WO2021088167A1 - 正极及包含其的电化学装置和电子装置 - Google Patents

正极及包含其的电化学装置和电子装置 Download PDF

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WO2021088167A1
WO2021088167A1 PCT/CN2019/122057 CN2019122057W WO2021088167A1 WO 2021088167 A1 WO2021088167 A1 WO 2021088167A1 CN 2019122057 W CN2019122057 W CN 2019122057W WO 2021088167 A1 WO2021088167 A1 WO 2021088167A1
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positive electrode
conductive agent
oxide
active material
lithium
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PCT/CN2019/122057
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English (en)
French (fr)
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周墨林
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宁德新能源科技有限公司
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Publication of WO2021088167A1 publication Critical patent/WO2021088167A1/zh
Priority to US17/708,089 priority Critical patent/US20220223878A1/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
    • H01M4/626—Metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • H01M4/623—Binders being polymers fluorinated polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • This application relates to the field of energy storage technology, and in particular to a positive electrode and an electrochemical device and an electronic device including the same.
  • the positive electrode includes a conductive agent containing a non-carbon material.
  • Lithium-ion batteries are widely used in portable electronic products, electric transportation, national defense aviation, energy storage and other fields because of their high energy density, high power density, long life, good safety, low self-discharge and wide temperature adaptation range. .
  • broadening the charge cut-off voltage of cathode materials and developing new materials with higher specific energy are becoming an imperative research direction.
  • Lithium-ion batteries are mainly composed of positive electrode, negative electrode, separator and electrolyte. Improving the performance of cathode materials is the key to improving the overall performance of lithium-ion batteries. This is not only because the cathode material accounts for more than 40% of the overall cost of the lithium-ion battery, but more importantly, for every 50% increase in the specific capacity of the cathode material, the power density of the lithium-ion battery increases by about 28%.
  • the material When 0.07 ⁇ x ⁇ 0.25, the material generates O3 phase (O is arranged along the (001) direction in the lattice structure according to ABCABC) Transition toward O2 phase (O is arranged in ABACABAC along the (001) direction in the lattice structure); when 0.25 ⁇ x ⁇ 0.43, the material changes from O2 phase to O1 phase (O in the lattice structure along (001) The direction is arranged according to ABABAB); when 0.43 ⁇ x ⁇ 0.52, the phase transition of the material from O2 phase to O1 phase is completed.
  • the structure of the positive electrode active material will become unstable, and in severe cases, the structure of the positive electrode active material will collapse.
  • Doping and coating can effectively improve the stability of the LiCoO 2 structure, thereby broadening its charge cut-off voltage and increasing the specific capacity.
  • the academic and industrial circles have adopted Al, Ti, Zr, Mg doping and Al 2 O 3 , MgO and ZrO 2 coatings to make LiCoO 2 materials achieve high voltage (>4.5V vs. Li/Li+) Important progress.
  • the positive electrode of a lithium ion battery also includes a conductive agent.
  • the current common conductive agent is carbon material.
  • the present application provides a positive electrode, an electrochemical device and an electronic device including the positive electrode, in an attempt to solve at least one problem in the related field at least to some extent.
  • the present application provides a positive electrode, which includes a conductive agent containing non-carbon materials, which can effectively improve the cycle performance of the positive electrode active material (for example, LiCoO 2 ) under high voltage, and has a high charge cut-off voltage and high Positive active materials with specific capacity (for example, lithium-rich manganese-based or nickel-manganese spinel materials, etc.) also show better application prospects.
  • a positive electrode active material for example, LiCoO 2
  • positive active material with specific capacity for example, lithium-rich manganese-based or nickel-manganese spinel materials, etc.
  • the present application provides a positive electrode, which includes a conductive agent, wherein the conductive agent includes a non-carbon material.
  • the non-carbon material includes a semiconductor oxide.
  • the semiconductor oxide includes at least one of tin oxide, indium oxide, tin antimony oxide, or indium tin oxide.
  • the semiconductor oxide when the semiconductor oxide is indium tin oxide and tin antimony oxide, the molar ratio of tin to indium or antimony to tin in the semiconductor oxide is about 0.1:1 to 0.5:1.
  • the particle size of the conductive agent is less than or equal to about 100 nm, preferably less than or equal to about 50 nm.
  • the positive electrode further includes a positive electrode active material and a binder, and the positive electrode active material includes a positive electrode active material having a charge cut-off voltage greater than or equal to 4.5V.
  • the positive active material with a charge cut-off voltage greater than or equal to 4.5V includes at least one of lithium cobaltate, spinel lithium nickel manganate, or lithium-rich manganese-based materials.
  • the adhesive includes at least one of a fluorine-containing resin, a polypropylene resin, a fiber-type adhesive, a rubber-type adhesive, or a polyimide-type adhesive.
  • the weight percentage of the conductive agent is about 3.5 wt% to about 10 wt%.
  • the present application also provides an electrochemical device, which includes any one of the above positive electrodes.
  • the present application also provides an electronic device, which includes any one of the above electrochemical devices.
  • FIG. 1 is an X-ray diffraction spectrum (XRD) chart of indium tin oxide in Example 3.
  • XRD X-ray diffraction spectrum
  • FIG. 2 is a scanning electron microscope (SEM) image of the positive pole piece in Example 3.
  • SEM scanning electron microscope
  • Figure 3(a) is an SEM image of the positive pole piece of Example 3.
  • Figures 3(b) to 3(d) are scanning electron microscopes of the cobalt, indium and tin elements of the positive pole piece of Example 3, respectively -Energy spectrum distribution (SEM-EDS) diagram.
  • the terms “approximately”, “substantially”, “substantially” and “about” are used to describe and illustrate small changes.
  • the term can refer to an example in which the event or situation occurs precisely and an example in which the event or situation occurs very closely.
  • the term can refer to a range of variation less than or equal to ⁇ 10% of the stated value, such as less than or equal to ⁇ 5%, less than or equal to ⁇ 4%, less than or equal to ⁇ 3%, Less than or equal to ⁇ 2%, less than or equal to ⁇ 1%, less than or equal to ⁇ 0.5%, less than or equal to ⁇ 0.1%, or less than or equal to ⁇ 0.05%.
  • the difference between two values is less than or equal to ⁇ 10% of the average value of the value (for example, less than or equal to ⁇ 5%, less than or equal to ⁇ 4%, less than or equal to ⁇ 3%, less than Or equal to ⁇ 2%, less than or equal to ⁇ 1%, less than or equal to ⁇ 0.5%, less than or equal to ⁇ 0.1%, or less than or equal to ⁇ 0.05%), then the two values can be considered "substantially" the same.
  • a list of items connected by the terms “at least one of”, “at least one of”, “at least one of” or other similar terms may mean the listed items Any combination of. For example, if items A and B are listed, then the phrase “at least one of A and B” means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C” means only A; or only B; only C; A and B (excluding C); A and C (exclude B); B and C (exclude A); or all of A, B, and C.
  • Project A can contain a single element or multiple elements.
  • Project B can contain a single element or multiple elements.
  • Project C can contain a single element or multiple elements.
  • conductive agents are all carbon-based materials, such as conductive carbon black, carbon fiber, acetylene black, Ketjen black, graphene, and carbon nanotubes. These carbon materials will oxidize to form carbonates when they are cycled for a long time in a high-voltage system, which deteriorates electrical conductivity and increases battery impedance, resulting in accelerated battery failure due to severe polarization.
  • the present application provides a new type of positive electrode containing no carbon material.
  • the positive electrode includes a non-carbon material-containing conductive agent.
  • the conductive agent may include a semiconductor oxide.
  • the semiconductor oxide has stable properties and is resistant to high-voltage oxidation. , Insensitive to the environment, excellent electrical conductivity can be maintained permanently, and can eliminate the adverse effect of the failure of the conductive agent on the high voltage system, thereby effectively improving the cycle performance of the electrochemical device under high voltage.
  • the present application provides a positive electrode, which includes a conductive agent, wherein the conductive agent includes a non-carbon material.
  • the non-carbon material includes a semiconductor oxide
  • the semiconductor oxide includes at least one of tin oxide, indium oxide, antimony tin oxide, or indium tin oxide.
  • the semiconductor oxide is antimony tin oxide, and the molar ratio of antimony to tin in the semiconductor oxide is about 0.1:1 to 0.5:1. In some embodiments, the semiconductor oxide is antimony tin oxide, and the molar ratio of antimony to tin in the semiconductor oxide is about 0.1:1 to 0.2:1, about 0.1:1 to 0.3:1, and about 0.1:1. -0.4:1 or about 0.2:1-0.5:1, etc.
  • the semiconductor oxide is indium tin oxide, and the molar ratio of tin to indium in the semiconductor oxide is about 0.1:1 to 0.5:1. In some embodiments, the semiconductor oxide is indium tin oxide, and the molar ratio of tin to indium in the semiconductor oxide is about 0.1:1 to 0.2:1, about 0.1:1 to 0.3:1, and about 0.1:1 -0.4:1 or about 0.2:1-0.5:1, etc.
  • the particle size of the conductive agent is less than or equal to about 100 nm. In some embodiments, the particle size of the conductive agent is less than or equal to about 90 nm, less than or equal to about 80 nm, or less than or equal to about 75 nm. In some embodiments, the particle size of the conductive agent is about 50 nm to about 75 nm, or about 50 nm to about 100 nm, or the like.
  • the particle size of the conductive agent is less than or equal to about 50 nm. In some embodiments, the particle size of the conductive agent is less than or equal to about 40 nm, less than or equal to about 30 nm, less than or equal to about 20 nm, or less than or equal to about 10 nm. In some embodiments, the particle size of the conductive agent is about 10 nm to about 20 nm, about 10 nm to about 30 nm, about 10 nm to about 50 nm, about 20 nm to about 40 nm, about 20 nm to about 50 nm, about 30 nm to about 50 nm, or about 40 nm. -About 50nm and so on.
  • the positive electrode of the present application further includes a positive electrode active material and a binder, and the positive electrode active material includes a positive electrode active material having a charge cut-off voltage greater than or equal to 4.5V.
  • the positive electrode active material with a charge cut-off voltage greater than or equal to 4.5V includes at least one of lithium cobaltate, spinel lithium nickel manganese oxide, or lithium-rich manganese-based materials. In some embodiments, the positive active material is lithium cobaltate.
  • the weight percentage of the positive electrode active material is about 80 wt% to about 95 wt%. In some embodiments, based on the total weight of the conductive agent, the positive electrode active material, and the binder, the weight percentage of the positive electrode active material is about 80% by weight to about 85% by weight, about 80% by weight to about 90% by weight, or about 85% by weight to about 85% by weight. 90% by weight or about 85% by weight to about 95% by weight, etc.
  • the adhesive includes at least one of a fluorine-containing resin, a polypropylene resin, a fiber-type adhesive, a rubber-type adhesive, or a polyimide-type adhesive.
  • the binder is a fluorine-containing resin.
  • the binder is polyvinylidene fluoride.
  • the weight percentage of the binder is about 1.5 wt% to about 10 wt%. In some embodiments, based on the total weight of the conductive agent, the positive electrode active material, and the binder, the weight percentage of the binder is about 1.5% by weight to about 5% by weight, about 5% by weight to about 10% by weight, or about 1.5% by weight. -About 3 wt%, about 3 wt% to about 5 wt%, about 5 wt% to about 8 wt%, or about 3 wt% to about 8 wt%, etc.
  • the weight percentage of the semiconductor oxide is about 3.5 wt% to about 10 wt%. In some embodiments, based on the total weight of the conductive agent, the positive active material, and the binder, the weight percentage of the conductive agent is about 3.5 wt% to about 5 wt%, or about 5 wt% to about 10 wt%, etc.
  • the positive electrode can be prepared by a preparation method known in the art.
  • the positive electrode can be obtained by mixing a positive electrode active material, a conductive agent, and a binder in a solvent in a certain ratio to prepare a positive electrode slurry, and coating the positive electrode slurry on a positive electrode current collector to prepare a positive electrode.
  • the solvent may include N-methylpyrrolidone and the like, but is not limited thereto.
  • the positive electrode current collector may be aluminum, but is not limited thereto.
  • the conductive agent of the present application is a non-carbon material, which eliminates the increase in electrical resistance and the accelerated failure of the battery due to polarization growth caused by the carbon material as the conductive agent being oxidized to form carbonate under high voltage for a long time in the prior art. risk.
  • nano-scale semiconductor oxide as a conductive agent, the cycle performance of lithium-ion batteries under high voltage has been effectively improved.
  • Semiconductor oxide has good electrical conductivity, is insensitive to external environments such as heat and humidity, and is resistant to high-voltage oxidation. It is an ideal conductive agent for high-voltage systems.
  • the conductive agent of the present application can be directly slurry-coated with the positive electrode active material and the binder, without changing the original production process, and without special production equipment and special processing steps.
  • the operation is simple and convenient, and it has a good commercial performance. Application prospects.
  • the electrochemical device of the present application includes any one of the above-mentioned positive electrodes of the present application.
  • the electrochemical device of the present application may include any device that undergoes an electrochemical reaction, and specific examples thereof include all kinds of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors.
  • the electrochemical device is a lithium secondary battery, including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.
  • the electrochemical device of the present application includes the positive electrode of the present application, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte.
  • the electrochemical device is a lithium ion battery.
  • the negative electrode includes a negative electrode current collector and a negative electrode active material layer on the negative electrode current collector.
  • the negative active material includes a material that reversibly intercalates/deintercalates lithium ions.
  • the material that reversibly intercalates/deintercalates lithium ions includes a carbon material.
  • the carbon material may be any carbon-based negative active material commonly used in lithium ion rechargeable batteries.
  • the carbon material includes, but is not limited to: crystalline carbon, amorphous carbon, or a mixture thereof.
  • the crystalline carbon may be amorphous, flake-shaped, flake-shaped, spherical or fibrous natural graphite or artificial graphite.
  • Amorphous carbon can be soft carbon, hard carbon, mesophase pitch carbide, calcined coke and the like.
  • the negative electrode active material includes, but is not limited to: lithium metal, structured lithium metal, natural graphite, artificial graphite, mesophase carbon microspheres (MCMB), hard carbon, soft carbon, silicon, silicon-carbon Composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO 2 , spinel structure lithiated TiO 2 -Li 4 Ti 5 O 12 , Li-Al alloy, or any combination thereof.
  • MCMB mesophase carbon microspheres
  • the negative electrode active material layer can be formed using a method such as a vapor deposition method, a sputtering method, or a plating method.
  • the negative electrode includes lithium metal, for example, a conductive skeleton having a spherical twisted shape and metal particles dispersed in the conductive skeleton are used to form the negative electrode active material layer.
  • the spherical stranded conductive skeleton may have a porosity of about 5% to about 85%.
  • a protective layer may be further provided on the lithium metal negative electrode active material layer.
  • the negative electrode may further include a binder.
  • the binder improves the bonding of the negative active material particles with each other and the bonding of the negative active material with the negative current collector.
  • the binder includes, but is not limited to: polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyfluoro Ethylene, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene butadiene rubber, acrylic (ester) styrene butadiene Rubber, epoxy resin, nylon, etc.
  • the negative electrode can also be a conductive agent.
  • Conductive agents include, but are not limited to: carbon-based materials, metal-based materials, conductive polymers, or mixtures thereof.
  • the carbon-based material is selected from natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof.
  • the metal-based material is selected from metal powder, metal fiber, copper, nickel, aluminum, silver.
  • the conductive polymer is a polyphenylene derivative.
  • the negative electrode current collector includes, but is not limited to: copper foil, nickel foil, stainless steel foil, titanium foil, foamed nickel, foamed copper, conductive metal-coated polymer substrate, and any combination thereof.
  • the negative electrode can be prepared by a preparation method known in the art.
  • the negative electrode can be obtained by mixing an active material, a conductive material, and a binder in a solvent to prepare an active material composition, and coating the active material composition on a current collector.
  • the solvent may include water and the like, but is not limited thereto.
  • the isolation film includes, but is not limited to, at least one selected from polyethylene, polypropylene, polyethylene terephthalate, polyimide, and aramid.
  • polyethylene includes at least one component selected from high-density polyethylene, low-density polyethylene, and ultra-high molecular weight polyethylene.
  • polyethylene and polypropylene they have a good effect on preventing short circuits, and can improve the stability of lithium-ion batteries through the shutdown effect.
  • the electrolyte may be one or more of a gel electrolyte, a solid electrolyte, and an electrolyte, and the electrolyte includes a lithium salt and a non-aqueous solvent.
  • the lithium salt may be 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 selected for 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.
  • examples of chain carbonate compounds are diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethylene propyl carbonate (EPC), ethyl methyl carbonate (MEC) and combinations thereof.
  • examples of the cyclic carbonate compound are ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinyl ethylene carbonate (VEC), or a combination thereof.
  • fluorocarbonate compound examples include fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-tricarbonate Fluoroethylene, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2 carbonate -Difluoro-1-methylethylene, 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-tricarbonate Fluoroethylene, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2 carbonate -Difluoro-1-methylethylene, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate,
  • examples of carboxylate compounds are methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, ⁇ -butyrolactone Ester, caprolactone, valerolactone, mevalonolactone, caprolactone, methyl formate, or combinations thereof.
  • examples of ether compounds are dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane , Ethoxymethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran or a combination thereof.
  • examples of other organic solvents are dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl -2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, phosphate ester, or a combination thereof.
  • the electrochemical device manufactured from the positive electrode described in this application is suitable for electronic devices in various fields.
  • the electrochemical device of the present application is not particularly limited, and it can be used for any purpose known in the prior art.
  • the electrochemical device of the present application can be used in, but not limited to, notebook computers, pen-input computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, and headsets.
  • the button half-cell is assembled with the prepared positive pole piece as the working electrode and metal lithium as the counter electrode, and the cycle performance of the assembled button half-cell is tested.
  • the weight ratio of LiCoO 2 : polyvinylidene fluoride: indium oxide 80:10:10 is mixed uniformly and then coated, cold pressed, and punched to prepare a positive pole piece, wherein the particle size of the indium oxide is 17nm-28nm.
  • the button half-cell is assembled with the prepared positive pole piece as the working electrode and metal lithium as the counter electrode, and the cycle performance of the assembled button half-cell is tested.
  • the button half-cell is assembled with the prepared positive pole piece as the working electrode and metal lithium as the counter electrode, and the cycle performance of the assembled button half-cell is tested.
  • the button half-cell is assembled with the prepared positive pole piece as the working electrode and metal lithium as the counter electrode, and the cycle performance of the assembled button half-cell is tested.
  • Example 2 It is basically the same as Example 1, except that the non-carbon conductive agent is tin oxide.
  • Example 2 It is basically the same as Example 1, except that the particle size of indium oxide is 50nm-75nm.
  • Example 2 It is basically the same as Example 2, except that the particle size of indium oxide is 50nm-75nm.
  • Example 3 It is basically the same as Example 3, except that the particle size of indium tin oxide is 50nm-75nm.
  • Example 4 It is basically the same as Example 4, except that the particle size of indium tin oxide is 50nm-75nm.
  • Example 2 It is basically the same as Example 1, except that the particle size of indium oxide is 1 nm-10 nm.
  • Example 3 It is basically the same as Example 3, except that the particle size of indium tin oxide is 1 nm-10 nm.
  • the weight ratio of LiCoO 2 : polyvinylidene fluoride: conductive carbon black 95: 1.5: 3.5 is mixed uniformly, then coated, cold pressed, and punched to prepare a positive pole piece.
  • the button half-cell is assembled with the prepared positive pole piece as the working electrode and metal lithium as the counter electrode, and the cycle performance of the assembled button half-cell is tested.
  • the weight ratio of LiCoO 2 : polyvinylidene fluoride: conductive carbon black 80:10:10 is mixed uniformly and then coated to prepare a positive pole piece.
  • the button half-cell is assembled with the prepared positive pole piece as the working electrode and metal lithium as the counter electrode, and the cycle performance of the assembled button half-cell is tested.
  • X-ray diffraction tester (XPertPro MPD, PANalytical, Netherlands), and set test conditions: Cu K ⁇ radiation
  • the working current is 250mA
  • the working voltage is 40kV
  • the scanning range 2 ⁇ is 10°-70°
  • the step length is 0.1°
  • the scanning speed is 0.2 seconds/step.
  • the sample powder is subjected to X-ray diffraction test to confirm the phase of the sample.
  • the present invention uses the Wuhan Landian CT2001A system to test the cycle performance of the electrochemical device.
  • the button cell to be tested is placed in an environment of 25 ⁇ 3°C for 30 minutes, with a rate of 0.1C (4.5V and 4.6V, LiCoO 2
  • the theoretical gram capacity is 190mAh/g and 220mAh/g respectively)
  • Charge with constant current to the voltage of 4.5V and 4.6V then charge with constant voltage to the current of 0.025C, then discharge to 3V at a rate of 0.1C, repeat the above 50 cycles of charge/discharge steps, record the discharge gram capacity before and after the cycle.
  • Discharge gram capacity discharge capacity/weight of positive electrode active material (lithium cobaltate).
  • Table 1 shows the cycle performance test results of Comparative Example 1-Comparative Example 2 and Example 1-Example 10.
  • FIG. 1 is an XRD pattern of indium tin oxide in Example 3.
  • FIG. 2 is an SEM image of the positive pole piece in Example 3.
  • FIG. Figure 3(a) is an SEM image of the positive pole piece of Example 3
  • Figures 3(b) to 3(d) are the SEM-EDS of the cobalt element, indium element and tin element of the positive pole piece of Example 3, respectively Figure.
  • Figures 3(a) to 3(d) show the distribution of indium tin oxide in the positive pole piece in the third embodiment. It can be seen from Figure 3 that indium tin oxide is uniformly dispersed around the positive electrode active material particles, and the distribution is relatively uniform.
  • Comparing Comparative Example 1 and Comparative Example 2 it can be seen that regardless of whether the cycle cut-off voltage is 4.5V or 4.6V, the cycle capacity retention rate of Comparative Example 2 is lower than that of Comparative Example 1, which is mainly due to the different proportions of the components of the positive electrode. .
  • the conductive carbon black content in Comparative Example 2 is higher, and the failure of oxidation during the high cut-off voltage cycle is more serious, which leads to a decrease in the electronic conductance of the lithium ion battery, serious polarization, and ineffective capacity. Play.
  • Comparative Example 1 Example 3, Example 5, Example 7, Example 9, and Comparative Example 1 (or Comparative Example 2, Example 4, Example 6, Example 8, Example 10, and Comparative Example 2 ) It can be seen that when the positive pole piece does not contain conductive carbon black, the capacity retention rate of the lithium ion battery can be greatly improved by cycling under the same cut-off voltage. Cycling for 50 cycles at 4.5V and the weight percentage of the conductive agent is 3.5%, the capacity retention rate of the example is in the range of 88.2%-91.5%, which is about 5.9%-9.2% higher than that of the comparative example 1; When the agent content is 10%, the capacity retention rate of the example is in the range of 89.1%-92.0%, which is about 12.9%-15.8% higher than that of the comparative example 2.
  • the capacity retention rate of the embodiment is improved more obviously.
  • the content of the conductive agent is 3.5% by weight
  • the capacity retention rate of the example is in the range of 83.1%-85.6%, which is about 8.8%-11.3% higher than that of the comparative example 1.
  • the capacity retention rate of the example is in the range of 83.5%-86.3%, which is about 14.4%-17.2% higher than that of the comparative example 2.
  • Example 11 and Example 12 Comparing Example 11 and Example 12 with Example 1 and Example 3, it can be seen that when the particle size of the conductive agent is less than 10nm, the capacity retention rate is not further improved, mainly because the particle size of 10nm-30nm is active in the positive electrode. The electron channel constructed between the material particles is saturated, and the effect of further reducing the particle size of the conductive agent is not obvious.
  • the positive electrode of this application uses semiconductor oxide as a conductive agent.
  • the semiconductor oxide is not sensitive to external environments such as heat and humidity, can withstand high-pressure oxidation and maintain excellent permanent conductivity. Compared with carbon materials, it is more suitable for high-voltage systems.
  • cathode active materials with high specific capacity and high cut-off voltage such as lithium-rich manganese-based or spinel lithium nickel manganese oxide materials, there will be greater application value.
  • references to “some embodiments”, “partial embodiments”, “one embodiment”, “another example”, “examples”, “specific examples” or “partial examples” throughout the specification mean At least one embodiment or example in this application includes the specific feature, structure, material, or characteristic described in the embodiment or example. Therefore, descriptions appearing in various places throughout the specification, such as: “in some embodiments”, “in embodiments”, “in one embodiment”, “in another example”, “in an example “In”, “in a specific example” or “exemplary”, which are not necessarily quoting the same embodiment or example in this application.
  • the specific features, structures, materials, or characteristics herein can be combined in one or more embodiments or examples in any suitable manner.

Abstract

本申请涉及一种正极及包括其的电化学装置和电子装置。所述正极包括导电剂，其中导电剂包含非碳材料。本申请提供了一种包含耐高电压氧化的导电剂的正极，可以有效地改善电化学装置的高电压循环性能。

Description

正极及包含其的电化学装置和电子装置 技术领域
本申请涉及储能技术领域，尤其涉及一种正极及包括其的电化学装置和电子装置，所述正极包括包含非碳材料的导电剂。
背景技术
锂离子电池因其具有能量密度高、功率密度大、寿命长、安全性好、自放电低和温度适应范围宽等优点，被广泛应用于便携式电子产品、电动交通、国防航空和能源储备等领域。为了进一步满足市场对高能量密度电池的需求，拓宽正极材料的充电截止电压和开发更高比能的新材料正成为一个势在必行的研究方向。
锂离子电池主要由正极、负极、隔离膜和电解液等组成。改善正极材料的性能是提高锂离子电池综合性能的关键。这不仅因为正极材料占锂离子电池整体成本的约40％以上，更重要的是，正极材料的比容量每增加50％，锂离子电池的功率密度约增加28％。
目前在市场中应用广泛的正极活性材料主要有层状结构的LiCoO 2和LiNi xCo yMn zO 2(x+y+z＝1)，尖晶石结构的LiMn 2O 4和橄榄石结构的LiFePO 4。LiCoO 2材料自1991年被索尼(Sony)公司实现商业化以来，在正极活性材料市场一直占据着举足轻重的地位。LiCoO 2的理论比容量约为274mAh/g，压实密度在4.1g/cm 3-4.2g/cm 3范围内。在充电过程中，Li +从LiCoO 2结构中脱出形成Li 1-xCoO 2，当0.07≤x≤0.25时，材料发生O3相(O在晶格结构中沿着(001)方向按ABCABC排列)朝O2相(O在晶格结构中沿着(001)方向按ABACABAC排列)的转变；当0.25≤x≤0.43时，材料发生O2相朝O1相(O在晶格结构中沿着(001)方向按ABABAB排列)的转变；当0.43≤x≤0.52时，材料由O2相朝O1相的相转变完成。继续脱锂，正极活性材料结构会变得不稳定，严重时，正极活性材料结构会坍塌。
通过掺杂和包覆可有效提高LiCoO 2结构的稳定性，进而拓宽其充电截止电压，提升比容量。目前学术界和产业界通过Al、Ti、Zr、Mg掺杂和Al 2O 3、MgO和ZrO 2包覆等手段，使得LiCoO 2材料在高电压(＞4.5V vs.Li/Li+)方向取得了重要的进展。近期， 已有文献(Zhang et al.，“Trace doping of multiple elements enables stable battery cycling of LiCoO2 at 4.6V”，2018，Nature energy，Volume 4，Pages 594-603)通过Ti-Mg-Al共掺的方式将LiCoO 2材料稳定充放电的截止电压提升到了4.6V。
锂离子电池的正极除了正极活性材料之外，还包括导电剂。目前常见的导电剂是碳材料。然而，已有文献(例如，Du et al.，“Influence of Electronic Conducting Additives on Cycle Performance of Garnet-based Solid Lithium Batteries”，2018，Journal of Inorganic Materials，Volume 33，Pages 462-468和Zhao et al.，“Solid Garnet Batteries”，2019，Joule，Volume 3，Pages 1-10)指出：在高电压体系中，碳材料并不是一种很好的导电剂；当锂离子电池在高截止电压(特别是对于截止电压大于等于4.5V)进行长时间充放电循环时，作为导电剂的碳材料会被加速氧化生成碳酸盐，导致电阻增大，电子电导降低，最终锂离子电池因极化增长而加速失效。
发明内容
本申请提供一种正极以及包括所述正极的电化学装置及电子装置以试图在至少某种程度上解决至少一个存在于相关领域中的问题。
本申请提供了一种正极，所述正极包括包含非碳材料的导电剂，可以有效地改善高电压下正极活性材料(例如，LiCoO 2)的循环性能，并且对于其它具有高充电截止电压和高比容量的正极活性材料(例如，富锂锰基或镍锰尖晶石材料等)，也显示出了较好的应用前景。
根据本申请的实施例，本申请提供了一种正极，其包括导电剂，其中所述导电剂包含非碳材料。
根据本申请的实施例，非碳材料包含半导体氧化物。
根据本申请的实施例，半导体氧化物包括氧化锡、氧化铟、氧化锡锑或氧化铟锡中的至少一种。
根据本申请的实施例，当半导体氧化物为氧化铟锡和氧化锡锑时，所述半导体氧化物中锡与铟或锑与锡的摩尔比为约0.1∶1-0.5∶1。
根据本申请的实施例，导电剂的粒径小于等于约100nm，优选小于等于约50nm。
根据本申请的实施例，正极还包括正极活性材料和粘结剂，所述正极活性材料包括 具有充电截止电压大于等于4.5V的正极活性材料。
根据本申请的实施例，具有充电截止电压大于等于4.5V的正极活性材料包括钴酸锂、尖晶石镍锰酸锂或富锂锰基材料中的至少一种。
根据本申请的实施例，粘结剂包括含氟树脂、聚丙烯树脂、纤维型粘结剂、橡胶型粘结剂或聚酰亚胺型粘结剂中的至少一种。
根据本申请的实施例，以所述导电剂、所述正极活性材料和所述粘结剂的总重量计，所述导电剂的重量百分比为约3.5wt％-约10wt％。
根据本申请的实施例，本申请还提供了一种电化学装置，其包括以上任意一种正极。
根据本申请的实施例，本申请还提供了一种电子装置，其包括以上任意一种电化学装置。
本申请实施例的额外层面及优点将部分地在后续说明中描述、显示、或是经由本申请实施例的实施而阐释。
附图说明
在下文中将简要地说明为了描述本申请实施例或现有技术所必要的附图以便于描述本申请的实施例。显而易见地，下文描述中的附图仅只是本申请中的部分实施例。对本领域技术人员而言，在不需要创造性劳动的前提下，依然可以根据这些附图中所例示的结构来获得其他实施例的附图。
图1是实施例3中的氧化铟锡的X射线衍射谱(XRD)图。
图2是实施例3中的正极极片的扫描电子显微镜(SEM)图。
图3(a)是实施例3的正极极片的SEM图，图3(b)至图3(d)分别是实施例3的正极极片的钴元素、铟元素和锡元素的扫描电子显微镜-能谱分布(SEM-EDS)图。
具体实施方式
本申请的实施例将会被详细的描示在下文中。在本申请说明书全文中，将相同或相似的组件以及具有相同或相似的功能的组件通过类似附图标记来表示。在此所描述的有关附图的实施例为说明性质的、图解性质的且用于提供对本申请的基本理解。本申请的 实施例不应该被解释为对本申请的限制。
如本文中所使用，术语“大致”、“大体上”、“实质”及“约”用以描述及说明小的变化。当与事件或情形结合使用时，所述术语可指代其中事件或情形精确发生的例子以及其中事件或情形极近似地发生的例子。举例来说，当结合数值使用时，术语可指代小于或等于所述数值的±10％的变化范围，例如小于或等于±5％、小于或等于±4％、小于或等于±3％、小于或等于±2％、小于或等于±1％、小于或等于±0.5％、小于或等于±0.1％、或小于或等于±0.05％。举例来说，如果两个数值之间的差值小于或等于所述值的平均值的±10％(例如小于或等于±5％、小于或等于±4％、小于或等于±3％、小于或等于±2％、小于或等于±1％、小于或等于±0.5％、小于或等于±0.1％、或小于或等于±0.05％)，那么可认为所述两个数值“大体上”相同。
另外，有时在本文中以范围格式呈现量、比率和其它数值。应理解，此类范围格式是用于便利及简洁起见，且应灵活地理解，不仅包含明确地指定为范围限制的数值，而且包含涵盖于所述范围内的所有个别数值或子范围，如同明确地指定每一数值及子范围一般。
在具体实施方式及权利要求书中，由术语“中的至少一者”、“中的至少一个”、“中的至少一种”或其他相似术语所连接的项目的列表可意味着所列项目的任何组合。例如，如果列出项目A及B，那么短语“A及B中的至少一者”意味着仅A；仅B；或A及B。在另一实例中，如果列出项目A、B及C，那么短语“A、B及C中的至少一者”意味着仅A；或仅B；仅C；A及B(排除C)；A及C(排除B)；B及C(排除A)；或A、B及C的全部。项目A可包含单个元件或多个元件。项目B可包含单个元件或多个元件。项目C可包含单个元件或多个元件。
拓宽正极活性材料的充电截止电压以获得更高的比容量是当前的一个研究热点，然而高电压体系对导电剂等也提出了更高的要求。传统的导电剂均为一些基于碳的材料，例如，导电碳黑、碳纤维、乙炔黑、科琴黑、石墨烯和碳纳米管等。这些碳材料在高电压体系中长时间循环时会氧化生成碳酸盐，恶化导电性能，增加电池阻抗，导致电池因极化严重而加速失效。
鉴于此，本申请提供了一种新型的、不含碳材料的正极，所述正极包括包含非碳材料的导电剂，导电剂可以包括半导体氧化物，半导体氧化物的性质稳定、耐高电压氧化、对环境不敏感、优良的导电性可永久性保持、并且能消除导电剂失效对高电压体系的不 利影响，从而有效地改善电化学装置在高电压下的循环性能。
一、正极
本申请提供了一种正极，其包括导电剂，其中所述导电剂包含非碳材料。
在一些实施例中，非碳材料包含半导体氧化物，半导体氧化物包括氧化锡、氧化铟、氧化锡锑或氧化铟锡中的至少一种。
在一些实施例中，半导体氧化物为氧化锡锑，所述半导体氧化物中的锑与锡的摩尔比为约0.1∶1-0.5∶1。在一些实施例中，半导体氧化物为氧化锡锑，所述半导体氧化物中的锑与锡的摩尔比为约0.1∶1-0.2∶1、约0.1∶1-0.3∶1、约0.1∶1-0.4∶1或约0.2∶1-0.5∶1等。
在一些实施例中，半导体氧化物为氧化铟锡，所述半导体氧化物中的锡与铟的摩尔比为约0.1∶1-0.5∶1。在一些实施例中，半导体氧化物为氧化铟锡，所述半导体氧化物中的锡与铟的摩尔比为约0.1∶1-0.2∶1、约0.1∶1-0.3∶1、约0.1∶1-0.4∶1或约0.2∶1-0.5∶1等。
在一些实施例中，导电剂的粒径小于等于约100nm。在一些实施例中，导电剂的粒径小于等于约90nm、小于等于约80nm或小于等于约75nm。在一些实施例中，导电剂的粒径为约50nm-约75nm或约50nm-约100nm等。
在一些实施例中，导电剂的粒径小于等于约50nm。在一些实施例中，导电剂的粒径小于等于约40nm、小于等于约30nm、小于等于约20nm或小于等于约10nm。在一些实施例中，导电剂的粒径为约10nm-约20nm、约10nm-约30nm、约10nm-约50nm、约20nm-约40nm、约20nm-约50nm、约30nm-约50nm或约40nm-约50nm等。
在一些实施例中，本申请的正极还包括正极活性材料和粘结剂，所述正极活性材料包括具有充电截止电压大于等于4.5V的正极活性材料。
在一些实施例中，具有充电截止电压大于等于4.5V的正极活性材料包括钴酸锂、尖晶石镍锰酸锂或富锂锰基材料中的至少一种。在一些实施例中，正极活性材料为钴酸锂。
在一些实施例中，以导电剂、正极活性材料和粘结剂的总重量计，正极活性材料的重量百分比为约80wt％-约95wt％。在一些实施例中，以导电剂、正极活性材料和粘结剂的总重量计，正极活性材料的重量百分比为约80wt％-约85wt％、约80wt％-约90wt％、约85wt％-约90wt％或约85wt％-约95wt％等。
在一些实施例中，粘结剂包括含氟树脂、聚丙烯树脂、纤维型粘结剂、橡胶型粘结 剂或聚酰亚胺型粘结剂中的至少一种。在一些实施例中，粘结剂为含氟树脂。在一些实施例中，粘结剂为聚偏氟乙烯。
在一些实施例中，以导电剂、正极活性材料和粘结剂的总重量计，粘结剂的重量百分比为约1.5wt％-约10wt％。在一些实施例中，以导电剂、正极活性材料和粘结剂的总重量计，粘结剂的重量百分比为约1.5wt％-约5wt％、约5wt％-约10wt％、约1.5wt％-约3wt％、约3wt％-约5wt％、约5wt％-约8wt％或约3wt％-约8wt％等。
在一些实施例中，以导电剂、正极活性材料和粘结剂的总重量计，所述半导体氧化物的重量百分比为约3.5wt％-约10wt％。在一些实施例中，以导电剂、正极活性材料和粘结剂的总重量计，所述导电剂的重量百分比为约3.5wt％-约5wt％或约5wt％-约10wt％等。
正极可以通过本领域公知的制备方法制备。例如，正极可以通过如下方法获得：在溶剂中将正极活性材料、导电剂和粘合剂按照一定的比例混合以制备正极浆料，并将正极浆料涂布在正极集流体上以制备正极。在一些实施例中，溶剂可以包括N-甲基吡咯烷酮等，但不限于此。在一些实施例中，正极集流体可以是铝，但不限于此。
本申请的导电剂为非碳材料，消除了现有技术中因导电剂碳材料在高电压下长时间循环被氧化生成碳酸盐而导致的电阻增大、电池因极化增长而加速失效的风险。通过添加纳米级的半导体氧化物作为导电剂，锂离子电池在高电压下的循环性能得到了有效的提升。半导体氧化物的导电性能良好，对热、湿度等外部环境不敏感，且耐高电压氧化，对于高电压体系是一种理想的导电剂。
此外，本申请的导电剂可直接与正极活性材料和粘结剂制浆涂布，而不改变原有的生产工艺，也无需特殊生产设备和特殊处理步骤，操作简单方便，具有很好的商业应用前景。
二、电化学装置
本申请的电化学装置包括本申请的上述任意一种正极。本申请的电化学装置可以包括发生电化学反应的任何装置，它的具体实例包括所有种类的一次电池、二次电池、燃料电池、太阳能电池或电容。特别地，该电化学装置是锂二次电池，包括锂金属二次电池、锂离子二次电池、锂聚合物二次电池或锂离子聚合物二次电池。在一些实施例中，本申请的电化学装置包括本申请的正极、负极、置于正极和负极之间的隔离膜以及电解液。在一些实施例中，所述电化学装置为锂离子电池。
在一些实施例中，负极包括负极集流体和位于负极集流体上的负极活性材料层。负极活性材料包括可逆地嵌入/脱嵌锂离子的材料。在一些实施例中，可逆地嵌入/脱嵌锂离子的材料包括碳材料。在一些实施例中，碳材料可以是在锂离子可充电电池中通常使用的任何基于碳的负极活性材料。在一些实施例中，碳材料包括，但不限于：结晶碳、非晶碳或它们的混合物。结晶碳可以是无定形的、片形的、小片形的、球形的或纤维状的天然石墨或人造石墨。非晶碳可以是软碳、硬碳、中间相沥青碳化物、煅烧焦等。
在一些实施例中，负极活性材料包括，但不限于：锂金属、结构化的锂金属、天然石墨、人造石墨、中间相微碳球(MCMB)、硬碳、软碳、硅、硅-碳复合物、Li-Sn合金、Li-Sn-O合金、Sn、SnO、SnO 2、尖晶石结构的锂化TiO 2-Li 4Ti 5O 12、Li-Al合金或其任意组合。
当负极包括硅碳化合物时，基于负极活性材料总重量，硅∶碳＝约1∶10～10∶1，硅碳化合物的中值粒径D50为约0.1μm-100μm。当负极包括合金材料时，可使用蒸镀法、溅射法、镀敷法等方法形成负极活性物质层。当负极包括锂金属时，例如用具有球形绞状的导电骨架和分散在导电骨架中的金属颗粒形成负极活性物质层。在一些实施例中，球形绞状的导电骨架可具有约5％-约85％的孔隙率。在一些实施例中，锂金属负极活性物质层上还可设置保护层。
在一些实施例中，负极还可以包括粘合剂。粘合剂提高负极活性材料颗粒彼此间的结合和负极活性材料与负极集流体的结合。在一些实施例中，粘合剂包括，但不限于：聚乙烯醇、羧甲基纤维素、羟丙基纤维素、二乙酰基纤维素、聚氯乙烯、羧化的聚氯乙烯、聚氟乙烯、含亚乙基氧的聚合物、聚乙烯吡咯烷酮、聚氨酯、聚四氟乙烯、聚偏1，1-二氟乙烯、聚乙烯、聚丙烯、丁苯橡胶、丙烯酸(酯)化的丁苯橡胶、环氧树脂、尼龙等。
在一些实施例中，负极还可以导电剂。导电剂包括，但不限于：基于碳的材料、基于金属的材料、导电聚合物或它们的混合物。在一些实施例中，基于碳的材料选自天然石墨、人造石墨、碳黑、乙炔黑、科琴黑、碳纤维或其任意组合。在一些实施例中，基于金属的材料选自金属粉、金属纤维、铜、镍、铝、银。在一些实施例中，导电聚合物为聚亚苯基衍生物。
在一些实施例中，负极集流体包括，但不限于：铜箔、镍箔、不锈钢箔、钛箔、泡沫镍、泡沫铜、覆有导电金属的聚合物基底和它们的任意组合。
负极可以通过本领域公知的制备方法制备。例如，负极可以通过如下方法获得：在 溶剂中将活性材料、导电材料和粘合剂混合，以制备活性材料组合物，并将该活性材料组合物涂覆在集流体上。在一些实施例中，溶剂可以包括水等，但不限于此。
在一些实施例中，隔离膜包括，但不限于，选自聚乙烯、聚丙烯、聚对苯二甲酸乙二醇酯、聚酰亚胺和芳纶中的至少一种。举例来说，聚乙烯包括选自高密度聚乙烯、低密度聚乙烯和超高分子量聚乙烯中的至少一种组分。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锂离子电池的稳定性。
在一些实施例中，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。
在一些实施例中，锂盐可以选自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。
在一些实施例中，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。
在一些实施例中，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。
在一些实施例中，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。
在一些实施例中，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。
在一些实施例中，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。
在一些实施例中，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、磷酸酯或者其组合。
三、应用
由本申请所述的正极制造的电化学装置适用于各种领域的电子装置。
本申请的电化学装置的用途没有特别限定，其可用于现有技术中已知的任何用途。在一个实施例中，本申请的电化学装置可用于，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。
四、实施例
以下，举出实施例和对比例对本申请进一步具体地进行说明，但只要不脱离其主旨，则本申请并不限定于这些实施例。
实施例1
以LiCoO 2∶聚偏氟乙烯∶氧化铟＝95∶1.5∶3.5的重量比将其混合均匀后涂布、冷压、冲片，制备正极极片，其中氧化铟的粒径为17nm-28nm。
以制备的正极极片为工作电极、金属锂为对电极来组装扣式半电池，对组装的扣式半电池进行循环性能测试。
实施例2
以LiCoO 2∶聚偏氟乙烯∶氧化铟＝80∶10∶10的重量比将其混合均匀后涂布、冷压、冲片，制备正极极片，其中氧化铟的粒径17nm-28nm。
以制备的正极极片为工作电极、金属锂为对电极来组装扣式半电池，对组装的扣式半电池进行循环性能测试。
实施例3
以LiCoO 2∶聚偏氟乙烯∶氧化铟锡(锡∶铟＝0.5∶1)＝95∶1.5∶3.5的重量比将其混合均匀 后涂布、冷压、冲片，制备正极极片，其中氧化铟锡的粒径17nm-28nm。
以制备的正极极片为工作电极、金属锂为对电极来组装扣式半电池，对组装的扣式半电池进行循环性能测试。
实施例4
以LiCoO 2∶聚偏氟乙烯∶氧化铟锡(锡∶铟＝0.1∶1)＝80∶10∶10的重量比将其混合均匀后涂布、冷压、冲片，制备正极极片，其中氧化铟锡的粒径17nm-28nm。
以制备的正极极片为工作电极、金属锂为对电极来组装扣式半电池，对组装的扣式半电池进行循环性能测试。
实施例5
与实施例1基本一致，不同之处在于非碳导电剂为氧化锡。
实施例6
与实施例4基本一致，不同之处在于非碳导电剂为氧化锡锑(锑∶锡＝0.1∶1)。
实施例7
与实施例1基本一致，不同之处在于氧化铟的粒径为50nm-75nm。
实施例8
与实施例2基本一致，不同之处在于氧化铟的粒径为50nm-75nm。
实施例9
与实施例3基本一致，不同之处在于氧化铟锡的粒径为50nm-75nm。
实施例10
与实施例4基本一致，不同之处在于氧化铟锡的粒径为50nm-75nm。
实施例11
与实施例1基本一致，不同之处在于氧化铟的粒径为1nm-10nm。
实施例12
与实施例3基本一致，不同之处在于氧化铟锡的粒径为1nm-10nm。
对比例1
以LiCoO 2∶聚偏氟乙烯∶导电碳黑＝95∶1.5∶3.5的重量比将其混合均匀后涂布、冷压、冲片，制备正极极片。
以制备的正极极片为工作电极、金属锂为对电极来组装扣式半电池，对组装的扣式半电池进行循环性能测试。
对比例2
以LiCoO 2∶聚偏氟乙烯∶导电碳黑＝80∶10∶10的重量比将其混合均匀后涂布、制备正极极片。
以制备的正极极片为工作电极、金属锂为对电极来组装扣式半电池，对组装的扣式半电池进行循环性能测试。
五、测试方法及测试结果
X射线衍射测试
采用X射线衍射测试仪(荷兰帕纳科，XPertPro MPD)，并设定测试条件：Cu K α辐射
Figure PCTCN2019122057-appb-000001
工作电流250mA，采用连续扫描，工作电压为40kV，扫描范围2θ为10°-70°，步长0.1°，扫描速度0.2秒/步，对样品粉末进行X衍射测试来确认样品物相。
循环性能测试
本发明采用武汉蓝电CT2001A系统对电化学装置的循环性能进行测试，将待测的扣式电池在25±3℃环境中静置30分钟，以0.1C的倍率(4.5V和4.6V，LiCoO 2理论克容量分别以190mAh/g和220mAh/g计)恒流充电至电压为4.5V和4.6V，随后分别恒压充电至电流为0.025C，然后以0.1C的倍率放电至3V，重复上述充/放电步骤50个循环，记录循环前和循环后的放电克容量。
放电克容量＝放电容量/正极活性物质(钴酸锂)重量。
表1示出了对比例1-对比例2以及实施例1-实施例10的循环性能测试结果。
表1
Figure PCTCN2019122057-appb-000002
Figure PCTCN2019122057-appb-000003
图1是实施例3中的氧化铟锡的XRD图。从图1中可以看出，谱峰尖锐，强度较高，说明氧化铟锡颗粒晶形完好，结晶度较高。图2是实施例3中的正极极片的SEM图。图3(a)是实施例3的正极极片的SEM图，图3(b)至图3(d)分别是实施例3的正极极片的钴元素、铟元素和锡元素的SEM-EDS图。图3(a)至图3(d)示出了实施例3中的氧化铟锡在正极极片中的分布。从图3中可以看出，氧化铟锡均匀分散在正极活性物质颗粒周围，分布较为均匀。
比较对比例1和对比例2可知，无论循环截止电压是4.5V还是4.6V，对比例2的循环容量保持率均低于对比例1，这主要是由于正极极片的各组分的比例不同。相比于对比例1，对比例2中的导电碳黑含量更高，在高截止电压循环过程中被氧化失效的情况更严重，导致锂离子电池的电子电导下降，极化严重，容量无法有效发挥。
比较实施例1、实施例3、实施例5、实施例7、实施例9和对比例1(或比较实施例2、实施例4、实施例6、实施例8、实施例10和对比例2)可知，当正极极片不含导电碳黑时，在相同截止电压下循环，锂离子电池的容量保持率可以得到较大的提升。在 4.5V下循环50圈，导电剂的重量百分含量为3.5％时，实施例的容量保持率在88.2％-91.5％范围内，比对比例1提升了约5.9％-9.2％；当导电剂含量为10％时，实施例的容量保持率在89.1％-92.0％范围内，比对比例2提升了约12.9％-15.8％。在4.6V下循环，相比于对比例，实施例的容量保持率提升得更加明显。当导电剂的重量百分含量为3.5％时，实施例的容量保持率在83.1％-85.6％范围内，比对比例1提升了约8.8％-11.3％；当导电剂含量为10％时，实施例的容量保持率在83.5％-86.3％范围内，比对比例2提升了约14.4％-17.2％。
比较实施例1至实施例6与实施例7至实施例10，可以得知，导电剂的颗粒尺寸较小时，对容量保持率的提升效果更好，这主要是因为导电剂颗粒尺寸越小，单位质量的导电剂颗粒数目越多，在正极活性材料间建构的电子通道更丰富，更有利于降低电池副反应产物带来的极化影响。当导电剂的粒径大于50nm时，不利于发挥导电剂的最佳性能。比较实施例11、实施例12与实施例1、实施例3可知，当导电剂的粒径小于10nm时，对容量保持率没有更进一步的提升，主要是因为10nm-30nm的粒径在正极活性材料颗粒间所建构的电子通道已饱和，更进一步减小导电剂的粒径对其影响不明显。
比较实施例1-实施例6、实施例11、实施例12可以得知，不同的导电剂，以及导电剂中不同的元素配比，其导电效果基本相同，因而对容量保持率的提升效果类似。
本申请的正极采用半导体氧化物作为导电剂，半导体氧化物对热，湿度等外部环境不敏感，能耐高压氧化和保持永久性优良的导电性质，相比于碳材料，更加适用于高电压体系，对于下一代高比容量、高截止电压的正极活性材料，如富锂锰基或尖晶石镍锰酸锂材料等，会有更大的应用价值。
整个说明书中对“一些实施例”、“部分实施例”、“一个实施例”、“另一举例”、“举例”、“具体举例”或“部分举例”的引用，其所代表的意思是在本申请中的至少一个实施例或举例包含了该实施例或举例中所描述的特定特征、结构、材料或特性。因此，在整个说明书中的各处所出现的描述，例如：“在一些实施例中”、“在实施例中”、“在一个实施例中”、“在另一个举例中”，“在一个举例中”、“在特定举例中”或“举例“，其不必然是引用本申请中的相同的实施例或示例。此外，本文中的特定特征、结构、材料或特性可以以任何合适的方式在一个或多个实施例或举例中结合。
尽管已经演示和描述了说明性实施例，本领域技术人员应该理解上述实施例不能被解释为对本申请的限制，并且可以在不脱离本申请的精神、原理及范围的情况下对实施 例进行改变，替代和修改。

Claims (11)

  1. 一种正极，其包括导电剂，其中所述导电剂包含非碳材料。
  2. 根据权利要求1所述的正极，其中所述非碳材料包含半导体氧化物。
  3. 根据权利要求2所述的正极，其中所述半导体氧化物包括氧化锡、氧化铟、氧化锡锑或氧化铟锡中的至少一种。
  4. 根据权利要求3所述的正极，其中当所述半导体氧化物为氧化铟锡和氧化锡锑时，所述半导体氧化物中的锡与铟或锑与锡的摩尔比为0.1∶1-0.5∶1。
  5. 根据权利要求1所述的正极，其中所述导电剂的粒径小于等于约100nm，优选小于等于约50nm。
  6. 根据权利要求1所述的正极，其还包括正极活性材料和粘结剂，所述正极活性材料包括具有充电截止电压大于等于4.5V的正极活性材料。
  7. 根据权利要求6所述的正极，其中所述具有充电截止电压大于等于4.5V的正极活性材料包括钴酸锂、尖晶石镍锰酸锂或富锂锰基材料中的至少一种。
  8. 根据权利要求6所述的正极，其中所述粘结剂包括含氟树脂、聚丙烯树脂、纤维型粘结剂、橡胶型粘结剂或聚酰亚胺型粘结剂中的至少一种。
  9. 根据权利要求6所述的正极，其中以所述导电剂、所述正极活性材料和所述粘结剂的总重量计，所述导电剂的重量百分比为3.5wt％-10wt％。
  10. 一种电化学装置，其包括权利要求1至9任意一项所述的正极。
  11. 一种电子装置，其包括权利要求10所述的电化学装置。
PCT/CN2019/122057 2019-11-04 2019-11-29 正极及包含其的电化学装置和电子装置 WO2021088167A1 (zh)

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