 WO 2022000226A1 CN 2020099112 W CN2020099112 W CN 2020099112W WO 2022000226 A1 WO2022000226 A1 WO 2022000226A1
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Prior art keywords
active material
electrode active
negative electrode
material layer
electrochemical device
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PCT/CN2020/099112
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French (fr)
Chinese (zh)
Inventor
龚锣
余红明
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宁德新能源科技有限公司
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Priority to CN202080025070.6A priority Critical patent/CN113728469B/en
Priority to PCT/CN2020/099112 priority patent/WO2022000226A1/en
Publication of WO2022000226A1 publication Critical patent/WO2022000226A1/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
    • H01M4/62—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
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • 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
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • 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
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present application relates to the field of electronic technology, in particular to electrochemical devices and electronic devices.
  • electrochemical devices eg, lithium-ion batteries
  • electrochemical devices eg, lithium-ion batteries
  • higher and higher requirements have been placed on their safety performance.
  • an important requirement is to suppress the formation of lithium precipitation and lithium dendrites on the negative electrode surface, because the formed lithium dendrites may pierce the separator, thereby affecting the safety performance of electrochemical devices.
  • the present application can improve the safety performance of the electrochemical device without substantially affecting the volume energy density of the electrochemical device.
  • the embodiment of the present application provides an electrochemical device, which includes a positive electrode piece, a separator, and a negative electrode piece, the separator is arranged between the positive electrode piece and the negative electrode piece, and the positive electrode piece includes a positive electrode current collector and is arranged on the The positive electrode active material layer on the positive electrode current collector, the positive electrode active material layer includes the positive electrode active material, wherein, the negative electrode sheet includes: the negative electrode current collector; the conductive material layer, including the conductive material; and the negative electrode active material layer, including the negative electrode active material, the negative electrode The active material layer is provided between the negative electrode current collector and the conductive material layer.
  • the specific surface area of the conductive material is 25 m 2 /g to 300 m 2 /g.
  • the conductive material includes at least one of acetylene black, conductive carbon black, activated carbon or carbon nanotubes.
  • the thickness h of the conductive material layer is 0.1 ⁇ m to 3 ⁇ m.
  • the compaction density of the negative electrode active material layer is 1.0 g/cm 3 to 1.9 g/cm 3 .
  • the negative electrode active material includes at least one of artificial graphite, natural graphite, hard carbon, mesocarbon microspheres, silicon oxide, silicon-carbon composite or pure silicon.
  • the electrochemical device satisfies the following relationship: 0.8 ⁇ (A'*B'*C')/(A*B*C) ⁇ 1.4, wherein A represents that the positive electrode active material accounts for the positive electrode activity
  • the mass ratio of the material layer, B represents the gram capacity of the positive electrode active material, in mAh/g
  • C represents the mass per unit area of the positive electrode active material layer, in mg/cm 2
  • A' represents the amount of the negative electrode active material in the negative electrode active material.
  • the mass ratio of the layer, B' represents the gram capacity of the negative electrode active material, in mAh/g
  • C' represents the mass per unit area of the negative electrode active material layer, in mg/cm 2 .
  • the value of C' ranges from 7.45 mg/cm 2 to 13.02 mg/cm 2 .
  • the electrochemical device further satisfies the following relational expression:
  • the h represents the value when the unit of the thickness of the conductive material layer is ⁇ m.
  • Embodiments of the present application also provide an electronic device, including the above electrochemical device.
  • the negative electrode active material layer is arranged between the negative electrode current collector and the conductive material layer, that is, a conductive material layer is also formed on the negative electrode active material layer, and the conductive material layer is conducive to the formation of more lithium deposition sites.
  • the lithium deposition preferentially occurs at the position where the conductive material layer is in contact with the negative electrode active material layer, so that no lithium deposition occurs on the surface of the negative electrode active material layer.
  • the conductive material can form a large number of nucleation sites, the formation of lithium dendrites can be effectively suppressed, and the safety performance of the electrochemical device can be improved.
  • FIG. 1 shows a schematic diagram of an electrode assembly of a conventional electrochemical device.
  • FIG. 2 shows a schematic diagram of the appearance of lithium dendrites on the surface of the negative electrode active material layer of the conventional electrochemical device.
  • FIG. 3 shows a schematic diagram of an electrode assembly of an electrochemical device of an embodiment of the present application.
  • the gram capacity and cyclic expansion ratio of anode active materials are getting closer and closer to the limit value, and the space for improving the volumetric energy density is limited.
  • increasing the compaction density of the negative pole piece is a common method to improve the volumetric energy density of an electrochemical device.
  • the compaction density of the negative pole piece increases to a certain level, the passage of lithium ions into and out of the negative pole piece is blocked, and the concentration of The increase of differential polarization will lead to lithium deposition on the surface of the negative electrode, which affects the electrochemical performance and safety performance of the electrochemical device.
  • the electrochemical device includes a positive pole piece 1 , a negative pole piece 2 , and a separator 3 disposed between the positive pole piece 1 and the negative pole piece 2 .
  • the positive electrode sheet 1 includes a positive electrode current collector 11 and positive electrode active material layers 12 and 13 provided on the positive electrode current collector 11 .
  • the negative electrode sheet 2 includes a negative electrode current collector 21 and negative electrode active material layers 22 and 23 provided on the negative electrode current collector 21 .
  • lithium metal and lithium dendrites 41 are formed on the surface of the negative electrode active material layer, The formed lithium dendrites 41 may pierce the isolation membrane 3, thereby affecting the safety performance of the electrochemical device. It should be understood that the shape of the lithium dendrites 41 is exemplary only.
  • the present application provides an electrochemical device having an additional conductive material layer on the negative electrode pole piece.
  • the electrochemical device includes a positive pole piece 1 , a negative pole piece 2 , and a separator 3 disposed between the positive pole piece 1 and the negative pole piece 2 .
  • the positive electrode sheet 1 includes a positive electrode current collector 11 and positive electrode active material layers 12 and 13 provided on the positive electrode current collector 11 .
  • the negative electrode piece 2 includes a negative electrode current collector 21 , negative electrode active material layers 22 and 23 provided on the negative electrode current collector 21 , and conductive material layers 24 and 25 respectively provided on the negative electrode active material layers 22 and 23 .
  • the positive electrode active material layers 12, 13 are shown on both sides of the positive electrode current collector 11 respectively in FIG. 3, this is only exemplary and only the positive electrode active material layer 12 may be present, for example.
  • the positive electrode current collector 11 can use Al foil, of course, other positive electrode current collectors commonly used in the art can also be used.
  • the thickness of the positive electrode current collector may be 1 ⁇ m ⁇ 200 ⁇ m.
  • the positive electrode active material layers 12 , 13 may only be coated on a partial area of the positive electrode current collector 11 .
  • the thicknesses of the positive electrode active material layers 12 and 13 may each independently be 10 ⁇ m ⁇ 500 ⁇ m.
  • the positive active material layers 12, 13 include a positive active material.
  • the positive active material may include at least one of lithium cobalt oxide, lithium manganate, lithium iron phosphate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, or lithium nickel manganate.
  • the positive active material layer further includes a binder and a conductive agent.
  • the binder in the positive active material layer 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 At least one of vinyl fluoride or polyhexafluoropropylene.
  • the conductive agent in the positive active material layer may include at least one of conductive carbon black, Ketjen black, lamellar graphite, graphene, carbon nanotubes, or carbon fibers.
  • the mass ratio of the positive electrode active material, the conductive agent and the binder in the positive electrode active material layer may be 70-98:1-15:1-15. It should be understood that the above descriptions are only examples, and any other suitable materials, thicknesses and mass ratios may be used for the positive electrode active material layer.
  • the isolation film 3 includes at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, or aramid.
  • the polyethylene includes at least one selected from high density polyethylene, low density polyethylene or ultra-high molecular weight polyethylene. Especially 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 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), 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.
  • the pores of the isolation membrane have diameters 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 carboxymethyl cellulose, polyamide At least one of vinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene or polyhexafluoropropylene.
  • the porous layer on the surface of the separator can improve the heat resistance, oxidation resistance and electrolyte wettability of the separator, and enhance the adhesion between the separator and the pole piece.
  • the negative electrode active material layer and the conductive material layer are shown as being disposed on both sides of the negative electrode current collector in FIG. 3 , this is only exemplary, and the negative electrode active material may only be present on one side of the negative electrode current collector Layer and conductive material layer, for example, only the negative electrode active material layer 22 and the conductive material layer 24 may be present, or only the negative electrode active material layer 23 and the conductive material layer 24 may be present.
  • the negative electrode current collector may use at least one of copper foil, nickel foil or carbon-based current collector.
  • the anode active material layer may include an anode active material. In some embodiments, as shown in FIG. 3 , the anode active material layer is disposed between the anode current collector and the conductive material layer.
  • the negative electrode active material layer By arranging the negative electrode active material layer between the negative electrode current collector and the conductive material layer, that is, a conductive material layer is also formed on the negative electrode active material layer, and the conductive material layer is conducive to the formation of more lithium deposition sites.
  • the material layer is filled with lithium and lithium deposition begins, lithium deposition preferentially occurs in the conductive material layer, so that lithium deposition does not occur in the negative electrode active material layer.
  • the conductive material can form a large number of nucleation sites, the formation of lithium dendrites can be effectively suppressed, and the safety performance of the electrochemical device can be improved.
  • the conductive material in the conductive material layer has a specific surface area of 25 m 2 /g to 300 m 2 /g. Due to the large specific surface area of the conductive material, it is beneficial to form a large number of nucleation sites, which can effectively inhibit the formation of lithium dendrites. In addition, if the specific surface area of the conductive material is too small, eg, below 25 m 2 /g, the formation of nucleation sites is unfavorable. If the specific surface area of the conductive material is too large, for example, greater than 300 m 2 /g, the particle size of the conductive material may be too small to facilitate the passage of lithium ions.
  • the conductive material includes at least one of acetylene black, conductive carbon black, activated carbon, or carbon nanotubes. These conductive materials have a three-dimensional structure, and the three-dimensional structure can provide a larger specific surface area and an internal hollow structure, which is conducive to the formation of more lithium deposition sites, and lithium deposition inside the material, thereby inhibiting the negative electrode active material chromatography lithium .
  • the thickness h of the conductive material layer is 0.1 ⁇ m to 3 ⁇ m. If the thickness of the conductive material layer is too thin, on the one hand, it is not conducive to processing, and on the other hand, the safety protection effect is limited. If the thickness of the conductive material layer is too thick, the conductive material layer occupies a larger volume and loses the volumetric energy density of the electrochemical device.
  • the conductive material layer may also include a dispersant and a binder.
  • the dispersant in the layer of conductive material may include, for example, sodium carboxymethyl cellulose (CMC).
  • the binder in the layer of conductive material may include, for example, styrene butadiene rubber (SBR).
  • SBR styrene butadiene rubber
  • the mass ratio of the conductive material, the dispersant and the binder in the conductive material layer is 95-99:0.5-2.5:0.5-2.5, it should be understood that this is only an example, and other suitable mass ratio.
  • the compaction density of the anode active material layer is 1.0 g/cm 3 to 1.9 g/cm 3 . If the compaction density of the negative electrode active material layer is too small, the volumetric energy density of the electrochemical device is lost. If the compaction density of the negative electrode active material layer is too large, it is not conducive to the passage of lithium ions, the polarization increases, the electrochemical performance is affected, and lithium is easily precipitated during the charging process of the electrochemical device.
  • the negative active material includes at least one of artificial graphite, natural graphite, hard carbon, mesocarbon microspheres, silicon oxide, silicon-carbon composite, or pure silicon.
  • the negative electrode active material layer may further include a conductive agent and a binder.
  • the conductive agent in the negative electrode active material layer may include at least one of conductive carbon black, Ketjen black, lamellar graphite, graphene, carbon nanotubes or carbon fibers.
  • the binder in the negative active material layer may include carboxymethyl cellulose (CMC), polyacrylic acid, polyvinylpyrrolidone, polyaniline, polyimide, polyamideimide, polysilicon At least one of oxane, styrene-butadiene rubber, epoxy resin, polyester resin, polyurethane resin or polyfluorene.
  • CMC carboxymethyl cellulose
  • the mass ratio of the negative electrode active material, the conductive agent and the binder in the negative electrode active material layer may be 70-98:1-15:1-15. It should be understood that the above are only examples and any other suitable mass ratios may be employed.
  • the electrochemical device satisfies the following relationship: 0.8 ⁇ (A'*B'*C')/(A*B*C) ⁇ 1.4, wherein A represents that the positive electrode active material accounts for the proportion of the positive electrode active material layer Mass ratio, B represents the gram capacity of the positive active material, in mAh/g, C represents the mass per unit area of the positive active material layer, in mg/cm 2 , A' represents the mass of the negative active material in the negative active material layer The ratio, B' represents the gram capacity of the negative electrode active material, in mAh/g, and C' represents the mass per unit area of the negative electrode active material layer, in mg/cm 2 .
  • the ratio (A'*B'*C')/(A*B*C) is referred to as CB, the closer CB is to 1, the larger the volumetric energy density of the electrochemical device is generally, and the greater the CB is than 1 is generally more favorable for suppressing the formation of lithium dendrites.
  • the embodiments of the present application can reduce the CB to less than 1 on the basis of suppressing the formation of lithium dendrites, which greatly enhances the volumetric energy density of the electrochemical device while ensuring the safety performance of the electrochemical device. For example, reducing the CB from 1.055 to 1, the volumetric energy density can be improved by about 3%.
  • the electrochemical device further satisfies the following relationship: 0.8 ⁇ (A'*B'*C')/(A*B*C) ⁇ 1.0, that is, CB ⁇ 1.0.
  • the CB in order to further improve the volumetric energy density of the electrochemical device, is less than 1 and greater than or equal to 0.8. Generally, the CB is less than 1 to make the formation of lithium dendrites easier. exists so that lithium dendrites do not form.
  • the CB can be set to be less than 1.0 while avoiding the formation of lithium dendrites on the surface of the negative electrode, so that while ensuring the safety performance of the electrochemical device, The volumetric energy density of electrochemical devices is greatly enhanced.
  • the CB is less than 0.8, the volumetric energy density of the electrochemical device will decrease instead, and the risk of lithium precipitation will be higher, so the CB is set to be greater than or equal to 0.8.
  • C' ranges from 7.45 mg/cm 2 to 13.02 mg/cm 2 . If C' is too small, the negative electrode active material layer is too thin or the compaction density is too low, resulting in too low volume energy density. If C' is too large, the negative electrode active material layer is too thick, resulting in a difference in the lithium ion conduction rate in the thickness direction of the negative electrode active material layer, and also causing lithium dendrites to form on the surface of the negative electrode active material layer.
  • the electrochemical device further satisfies the following relation: 0 ⁇ h*
  • 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, although the present application is not so limited.
  • the electrochemical device may also include an electrolyte.
  • the electrolyte may be one or more of a gel electrolyte, a solid electrolyte, and an electrolytic solution, and the electrolytic 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 , LiSiF 6 , LiBOB or one or more of lithium difluoroborate.
  • LiPF 6 is chosen as the lithium salt because it can give high ionic conductivity and improve cycle 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 esters (MEC) and combinations thereof.
  • chain carbonate compounds are diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methyl carbonate Ethyl esters (MEC) and combinations thereof.
  • Examples of the cyclic carbonate compound are ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylethylene carbonate (VEC), or a combination thereof.
  • fluorocarbonate compound examples include fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate Fluoroethylene, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-carbonate -Difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate, or a combination thereof.
  • FEC fluoroethylene carbonate
  • 1,2-difluoroethylene carbonate 1,1-difluoroethylene carbonate
  • 1,1,2-trifluoroethylene carbonate Fluoroethylene, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-carbonate -Difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene
  • carboxylate compounds are methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, ⁇ -butyrolactone, decolactone, Valerolactone, mevalonolactone, caprolactone, methyl formate, or a combination thereof.
  • ether compounds are dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxy Ethane, 2-methyltetrahydrofuran, tetrahydrofuran, or a combination thereof.
  • organic solvents examples include dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, methyl amide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters or combinations thereof.
  • the positive electrode, separator, and negative electrode are sequentially wound or stacked to form electrode parts, which are then packaged in, for example, an aluminum-plastic film, and then injected into an electrolytic film. Liquid, chemical formation, packaging, that is, into a lithium-ion battery. Then, the performance test of the prepared lithium-ion battery was carried out.
  • electrochemical devices eg, lithium ion batteries
  • electrochemical devices eg, lithium ion batteries
  • Other methods commonly used in the art may be employed without departing from the disclosure of the present application.
  • Embodiments of the present application also provide electronic devices including the above electrochemical devices.
  • the electronic device in the embodiment of the present application is not particularly limited, and it may 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 telephones, portable fax machines, portable copiers, portable printers, headsets, VCRs, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic notepads, 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-scale household storage batteries and lithium-ion capacitors, etc.
  • the preparation of the positive electrode plate the positive active material lithium cobalt oxide (g capacity is 181mAh/g), the conductive agent conductive carbon black, and the binder polyvinylidene fluoride (PVDF) are dissolved in a weight ratio of 97.6: 1.1: 1.3.
  • NMP N-methylpyrrolidone
  • a positive electrode slurry is formed.
  • the positive electrode slurry was coated on the positive electrode current collector with a coating amount of 18.37 mg/cm 2 , and the positive electrode sheet was obtained after drying, cold pressing and cutting.
  • the positive electrode active material in the cold pressing process The compacted density of the layer was 4.15 g/cm 3 .
  • negative pole piece The negative active material artificial graphite (g capacity is 357mAh/g), dispersant sodium carboxymethyl cellulose and binder styrene-butadiene rubber are dissolved in deionized water in a weight ratio of 97.7:1.1:1.2 In water, an active material layer slurry is formed. Using 10 ⁇ m thick copper foil as the negative electrode current collector, coating the negative electrode slurry on the negative electrode current collector with a coating amount of 9.3 mg/cm 2 , and drying to obtain a negative electrode active material layer;
  • the negative electrode active material layer one side was coated with a thickness of 2 ⁇ m, dried, and cold pressed twice (the first target compaction density was 1.70 g/cm 3 , and the second target compaction density was 1.76 g/cm 3 ).
  • the intermediate interval is more than 2 hours), and the negative pole piece is obtained after cutting.
  • the isolation film substrate is polyethylene (PE) with a thickness of 8 ⁇ m, and 2 ⁇ m alumina ceramic layers are coated on both sides of the isolation film substrate, and finally, 2.5 ⁇ m alumina ceramic layers are coated on both sides of the coated ceramic layer. mg of binder polyvinylidene fluoride (PVDF), dried.
  • PE polyethylene
  • PVDF binder polyvinylidene fluoride
  • Preparation of lithium ion battery stack the positive pole piece, the separator and the negative pole piece in order, so that the separator is in the middle of the positive pole piece and the negative pole piece to play a role of isolation, and coil to obtain the electrode assembly.
  • the electrode assembly is placed in the outer packaging aluminum-plastic film, and after dehydration at 80°C, the above electrolyte is injected and packaged, and the lithium ion battery is obtained through the process of forming, degassing, and trimming.
  • the positive pole piece or the negative pole piece and the counter electrode lithium piece can be made into a button battery for capacity testing to obtain the gram capacity of the positive active material or the negative active material.
  • the adsorption amount of the sample monolayer is obtained based on the Brownnauer-Etter-Taylor adsorption theory and its formula, and the specific surface area of the solid is calculated. .
  • W mass of gas adsorbed by solid sample under relative pressure
  • the lithium-ion battery that reached a constant temperature was charged at a constant current of 0.5C to a voltage of 4.4V, then charged at a constant voltage of 4.4V to a current of 0.05C, discharged at 0.5C to a voltage of 3.0V, and the discharge energy was recorded.
  • Volume energy density discharge energy/(length*width*thickness of lithium-ion battery).
  • Table 1 shows various parameters and evaluation results of Examples 1-5 and Comparative Example 1.
  • Table 2 shows various parameters and evaluation results of Examples 4, 6-10.
  • the volumetric energy density of the electrochemical device is basically unaffected, but it helps to suppress the formation of lithium dendrites, thereby improving the electrochemical device. safety performance.
  • Table 3 shows various parameters and evaluation results of Examples 8, 11-14.
  • Table 4 shows various parameters and evaluation results of Examples 8, 15-19.
  • Table 5 shows various parameters and evaluation results of Examples 20-25.
  • the electrochemical device satisfies 0 ⁇ h*
  • Table 6 shows various parameters and evaluation results of Examples 26-32 and Comparative Examples 2-5.
  • Example 29 and Comparative Example 2 By comparing Example 29 and Comparative Example 2, comparing Example 30 and Comparative Example 3, comparing Example 31 and Comparative Example 4, and comparing Example 32 and Comparative Example 5, by forming a conductive material layer, the volume energy density is guaranteed to be substantially unchanged. The formation of lithium dendrites is suppressed and the safety performance of the electrochemical device is improved.

Abstract

The present application provides an electrochemical device and an electronic device. The electrochemical device comprises a positive electrode plate, a separator, and a negative electrode plate. The separator is provided between the positive electrode plate and the negative electrode plate. The positive electrode plate comprises a positive electrode current collector and a positive electrode active substance layer provided on the positive electrode current collector, and the positive electrode active substance layer comprises a positive electrode active substance. The negative electrode plate comprises: a negative electrode current collector; a conductive material layer comprising a conductive material; and a negative electrode active substance layer comprising a negative electrode active substance, the negative electrode active substance layer being provided between the negative electrode current collector and the conductive material layer. According to the electrochemical device in the present application, the safety performance of the electrochemical device can be improved without basically affecting the volumetric energy density.

Description

电化学装置和电子装置Electrochemical and electronic devices 技术领域technical field
本申请涉及电子技术领域，尤其涉及电化学装置和电子装置。The present application relates to the field of electronic technology, in particular to electrochemical devices and electronic devices.
背景技术Background technique
随着电化学装置(例如，锂离子电池)的发展和进步，对其安全性能提出了越来越高的要求。为了提高电化学装置的安全性能，一个重要的要求是抑制负极表面的析锂和锂枝晶的形成，因为形成的锂枝晶可能会刺穿隔离膜，进而影响电化学装置的安全性能。With the development and progress of electrochemical devices (eg, lithium-ion batteries), higher and higher requirements have been placed on their safety performance. In order to improve the safety performance of electrochemical devices, an important requirement is to suppress the formation of lithium precipitation and lithium dendrites on the negative electrode surface, because the formed lithium dendrites may pierce the separator, thereby affecting the safety performance of electrochemical devices.
发明内容SUMMARY OF THE INVENTION
本申请能够在基本不影响电化学装置的体积能量密度的情况下，提升电化学装置的安全性能。The present application can improve the safety performance of the electrochemical device without substantially affecting the volume energy density of the electrochemical device.
本申请的实施例提供了一种电化学装置，其包括正极极片、隔离膜和负极极片，隔离膜设置在正极极片和负极极片之间，正极极片包括正极集流体和设置在正极集流体上的正极活性物质层，正极活性物质层包括正极活性物质，其中，负极极片包括：负极集流体；导电材料层，包括导电材料；以及负极活性物质层，包括负极活性物质，负极活性物质层设置在负极集流体和导电材料层之间。The embodiment of the present application provides an electrochemical device, which includes a positive electrode piece, a separator, and a negative electrode piece, the separator is arranged between the positive electrode piece and the negative electrode piece, and the positive electrode piece includes a positive electrode current collector and is arranged on the The positive electrode active material layer on the positive electrode current collector, the positive electrode active material layer includes the positive electrode active material, wherein, the negative electrode sheet includes: the negative electrode current collector; the conductive material layer, including the conductive material; and the negative electrode active material layer, including the negative electrode active material, the negative electrode The active material layer is provided between the negative electrode current collector and the conductive material layer.
在上述电化学装置中，其中，导电材料的比表面积为25m 2/g至300m 2/g。 In the above electrochemical device, wherein the specific surface area of the conductive material is 25 m 2 /g to 300 m 2 /g.
在上述电化学装置中，其中，导电材料包括乙炔黑、导电炭黑、活性炭或碳纳米管中的至少一种。In the above electrochemical device, the conductive material includes at least one of acetylene black, conductive carbon black, activated carbon or carbon nanotubes.
在上述电化学装置中，其中，导电材料层的厚度h为0.1μm至3μm。In the above electrochemical device, the thickness h of the conductive material layer is 0.1 μm to 3 μm.
在上述电化学装置中，其中，负极活性物质层的压实密度为1.0g/cm 3至1.9g/cm 3。 In the above electrochemical device, wherein the compaction density of the negative electrode active material layer is 1.0 g/cm 3 to 1.9 g/cm 3 .
在上述电化学装置中，其中，负极活性物质包括人造石墨、天然石墨、硬碳、中间相碳微球、氧化硅、硅碳复合物或纯硅中的至少一种。In the above electrochemical device, the negative electrode active material includes at least one of artificial graphite, natural graphite, hard carbon, mesocarbon microspheres, silicon oxide, silicon-carbon composite or pure silicon.
在上述电化学装置中，其中，电化学装置满足如下关系式：0.8≤(A’*B’*C’)/(A*B*C)≤1.4，其中，A表示正极活性物质占正极活性物质层的质量比例，B表示正极活性物质的克容量，单位为mAh/g，C表示正极活性物质层的单位面积的质量，单位为mg/cm 2，A’表示负极活性物质占负极活性物质层的质量比例，B’表示负极活性物质的克容量，单位为mAh/g，C’表示负极活性物质层的单位面积的质量，单位为mg/cm 2。 In the above electrochemical device, wherein, the electrochemical device satisfies the following relationship: 0.8≤(A'*B'*C')/(A*B*C)≤1.4, wherein A represents that the positive electrode active material accounts for the positive electrode activity The mass ratio of the material layer, B represents the gram capacity of the positive electrode active material, in mAh/g, C represents the mass per unit area of the positive electrode active material layer, in mg/cm 2 , and A' represents the amount of the negative electrode active material in the negative electrode active material. The mass ratio of the layer, B' represents the gram capacity of the negative electrode active material, in mAh/g, and C' represents the mass per unit area of the negative electrode active material layer, in mg/cm 2 .
在上述电化学装置中，其中，电化学装置进一步满足如下关系式：0.8≤(A’*B’*C’)/(A*B*C)<1.0。In the above electrochemical device, wherein the electrochemical device further satisfies the following relational expression: 0.8≤(A'*B'*C')/(A*B*C)<1.0.
在上述电化学装置中，其中，C’的取值范围为7.45mg/cm 2至13.02mg/cm 2。 In the above electrochemical device, the value of C' ranges from 7.45 mg/cm 2 to 13.02 mg/cm 2 .
在上述电化学装置中，其中，电化学装置进一步满足如下关系式：In the above electrochemical device, wherein, the electrochemical device further satisfies the following relational expression:
0≤h*|[(A’*B’*C’)/(A*B*C)-1]|≤0.4，0≤h*|[(A’*B’*C’)/(A*B*C)-1]|≤0.4,
其中所述h表示所述导电材料层厚度的单位为μm时的取值。The h represents the value when the unit of the thickness of the conductive material layer is μm.
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。Embodiments of the present application also provide an electronic device, including the above electrochemical device.
本申请通过将负极活性物质层设置在负极集流体和导电材料层之间，即在负极活性物质层上还形成有导电材料层，该导电材料层有利于形成较多的析锂位点，当负极活性物质层嵌满锂而开始析锂时，析锂优先发生在该导电材料层与负极活性物质层接触的部位，使得负极活性物质层表面不会出现析锂。另外，由于该导电材料可以形成大量的成核位点，从而可以有效抑制锂枝晶的形成，提升电化学装置的安全性能。In the present application, the negative electrode active material layer is arranged between the negative electrode current collector and the conductive material layer, that is, a conductive material layer is also formed on the negative electrode active material layer, and the conductive material layer is conducive to the formation of more lithium deposition sites. When the negative electrode active material layer is filled with lithium and begins to evolve lithium, the lithium deposition preferentially occurs at the position where the conductive material layer is in contact with the negative electrode active material layer, so that no lithium deposition occurs on the surface of the negative electrode active material layer. In addition, since the conductive material can form a large number of nucleation sites, the formation of lithium dendrites can be effectively suppressed, and the safety performance of the electrochemical device can be improved.
附图说明Description of drawings
图1示出了现有的电化学装置的电极组件的示意图。FIG. 1 shows a schematic diagram of an electrode assembly of a conventional electrochemical device.
图2示出了现有的电化学装置的负极活性物质层表面出现锂枝晶的示意图。FIG. 2 shows a schematic diagram of the appearance of lithium dendrites on the surface of the negative electrode active material layer of the conventional electrochemical device.
图3示出了本申请的实施例的电化学装置的电极组件的示意图。FIG. 3 shows a schematic diagram of an electrode assembly of an electrochemical device of an embodiment of the present application.
具体实施方式detailed description
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。The following examples may enable those skilled in the art to more fully understand the present application, but do not limit the present application in any way.
目前，随着电化学装置的发展和进步，负极活性物质的克容量和循环膨胀比例越来越逼近极限值，体积能量密度的提升空间有限。目前，增大负极极片的压实密度是提升电化学装置的体积能量密度的常用方法，但是当负极极片的压实密度提升到一定程度以后，锂离子进出负极极片的通道受阻，浓差极化增大，会导致负极极片表面析锂，影响电化学装置的电化学性能和安全性能。At present, with the development and progress of electrochemical devices, the gram capacity and cyclic expansion ratio of anode active materials are getting closer and closer to the limit value, and the space for improving the volumetric energy density is limited. At present, increasing the compaction density of the negative pole piece is a common method to improve the volumetric energy density of an electrochemical device. However, when the compaction density of the negative pole piece increases to a certain level, the passage of lithium ions into and out of the negative pole piece is blocked, and the concentration of The increase of differential polarization will lead to lithium deposition on the surface of the negative electrode, which affects the electrochemical performance and safety performance of the electrochemical device.
如图1所示，提供了现有的电化学装置的示意图。电化学装置包括正极极片1、负极极片2以及设置在正极极片1和负极极片2之间的隔离膜3。正极极片1包括正极集流体11和设置在正极集流体11上的正极活性物质层12、13。负极极片2包括负极集流体21和设置在负极集流体21上的负极活性物质层22、23。As shown in Figure 1, a schematic diagram of an existing electrochemical device is provided. The electrochemical device includes a positive pole piece 1 , a negative pole piece 2 , and a separator 3 disposed between the positive pole piece 1 and the negative pole piece 2 . The positive electrode sheet 1 includes a positive electrode current collector 11 and positive electrode active material layers 12 and 13 provided on the positive electrode current collector 11 . The negative electrode sheet 2 includes a negative electrode current collector 21 and negative electrode active material layers 22 and 23 provided on the negative electrode current collector 21 .
如图2所示，在这种电化学装置的结构中，当负极活性物质层(例如，22)嵌满锂而开始析锂时，在负极活性物质层表面形成锂金属和锂枝晶41，形成的锂枝晶41可能会刺穿隔离膜3，进而影响电化学装置的安全性能。应该理解，锂枝晶41的形状仅是示例性的。As shown in FIG. 2, in the structure of this electrochemical device, when the negative electrode active material layer (for example, 22) is filled with lithium and begins to precipitate lithium, lithium metal and lithium dendrites 41 are formed on the surface of the negative electrode active material layer, The formed lithium dendrites 41 may pierce the isolation membrane 3, thereby affecting the safety performance of the electrochemical device. It should be understood that the shape of the lithium dendrites 41 is exemplary only.
为了抑制负极活性物质层表面处的锂枝晶的形成，本申请提供了一种在负极极片上具有额外的导电材料层的电化学装置。如图3所示，电化学装置包括正极极片1、负极极片2以及设置在正极极片1和负极极片2之间的隔离膜3。正极极片1包括正极集流体11和设置在正极集流体11上的正极活性物质层12、13。负极极片2包括负极集流体21、设置在负极集流体21上的负极活性物质层22、23以及分别设置在负极活性物质层22、23上的导电材料层24、25。In order to suppress the formation of lithium dendrites at the surface of the negative electrode active material layer, the present application provides an electrochemical device having an additional conductive material layer on the negative electrode pole piece. As shown in FIG. 3 , the electrochemical device includes a positive pole piece 1 , a negative pole piece 2 , and a separator 3 disposed between the positive pole piece 1 and the negative pole piece 2 . The positive electrode sheet 1 includes a positive electrode current collector 11 and positive electrode active material layers 12 and 13 provided on the positive electrode current collector 11 . The negative electrode piece 2 includes a negative electrode current collector 21 , negative electrode active material layers 22 and 23 provided on the negative electrode current collector 21 , and conductive material layers 24 and 25 respectively provided on the negative electrode active material layers 22 and 23 .
应该理解，虽然图3中将正极活性物质层12、13示出为分别位于正极集流体11的两侧上，但是这仅是示例性的，可以例如仅存在正极活性物质层12。在一些实施例中，正极集流体11可以采用Al箔，当然，也可以采用本领域常用的其他正极集流体。在一些实施例中，正极集流体的厚度可以为1μm～200μm。在一些实施例中，正极活性物质层12、13可以仅涂覆在正极集流体11的部分区域上。在一些实施例中，正极活性物质层12、13的厚度可以各自独立地为10μm～500μm。It should be understood that although the positive electrode active material layers 12, 13 are shown on both sides of the positive electrode current collector 11 respectively in FIG. 3, this is only exemplary and only the positive electrode active material layer 12 may be present, for example. In some embodiments, the positive electrode current collector 11 can use Al foil, of course, other positive electrode current collectors commonly used in the art can also be used. In some embodiments, the thickness of the positive electrode current collector may be 1 μm˜200 μm. In some embodiments, the positive electrode active material layers 12 , 13 may only be coated on a partial area of the positive electrode current collector 11 . In some embodiments, the thicknesses of the positive electrode active material layers 12 and 13 may each independently be 10 μm˜500 μm.
在一些实施例中，正极活性物质层12、13包括正极活性物质。在一些实施例中，正极活性物质可以包括钴酸锂、锰酸锂、磷酸铁锂、镍钴锰酸锂、镍钴铝酸锂或镍锰酸锂中的至少一种。在一些实施例中，正极活性物质层还包括粘结剂和导电剂。在一些实施例中，正极活性物质层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、羧甲基纤维素钠、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。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活性物质、导电剂和粘结剂的质量比可以为70～98：1～15：1～15。应该理解，以上所述仅是示例，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。In some embodiments, the positive active material layers 12, 13 include a positive active material. In some embodiments, the positive active material may include at least one of lithium cobalt oxide, lithium manganate, lithium iron phosphate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, or lithium nickel manganate. In some embodiments, the positive active material layer further includes a binder and a conductive agent. In some embodiments, the binder in the positive active material layer 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 At least one of vinyl fluoride or polyhexafluoropropylene. In some embodiments, the conductive agent in the positive active material layer may include at least one of conductive carbon black, Ketjen black, lamellar graphite, graphene, carbon nanotubes, or carbon fibers. In some embodiments, the mass ratio of the positive electrode active material, the conductive agent and the binder in the positive electrode active material layer may be 70-98:1-15:1-15. It should be understood that the above descriptions are only examples, and any other suitable materials, thicknesses and mass ratios may be used for the positive electrode active material layer.
在一些实施例中，隔离膜3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。In some embodiments, the isolation film 3 includes at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, or aramid. For example, the polyethylene includes at least one selected from high density polyethylene, low density polyethylene or ultra-high molecular weight polyethylene. Especially polyethylene and polypropylene, they have a good effect on preventing short circuits and can improve the stability of the battery through the shutdown effect. In some embodiments, the thickness of the isolation film is in the range of about 5 μm to 500 μm.
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。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接性。 In some embodiments, 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 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), 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. In some embodiments, the pores of the isolation membrane have diameters in the range of about 0.01 μm to 1 μm. The binder of the porous layer is selected from polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyamide At least one of vinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene or polyhexafluoropropylene. The porous layer on the surface of the separator can improve the heat resistance, oxidation resistance and electrolyte wettability of the separator, and enhance the adhesion between the separator and the pole piece.
应该理解，虽然图3中将负极活性物质层和导电材料层示出为设置在负极集流体的两侧上，但是这仅是示例性的，可以仅在负极集流体的一侧存在负极活性物质层和导电材料层，例如，可以仅存在负极活性物质层22和导电材料层24，或者仅存在负极活性物质层23和导电材料层24。在一些实施例中，负极集流体可以采用铜箔、镍箔或碳基集流体中的至少一种。在一些实施例中，负极活性物质层可以包括负极活性物质。在一些实施例中，如图3所示，负极活性物质层设置在负极集流体和导电材料层之间。It should be understood that although the negative electrode active material layer and the conductive material layer are shown as being disposed on both sides of the negative electrode current collector in FIG. 3 , this is only exemplary, and the negative electrode active material may only be present on one side of the negative electrode current collector Layer and conductive material layer, for example, only the negative electrode active material layer 22 and the conductive material layer 24 may be present, or only the negative electrode active material layer 23 and the conductive material layer 24 may be present. In some embodiments, the negative electrode current collector may use at least one of copper foil, nickel foil or carbon-based current collector. In some embodiments, the anode active material layer may include an anode active material. In some embodiments, as shown in FIG. 3 , the anode active material layer is disposed between the anode current collector and the conductive material layer.
通过将负极活性物质层设置在负极集流体和导电材料层之间，即在负极活性物质层上还形成有导电材料层，该导电材料层有利于形成较多的析锂位点，当负极活性物质层嵌满锂而开始析锂时，析锂优先发生在该导电材料层内，使得负极活性物质层不会出现析锂。另外，由于该导电材料可以形成大量的成核位点，从而可以有效抑制锂枝晶的形成，提升电化学装置的安全性能。By arranging the negative electrode active material layer between the negative electrode current collector and the conductive material layer, that is, a conductive material layer is also formed on the negative electrode active material layer, and the conductive material layer is conducive to the formation of more lithium deposition sites. When the material layer is filled with lithium and lithium deposition begins, lithium deposition preferentially occurs in the conductive material layer, so that lithium deposition does not occur in the negative electrode active material layer. In addition, since the conductive material can form a large number of nucleation sites, the formation of lithium dendrites can be effectively suppressed, and the safety performance of the electrochemical device can be improved.
在一些实施例中，导电材料层中的导电材料的比表面积为25m 2/g至300m 2/g。由于该导电材料的大的比表面积，有利于形成大量的成核位点，从而可以有效抑制锂枝晶的形成。另外，如果导电材料的比表面积太小，例如，低于25m 2/g，则不利于成核位点的形成。如果导电材料的比表面积太大，例如，大于300m 2/g，则可能使得导电材料的粒度太小而不利于锂离子通过。 In some embodiments, the conductive material in the conductive material layer has a specific surface area of 25 m 2 /g to 300 m 2 /g. Due to the large specific surface area of the conductive material, it is beneficial to form a large number of nucleation sites, which can effectively inhibit the formation of lithium dendrites. In addition, if the specific surface area of the conductive material is too small, eg, below 25 m 2 /g, the formation of nucleation sites is unfavorable. If the specific surface area of the conductive material is too large, for example, greater than 300 m 2 /g, the particle size of the conductive material may be too small to facilitate the passage of lithium ions.
在一些实施例中，导电材料包括乙炔黑、导电炭黑、活性炭或碳纳米管中的至少一种。这些导电材料具有三维立体结构，而三维立体结构能提供较大的比表面积和内部中空结构，有利于形成较多的析锂位点，在其材料内部析锂，从而抑制负极活性物质层析锂。在一些实施例中，导电材料层的厚度h为0.1μm至3μm。如果导电材料层的厚度太薄，一方面不利于加工，另一方面安全保护作用有限。如果导电材料层的厚度太厚，则导电材料层占据较大的体积，损失电化学装置的体积能量密度。In some embodiments, the conductive material includes at least one of acetylene black, conductive carbon black, activated carbon, or carbon nanotubes. These conductive materials have a three-dimensional structure, and the three-dimensional structure can provide a larger specific surface area and an internal hollow structure, which is conducive to the formation of more lithium deposition sites, and lithium deposition inside the material, thereby inhibiting the negative electrode active material chromatography lithium . In some embodiments, the thickness h of the conductive material layer is 0.1 μm to 3 μm. If the thickness of the conductive material layer is too thin, on the one hand, it is not conducive to processing, and on the other hand, the safety protection effect is limited. If the thickness of the conductive material layer is too thick, the conductive material layer occupies a larger volume and loses the volumetric energy density of the electrochemical device.
在一些实施例中，导电材料层还可以包括分散剂和粘结剂。在一些实施例中，导电材料层中的分散剂可以包括例如羧甲基纤维素钠(CMC)。在一些实施例中，导电材料层中的粘结剂可以包括例如丁苯橡胶(SBR)。在一 些实施例中，导电材料层中的导电材料、分散剂和粘结剂的质量比例为95～99：0.5～2.5：0.5～2.5，应该理解，这仅是示例性的，可以采用其他合适的质量比例。In some embodiments, the conductive material layer may also include a dispersant and a binder. In some embodiments, the dispersant in the layer of conductive material may include, for example, sodium carboxymethyl cellulose (CMC). In some embodiments, the binder in the layer of conductive material may include, for example, styrene butadiene rubber (SBR). In some embodiments, the mass ratio of the conductive material, the dispersant and the binder in the conductive material layer is 95-99:0.5-2.5:0.5-2.5, it should be understood that this is only an example, and other suitable mass ratio.
在一些实施例中，负极活性物质层的压实密度为1.0g/cm 3至1.9g/cm 3。如果负极活性物质层的压实密度太小，则损失电化学装置的体积能量密度。如果负极活性物质层的压实密度太大，则不利于锂离子通过，极化增大，影响电化学性能，并且在电化学装置的充电过程中容易析锂。 In some embodiments, the compaction density of the anode active material layer is 1.0 g/cm 3 to 1.9 g/cm 3 . If the compaction density of the negative electrode active material layer is too small, the volumetric energy density of the electrochemical device is lost. If the compaction density of the negative electrode active material layer is too large, it is not conducive to the passage of lithium ions, the polarization increases, the electrochemical performance is affected, and lithium is easily precipitated during the charging process of the electrochemical device.
在一些实施例中，负极活性物质包括人造石墨、天然石墨、硬碳、中间相碳微球、氧化硅、硅碳复合物或纯硅中的至少一种。在一些实施例中，负极活性物质层中还可以包括导电剂和粘结剂。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、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。应该理解，以上公开的材料仅是示例性，负极活性物质层可以采用任何其他合适的材料。在一些实施例中，负极活性物质层中的负极活性物质、导电剂和粘结剂的质量比可以为70～98：1～15：1～15。应该理解，以上所述仅是示例，可以采用任何其他合适的质量比。In some embodiments, the negative active material includes at least one of artificial graphite, natural graphite, hard carbon, mesocarbon microspheres, silicon oxide, silicon-carbon composite, or pure silicon. In some embodiments, the negative electrode active material layer may further include a conductive agent and a binder. The conductive agent in the negative electrode active material layer may include at least one of conductive carbon black, Ketjen black, lamellar graphite, graphene, carbon nanotubes or carbon fibers. In some embodiments, the binder in the negative active material layer may include carboxymethyl cellulose (CMC), polyacrylic acid, polyvinylpyrrolidone, polyaniline, polyimide, polyamideimide, polysilicon At least one of oxane, styrene-butadiene rubber, epoxy resin, polyester resin, polyurethane resin or polyfluorene. It should be understood that the materials disclosed above are only exemplary, and any other suitable materials may be used for the negative electrode active material layer. In some embodiments, the mass ratio of the negative electrode active material, the conductive agent and the binder in the negative electrode active material layer may be 70-98:1-15:1-15. It should be understood that the above are only examples and any other suitable mass ratios may be employed.
在一些实施例中，电化学装置满足如下关系式：0.8≤(A’*B’*C’)/(A*B*C)≤1.4，其中，A表示正极活性物质占正极活性物质层的质量比例，B表示正极活性物质的克容量，单位为mAh/g，C表示正极活性物质层的单位面积的质量，单位为mg/cm 2，A’表示负极活性物质占负极活性物质层的质量比例，B’表示负极活性物质的克容量，单位为mAh/g，C’表示负极活性物质层的单位面积的质量，单位为mg/cm 2。在一些实施例中，将比例(A’*B’*C’)/(A*B*C)称为CB，CB越接近1，电化学装置的体积能量密度通常越大，而CB越大于1通常越有利于抑制锂枝晶的形成。本申请的实施例能够在抑制锂枝晶的形成的基础上，将CB降低到1以下，这样在确保电化学装置的安全性能的同时，大大增强了电化学装置的体积能量密度。例如，将CB从1.055降低到1，体积能量密度可以提升约3％。 In some embodiments, the electrochemical device satisfies the following relationship: 0.8≤(A'*B'*C')/(A*B*C)≤1.4, wherein A represents that the positive electrode active material accounts for the proportion of the positive electrode active material layer Mass ratio, B represents the gram capacity of the positive active material, in mAh/g, C represents the mass per unit area of the positive active material layer, in mg/cm 2 , A' represents the mass of the negative active material in the negative active material layer The ratio, B' represents the gram capacity of the negative electrode active material, in mAh/g, and C' represents the mass per unit area of the negative electrode active material layer, in mg/cm 2 . In some embodiments, the ratio (A'*B'*C')/(A*B*C) is referred to as CB, the closer CB is to 1, the larger the volumetric energy density of the electrochemical device is generally, and the greater the CB is than 1 is generally more favorable for suppressing the formation of lithium dendrites. The embodiments of the present application can reduce the CB to less than 1 on the basis of suppressing the formation of lithium dendrites, which greatly enhances the volumetric energy density of the electrochemical device while ensuring the safety performance of the electrochemical device. For example, reducing the CB from 1.055 to 1, the volumetric energy density can be improved by about 3%.
在一些实施例中，电化学装置进一步满足如下关系式：0.8≤(A’*B’*C’)/(A*B*C)<1.0，即，CB＜1.0。在一些实施例中，为了进一步提升电化学装置的体积能量密度，使CB小于1并且大于等于0.8，通常地，CB小于1使得锂枝晶更容易形成，但是由于本申请中的导电材料层的存在，使得并不会形成锂枝晶。在本申请的实施例中，通过形成额外的导电材料层，能够在避免负极极片表面的锂枝晶形成的同时，将CB设置为小于1.0，使得在确保电化学装置的安全性能的同时，大大增强了电化学装置的体积能量密度。另外，在CB小于0.8时，电化学装置的体积能量密度反而会下降，同时析锂风险更高，因此将CB设置为大于等于0.8。In some embodiments, the electrochemical device further satisfies the following relationship: 0.8≤(A'*B'*C')/(A*B*C)<1.0, that is, CB<1.0. In some embodiments, in order to further improve the volumetric energy density of the electrochemical device, the CB is less than 1 and greater than or equal to 0.8. Generally, the CB is less than 1 to make the formation of lithium dendrites easier. exists so that lithium dendrites do not form. In the embodiments of the present application, by forming an additional conductive material layer, the CB can be set to be less than 1.0 while avoiding the formation of lithium dendrites on the surface of the negative electrode, so that while ensuring the safety performance of the electrochemical device, The volumetric energy density of electrochemical devices is greatly enhanced. In addition, when the CB is less than 0.8, the volumetric energy density of the electrochemical device will decrease instead, and the risk of lithium precipitation will be higher, so the CB is set to be greater than or equal to 0.8.
在一些实施例中，C’的取值范围为7.45mg/cm 2至13.02mg/cm 2。如果C’太小，则负极活性物质层太薄或压实密度太低，导致体积能量密度过低。如果C’太大，则负极活性物质层太厚，导致负极活性物质层在厚度方向的锂离子传导速率差异，也会导致锂枝晶在负极活性物质层的表层形成。 In some embodiments, C' ranges from 7.45 mg/cm 2 to 13.02 mg/cm 2 . If C' is too small, the negative electrode active material layer is too thin or the compaction density is too low, resulting in too low volume energy density. If C' is too large, the negative electrode active material layer is too thick, resulting in a difference in the lithium ion conduction rate in the thickness direction of the negative electrode active material layer, and also causing lithium dendrites to form on the surface of the negative electrode active material layer.
在一些实施例中，电化学装置进一步满足如下关系式：0≤h*|[(A’*B’*C’)/(A*B*C)-1]|≤0.4，所述h表示所述导电材料层厚度的单位为μm时的取值，当所述电化学装置满足该范围时，电化学装置的CB和导电材料层的厚度达到一个均衡，因为CB偏离1越远，导电材料层的厚度需要越薄，这样才能使得电化学装置不析锂的同时，能量密度更高。In some embodiments, the electrochemical device further satisfies the following relation: 0≤h*|[(A'*B'*C')/(A*B*C)-1]|≤0.4, where h represents The value of the thickness of the conductive material layer in μm, when the electrochemical device satisfies this range, the thickness of the CB of the electrochemical device and the thickness of the conductive material layer reach a balance, because the farther the CB deviates from 1, the more conductive material is. The thickness of the layer needs to be thinner, so that the electrochemical device can have a higher energy density without lithium precipitation.
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或堆叠式电极组件。In some embodiments of the present application, the electrode assembly of the electrochemical device is a wound electrode assembly or a stacked electrode assembly.
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，因为它可以给出高的离子导电率并改善循环特性。 In some embodiments, the electrochemical device includes a lithium-ion battery, although the present application is not so limited. In some embodiments, the electrochemical device may also include an electrolyte. The electrolyte may be one or more of a gel electrolyte, a solid electrolyte, and an electrolytic solution, and the electrolytic 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 , LiSiF 6 , LiBOB or one or more of lithium difluoroborate. For example, LiPF 6 is chosen as the lithium salt because it can give high ionic conductivity and improve cycle characteristics.
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。The non-aqueous solvent may be a carbonate compound, a carboxylate compound, an ether compound, other organic solvents, or a combination thereof.
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。The carbonate compound may be a chain carbonate compound, a cyclic carbonate compound, a fluorocarbonate compound, or a combination thereof.
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。Examples of chain carbonate compounds are diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methyl carbonate Ethyl esters (MEC) and combinations thereof. Examples of the cyclic carbonate compound are ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylethylene carbonate (VEC), or a combination thereof. Examples of the fluorocarbonate compound are fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate Fluoroethylene, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-carbonate -Difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate, or a combination thereof.
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。Examples of carboxylate compounds are methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decolactone, Valerolactone, mevalonolactone, caprolactone, methyl formate, or a combination thereof.
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。Examples of ether compounds are dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxy Ethane, 2-methyltetrahydrofuran, tetrahydrofuran, or a combination thereof.
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。Examples of other organic solvents are dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, methyl amide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters or combinations thereof.
在本申请的一些实施例中，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。In some embodiments of the present application, taking a lithium-ion battery as an example, the positive electrode, separator, and negative electrode are sequentially wound or stacked to form electrode parts, which are then packaged in, for example, an aluminum-plastic film, and then injected into an electrolytic film. Liquid, chemical formation, packaging, that is, into a lithium-ion battery. Then, the performance test of the prepared lithium-ion battery was carried out.
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。Those skilled in the art will understand that the methods of making electrochemical devices (eg, lithium ion batteries) described above are only examples. Other methods commonly used in the art may be employed without departing from the disclosure of the present application.
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离子电容器等。Embodiments of the present application also provide electronic devices including the above electrochemical devices. The electronic device in the embodiment of the present application is not particularly limited, and it may be used in any electronic device known in the prior art. In some embodiments, electronic devices may include, but are not limited to, notebook computers, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, headsets, VCRs, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic notepads, 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-scale household storage batteries and lithium-ion capacitors, etc.
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。Some specific embodiments and comparative examples are listed below to better illustrate the present application, wherein a lithium-ion battery is used as an example.
实施例1Example 1
正极极片的制备：将正极活性物质钴酸锂(克容量为181mAh/g)、导电剂导电炭黑、粘结剂聚偏氟乙烯(PVDF)按重量比97.6：1.1：1.3的比例溶于N-甲基吡咯烷酮(NMP)溶液中，形成正极浆料。采用铝箔作为正极集流体，将正极浆料涂覆于正极集流体上，涂覆量为18.37mg/cm 2，经过干燥、冷压、裁切后得到正极极片，冷压过程的正极活性物质层的压实密度为4.15g/cm 3。 The preparation of the positive electrode plate: the positive active material lithium cobalt oxide (g capacity is 181mAh/g), the conductive agent conductive carbon black, and the binder polyvinylidene fluoride (PVDF) are dissolved in a weight ratio of 97.6: 1.1: 1.3. In N-methylpyrrolidone (NMP) solution, a positive electrode slurry is formed. Using aluminum foil as the positive electrode current collector, the positive electrode slurry was coated on the positive electrode current collector with a coating amount of 18.37 mg/cm 2 , and the positive electrode sheet was obtained after drying, cold pressing and cutting. The positive electrode active material in the cold pressing process The compacted density of the layer was 4.15 g/cm 3 .
负极极片的制备：将负极活性物质人造石墨(克容量为357mAh/g)、分散剂羧甲基纤维素钠和粘结剂丁苯橡胶按重量比97.7：1.1：1.2的比例溶于去离子水中，形成活性物质层浆料。采用10μm厚度铜箔作为负极集流体，将负极浆料涂覆于负极集流体上，涂覆量为9.3mg/cm 2，干燥，得到负极活性物质层； Preparation of negative pole piece: The negative active material artificial graphite (g capacity is 357mAh/g), dispersant sodium carboxymethyl cellulose and binder styrene-butadiene rubber are dissolved in deionized water in a weight ratio of 97.7:1.1:1.2 In water, an active material layer slurry is formed. Using 10 μm thick copper foil as the negative electrode current collector, coating the negative electrode slurry on the negative electrode current collector with a coating amount of 9.3 mg/cm 2 , and drying to obtain a negative electrode active material layer;
将导电材料乙炔黑、分散剂羧甲基纤维素钠和粘结剂丁苯橡胶按重量比96：2：2的比例溶于去离子水中，形成导电材料浆料，将导电材料浆料涂覆于负极活性物质层上，单面涂覆厚度为2μm，干燥，进行两次冷压(第一次目标压实密度为1.70g/cm 3，第二次目标压实密度为1.76g/cm 3，中间间隔2小时以上)，裁切后得到负极极片。 Dissolve conductive material acetylene black, dispersant sodium carboxymethyl cellulose and binder styrene-butadiene rubber in deionized water at a weight ratio of 96:2:2 to form conductive material slurry, and coat the conductive material slurry On the negative electrode active material layer, one side was coated with a thickness of 2 μm, dried, and cold pressed twice (the first target compaction density was 1.70 g/cm 3 , and the second target compaction density was 1.76 g/cm 3 ). , the intermediate interval is more than 2 hours), and the negative pole piece is obtained after cutting.
隔离膜的制备：隔离膜基材为8μm厚的聚乙烯(PE)，在隔离膜基材的两侧各涂覆2μm氧化铝陶瓷层，最后在涂布了陶瓷层的两侧各涂覆2.5mg的粘结剂聚偏氟乙烯(PVDF)，烘干。Preparation of isolation film: The isolation film substrate is polyethylene (PE) with a thickness of 8 μm, and 2 μm alumina ceramic layers are coated on both sides of the isolation film substrate, and finally, 2.5 μm alumina ceramic layers are coated on both sides of the coated ceramic layer. mg of binder polyvinylidene fluoride (PVDF), dried.
电解液的制备：在含水量小于10ppm的环境下，将六氟磷酸锂与非水有机溶剂(碳酸乙烯酯(EC)：碳酸二甲酯(DMC)＝40：60，重量比)按重量比8：92配制以形成电解液。Preparation of electrolyte: in an environment with a water content of less than 10 ppm, mix lithium hexafluorophosphate with a non-aqueous organic solvent (ethylene carbonate (EC): dimethyl carbonate (DMC) = 40:60, weight ratio) in a weight ratio of 8:92 Formulated to form an electrolyte.
锂离子电池的制备：将正极极片、隔离膜、负极极片按顺序依次叠好，使隔离膜处于正极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，在80℃下脱去水分后，注入上述电解液并封装，经过化成，脱气，切边等工艺流程得到锂离子电池。Preparation of lithium ion battery: stack the positive pole piece, the separator and the negative pole piece in order, so that the separator is in the middle of the positive pole piece and the negative pole piece to play a role of isolation, and coil to obtain the electrode assembly. The electrode assembly is placed in the outer packaging aluminum-plastic film, and after dehydration at 80°C, the above electrolyte is injected and packaged, and the lithium ion battery is obtained through the process of forming, degassing, and trimming.
实施例2～31和对比例1～5是在实施例1步骤的基础上进行参数变更，具体变更的参数如下表1-表6所示。In Examples 2 to 31 and Comparative Examples 1 to 5, parameters were changed on the basis of the steps of Example 1, and the specific changed parameters are shown in Tables 1 to 6 below.
下面描述本申请的各个参数的测试方法。The test methods for each parameter of the present application are described below.
克容量测试：Gram capacity test:
可以将锂离子电池拆开后，将正极极片或负极极片与对电极锂片做成扣式电池进行容量测试，以获得正极活性物质或负极活性物质的克容量。After the lithium ion battery is disassembled, the positive pole piece or the negative pole piece and the counter electrode lithium piece can be made into a button battery for capacity testing to obtain the gram capacity of the positive active material or the negative active material.
导电材料的比表面积测试：Specific surface area test of conductive materials:
在恒温低温下，测定不同相对压力时的气体在固体表面的吸附量后，基于布朗诺尔-埃特-泰勒吸附理论及其公式求得试样单分子层吸附量，从而计算出固体的比表面积。At a constant temperature and low temperature, after measuring the adsorption amount of gas on the solid surface at different relative pressures, the adsorption amount of the sample monolayer is obtained based on the Brownnauer-Etter-Taylor adsorption theory and its formula, and the specific surface area of the solid is calculated. .
BET公式：
Figure PCTCN2020099112-appb-000001
BET formula:
Figure PCTCN2020099112-appb-000001
其中：W—相对压力下固体样品所吸附的气体的质量Where: W—mass of gas adsorbed by solid sample under relative pressure
W m---铺满一单分子层的气体饱和吸附量 W m --- the gas saturation adsorption capacity covering a monolayer
斜率：(c-1)/(WmC)，截距：1/WmC，总比表面积：(Wm*N*Acs/M)Slope: (c-1)/(WmC), Intercept: 1/WmC, Total Surface Area: (Wm*N*Acs/M)
比表面积：S＝St/m，其中m为样品质量，Acs：每个N 2分子的所占据的平均面积16.2A 2。 Specific surface area: S=St/m, where m is the sample mass, Acs: the average area occupied by each N 2 molecule 16.2A 2 .
称取1.5～3.5g粉末样品装入TriStar II 3020的测试测试样品管中，200℃脱气120min后进行测试。Weigh 1.5-3.5g powder samples into the test sample tube of TriStar II 3020, and test after degassing at 200°C for 120min.
负极活性物质层的压实密度测试：Compaction density test of negative active material layer:
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，去除负极集流体的厚度和质量，计算圆片中的负极活性物质层的质量和体积，即可计算出负极活性物质层的压实密度。 30t compaction pressure employed, out of the area of the wafer 2 1540.25mm, measured with a micrometer thickness of the wafer, the wafer is weighed, removed thickness and quality of the negative electrode current collector, the wafer is calculated in the negative electrode active material layer From the mass and volume, the compaction density of the negative active material layer can be calculated.
体积能量密度的测试方法：Test method for volumetric energy density:
将锂离子电池置于25℃恒温箱中，静置30分钟，使锂离子电池达到恒温。将达到恒温的锂离子电池以0.5C恒流充电至电压为4.4V，然后以4.4V恒压充电至电流为0.05C，0.5C放电至电压为3.0V，记录放电能量。Place the lithium-ion battery in a 25°C incubator for 30 minutes so that the lithium-ion battery reaches a constant temperature. The lithium-ion battery that reached a constant temperature was charged at a constant current of 0.5C to a voltage of 4.4V, then charged at a constant voltage of 4.4V to a current of 0.05C, discharged at 0.5C to a voltage of 3.0V, and the discharge energy was recorded.
体积能量密度＝放电能量/(锂离子电池的长度*宽度*厚度)。Volume energy density=discharge energy/(length*width*thickness of lithium-ion battery).
负极极片是否析锂和形成锂枝晶：Whether the negative pole piece precipitates lithium and forms lithium dendrites:
在17℃下，以0.7C恒定电流将锂离子电池充电至4.45V，然后以4.45V的恒定电压充电至电流为0.05C，静置2min，然后再以1C的恒定电流放电至3.0V，静置2min，以此为一个循环，重复10个循环后，拆解锂离子电池获得电极组件，将电极组件平展铺开，若发现负极极片有任意一处>2mm 2的区域析锂则判定为负极极片析锂。另外，可以通过扫描电镜观察是否形成锂枝晶。 At 17°C, charge the lithium-ion battery to 4.45V with a constant current of 0.7C, then charge it to a current of 0.05C with a constant voltage of 4.45V, let it stand for 2 minutes, and then discharge it to 3.0V with a constant current of 1C. set 2min, thus as one cycle, was repeated 10 cycles, to obtain a lithium ion battery dismantling the electrode assembly, the electrode assembly is rolled out flat, if found negative electrode sheet has an arbitrary> lithium analysis region is determined to 2mm 2 Lithium is deposited on the negative electrode. In addition, the formation of lithium dendrites can be observed by scanning electron microscopy.
表1示出了实施例1-5和对比例1的各个参数和评估结果。Table 1 shows various parameters and evaluation results of Examples 1-5 and Comparative Example 1.
表1Table 1
Figure PCTCN2020099112-appb-000002
Figure PCTCN2020099112-appb-000002
通过比较实施例1～5和对比例1可知，通过在负极活性物质层上形成导电材料层，使得负极极片表面最多存在轻微析锂，而不产生锂枝晶，相对于没有导电材料层的对比例1，实施例1～5中的电化学装置的安全性能得到大幅提升。另外，相对于没有导电材料层的对比例1，实施例1～5中的锂离子电池的体积能量密度变化不大。By comparing Examples 1 to 5 and Comparative Example 1, it can be seen that by forming a conductive material layer on the negative electrode active material layer, the surface of the negative electrode pole piece has a slight lithium precipitation at most, and no lithium dendrites are generated. In Comparative Example 1, the safety performance of the electrochemical devices in Examples 1 to 5 was greatly improved. In addition, the volume energy density of the lithium ion batteries in Examples 1 to 5 did not change much with respect to Comparative Example 1 without the conductive material layer.
通过比较实施例1～5可知，随着导电材料层的厚度的增大，电化学装置的体积能量密度有减小的趋势，但是在抑制锂枝晶的性能方面有提升。通过 采用0.1μm至3μm的厚度的导电材料层，在保持较高的体积能量密度的基础上，抑制了锂枝晶的形成，提升了电化学装置的安全性能。By comparing Examples 1 to 5, it can be seen that with the increase of the thickness of the conductive material layer, the volume energy density of the electrochemical device tends to decrease, but the performance of suppressing lithium dendrites is improved. By using a conductive material layer with a thickness of 0.1 μm to 3 μm, the formation of lithium dendrites is suppressed on the basis of maintaining a high volume energy density, and the safety performance of the electrochemical device is improved.
表2示出了实施例4、6-10的各个参数和评估结果。Table 2 shows various parameters and evaluation results of Examples 4, 6-10.
表2Table 2
Figure PCTCN2020099112-appb-000003
Figure PCTCN2020099112-appb-000003
通过比较实施例4和6～10可知，随着导电材料的比表面积的增大，电化学装置的体积能量密度基本不受影响，但是有助于抑制锂枝晶的形成，从而提升电化学装置的安全性能。By comparing Examples 4 and 6 to 10, it can be seen that with the increase of the specific surface area of the conductive material, the volumetric energy density of the electrochemical device is basically unaffected, but it helps to suppress the formation of lithium dendrites, thereby improving the electrochemical device. safety performance.
表3示出了实施例8、11-14的各个参数和评估结果。Table 3 shows various parameters and evaluation results of Examples 8, 11-14.
表3table 3
Figure PCTCN2020099112-appb-000004
Figure PCTCN2020099112-appb-000004
通过比较实施例8和11～14可知，随着负极活性物质层的压实密度的提高，电化学装置的体积能量密度有增大的趋势。通过使负极活性物质层的压实密度为1.0g/cm 3至1.9g/cm 3，既能获得较大的体积能量密度，同时能够抑制锂枝晶的形成，确保电化学装置的安全性能。 By comparing Examples 8 and 11 to 14, it can be seen that with the increase of the compaction density of the negative electrode active material layer, the volume energy density of the electrochemical device tends to increase. By setting the compaction density of the negative electrode active material layer to be 1.0 g/cm 3 to 1.9 g/cm 3 , a large volume energy density can be obtained, and the formation of lithium dendrites can be suppressed at the same time, thereby ensuring the safety performance of the electrochemical device.
表4示出了实施例8、15-19的各个参数和评估结果。Table 4 shows various parameters and evaluation results of Examples 8, 15-19.
表4Table 4
Figure PCTCN2020099112-appb-000005
Figure PCTCN2020099112-appb-000005
通过比较实施例8和15～19可知，随着负极活性物质层的单位面积涂覆量的减小，即随着CB的减小，体积能量密度有增大的趋势。By comparing Examples 8 and 15-19, it can be seen that with the decrease of the coating amount per unit area of the negative electrode active material layer, that is, with the decrease of CB, the volume energy density has a tendency to increase.
表5示出了实施例20-25的各个参数和评估结果。Table 5 shows various parameters and evaluation results of Examples 20-25.
表5table 5
Figure PCTCN2020099112-appb-000006
Figure PCTCN2020099112-appb-000006
通过比较实施例8和20～25可知，所述电化学装置满足0≤h*|[(A’*B’*C’)/(A*B*C)-1]|≤0.4，不仅具有更高的能量密度，同时也有很好的抑制锂枝晶的效果。By comparing Examples 8 and 20 to 25, it can be seen that the electrochemical device satisfies 0≤h*|[(A'*B'*C')/(A*B*C)-1]|≤0.4, and not only has Higher energy density, and also has a good effect of inhibiting lithium dendrites.
表6示出了实施例26-32和对比例2-5的各个参数和评估结果。Table 6 shows various parameters and evaluation results of Examples 26-32 and Comparative Examples 2-5.
表6Table 6
Figure PCTCN2020099112-appb-000007
Figure PCTCN2020099112-appb-000007
通过比较实施例26～28可知，具有三维立体结构的导电材料的种类的不同，均能抑制锂枝晶的形成，并且对电化学装置的体积能量密度基本没有影响。By comparing Examples 26 to 28, it can be seen that different types of conductive materials with a three-dimensional structure can inhibit the formation of lithium dendrites, and have little effect on the volumetric energy density of the electrochemical device.
通过比较实施例29和对比例2，比较实施例30和对比例3，比较实施例31和对比例4，比较实施例32和对比例5，通过形成导电材料层，在保证体积能量密度基本不变的情况下，抑制了锂枝晶的形成，提升了电化学装置的安全性能。By comparing Example 29 and Comparative Example 2, comparing Example 30 and Comparative Example 3, comparing Example 31 and Comparative Example 4, and comparing Example 32 and Comparative Example 5, by forming a conductive material layer, the volume energy density is guaranteed to be substantially unchanged. The formation of lithium dendrites is suppressed and the safety performance of the electrochemical device is improved.
通过比较实施例1和29～32可知，采用的负极活性物质的不同，会影响电化学装置的体积能量密度，但是并不会影响抑制锂枝晶的性能的实现。By comparing Examples 1 and 29 to 32, it can be seen that the difference in the negative active material used will affect the volumetric energy density of the electrochemical device, but will not affect the realization of the performance of inhibiting lithium dendrites.
以上描述仅为本申请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，本申请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。例如上述特征与本申请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。The above description is only a preferred embodiment of the present application and an illustration of the applied technical principles. Those skilled in the art should understand that the scope of disclosure involved in this application is not limited to the technical solutions formed by the specific combination of the above-mentioned technical features, but also covers other technical solutions formed by any combination of the above-mentioned technical features or their equivalents. Technical solutions. For example, a technical solution is formed by replacing the above-mentioned features with the technical features disclosed in this application with similar functions.

Claims (11)

  1. 一种电化学装置，其包括正极极片、隔离膜和负极极片，所述隔离膜设置在所述正极极片和所述负极极片之间，所述正极极片包括正极集流体和设置在所述正极集流体上的正极活性物质层，所述正极活性物质层包括正极活性物质，其中，所述负极极片包括：An electrochemical device comprising a positive pole piece, a separator and a negative pole piece, the separator is arranged between the positive pole piece and the negative pole piece, the positive pole piece includes a positive current collector and is provided with The positive electrode active material layer on the positive electrode current collector, the positive electrode active material layer includes a positive electrode active material, wherein the negative electrode sheet includes:
    负极集流体；Negative current collector;
    导电材料层，包括导电材料；以及a layer of conductive material, including conductive material; and
    负极活性物质层，包括负极活性物质，所述负极活性物质层设置在所述负极集流体和所述导电材料层之间。The negative electrode active material layer includes a negative electrode active material, and the negative electrode active material layer is arranged between the negative electrode current collector and the conductive material layer.
  2. 根据权利要求1所述的电化学装置，其中，所述导电材料的比表面积为25m 2/g至300m 2/g。 The electrochemical device of claim 1, wherein the conductive material has a specific surface area of 25 m 2 /g to 300 m 2 /g.
  3. 根据权利要求1所述的电化学装置，其中，所述导电材料包括乙炔黑、导电炭黑、活性炭或碳纳米管中的至少一种。The electrochemical device of claim 1, wherein the conductive material comprises at least one of acetylene black, conductive carbon black, activated carbon, or carbon nanotubes.
  4. 根据权利要求1所述的电化学装置，其中，所述导电材料层的厚度h为0.1μm至3μm。The electrochemical device according to claim 1, wherein the thickness h of the conductive material layer is 0.1 μm to 3 μm.
  5. 根据权利要求1所述的电化学装置，其中，所述负极活性物质层的压实密度为1.0g/cm 3至1.9g/cm 3。 The electrochemical device according to claim 1, wherein a compaction density of the negative electrode active material layer is 1.0 g/cm 3 to 1.9 g/cm 3 .
  6. 根据权利要求1所述的电化学装置，其中，所述负极活性物质包括人造石墨、天然石墨、硬碳、中间相碳微球、氧化硅、硅碳复合物或纯硅中的至少一种。The electrochemical device according to claim 1, wherein the negative electrode active material comprises at least one of artificial graphite, natural graphite, hard carbon, mesocarbon microspheres, silicon oxide, silicon carbon composite or pure silicon.
  7. 根据权利要求4所述的电化学装置，其中，所述电化学装置满足如下关系式：The electrochemical device of claim 4, wherein the electrochemical device satisfies the following relationship:
    0.8≤(A’*B’*C’)/(A*B*C)≤1.40.8≤(A’*B’*C’)/(A*B*C)≤1.4
    其中，A表示所述正极活性物质占所述正极活性物质层的质量比例，B表示所述正极活性物质的克容量，单位为mAh/g，C表示所述正极活性物质层的单位面积的质量，单位为mg/cm 2，A’表示所述负极活性物质占所述负极活性物质层的质量比例，B’表示所述负极活性物质的克容量，单位为mAh/g，C’表示所述负极活性物质层的单位面积的质量，单位为mg/cm 2。 Wherein, A represents the mass ratio of the positive electrode active material to the positive electrode active material layer, B represents the gram capacity of the positive electrode active material, in mAh/g, and C represents the mass per unit area of the positive electrode active material layer , the unit is mg/cm 2 , A' represents the mass ratio of the negative electrode active material to the negative electrode active material layer, B' represents the gram capacity of the negative electrode active material, the unit is mAh/g, and C' represents the The mass per unit area of the negative electrode active material layer is in mg/cm 2 .
  8. 根据权利要求7所述的电化学装置，其中，所述电化学装置进一步满足如下关系式：The electrochemical device of claim 7, wherein the electrochemical device further satisfies the following relationship:
    0.8≤(A’*B’*C’)/(A*B*C)<1.0。0.8≤(A’*B’*C’)/(A*B*C)<1.0.
  9. 根据权利要求7所述的电化学装置，其中，所述C’的取值范围为7.45mg/cm 2至13.02mg/cm 2。 The electrochemical device according to claim 7, wherein the value of C' ranges from 7.45 mg/cm 2 to 13.02 mg/cm 2 .
  10. 根据权利要求7所述的电化学装置，其中，所述电化学装置满足如下关系式：The electrochemical device of claim 7, wherein the electrochemical device satisfies the following relationship:
    0≤h*|[(A’*B’*C’)/(A*B*C)-1]|≤0.4，0≤h*|[(A’*B’*C’)/(A*B*C)-1]|≤0.4,
    其中所述h表示所述导电材料层厚度的单位为μm时的取值。The h represents the value when the unit of the thickness of the conductive material layer is μm.
  11. 一种电子装置，其包括根据权利要求1至10中任一项所述的电化学装置。An electronic device comprising the electrochemical device according to any one of claims 1 to 10.
PCT/CN2020/099112 2020-06-30 2020-06-30 Electrochemical device and electronic device WO2022000226A1 (en)

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