WO2022188037A1 - 正极、电化学装置和电子装置 - Google Patents

正极、电化学装置和电子装置 Download PDF

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WO2022188037A1
WO2022188037A1 PCT/CN2021/079807 CN2021079807W WO2022188037A1 WO 2022188037 A1 WO2022188037 A1 WO 2022188037A1 CN 2021079807 W CN2021079807 W CN 2021079807W WO 2022188037 A1 WO2022188037 A1 WO 2022188037A1
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Prior art keywords
positive electrode
active material
material layer
cycle
electrode material
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PCT/CN2021/079807
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English (en)
French (fr)
Inventor
张洋洋
郎野
彭刚
刘文元
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宁德新能源科技有限公司
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Priority to PCT/CN2021/079807 priority Critical patent/WO2022188037A1/zh
Priority to EP21929519.3A priority patent/EP4207371A1/en
Priority to CN202180004744.9A priority patent/CN114207871B/zh
Publication of WO2022188037A1 publication Critical patent/WO2022188037A1/zh
Priority to US18/129,170 priority patent/US20230246185A1/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
    • H01M4/13—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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0569—Liquid materials characterised by the solvents
    • 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
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • 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
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/381—Alkaline or alkaline earth metals elements
    • H01M4/382—Lithium
    • 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
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • 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
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/46—Separators, membranes or diaphragms characterised by their combination with electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of electrochemical energy storage, and in particular, to positive electrodes, electrochemical devices and electronic devices.
  • electrochemical devices eg, lithium-ion batteries
  • higher and higher requirements have been placed on their high-temperature cycling performance and safety performance.
  • the current technologies for improving electrochemical devices can improve the high-temperature cycle performance and safety performance of electrochemical devices to a certain extent, they are not satisfactory, and further improvements are expected.
  • the embodiments of the present application provide a positive electrode, including: a positive electrode current collector and a positive electrode active material layer; the positive electrode active material layer is located on at least part of one side or both sides of the positive electrode current collector, the positive electrode active material layer includes a positive electrode material, and the positive electrode material Contains Li element; using inductively coupled plasma spectrometer (ICP) to test the Li element of the positive electrode When the mass content of the positive electrode active material layer is 1.45% to 1.55%, use differential electrochemical mass spectrometry to test the positive electrode. The integral intensity Q of CO2 ⁇ 2000nmol/mg.
  • ICP inductively coupled plasma spectrometer
  • the positive electrode material contains Zr element and B element, and the mass content of Zr element in the positive electrode material is greater than or equal to the mass content of B element.
  • the coating mass of the positive active material layer is 0.78 g/m 2 to 1.62 g/m 2
  • the compaction density is 3.1 g/cm 3 to 3.55 g/cm 3 .
  • the elongation of the cathode material is ⁇ 1%.
  • the positive electrode material includes primary particles and secondary particles, the Dv50 of the secondary particles is greater than 1.5 times the Dv50 of the primary particles; the full width at half maximum FWHM1 of the diffraction peak of the (003) plane in the X-ray diffraction pattern of the secondary particles Satisfaction: 0.140° ⁇ FWHM1 ⁇ 0.25°; the full width at half maximum FWHM2 of the diffraction peak of the (003) plane in the X-ray diffraction pattern of the primary particle satisfies: 0.12° ⁇ FWHM2 ⁇ 0.19°.
  • the positive electrode material includes primary particles; the average particle size of the primary particles is 1.5 ⁇ m to 2.5 ⁇ m.
  • an electrochemical device comprising: the positive electrode of any one of the above, a negative electrode and a separator, and the separator is located between the positive electrode and the negative electrode.
  • the electrochemical device has an N-th cycle during cycling at 45°C, where N>400, and the capacity retention rate of the N-3th cycle P(N-3) and the N+3th cycle
  • the capacity retention rate P(N+3) of satisfies: P(N-3)-P(N+3)>10%, and the volume expansion rate of the N-th cycle of the electrochemical device is less than 10%.
  • the electrochemical device further includes: an electrolyte, the electrolyte includes a polynitrile compound; the polynitrile compound includes: 1,3,6-hexanetricarbonitrile, 1,2,6-hexanetricarbonitrile, 1,3,6-hexanetricarbonitrile At least one of 3,5-pentanetricarbonitrile, 1,2,3-tris(2-cyanooxy)propane, succinonitrile or adiponitrile; wherein, the mass ratio of positive electrode material to polynitrile compound is 1 : (0.001 to 0.005).
  • an electronic device including the electrochemical device of any one of the above.
  • Electrochemical devices such as lithium-ion batteries are widely used in various fields.
  • electrochemical devices have reduced cycle performance at high temperatures, and are prone to gas generation, resulting in reduced safety performance.
  • cathode materials with secondary particle morphology are used. Doping and surface coating reduce the interfacial side reactions between the cathode material and the electrolyte, and inhibit the dissolution of metal elements in the cathode material, thereby improving the high-temperature cycle performance and reducing high-temperature gas production to a certain extent.
  • a positive electrode material with a primary particle morphology is used, which has a larger average particle size of the primary particle and relatively low residual Li on the surface, and the surface of the primary particle has a better surface coating. There is less interaction stress between particles in the medium, resulting in better high temperature cycling performance.
  • a positive electrode is proposed.
  • the positive electrode can be a positive electrode of an electrochemical device.
  • the positive electrode includes a positive electrode current collector and a positive electrode active material layer.
  • the positive electrode current collector can be, for example, aluminum foil or copper foil.
  • the positive electrode active material layer Located on at least part of the area of one or both sides of the positive electrode current collector, the positive electrode active material layer may include a positive electrode material, the positive electrode material may include one or both of cobalt lithium manganate or nickel cobalt lithium aluminate, and the positive electrode material contains Li element ;
  • ICP Inductively Coupled Plasma Spectrometer
  • DEMS Differential Electrochemical Mass Spectrometry
  • the principle and method of using differential electrochemical mass spectrometry (DEMS) to test positive electrodes in some embodiments are schematically described below.
  • the basic principle is: combine an electrochemical workstation including an in-situ battery with a mass spectrometer measurement system, use a vacuum system to form a pressure difference, and transport the gas products of the battery into the detector to realize online detection of the gas production of the battery under different conditions.
  • the test method is: use 0.1C current for the positive electrode to be tested to adjust the delithiation amount until the mass content of the positive electrode Li element in the positive electrode active material layer is 1.45% to 1.55% tested by inductively coupled plasma spectrometer (ICP), and then use carbonic acid.
  • ICP inductively coupled plasma spectrometer
  • the basic principle is: qualitative and quantitative analysis based on the emission of characteristic spectral lines of atoms or ions of different elements under thermal excitation. Due to the different energy level structures of the atoms of the element to be measured, the characteristics of the emission lines are different, according to which qualitative analysis can be performed, and according to the concentration of the atoms of the element to be measured, the emission intensity is different, and the quantitative determination of the element can be realized.
  • the test method is as follows: take 6 parallel samples of the pole piece to be tested, weigh, digest and dilute respectively, and then use the inductively coupled plasma emission spectrometer of the Thermo ICAP6300 model to test the mass content of the element Li to obtain the average value, and the content of the element Li is averaged.
  • the mass content is the mass percentage of the active material after deducting the substrate from the pole piece.
  • inductively coupled plasma spectrometer is used to test the mass content of Li element in the positive electrode active material layer in the range of 1.45% to 1.55%
  • DEMS differential electrochemical mass spectrometry
  • the positive electrode material includes: LiNi x Co y M1 1-xyz M2 z O 2 ; wherein 0.5 ⁇ x ⁇ 1, 0 ⁇ y ⁇ 0.5, 0 ⁇ z ⁇ 0.005, and M1 includes Mn or Al At least one of M2 includes at least one of Mg, Ti, Zr, Ce, Sr, Y, Hf, Ba, Nb, V, Al, Ge, Sn, W, Mo, Si or B.
  • Al element can stabilize oxygen in the cathode material and reduce high temperature gas generation.
  • the positive electrode material includes primary particles and secondary particles, and the Dv50 of the secondary particles is greater than 1.5 times that of the primary particles;
  • the height and width FWHM1 satisfies: 0.140° ⁇ FWHM1 ⁇ 0.25°; the full width at half maximum FWHM2 of the diffraction peak of the (003) plane in the X-ray diffraction pattern of the primary particle satisfies: 0.12° ⁇ FWHM2 ⁇ 0.19°.
  • the secondary particles with polycrystalline morphology in the positive electrode material are beneficial to improve the rate performance of the positive electrode material, and the primary particles with single crystal morphology in the positive electrode material are beneficial to improve the cycle performance of the positive electrode material.
  • Test method for Dv50 of primary particles and Dv50 of secondary particles Take a part of the positive electrode material in a drying room with 2% relative humidity, uniformly disperse it in the NMP solution, ultrasonically disperse for 12 hours, and stir evenly to obtain a suspension containing the positive electrode material. The suspension was slowly poured into a 1500-mesh sieve while stirring, and a part of the small particles entered the filtrate through the sieve. After the filtrate was allowed to stand for 24 hours, the supernatant was poured out, and the powder obtained after drying That is, the primary particles, the other part of the large particles are on the screen, and the powder obtained after drying is the secondary particles.
  • the average particle size of the primary particles is less than 1.5 ⁇ m, which may lead to increased electrolyte consumption and side reactions because the contact surface with the electrolyte is too large, and the average particle size of the primary particles is larger than 2.5 ⁇ m. Reduced rate performance.
  • the positive electrode material is primary particles.
  • the positive electrode material contains Zr element and B element, and the mass content of Zr element in the positive electrode material is greater than or equal to the mass content of B element.
  • the Zr element is beneficial to improve the structural stability of the cathode material, thereby improving the cycle performance and safety performance
  • the B element is beneficial to improve the residual lithium on the surface of the cathode material, but when the mass content of the B element is too high, it may lead to kinetic energy. Decreased academic performance.
  • the coating mass of the positive electrode active material layer is 0.78 g/m 2 to 1.62 g/m 2
  • the compaction density is 3.1 g/cm 3 to 3.55 g/cm 3
  • the coating quality refers to the ratio of the quality of the positive electrode active material layer to the coating area.
  • the coating quality of the positive electrode active material layer is less than 0.78 g /m Too little material layer reduces the volumetric energy density.
  • the coating mass of the positive electrode active material layer is greater than 1.62 g/m 2 , too much positive electrode active material layer is loaded on the positive electrode current collector, which will lead to poor infiltration and transmission of the electrolyte. , resulting in a decrease in electrical conductivity.
  • the compacted density when the compacted density is lower than 3.1 g/cm 3 , it may be unfavorable to improve the volumetric energy density and lead to an increase in internal resistance, and if the compacted density is greater than 3.55 g/cm 3 , the positive electrode material may be ruptured due to excessive pressure. , which is detrimental to cycle performance.
  • the positive electrode material Mix the positive electrode material, acetylene black (conducting agent), and polyvinylidene fluoride (binder) uniformly in the ratio of 96.0:2.0:2.0, add an appropriate amount of N-methylpyrrolidone (NMP) and stir well to prepare a uniform slurry
  • NMP N-methylpyrrolidone
  • the material is coated on the 10um Al foil (current collector) with an areal density of 90g/ m2 , and after drying, a pole piece with a length of 1m is taken, and the cold pressing is controlled to be 3.5g/ cm3 .
  • the length of the pole piece after pressing is L, then the elongation of the positive electrode material is: (L-1)/1.
  • an electrochemical device comprising: the positive electrode of any one of the above, a negative electrode and a separator, and the separator is located between the positive electrode and the negative electrode.
  • the electrochemical device has an N-th cycle during cycling at 45°C, where N>400, and the capacity retention rate of the N-3th cycle P(N-3) and the N+3th cycle
  • the capacity retention rate P(N+3) of satisfies: P(N-3)-P(N+3)>10%
  • the volume expansion rate of the N-th cycle of the electrochemical device is less than 10%.
  • functional failure occurs when the cycle life of the cathode material is approaching, and the cycle capacity retention is greatly reduced resulting in P(N-3)-P(N+3)>10%, while the electrochemical device is in The volume expansion rate of the Nth cycle is still less than 10%, which indicates that the electrochemical device produces less gas at this time and has better safety performance.
  • the negative electrode includes a negative electrode current collector and a negative electrode active material layer.
  • the negative electrode current collector can be at least one of copper foil, nickel foil or carbon-based current collector.
  • a conductive agent may be further included in the negative electrode active material layer.
  • the conductive agent may include at least one of conductive carbon black, Ketjen black, lamellar graphite, graphene, carbon nanotubes, or carbon fibers.
  • the negative electrode active material layer includes a negative electrode material, and the negative electrode material may include, for example, at least one of artificial graphite, natural graphite, mesophase microspheres, hard carbon, or silicon-containing materials.
  • the release membrane 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 separator may further include a porous layer, the porous layer is disposed on at least one surface of the substrate of the separator, the porous layer includes inorganic particles and a binder, and the inorganic particles are selected from alumina (Al 2 O 3 ), silicon oxide (SiO 2 ), magnesium oxide (MgO), titanium oxide (TiO 2 ), hafnium dioxide (HfO 2 ), tin oxide (SnO 2 ), ceria (CeO 2 ), nickel oxide (NiO) ), zinc oxide (ZnO), calcium oxide (CaO), zirconium oxide (ZrO 2 ), yttrium oxide (Y 2 O 3 ), silicon carbide (SiC), boehmite, aluminum hydroxide, magnesium hydroxide, hydroxide At least one of calcium or barium sulfate.
  • alumina Al 2 O 3
  • silicon oxide SiO 2
  • magnesium oxide MgO
  • titanium oxide TiO 2
  • hafnium dioxide
  • the pores of the isolation membrane have diameters in the range of about 0.01 ⁇ m to 1 ⁇ m.
  • the adhesive 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 electrochemical device is a wound electrochemical device or a stacked electrochemical device.
  • the electrochemical device includes a lithium-ion battery, although the present application is not so limited.
  • the electrochemical device further includes: an electrolyte, the electrolyte includes a polynitrile compound; the polynitrile compound includes: 1,3,6-hexanetricarbonitrile, 1,2,6-hexanetricarbonitrile, 1,3,6-hexanetricarbonitrile At least one of 3,5-pentanetricarbonitrile, 1,2,3-tris(2-cyanooxy)propane, succinonitrile or adiponitrile; wherein, the mass ratio of positive electrode material to polynitrile compound is 1 : (0.001 to 0.005).
  • the electrolyte further includes a lithium salt and a non-aqueous solvent.
  • the lithium salt is selected from LiPF6, LiBF4 , LiAsF6, LiClO4 , LiB ( C6H5 ) 4 , LiCH3SO3 , LiCF3SO3 , LiN ( SO2CF3 ) 2 , LiC ( SO2CF3 ) 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.
  • Examples of cyclic carbonate compounds are ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylethylene carbonate (VEC), or combinations thereof.
  • Fluorocarbonate compounds include fluoroethylene carbonate (FEC).
  • Examples of 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, the separator, and the negative electrode are wound or stacked in sequence to form electrode parts, and then packed into, for example, an aluminum-plastic film for encapsulation, injected with electrolyte, and formed into, Encapsulation, that is, to make 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 and large batteries for household use, etc.
  • Preparation of the positive electrode The precursor of nickel cobalt lithium manganate and lithium hydroxide (LiOH) were prepared according to the stoichiometric ratio of LiNi 0.83 Co 0.12 Mn 0.05 O 2 and were uniformly mixed and dried. After drying, a calcination was performed at 820 °C ( Sintering) for 15h, and then the temperature was lowered at a rate of 5°C/min to obtain a finished product, and the Dv50 of the positive electrode material particles was controlled to be 3.5 ⁇ m. The average particle size of the primary particles of the positive electrode material is 1.8 ⁇ m.
  • the prepared positive electrode material, acetylene black and polyvinylidene fluoride are mixed uniformly in a certain proportion, and N-methylpyrrolidone is added and fully stirred to prepare a uniform slurry, which is coated on Al foil (positive electrode current collector), and then passes through After drying and cold pressing, a positive electrode is obtained.
  • the coating quality of the positive active material layer of the positive electrode is 1.2 g/m 2 , and the compaction density is 3.5 g/cm 3 .
  • ICP Inductively Coupled Plasma Spectrometer
  • Preparation of negative electrode Mix artificial graphite, acetylene black, styrene-butadiene rubber, and sodium carboxymethyl cellulose in a weight ratio of 95:2:2:1. Add deionized water and mix thoroughly to prepare a uniform slurry. On Cu foil (negative electrode current collector), the negative electrode is obtained by drying and cold pressing.
  • Preparation of lithium ion battery stack the positive electrode, the separator and the negative electrode in sequence, so that the separator is placed between the positive electrode and the negative electrode for isolation, and then the electrode assembly is obtained by winding.
  • the electrode assembly is placed in the outer packaging aluminum-plastic film, and after removing moisture at 80 °C, the electrolyte is injected and packaged, and the lithium ion battery is obtained through the process of formation, degassing, and trimming.
  • Example 2 The difference between Example 2 and Example 1 is that the preparation steps of the positive electrode are different, and the remaining steps are the same.
  • Positive electrode preparation Prepare nickel cobalt lithium manganate precursor and lithium carbonate (Li 2 CO 3 ) according to the stoichiometric ratio of LiNi 0.5 Co 0.2 Mn 0.3 O 2 and mix them uniformly and dry them. After drying, calcination is carried out at 910 °C once After 15 hours, the temperature was lowered at a rate of 5°C/min to obtain a finished product, and the Dv50 of the positive electrode material particles was controlled to be 3.5 ⁇ m. The average particle size of the primary particles of the positive electrode material is 1.8 ⁇ m.
  • the prepared positive electrode material, acetylene black and polyvinylidene fluoride are mixed uniformly in a certain proportion, and N-methylpyrrolidone is added and fully stirred to prepare a uniform slurry, which is coated on Al foil (positive electrode current collector), and then passes through After drying and cold pressing, a positive electrode is obtained.
  • the coating quality of the positive active material layer is set to 1.2g/m 2 , and the compaction density is controlled to 3.5g/cm 3 .
  • ICP Inductively Coupled Plasma Spectrometer
  • Example 3 The difference between Example 3 and Example 1 is that the preparation steps of the positive electrode are different, and the remaining steps are the same.
  • Cathode preparation Prepare nickel cobalt lithium aluminate precursor and lithium hydroxide (LiOH) according to the stoichiometric ratio of LiNi 0.83 Co 0.12 Al 0.05 O 2 and mix and dry them uniformly. Then, the temperature was lowered at a rate of 5°C/min to obtain a finished product, and the Dv50 of the positive electrode material particles was controlled to be 3.5 ⁇ m. The average particle size of the primary particles of the positive electrode material is 1.8 ⁇ m. The coating quality of the positive active material layer is set at 1.2g/m 2 , and the compaction density is controlled at 3.5g/cm 3 .
  • the prepared positive electrode material, acetylene black and polyvinylidene fluoride are mixed uniformly in a certain proportion, and N-methylpyrrolidone is added and fully stirred to prepare a uniform slurry, which is coated on Al foil (positive electrode current collector), and then passes through After drying and cold pressing, a positive electrode is obtained.
  • ICP Inductively Coupled Plasma Spectrometer
  • DEMS Differential Electrochemical Mass Spectrometry
  • Example 4 The difference between Example 4 and Example 1 is that the preparation steps of the positive electrode are different, and the remaining steps are the same.
  • Cathode preparation Prepare nickel cobalt lithium manganate precursor and lithium hydroxide (LiOH) according to the stoichiometric ratio of LiNi 0.88 Co 0.07 Mn 0.05 O 2 and mix and dry them uniformly. Then, the temperature was lowered at a rate of 5°C/min to obtain a finished product, and the Dv50 of the positive electrode material particles was controlled to be 3.5 ⁇ m. The average particle size of the primary particles of the positive electrode material is 1.8 ⁇ m.
  • the prepared positive electrode material, acetylene black and polyvinylidene fluoride are mixed uniformly in a certain proportion, and N-methylpyrrolidone is added and fully stirred to prepare a uniform slurry, which is coated on Al foil (positive electrode current collector), and then passes through After drying and cold pressing, a positive electrode is obtained.
  • the coating quality of the positive electrode active material layer of the positive electrode is set at 1.2 g/m 2 , and the compaction density is controlled at 3.5 g/cm 3 .
  • ICP Inductively Coupled Plasma Spectrometer
  • ICP inductively coupled plasma spectrometer
  • ICP inductively coupled plasma spectrometer
  • DEMS differential electrochemical mass spectrometry
  • ICP inductively coupled plasma spectrometer
  • DEMS differential electrochemical mass spectrometry
  • Example 8 The difference between Example 8 and Example 1 is that the preparation steps of the positive electrode are different, and the remaining steps are the same.
  • Cathode preparation Prepare nickel cobalt lithium manganate precursor, lithium hydroxide (LiOH) and zirconium oxide (ZrO 2 ) according to the stoichiometric ratio of LiNi 0.83 Co 0.12 Mn 0.047 Zr 0.003 O 2 and mix and dry them uniformly, after drying One calcination was carried out at 820 °C for 15 h, and then the temperature was lowered at a rate of 5 °C/min to obtain a finished product, and the Dv50 of the positive electrode material particles was controlled to be 3.5 ⁇ m.
  • LiOH lithium hydroxide
  • ZrO 2 zirconium oxide
  • the prepared positive electrode material, acetylene black and polyvinylidene fluoride are mixed uniformly in a certain proportion, and N-methylpyrrolidone is added and fully stirred to prepare a uniform slurry, which is coated on Al foil (positive electrode current collector), and then passes through After drying and cold pressing, a positive electrode is obtained.
  • the average particle size of the primary particles of the positive electrode material is 1.8 ⁇ m.
  • the coating quality of the positive active material layer is set at 1.2g/m 2 , and the compaction density is controlled at 3.5g/cm 3 .
  • ICP Inductively Coupled Plasma Spectrometer
  • DEMS differential electrochemical mass spectrometry
  • Example 9 The difference between Example 9 and Example 1 is that the preparation steps of the positive electrode are different, and the remaining steps are the same.
  • Positive electrode preparation Prepare nickel cobalt lithium manganate precursor, lithium hydroxide (LiOH) and alumina (Al 2 O 3 ) according to the stoichiometric ratio of LiNi 0.83 Co 0.12 Mn 0.047 Al 0.003 O 2 and mix and dry them uniformly, After drying, calcination was carried out at 820 °C for 15 h, and then the temperature was lowered at a rate of 5 °C/min to obtain a finished product, and the Dv50 of the positive electrode material particles was controlled to be 3.5 ⁇ m. The average particle size of the primary particles of the positive electrode material is 1.8 ⁇ m.
  • the prepared positive electrode material, acetylene black and polyvinylidene fluoride are mixed uniformly in a certain proportion, and N-methylpyrrolidone is added and fully stirred to prepare a uniform slurry, which is coated on Al foil (positive electrode current collector), and then passes through After drying and cold pressing, a positive electrode is obtained.
  • the coating quality of the positive active material layer is set to 1.2g/m 2 , and the compaction density is controlled to 3.5g/cm 3 .
  • ICP Inductively Coupled Plasma Spectrometer
  • DEMS differential electrochemical mass spectrometry
  • Example 10 The difference between Example 10 and Example 1 is that the preparation steps of the positive electrode are different, and the remaining steps are the same.
  • Cathode preparation Prepare nickel cobalt lithium manganate precursor, lithium hydroxide (LiOH) and strontium oxide (SrO) according to the stoichiometric ratio of LiNi 0.83 Co 0.12 Mn 0.047 Sr 0.003 O 2 and mix and dry them uniformly.
  • One calcination was carried out at 820 °C for 15 h, and then the temperature was lowered at a rate of 5 °C/min, so that the surface oxygen and transition metals of the material particles met certain conditions, and the finished product was obtained, and the Dv50 of the positive electrode material particles was controlled to be 3.5 ⁇ m.
  • the average particle size of the primary particles of the positive electrode material is 1.8 ⁇ m.
  • the prepared positive electrode material, acetylene black and polyvinylidene fluoride are mixed uniformly in a certain proportion, and N-methylpyrrolidone is added and fully stirred to prepare a uniform slurry, which is coated on Al foil (positive electrode current collector), and then passes through After drying and cold pressing, a positive electrode is obtained.
  • the coating quality of the positive active material layer is set at 1.2g/m 2 , and the compaction density is controlled at 3.5g/cm 3 .
  • ICP Inductively Coupled Plasma Spectrometer
  • Example 11 The difference between Example 11 and Example 1 is that the preparation steps of the positive electrode are different, and the remaining steps are the same.
  • Positive electrode preparation Prepare nickel cobalt lithium manganate precursor, lithium hydroxide (LiOH) and tungsten oxide (WO 3 ) according to the stoichiometric ratio of LiNi 0.83 Co 0.12 Mn 0.047 W 0.003 O 2 and mix and dry them uniformly, after drying One calcination was carried out at 820 °C for 15 h, and then the temperature was lowered at a rate of 5 °C/min to obtain a finished product, and the Dv50 of the positive electrode material particles was controlled to be 3.5 ⁇ m. The average particle size of the primary particles of the positive electrode material is 1.8 ⁇ m.
  • the prepared positive electrode material, acetylene black and polyvinylidene fluoride are mixed uniformly in a certain proportion, and N-methylpyrrolidone is added and fully stirred to prepare a uniform slurry, which is coated on Al foil (positive electrode current collector), and then passes through After drying and cold pressing, a positive electrode is obtained.
  • the coating quality of the positive active material layer is set to 1.2g/m 2 , and the compaction density is controlled to 3.5g/cm 3 .
  • ICP Inductively Coupled Plasma Spectrometer
  • ICP inductively coupled plasma spectrometer
  • DEMS differential electrochemical mass spectrometry
  • ICP inductively coupled plasma spectrometer
  • DEMS differential electrochemical mass spectrometry
  • Example 14 The difference between Example 14 and Example 1 is that the preparation steps of the positive electrode are different, and the remaining steps are the same.
  • Cathode preparation Prepare nickel cobalt lithium manganate precursor, lithium hydroxide (LiOH) and zirconium oxide (ZrO 2 ) according to the stoichiometric ratio of LiNi 0.83 Co 0.12 Mn 0.047 Zr 0.003 O 2 and mix and dry them uniformly, after drying One calcination was carried out at 820 °C for 15 h, and then the temperature was lowered at a rate of 5 °C/min to obtain a semi-finished product, and the particle Dv50 was controlled to be 3.5 ⁇ m. The above-mentioned semi-finished product is mixed with boric acid (H 3 BO 3 ) uniformly, and sintered at 400° C.
  • H 3 BO 3 boric acid
  • the prepared positive electrode material, acetylene black and polyvinylidene fluoride are mixed uniformly in a certain proportion, and N-methylpyrrolidone is added and fully stirred to prepare a uniform slurry, which is coated on Al foil (positive electrode current collector), and then passes through After drying and cold pressing, a positive electrode is obtained.
  • the average particle size of the primary particles of the positive electrode material is 1.8 ⁇ m.
  • the coating quality of the positive active material layer is set to 1.2g/m 2 , and the compaction density is controlled to 3.5g/cm 3 .
  • ICP Inductively Coupled Plasma Spectrometer
  • DEMS differential electrochemical mass spectrometry
  • ICP inductively coupled plasma spectrometer
  • DEMS differential electrochemical mass spectrometry
  • Example 16 by controlling the sintering temperature, the average particle size of the primary particles of the material is 1.5 ⁇ m, and the mass content of the Li element of the positive electrode in the positive electrode active material layer is measured by using an inductively coupled plasma spectrometer (ICP) to be 1.45 ⁇ m.
  • ICP inductively coupled plasma spectrometer
  • the integrated intensity Q 1150 nmol/mg of CO2 measured using differential electrochemical mass spectrometry (DEMS) in the range of % to 1.55%.
  • DEMS differential electrochemical mass spectrometry
  • Example 17 The difference between Example 17 and Example 8 is that the sintering temperature is controlled so that the average particle size of the primary particles of the material is 2.5 ⁇ m, and the mass content of the Li element of the positive electrode in the positive electrode active material layer is tested by using an inductively coupled plasma spectrometer (ICP) to be 1.45%.
  • ICP inductively coupled plasma spectrometer
  • DEMS differential electrochemical mass spectrometry
  • Ni 0.83 Co 0.12 Mn 0.05 O 2 nickel cobalt lithium manganate precursor and lithium hydroxide (LiOH) were prepared and uniformly mixed and dried. The temperature was lowered at a rate of 5°C/min to obtain secondary particles. The Dv50 of the secondary particle positive electrode material particles was controlled to be 10 ⁇ m. The diffraction peak width at half maximum FWHM1 of the (003) plane in the X-ray diffraction pattern of the prepared secondary particles is 0.19°.
  • Ni 0.83 Co 0.12 Mn 0.05 O 2 nickel cobalt lithium manganate precursor and lithium hydroxide (LiOH) were prepared and uniformly mixed and dried. The temperature is lowered at a rate of °C/min to obtain primary particles. The Dv50 of the primary particle positive electrode material particles was controlled to be 3.5 ⁇ m. The diffraction peak width at half maximum FWHM1 of the (003) plane in the X-ray diffraction pattern of the prepared primary particles is 0.15°.
  • the prepared positive electrode material including primary particles, secondary particles, acetylene black, and polyvinylidene fluoride are mixed uniformly in a certain proportion, and N-methylpyrrolidone is added and stirred to prepare a uniform slurry, which is coated on Al foil (positive electrode). collector), and then drying and cold pressing to obtain a positive electrode.
  • the coating quality of the positive active material layer is 1.2 g/m 2 , and the compaction density is 3.5 g/cm 3 .
  • ICP Inductively Coupled Plasma Spectrometer
  • Preparation of negative electrode Mix artificial graphite, acetylene black, styrene-butadiene rubber, and sodium carboxymethyl cellulose in a weight ratio of 95:2:2:1. Add deionized water and mix thoroughly to prepare a uniform slurry. On Cu foil (negative electrode current collector), the negative electrode is obtained by drying and cold pressing.
  • Preparation of lithium ion battery stack the positive electrode, the separator and the negative electrode in sequence, so that the separator is placed between the positive electrode and the negative electrode for isolation, and then the electrode assembly is obtained by winding.
  • the electrode assembly is placed in the outer packaging aluminum-plastic film, and after removing moisture at 80 °C, the electrolyte is injected and packaged, and the lithium ion battery is obtained through the process of formation, degassing, and trimming.
  • Example 19 The difference between Example 19 and Example 18 is that the particle size, sintering temperature and sintering time of the nickel-cobalt lithium manganate precursor are controlled, so that the Dv50 of the secondary particles is 8 ⁇ m, and the diffraction peak of the (003) plane in the X-ray diffraction pattern is half.
  • the height and width FWHM1 is 0.20°.
  • ICP inductively coupled plasma spectrometer
  • DEMS differential electrochemical mass spectrometry
  • ICP inductively coupled plasma spectrometer
  • DEMS differential electrochemical mass spectrometry
  • ICP inductively coupled plasma spectrometer
  • DEMS differential electrochemical mass spectrometry
  • ICP inductively coupled plasma spectrometer
  • ICP inductively coupled plasma spectrometer
  • ICP inductively coupled plasma spectrometer
  • ICP inductively coupled plasma spectrometer
  • Example 26 contains 0.005 (g) of 1,3,6-hexanetrinitrile per 1 g of the positive electrode material, which is tested by inductively coupled plasma spectrometer (ICP)
  • ICP inductively coupled plasma spectrometer
  • the mass content of the positive electrode active material layer of Li element in the positive electrode is in the range of 1.45% to 1.55%
  • Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the cooling rate after primary sintering is controlled so that the mass content of Li element in the positive electrode active material layer of the positive electrode tested by inductively coupled plasma spectrometer (ICP) is in the range of 1.45% to 1.55%.
  • ICP inductively coupled plasma spectrometer
  • DEMS differential electrochemical mass spectrometry
  • Comparative Example 2 and Example 25 The difference between Comparative Example 2 and Example 25 is that the particle size, sintering temperature and sintering time of the nickel-cobalt lithium manganate precursor are controlled, so that the Dv50 of the secondary particles is 5 ⁇ m, and the diffraction peak of the (003) plane in the X-ray diffraction pattern is half.
  • the height and width FWHM1 is 0.21°.
  • ICP inductively coupled plasma spectrometer
  • DEMS differential electrochemical mass spectrometry
  • Basic principle Combine an electrochemical workstation including an in-situ battery with a mass spectrometry test system, use a vacuum system to form a pressure difference, transport the gas products in the battery into the detector, and realize on-line detection of the gas production of the battery under different conditions .
  • Sample pretreatment method Take the positive electrode after the dismantling of the battery core and use a small current of 0.1C to adjust the delithiation amount of the electrode piece, so that the mass content of the positive electrode Li element in the positive electrode active material layer is measured by inductively coupled plasma spectrometer (ICP). 1.45% to 1.55% range, then soak in DMC solution for 24 hours, vacuum dry and seal for later use.
  • ICP inductively coupled plasma spectrometer
  • the electrolyte composition is composed of 30% EC and 70% DEC (mass percentage) and 1mol LiPF 6 , the electrolyte is added The amount is 3g/Ah to 4g/Ah, then the ambient temperature of the battery is adjusted to 85°C and stored, and the CO2 gas signal in the time period of 0 to 500000s is detected in real time.
  • ICP Inductively coupled plasma spectrometer
  • the basic principle is: qualitative and quantitative analysis based on the emission of characteristic spectral lines of atoms or ions of different elements under thermal excitation. Due to the different energy level structures of the atoms of the element to be measured, the characteristics of the emission lines are different, according to which qualitative analysis can be carried out, and according to the concentration of the atoms of the element to be measured, the emission intensity is different, and the quantitative determination of the element can be realized.
  • the test method is as follows: take 6 parallel samples of the pole piece to be tested, weigh, digest and dilute respectively, and then use the inductively coupled plasma emission spectrometer of the Thermo ICAP6300 model to test the mass content of the element Li to obtain the average value, and the content of the element Li is averaged.
  • the mass content is the mass percentage of the active material after deducting the substrate from the pole piece.
  • lithium-ion batteries were taken from each group in the examples and comparative examples, and the lithium-ion batteries were repeatedly charged and discharged through the following steps, and the discharge capacity retention rate of the lithium-ion batteries was calculated.
  • 400-cycle cycle capacity retention rate (discharge capacity at the 400th cycle/discharge capacity at the first cycle) ⁇ 100%.
  • Thickness expansion ratio stored at 85°C for 24h ((thickness stored at 85°C for 24h-initial full punch thickness)/initial full charge thickness) ⁇ 100%.
  • the lithium-ion battery was allowed to stand for 30 minutes at 25°C, then charged to 4.2V with a constant current rate of 0.5C, charged to 0.05C with a constant voltage of 4.2V, left standing for 30 minutes, and then discharged to 2.8 with a rate of 0.2C V, the discharge capacity recorded at this time is the actual capacity C1 of the lithium-ion battery; after standing for 30 minutes, charge to 4.2V with a constant current of 0.5C, charge to 0.05C with a constant voltage of 4.2V, stand for 30 minutes, and then Discharge to 2.8V at a rate of 10C, and record the discharge capacity at this time as the actual capacity C2 of the lithium-ion battery.
  • Calculate the 10C discharge capacity retention rate by the following formula:
  • the cycle retention rate P(N) of the N-th cycle and the expansion rate of the electrochemical device in the N-th cycle during the 45°C cycle were obtained, and then the N-th cycle before and after the N-th cycle (N>400) was satisfied according to the N-th cycle (N>400).
  • N is the N value.
  • Obtaining the active material disassemble the fully discharged cell to obtain the fully discharged positive electrode, soak it in DMC solvent for 48 hours for cleaning, dry it and scrape the powder, and sinter in an oxygen atmosphere of 500°C for about 6 hours to remove the conductive agent and bonding agent to obtain a positive electrode material.
  • Table 1 shows the respective parameters and evaluation results of Examples 1 to 13 and Comparative Example 1.
  • Table 1 shows the effect of controlling the CO 2 integral intensity of the cathode material under a certain Li content on the high-temperature storage performance, high-temperature cycling retention rate and high-temperature cycling gas production performance, including cathode material composition, doping elements and doping amount Impact.
  • the B element content of the examples and the comparative examples are both 0 ppm, and the average particle size of the primary particles is both 1.8 ⁇ m, the coating quality is both 1.2 g/cm 2 , and the compaction density is both 3.5 g/cm 3 , the amount of 1,3,6-hexanetricarbonitrile contained in 1g of positive electrode material is 0g.
  • the integral intensity Q of CO 2 obtained by the differential electrochemical mass spectrometry test positive electrode is less than or equal to 2000 nmol/mg, the high temperature cycle performance of the lithium ion battery can be improved, the high temperature gas production can be reduced, and the safety and reliability of the battery can be improved.
  • Example 3 Comparing Example 1 and Example 3, it can be seen that the high-temperature storage gas production and the high-temperature cycle gas production of Example 3 are both less than those of Example 1, because Al element is used to replace Mn in Example 1 in Example 3. element, which can better stabilize the oxygen in the structure, reduce the integral intensity of CO2 , and improve the high temperature performance.
  • Comparing Example 1, Examples 5 to 7 and Comparative Example 1 it can be seen that the components of the positive electrode material in Example 1 and Example 5 to 7 are the same as those of Comparative Example 1, and Examples 1 and 5 to 7 are sintered by regulation and control.
  • the integral intensity of CO 2 is reduced to 1200 nmol/mg to 2000 nmol/mg, which greatly reduces the oxygen release of the cathode material in the high delithiation state, and inhibits the interface reaction between the cathode material and the electrolyte. , which significantly improved the storage performance at 85°C and the high-temperature cycle performance of lithium-ion batteries.
  • Example 1 and Examples 5 to 7 have the Nth cycle (N>400), the Nth cycle capacity retention rate P(N-3) and the Nth cycle during the cycle at 45°C.
  • the difference in cycle retention rate P(N+3) for +3 weeks P(N-3)-P(N+3)>10%, and the swelling rate of the electrochemical device in the Nth week is less than 10%.
  • the cycle retention rate of Example 1 at the 497th cycle and the 503rd cycle differs by more than 10%, and its expansion rate at the 500th cycle is less than 10%, indicating that the electrochemical device of Example 1 has a functional type before and after the 500th cycle.
  • Comparative Example 1 has no such characteristics, and its high temperature cycle performance is poor (400 cycle retention rate is 53%) and there is a greater safety risk (400 cycle expansion rate reaches 29%).
  • Examples 8 to 13 demonstrate the effects of different doping elements and doping amounts on the CO 2 integral intensity, and improve the high-temperature storage and high-temperature cycling performance by regulating it.
  • Examples 8 to 11 achieved the reduction of CO 2 integral intensity through the doping of Zr, Al, Sr, and W, respectively, and further improved the high-temperature performance of lithium-ion batteries.
  • the effects of different doping elements are similar, among which Al and W elements are better, but the introduction of Al will lead to a decrease in the gram capacity. Comparing Example 8 with Examples 12 to 13, it can be seen that with the increase of doping amount, the integrated intensity of CO 2 is further reduced, but too high doping amount will lead to the decrease of gram capacity.
  • Table 2 shows the respective parameters and evaluation results of Examples 8, 14 to 17.
  • Table 2 shows the effects of the content of element B and the average particle size of primary particles on high temperature storage performance, high temperature cycle retention rate and high temperature cycle gas production performance.
  • the coating mass was 1.2 g/cm 2
  • the compaction density was 3.5 g/cm 3
  • the addition amount of 1,3,6-hexanetricarbonitrile was 0 g.
  • Example 8 and Examples 14 to 15 it can be seen that the coating with a certain B content can improve the surface stability of the material, reduce the CO 2 integral strength of the positive electrode, and improve the high-temperature storage and high-temperature cycling performance of lithium-ion batteries.
  • the content of B element is too high and exceeds the content of Zr element, the existence of excess B will bring about a significant decrease in rate performance and also affect high-temperature gas production. Therefore, it is preferable that the mass content of Zr element in the positive electrode material is greater than or equal to that of B element. quality content.
  • Example 8 and Examples 16 to 17 that by adjusting the sintering temperature to increase the average particle size of the primary particles of the positive electrode material, the high-temperature cycle performance and high-temperature storage performance of the lithium ion battery can be improved, because the primary particles
  • the increase in the particle size of the cathode material reduces the contact and side reactions between the surface of the cathode material and the electrolyte, thereby reducing the integral intensity of CO2 and improving the high temperature performance.
  • the average particle size of the primary particles is too large, the Li + transmission path is reduced, which affects the gram capacity.
  • the average particle size of the primary particles is too small, the side reactions on the surface of the particles will increase, which will affect the high-temperature gas production and cycle performance. Therefore, the average particle size of the primary particles When it is 1.5 ⁇ m to 2.5 ⁇ m, both high temperature gas generation and cycle performance can be achieved.
  • Table 3 shows the respective parameters and evaluation results of Examples 1, 18 to 19.
  • Table 3 shows the effect of using a combination of primary particles and secondary particles in the positive electrode on high-temperature storage performance, high-temperature cycle retention and high-temperature cycle gas production performance.
  • no doping element the primary particle Dv50 is 3.5 ⁇ m
  • the primary particle FWHM2 is 0.15°
  • the coating mass of the positive electrode is 1.2 g/cm 2
  • the compaction density is 3.5 g/cm 3
  • the addition amount of 1,3,6-hexanetricarbonitrile is 0 g.
  • Example 1 and Examples 18 to 19 From Comparative Example 2, Example 1 and Examples 18 to 19, it can be seen that, compared with the single particle design in Example 1, in Example 19, a mixture of primary particles and secondary particles is used, wherein the particle diameters of the two are mixed. Satisfying a certain size relationship can achieve a larger bulk density, so that the same compaction density can be achieved at a lower pressure during the cold-pressing process of the pole piece, reducing particle breakage, and improving high-temperature storage and high-temperature cycle performance.
  • Example 18 can further reduce the exposed surface of primary particles, suppress surface side reactions, and improve cycle and storage performance by increasing the Dv50 of the secondary particles under the condition that the size relationship between the primary particles and the secondary particles is satisfied.
  • Comparative Example 2 also adopted a mixed design of primary particles and secondary particles, but since the Dv50 of the two particles did not meet the range of Dv50 of the secondary particles greater than 1.5 times that of the primary particles, the size of the particles could not achieve the best results. Excellent gradation, limited cycle performance and high temperature performance.
  • Table 4 shows the respective parameters and evaluation results of Examples 8, 20 to 23.
  • Table 4 shows the influence of cathode coating quality and compaction density on high temperature cycle retention rate and high temperature cycle gas production performance.
  • the doping element is Zr, and the doping amount is 3000 ppm, and the element content of Example B is 0. , the addition amount of 1,3,6-hexanetricarbonitrile is 0g, the gram capacity is 199mAh/g, and the average particle size of primary particles is 1.8 ⁇ m.
  • Example 8 and Example 20 to Example 21 that by reducing the coating quality of the positive electrode, the high temperature cycle performance of the lithium ion battery can be improved, because reducing the coating quality of the positive electrode can reduce the amount of lithium ions in the positive electrode. In the transfer path, the temperature rise during the cycle is reduced, thereby improving the high-temperature cycle performance.
  • Examples 22 to 23 It can be seen from Examples 22 to 23 that the compaction density is too large, the high temperature cycle performance of the lithium ion battery is significantly reduced, resulting in the fragmentation of the particles of the positive electrode material, which increases the contact area with the electrolyte, resulting in an increase in side reactions. Examples 22 and 23 In Example 23, by selecting an appropriate compaction density, the extrusion and cracking between the particles of the positive electrode material were reduced, the exposure of the fresh surface in the material was reduced, and the CO 2 integral intensity was reduced, thereby improving the high temperature cycling of the lithium ion battery.
  • Table 5 shows the effect of the mass ratio of the polynitrile compound in the electrolyte to the positive electrode material on the positive electrode gram capacity, high temperature cycle performance, high temperature storage performance and rate performance of lithium ion batteries.
  • the doping elements in the examples in Table 5 are all Zr, and the doping amount is all 3000ppm, the B element content of the examples is all 0, the average particle size of the primary particles is all 1.8 ⁇ m, the coating quality is all 1.2g/cm 2 , and the compaction density is all 3.5g/cm 3 , the gram capacity is 199mAh/g.

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Abstract

本申请提供了一种正极、电化学装置和电子装置，其中正极，包括：正极集流体和正极活性物质层；正极活性物质层位于正极集流体一面或两面的至少部分区域上，正极活性物质层包括正极材料，正极材料中含有Li元素；使用电感耦合等离子体光谱仪(ICP)测试正极的Li元素在正极活性物质层的质量含量为1.45％至1.55％范围时，使用差分电化学质谱测试正极得到的CO 2的积分强度Q≤2000nmol/mg。本申请能够改善电化学装置的高温循环性能和安全性。

Description

正极、电化学装置和电子装置 技术领域
本申请涉及电化学储能领域，尤其涉及正极、电化学装置和电子装置。
背景技术
随着电化学装置(例如，锂离子电池)的发展和进步，对其高温循环性能和安全性能提出了越来越高的要求。虽然目前的改进电化学装置的技术能够在一定程度上提升电化学装置的高温循环性能和安全性能，但是并不令人满意，期待进一步的改进。
发明内容
本申请的实施例中提供了一种正极，包括：正极集流体和正极活性物质层；正极活性物质层位于正极集流体一面或两面的至少部分区域上，正极活性物质层包括正极材料，正极材料中含有Li元素；使用电感耦合等离子体光谱仪(ICP)测试正极的Li元素在正极活性物质层的质量含量为1.45％至1.55％时，使用差分电化学质谱测试正极得到的CO 2的积分强度Q≤2000nmol/mg。
在一些实施例中，正极材料包括：LiNi xCo yM1 1-x-y-zM2 zO 2；其中0.5≤x<1,0≤y<0.5,0≤z≤0.005，M1包括Mn或者Al中的至少一种，M2包括Mg、Ti、Zr、Ce、Sr、Y、Hf、Ba、Nb、V、Al、Ge、Sn、W、Mo、Si或B中的至少一种。
在一些实施例中，正极材料中含有Zr元素和B元素，且正极材料中Zr元素的质量含量大于或等于B元素的质量含量。在一些实施例中，正极活性物质层的涂覆质量为0.78g/m 2至1.62g/m 2,压实密度为3.1g/cm 3至3.55g/cm 3。在一些实施例中，正极材料的延伸率≤1％。
在一些实施例中，正极材料包括一次颗粒和二次颗粒，二次颗粒Dv50大于一次颗粒的Dv50的1.5倍；二次颗粒的X射线衍射图谱中(003)面的衍射峰的半高宽FWHM1满足：0.140°≤FWHM1≤0.25°；一次颗粒的X 射线衍射图谱中(003)面的衍射峰的半高宽FWHM2满足：0.12°≤FWHM2≤0.19°。
在一些实施例中，正极材料包括一次颗粒；一次颗粒的平均粒径为1.5μm至2.5μm。
在本申请的一些实施例中提出一种电化学装置，包括：上述任一项的正极、负极和隔离膜，隔离膜位于正极和负极之间。
在一些实施例中，电化学装置在45℃循环过程中存在第N圈循环，其中N>400，且第N-3圈循环的容量保持率P(N-3)和第N+3圈循环的容量保持率P(N+3)满足：P(N-3)-P(N+3)>10％，且电化学装置第N圈循环的体积膨胀率小于10％。
在一些实施例中，电化学装置还包括：电解液，电解液包括有多腈化合物；多腈化合物包括：1,3,6-己三甲腈、1,2,6-己三甲腈、1,3,5-戊三甲腈、1,2,3-三(2-氰氧基)丙烷、丁二腈或己二腈中的至少一种；其中，正极材料与多腈化合物的质量比为1：(0.001至0.005)。
在本申请的一些实施例中提出一种电子装置，包括上述任一项的电化学装置。
本申请的一些实施例中提出的正极，使用电感耦合等离子体光谱仪(ICP)测试正极的Li元素在正极活性物质层的质量含量为1.45％至1.55％时，使用差分电化学质谱(DEMS)测试正极得到的CO 2的积分强度Q≤2000nmol/mg。正极在较高脱锂状态下产生的CO 2的含量较少，表明正极材料结构稳定，在脱锂的过程中能够保持正极材料的晶体结构，释氧量少，因此具有更优的高温循环性能和安全性能。
具体实施方式
下面的实施例可以使本领域技术人员更全面地理解本申请，但不以任何方式限制本申请。
电化学装置(例如锂离子电池)被广泛应用在各个领域，相关技术中电化学装置在高温下循环性能降低、且易于产气导致安全性能降低。
为了提高高温循环性能并减少高温产气，一些相关技术中，采用具有二次颗粒形貌的正极材料，二次颗粒由纳米级的一次颗粒团聚而成，其具 有较好的倍率性能，并结合掺杂及表面包覆减少正极材料和电解液的界面副反应，抑制正极材料中金属元素溶出，从而在一定程度上改善高温循环性能以及减少高温产气。在另一些相关技术中，采用具有一次颗粒形貌的正极材料，其具有较大的一次颗粒平均粒径和相对较低的表面残余Li，一次颗粒表面具有更好的表面包覆，充放电过程中颗粒之间相互作用应力更少，从而获得更好的高温循环性能。
然而，对于采用二次颗粒形貌的正极材料，其在充放电过程中由于晶格膨胀和晶格收缩会导致一次颗粒之间存在相互作用的应力，导致颗粒破碎，并且二次颗粒内部的一次颗粒无法被很好的包覆，这些问题都会导致正极材料和电解液之间的副反应加剧，导致性能降低、产气增加。对于采用一次颗粒形貌的正极材料，由于其较大的一次颗粒平均粒径，不利于锂离子传输，大倍率放电容量保持率低，温升高，大倍率高温循环性能差。
在本申请的一些实施例中，提出了一种正极，正极可以是电化学装置的正极，正极包括正极集流体和正极活性物质层，正极集流体例如可以是铝箔或铜箔，正极活性物质层位于正极集流体一面或两面的至少部分区域上，正极活性物质层可以包括正极材料，正极材料可以包括钴锰酸锂或镍钴铝酸锂中的一种或两种，正极材料中含有Li元素；使用电感耦合等离子体光谱仪(ICP)测试正极的Li元素在正极活性物质层的质量含量为1.45％至1.55％时，使用差分电化学质谱(DEMS)测试正极得到的CO 2的积分强度Q≤2000nmol/mg。
以下示意性的描述一些实施例中采用差分电化学质谱(DEMS)测试正极的原理和方法。基本原理为：将包含原位电池的电化学工作站和质谱测量系统联用，使用真空系统形成压力差，运送电池的气体产物进入检测器，实现对电池在不同条件下工作产气情况的在线检测。测试方法为：对于要进行测试的正极使用0.1C电流调节脱锂量，直到电感耦合等离子体光谱仪(ICP)测试正极Li元素在正极活性物质层的质量含量为1.45％至1.55％，然后使用碳酸二甲酯(DMC)溶液浸泡正极24小时，真空烘干，将烘干后的正极装在上述的原位电池中，电解液成分由30％碳酸亚乙酯(EC)和70％碳酸二乙酯(DEC)(质量百分比)以及1mol/L LiPF 6组成，电解液添加量为3g/Ah 至4g/Ah，然后调节电池的环境温度为85℃并进行存储，同时实时检测在0至500000秒时间段内的CO 2气体信号，得到CO 2的积分强度Q。
以下示意性的描述一些实施例中采用电感耦合等离子体光谱仪(ICP)测试正极的原理和方法。基本原理为：根据不同元素的原子或离子在热激发下，发射特征谱线而进行的定性和定量分析。由于待测元素原子的能级结构不同，因此发射谱线的特征不同，据此可以进行定性分析，而根据待测元素原子的浓度不同，因此发射强度不同，可实现元素的定量测定。测试方法为：将待测试的极片取6个平行样，分别称重、消解、稀释，然后使用Thermo ICAP6300型号的电感耦合等离子体发射光谱仪测试Li元素的质量含量求平均值，其Li元素的质量含量为极片扣除基材后活性材料中的质量百分比。
在本申请的一些实施例中，使用电感耦合等离子体光谱仪(ICP)测试正极的Li元素在正极活性物质层的质量含量为1.45％至1.55％范围，使用差分电化学质谱(DEMS)测试正极得到的CO 2的积分强度Q≤2000nmol/mg。这表明正极在较高脱锂状态下产生的CO 2的含量较少，正极材料本身结构稳定，在脱锂的过程中能够保持正极材料初始的结构，释氧量少，因此具有更优的循环性能和安全可靠性。
在本申请的一些实施例中，正极材料包括：LiNi xCo yM1 1-x-y-zM2 zO 2；其中0.5≤x<1,0≤y<0.5,0≤z≤0.005，M1包括Mn或者Al中的至少一种，M2包括Mg、Ti、Zr、Ce、Sr、Y、Hf、Ba、Nb、V、Al、Ge、Sn、W、Mo、Si或B中的至少一种。一些实施例中，Al元素能够稳定正极材料中的氧，减少高温产气。
在本申请的一些实施例中，正极材料包括一次颗粒和二次颗粒，二次颗粒Dv50大于一次颗粒的Dv50的1.5倍；二次颗粒的X射线衍射图谱中(003)面的衍射峰的半高宽FWHM1满足：0.140°≤FWHM1≤0.25°；一次颗粒的X射线衍射图谱中(003)面的衍射峰的半高宽FWHM2满足：0.12°≤FWHM2≤0.19°。一些实施例中，正极材料中具有多晶形貌的二次颗粒有利于提高正极材料的倍率性能，正极材料中含有单晶形貌的一次颗粒，有利于提高正极材料的循环性能，正极材料中同时包括一次颗粒和二次颗粒从而兼顾倍率性能和循环性能。一次颗粒Dv50和二次颗粒的Dv50的测试方法：在2％相对湿度的干燥房内取一部分用正极材料，均匀分散在NMP溶液内，超 声分散12h后，搅拌均匀，得到含正极材料的悬浊液，将该悬浊液一边搅，一边缓慢倒入1500目的筛网上，一部分小颗粒通过筛网进入到滤液中，将这些滤液静置24h后，倒掉上清液，烘干后得到的粉末即为一次颗粒，另一部分大颗粒在筛网上，烘干后得到的粉末即为二次颗粒。
在本申请的一些实施例中，正极材料包括一次颗粒；一次颗粒平均粒径为1.5μm至2.5μm。在一些实施例中，当一次颗粒为球形时，一次颗粒平均粒径是指颗粒的平均直径，当一次颗粒为非球形时，一次颗粒平均粒径是指颗粒最长轴的长度。一次颗粒的粒径可以通过扫描电子显微镜(SEM)观察并测量，统计包含50颗以上一次颗粒的粒径并求均值，其均值为其正极材料的一次颗粒平均粒径。一些实施例中，一次颗粒平均粒径小于1.5μm可能因为与电解液的接触面过大导致电解液消耗增多并增加副反应，一次颗粒平均粒径大于2.5μm可能会不利于锂离子的传输，降低倍率性能。一些实施例中，正极材料为一次颗粒。
在本申请的一些实施例中，正极材料中含有Zr元素和B元素，且正极材料中Zr元素的质量含量大于或等于B元素的质量含量。一些实施例中，Zr元素有利于提高正极材料的结构稳定性，从而提高循环性能和安全性能，B元素有利于改善正极材料表面的残余锂，但是当B元素的质量含量过高时可能导致动力学性能降低。
在本申请的一些实施例中，正极活性物质层的涂覆质量为0.78g/m 2至1.62g/m 2,压实密度为3.1g/cm 3至3.55g/cm 3。一些实施例中，涂覆质量是指正极活性物质层的质量与涂覆面积的比值，当正极活性物质层的涂覆质量小于0.78g/m 2时，可能因为正极集流体上负载的正极活性物质层过少，降低体积能量密度，当正极活性物质层的涂覆质量大于1.62g/m 2时，正极集流体上负载的正极活性物质层过多，会导致电解液的浸润和传输变差，从而造成导电性能降低。一些实施例中，压实密度低于3.1g/cm 3时，可能不利于提高体积能量密度，并导致内阻增加，压实密度大于3.55g/cm 3可能会因为压力过大造成正极材料破裂，不利于循环性能。
在本申请的一些实施例中，正极材料的延伸率≤1％。一些实施例中，正极材料的延伸率大于1％可能会导致较多的正极材料破碎，导致充放电过程的产气增加，并且会降低正极集流体的强度，造成可加工性能降低。正极材料 的延伸率通过以下方法获得：将满放态的电芯拆解，得到满放正极，使用DMC溶剂浸泡48h进行清洗，烘干后刮粉，并在500℃的氧气气氛下烧结约6h除去导电剂和粘结剂，得到正极材料。将正极材料和乙炔黑(导电剂)、聚偏二氟乙烯(粘结剂)按照96.0：2.0：2.0的比例混合均匀，添加适量的N-甲基吡咯烷酮(NMP)充分搅拌配制成均匀的浆料，以90g/m 2的面密度涂覆于10um Al箔(集流体)上，经过烘干后取长度为1m极片，控制冷压压密为3.5g/cm 3进行冷压，得到冷压后的极片长度为L，则正极材料的延伸率为：(L-1)/1。
在本申请的一些实施例中提出一种电化学装置，包括：上述任一项的正极、负极和隔离膜，隔离膜位于正极和负极之间。
在一些实施例中，电化学装置在45℃循环过程中存在第N圈循环，其中N>400，且第N-3圈循环的容量保持率P(N-3)和第N+3圈循环的容量保持率P(N+3)满足：P(N-3)-P(N+3)>10％，且电化学装置第N圈循环的体积膨胀率小于10％。在一些实施例中，当正极材料的循环寿命将尽时会发生功能性失效，循环容量保持率大幅下降导致P(N-3)-P(N+3)>10％，而电化学装置在第N圈循环的体积膨胀率仍然小于10％，这表明电化学装置在此时的产气较少，安全性能较好。
在一些实施例中，负极包括负极集流体和负极活性物质层。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，负极活性物质层中还可以包括导电剂。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，负极活性物质层中包括负极材料，负极材料例如可以包括人造石墨、天然石墨、中间相微球、硬碳或含硅材料中的至少一种。
在一些实施例中，隔离膜包括聚乙烯、聚丙烯、聚偏氟乙烯、聚对苯二甲酸乙二醇酯、聚酰亚胺或芳纶中的至少一种。例如，聚乙烯包括选自高密度聚乙烯、低密度聚乙烯或超高分子量聚乙烯中的至少一种。尤其是聚乙烯和聚丙烯，它们对防止短路具有良好的作用，并可以通过关断效应改善电池的稳定性。在一些实施例中，隔离膜的厚度在约5μm至500μm的范围内。
在一些实施例中，隔离膜表面还可以包括多孔层，多孔层设置在隔离膜的基材的至少一个表面上，多孔层包括无机颗粒和粘接剂，无机颗粒选自氧化铝(Al 2O 3)、氧化硅(SiO 2)、氧化镁(MgO)、氧化钛(TiO 2)、二氧化铪(HfO 2)、氧化锡(SnO 2)、二氧化铈(CeO 2)、氧化镍(NiO)、氧化锌(ZnO)、氧化钙(CaO)、氧化锆(ZrO 2)、氧化钇(Y 2O 3)、碳化硅(SiC)、勃姆石、氢氧化铝、氢氧化镁、氢氧化钙或硫酸钡中的至少一种。在一些实施例中，隔离膜的孔具有在约0.01μm至1μm的范围的直径。多孔层的粘接剂选自聚偏氟乙烯、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。
在本申请的一些实施例中，电化学装置为卷绕式电化学装置或堆叠式电化学装置。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，电化学装置还包括：电解液，电解液包括有多腈化合物；多腈化合物包括：1,3,6-己三甲腈、1,2,6-己三甲腈、1,3,5-戊三甲腈、1,2,3-三(2-氰氧基)丙烷、丁二腈或己二腈中的至少一种；其中，正极材料与多腈化合物的质量比为1：(0.001至0.005)。
在一些实施例中，电解液中还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。
非水溶剂可为碳酸酯化合物、羧酸酯化合物、醚化合物、其它有机溶剂或它们的组合。碳酸酯化合物可为链状碳酸酯化合物、环状碳酸酯化合物、氟代碳酸酯化合物或其组合。链状碳酸酯化合物的实例为碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸甲乙酯(MEC)及其组合。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。氟代碳酸酯化合物包括碳酸氟代 亚乙酯(FEC)。羧酸酯化合物的实例为乙酸甲酯、乙酸乙酯、乙酸正丙酯、乙酸叔丁酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、γ-丁内酯、癸内酯、戊内酯、甲瓦龙酸内酯、己内酯、甲酸甲酯或者其组合。醚化合物的实例为二丁醚、四甘醇二甲醚、二甘醇二甲醚、1,2-二甲氧基乙烷、1,2-二乙氧基乙烷、乙氧基甲氧基乙烷、2-甲基四氢呋喃、四氢呋喃或者其组合。其它有机溶剂的实例为二甲亚砜、1,2-二氧戊环、环丁砜、甲基环丁砜、1,3-二甲基-2-咪唑烷酮、N-甲基-2-吡咯烷酮、甲酰胺、二甲基甲酰胺、乙腈、磷酸三甲酯、磷酸三乙酯、磷酸三辛酯、和磷酸酯或者其组合。
在本申请的一些实施例中，以锂离子电池为例，将正极、隔离膜、负极按顺序卷绕或堆叠成电极件，之后装入例如铝塑膜中进行封装，注入电解液，化成、封装，即制成锂离子电池。然后，对制备的锂离子电池进行性能测试。
本领域的技术人员将理解，以上描述的电化学装置(例如，锂离子电池)的制备方法仅是实施例。在不背离本申请公开的内容的基础上，可以采用本领域常用的其他方法。
本申请的实施例还提供了包括上述电化学装置的电子装置。本申请实施例的电子装置没有特别限定，其可以是用于现有技术中已知的任何电子装置。在一些实施例中，电子装置可以包括，但不限于，笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机和家庭用大型蓄电池等。
下面列举了一些具体实施例和对比例以更好地对本申请进行说明，其中，采用锂离子电池作为示例。
实施例1：
正极的制备：按照LiNi 0.83Co 0.12Mn 0.05O 2的化学计量比准备镍钴锰酸锂前驱体、氢氧化锂(LiOH)并将其均匀混合和干燥，干燥后在820℃下进行 一次煅烧(烧结)15h，然后以5℃/min的速率降温，得到成品，控制正极材料颗粒的Dv50为3.5μm。其中正极材料一次颗粒平均粒径为1.8μm。将制备的正极材料和乙炔黑、聚偏二氟乙烯按一定的比例混合均匀，添加N-甲基吡咯烷酮充分搅拌配制成均匀的浆料，涂覆于Al箔(正极集流体)上，再经过烘干、冷压，得到正极。其中正极的正极活性物质层涂覆质量为1.2g/m 2,压实密度为3.5g/cm 3。使用电感耦合等离子体光谱仪(ICP)测试正极的Li元素在正极活性物质层的质量含量在1.45％至1.55％范围时，使用差分电化学质谱(DEMS)测试得到的CO 2的积分强度Q＝1800nmol/mg。
负极的制备：将人造石墨、乙炔黑、丁苯橡胶、羧甲基纤维素钠按照重量比95：2：2：1混合均匀，添加去离子水充分搅拌后配制成均匀的浆料，涂覆于Cu箔(负极集流体)上，经过烘干、冷压，得到负极。
隔离膜的制备：使用多孔聚乙烯(PE)薄膜作为隔离膜；
锂离子电池的制备：将正极、隔离膜、负极按顺序依次叠好，使隔离膜处于正极和负极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。
实施例2：
实施例2与实施例1的区别在于正极制备步骤不同，其余步骤相同。
正极制备：按照LiNi 0.5Co 0.2Mn 0.3O 2的化学计量比准备镍钴锰酸锂前驱体、碳酸锂(Li 2CO 3)并将其均匀混合和干燥，干燥后在910℃下进行一次煅烧15h，然后以5℃/min的速率降温，得到成品，控制正极材料颗粒Dv50为3.5μm。其中正极材料一次颗粒平均粒径为1.8μm。将制备的正极材料和乙炔黑、聚偏二氟乙烯按一定的比例混合均匀，添加N-甲基吡咯烷酮充分搅拌配制成均匀的浆料，涂覆于Al箔(正极集流体)上，再经过烘干、冷压，得到正极。正极活性物质层涂覆质量设置为1.2g/m 2,压实密度控制在3.5g/cm 3。使用电感耦合等离子体光谱仪(ICP)测试正极的Li元素在正极活性物质层的质量含量在1.45％至1.55％范围时，使用差分电化学质谱(DEMS)测试得到的CO 2的积分强度Q＝1200nmol/mg。
实施例3：
实施例3与实施例1的区别在于正极制备步骤不同，其余步骤相同。
正极制备：按照LiNi 0.83Co 0.12Al 0.05O 2的化学计量比准备镍钴铝酸锂前驱体、氢氧化锂(LiOH)并将其均匀混合和干燥，干燥后在820℃下进行一次煅烧15h，然后以5℃/min的速率降温，得到成品，控制正极材料颗粒Dv50为3.5μm。其中正极材料一次颗粒平均粒径为1.8μm。其中正极活性物质层涂覆质量设置在为1.2g/m 2,压实密度控制在3.5g/cm 3。将制备的正极材料和乙炔黑、聚偏二氟乙烯按一定的比例混合均匀，添加N-甲基吡咯烷酮充分搅拌配制成均匀的浆料，涂覆于Al箔(正极集流体)上，再经过烘干、冷压，得到正极。使用电感耦合等离子体光谱仪(ICP)测试正极的Li元素在正极活性物质层的质量含量在1.45％至1.55％范围时，使用差分电化学质谱(DEMS)测试得到的CO 2的积分强度Q＝1700nmol/mg。
实施例4：
实施例4与实施例1的区别在于正极制备步骤不同，其余步骤相同。
正极制备：按照LiNi 0.88Co 0.07Mn 0.05O 2的化学计量比准备镍钴锰酸锂前驱体、氢氧化锂(LiOH)并将其均匀混合和干燥，干燥后在800℃下进行一次煅烧15h，然后以5℃/min的速率降温，得到成品，控制正极材料颗粒Dv50为3.5μm。其中正极材料一次颗粒平均粒径为1.8μm。将制备的正极材料和乙炔黑、聚偏二氟乙烯按一定的比例混合均匀，添加N-甲基吡咯烷酮充分搅拌配制成均匀的浆料，涂覆于Al箔(正极集流体)上，再经过烘干、冷压，得到正极。其中正极的正极活性物质层涂覆质量设置在为1.2g/m 2,压实密度控制在3.5g/cm 3。使用电感耦合等离子体光谱仪(ICP)测试正极的Li元素在正极活性物质层的质量含量在1.45％至1.55％范围时，使用差分电化学质谱(DEMS)测试得到的CO 2的积分强度Q＝2000nmol/mg。
实施例5：
实施例5正极的制备方法与实施例1的区别在于：控制一次烧结后的降温速率，使得采用电感耦合等离子体光谱仪(ICP)测试正极的Li元素在正极活性物质层的质量含量在1.45％至1.55％范围时，使用差分电化学质谱(DEMS)测试得到的CO 2的积分强度Q＝2000nmol/mg。其余步骤与实施例1相同。
实施例6：
实施例6与实施例1的区别在于：控制一次烧结后的降温速率，使得采用电感耦合等离子体光谱仪(ICP)测试正极的Li元素在正极活性物质层的质量含量在1.45％至1.55％范围时，使用差分电化学质谱(DEMS)测试得到的CO 2的积分强度Q＝1500nmol/mg。其余步骤与实施例1相同。
实施例7：
实施例7与实施例1的区别在于：控制一次烧结后的降温速率，使得采用电感耦合等离子体光谱仪(ICP)测试正极的Li元素在正极活性物质层的质量含量在1.45％至1.55％范围时，使用差分电化学质谱(DEMS)测试得到的CO 2的积分强度Q＝1200nmol/mg。其余步骤与实施例1相同。
实施例8：
实施例8与实施例1的区别在于正极制备步骤不同，其余步骤相同。
正极制备：按照LiNi 0.83Co 0.12Mn 0.047Zr 0.003O 2的化学计量比准备镍钴锰酸锂前驱体、氢氧化锂(LiOH)和氧化锆(ZrO 2)并将其均匀混合和干燥，干燥后在820℃下进行一次煅烧15h，然后以5℃/min的速率降温，得到成品，控制正极材料颗粒Dv50为3.5μm。将制备的正极材料和乙炔黑、聚偏二氟乙烯按一定的比例混合均匀，添加N-甲基吡咯烷酮充分搅拌配制成均匀的浆料，涂覆于Al箔(正极集流体)上，再经过烘干、冷压，得到正极。其中正极材料一次颗粒平均粒径为1.8μm。其中正极活性物质层涂覆质量设置在为1.2g/m 2,压实密度控制在3.5g/cm 3。使用电感耦合等离子体光谱仪(ICP)测试正极的Li元素在正极活性物质层的质量含量在1.45％至1.55％范围时，使用差分电化学质谱(DEMS)测试得到的CO 2的积分强度Q＝1000nmol/mg。
实施例9：
实施例9与实施例1的区别在于正极制备步骤不同，其余步骤相同。
正极制备：按照LiNi 0.83Co 0.12Mn 0.047Al 0.003O 2的化学计量比准备镍钴锰酸锂前驱体、氢氧化锂(LiOH)和氧化铝(Al 2O 3)并将其均匀混合和干燥，干燥后在820℃下进行一次煅烧15h，然后以5℃/min的速率降温，得到成品，控制正极材料颗粒Dv50为3.5μm。其中正极材料一次颗粒平均粒径为1.8μm。将制备的正极材料和乙炔黑、聚偏二氟乙烯按一定的比例混合均匀，添 加N-甲基吡咯烷酮充分搅拌配制成均匀的浆料，涂覆于Al箔(正极集流体)上，再经过烘干、冷压，得到正极。其中正极活性物质层涂覆质量设置为1.2g/m 2,压实密度控制在3.5g/cm 3。使用电感耦合等离子体光谱仪(ICP)测试正极的Li元素在正极活性物质层的质量含量在1.45％至1.55％范围时，使用差分电化学质谱(DEMS)测试得到的CO 2的积分强度Q＝1000nmol/mg。
实施例10：
实施例10与实施例1的区别在于正极制备步骤不同，其余步骤相同。
正极制备：按照LiNi 0.83Co 0.12Mn 0.047Sr 0.003O 2的化学计量比准备镍钴锰酸锂前驱体、氢氧化锂(LiOH)和氧化锶(SrO)并将其均匀混合和干燥，干燥后在820℃下进行一次煅烧15h，然后以5℃/min的速率降温，使其材料颗粒表面氧和过渡金属满足一定的条件，得到成品，控制正极材料颗粒Dv50为3.5μm。其中正极材料一次颗粒平均粒径为1.8μm。将制备的正极材料和乙炔黑、聚偏二氟乙烯按一定的比例混合均匀，添加N-甲基吡咯烷酮充分搅拌配制成均匀的浆料，涂覆于Al箔(正极集流体)上，再经过烘干、冷压，得到正极。其中正极活性物质层涂覆质量设置在为1.2g/m 2,压实密度控制在3.5g/cm 3。使用电感耦合等离子体光谱仪(ICP)测试正极的Li元素在正极活性物质层的质量含量在1.45％至1.55％范围时，使用差分电化学质谱(DEMS)测试得到的CO 2的积分强度Q＝1100nmol/mg。
实施例11：
实施例11与实施例1的区别在于正极制备步骤不同，其余步骤相同。
正极制备：按照LiNi 0.83Co 0.12Mn 0.047W 0.003O 2的化学计量比准备镍钴锰酸锂前驱体、氢氧化锂(LiOH)和氧化钨(WO 3)并将其均匀混合和干燥，干燥后在820℃下进行一次煅烧15h，然后以5℃/min的速率降温，得到成品，控制正极材料颗粒Dv50为3.5μm。其中正极材料一次颗粒平均粒径为1.8μm。将制备的正极材料和乙炔黑、聚偏二氟乙烯按一定的比例混合均匀，添加N-甲基吡咯烷酮充分搅拌配制成均匀的浆料，涂覆于Al箔(正极集流体)上，再经过烘干、冷压，得到正极。其中正极活性物质层涂覆质量设置为1.2g/m 2,压实密度控制在3.5g/cm 3。使用电感耦合等离子体光谱仪(ICP)测试 正极的Li元素在正极活性物质层的质量含量在1.45％至1.55％范围时，使用差分电化学质谱(DEMS)测试得到的CO 2的积分强度Q＝900nmol/mg。
实施例12：
实施例12与实施例8的区别在于：控制Zr的掺杂量为1000ppm，使用电感耦合等离子体光谱仪(ICP)测试正极的Li元素在正极活性物质层的质量含量在1.45％至1.55％范围时，使用差分电化学质谱(DEMS)测试得到的CO 2的积分强度Q＝1080nmol/mg。其余步骤与实施例8相同。
实施例13：
实施例13与实施例8的区别在于：控制Zr的掺杂量为5000ppm，使用电感耦合等离子体光谱仪(ICP)测试正极的Li元素在正极活性物质层的质量含量在1.45％至1.55％范围时，使用差分电化学质谱(DEMS)测试得到的CO 2的积分强度Q＝910nmol/mg。其余步骤与实施例8相同。
实施例14：
实施例14与实施例1的区别在于正极制备步骤不同，其余步骤相同。
正极制备：按照LiNi 0.83Co 0.12Mn 0.047Zr 0.003O 2的化学计量比准备镍钴锰酸锂前驱体、氢氧化锂(LiOH)和氧化锆(ZrO 2)并将其均匀混合和干燥，干燥后在820℃下进行一次煅烧15h，然后以5℃/min的速率降温，得到半成品，控制颗粒Dv50为3.5μm。将上述半成品与硼酸(H 3BO 3)混合均匀，在400℃烧结4小时以进行硼包覆，其中硼元素的含量为400ppm，得到正极材料的成品。将制备的正极材料和乙炔黑、聚偏二氟乙烯按一定的比例混合均匀，添加N-甲基吡咯烷酮充分搅拌配制成均匀的浆料，涂覆于Al箔(正极集流体)上，再经过烘干、冷压，得到正极。其中正极材料一次颗粒平均粒径为1.8μm。其中正极活性物质层涂覆质量设置为1.2g/m 2,压实密度控制在3.5g/cm 3。使用电感耦合等离子体光谱仪(ICP)测试正极的Li元素在正极活性物质层的质量含量在1.45％至1.55％范围时，其使用差分电化学质谱(DEMS)测试得到的CO 2的积分强度Q＝800nmol/mg。
实施例15：
实施例15与实施例14的区别在于：控制B元素的包覆量为800ppm，使用电感耦合等离子体光谱仪(ICP)测试正极的Li元素在正极活性物质层 的质量含量在1.45％至1.55％范围时，使用差分电化学质谱(DEMS)测试得到的CO 2的积分强度Q＝900nmol/mg。其余步骤与实施例14相同。
实施例16：
实施例16与实施例8的区别在于：通过控制烧结温度使材料一次颗粒平均粒径为1.5μm，使用电感耦合等离子体光谱仪(ICP)测试正极的Li元素在正极活性物质层的质量含量在1.45％至1.55％范围时，使用差分电化学质谱(DEMS)测试得到的CO 2的积分强度Q＝1150nmol/mg。其余步骤与实施例8相同。
实施例17：
实施例17与实施例8的区别在于：控制烧结温度使材料一次颗粒平均粒径为2.5μm，使用电感耦合等离子体光谱仪(ICP)测试正极的Li元素在正极活性物质层的质量含量在1.45％至1.55％范围时，使用差分电化学质谱(DEMS)测试得到的CO 2的积分强度Q＝830nmol/mg。其余步骤与实施例8相同。
实施例18：
按照LiNi 0.83Co 0.12Mn 0.05O 2的化学计量比准备镍钴锰酸锂前驱体、氢氧化锂(LiOH)并将其均匀混合和干燥，干燥后在780℃下进行一次煅烧16小时，然后以5℃/min的速率降温，得到二次颗粒。控制二次颗粒正极材料颗粒的Dv50为10μm。其中所制备二次颗粒的X射线衍射图谱中(003)面的衍射峰半高宽FWHM1为0.19°。
按照LiNi 0.83Co 0.12Mn 0.05O 2的化学计量比准备镍钴锰酸锂前驱体、氢氧化锂(LiOH)并将其均匀混合和干燥，干燥后在820℃下进行一次煅烧15h，然后以5℃/min的速率降温，得到一次颗粒。控制一次颗粒正极材料颗粒的Dv50为3.5μm。其中所制备一次颗粒的X射线衍射图谱中(003)面的衍射峰半高宽FWHM1为0.15°。
将制备的正极材料包括一次颗粒、二次颗粒和乙炔黑、聚偏二氟乙烯按一定的比例混合均匀，添加N-甲基吡咯烷酮充分搅拌配制成均匀的浆料，涂覆于Al箔(正极集流体)上，再经过烘干、冷压，得到正极。其中正极活性物质的层涂覆质量为1.2g/m 2,压实密度为3.5g/cm 3。使用电感耦合等离子体 光谱仪(ICP)测试正极的Li元素在正极活性物质层的质量含量在1.45％至1.55％范围时，使用差分电化学质谱(DEMS)测试得到的CO 2的积分强度Q＝1400nmol/mg。
负极的制备：将人造石墨、乙炔黑、丁苯橡胶、羧甲基纤维素钠按照重量比95：2：2：1混合均匀，添加去离子水充分搅拌后配制成均匀的浆料，涂覆于Cu箔(负极集流体)上，经过烘干、冷压，得到负极。
隔离膜的制备：使用多孔聚乙烯(PE)薄膜作为隔离膜；
锂离子电池的制备：将正极、隔离膜、负极按顺序依次叠好，使隔离膜处于正极和负极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。
实施例19：
实施例19与实施例18的区别在于：控制镍钴锰酸锂前驱体的颗粒度及烧结温度和烧结时间，使二次颗粒Dv50为8μm，X射线衍射图谱中(003)面的衍射峰半高宽FWHM1为0.20°，使用电感耦合等离子体光谱仪(ICP)测试正极的Li元素在正极活性物质层的质量含量在1.45％至1.55％范围时，使用差分电化学质谱(DEMS)测试得到的CO 2的积分强度Q＝1500nmol/mg。其余步骤与实施例18相同。
实施例20：
实施例20与实施例8的区别在于：控制正极活性物质层涂覆质量为0.78g/m 2，使用电感耦合等离子体光谱仪(ICP)测试正极的Li元素在正极活性物质层的质量含量在1.45％至1.55％范围时，使用差分电化学质谱(DEMS)测试得到的CO 2的积分强度Q＝1000nmol/mg。其余步骤与实施例8相同。
实施例21：
实施例21与实施例8的区别在于：控制正极活性物质层涂覆质量为1.62g/m 2，使用电感耦合等离子体光谱仪(ICP)测试正极的Li元素在正极活性物质层的质量含量在1.45％至1.55％范围时，使用差分电化学质谱(DEMS)测试得到的CO 2的积分强度Q＝1000nmol/mg。其余步骤与实施例8相同。
实施例22：
实施例22与实施例8的区别在于：控制正极压实密度为3.1g/cm 3，使用电感耦合等离子体光谱仪(ICP)测试正极的Li元素在正极活性物质层的质量含量在1.45％至1.55％范围时，使用差分电化学质谱(DEMS)测试得到的CO 2的积分强度Q＝910nmol/mg。其余步骤与实施例8相同。
实施例23：
实施例23与实施例8的区别在于：控制正极压实密度为3.55g/cm 3，使用电感耦合等离子体光谱仪(ICP)测试正极的Li元素在正极活性物质层的质量含量在1.45％至1.55％范围时，使用差分电化学质谱(DEMS)测试得到的CO 2的积分强度Q＝1150nmol/mg。其余步骤与实施例8相同。
实施例24：
实施例24与实施例8的区别在于：实施例24所使用的电解液中每1g正极材料含1,3,6-己烷三腈0.001g，使用电感耦合等离子体光谱仪(ICP)测试正极的Li元素在正极活性物质层的质量含量在1.45％至1.55％范围时，使用差分电化学质谱(DEMS)测试得到的CO 2的积分强度Q＝950nmol/mg。其余步骤与实施例8相同。
实施例25：
实施例25与实施例8的区别在于：实施例25所使用的电解液中每1g正极材料含1,3,6-己烷三腈0.003g，使用电感耦合等离子体光谱仪(ICP)测试正极的Li元素在正极活性物质层的质量含量在1.45％至1.55％范围时，使用差分电化学质谱(DEMS)测试得到的CO 2的积分强度Q＝890nmol/mg，其余步骤与实施例8相同。
实施例26：
实施例26与实施例8的区别在于：实施例26所使用的电解液中每1g正极材料含1,3,6-己烷三腈0.005(g)，使用电感耦合等离子体光谱仪(ICP)测试正极的Li元素在正极活性物质层的质量含量在1.45％至1.55％范围时，使用差分电化学质谱(DEMS)测试得到的CO 2的积分强度Q＝800nmol/mg，其余步骤与实施例8相同。
对比例1：
对比例1与实施例1的区别在于：控制一次烧结后的降温速率，以使采用电感耦合等离子体光谱仪(ICP)测试正极的Li元素在正极活性物质层的质量含量在1.45％至1.55％范围时，使用差分电化学质谱(DEMS)测试得到的CO 2的积分强度Q＝3000nmol/mg，其余步骤与实施例1相同。
对比例2：
对比例2与实施例25的区别在于：控制镍钴锰酸锂前驱体的颗粒度及烧结温度和烧结时间，使二次颗粒Dv50为5μm，X射线衍射图谱中(003)面的衍射峰半高宽FWHM1为0.21°，使用电感耦合等离子体光谱仪(ICP)测试正极的Li元素在正极活性物质层的质量含量在1.45％至1.55％范围时，使用差分电化学质谱(DEMS)测试得到的CO 2的积分强度Q＝2200nmol/mg。其余步骤与实施例25相同。
下面描述本申请的各个参数的测试方法。
1.差分电化学质谱(DEMS)测试
基本原理：将包含原位电池的电化学工作站和质谱测试系统联用，使用真空系统形成压力差，运送电池中的气体产物进入检测器，实现对电池在不同条件下工作产气情况的在线检测。
样品前处理方法：取电芯拆解后的正极使用0.1C的小电流调节极片的脱锂量，使得采用电感耦合等离子体光谱仪(ICP)测试正极Li元素在正极活性物质层的质量含量为1.45％至1.55％范围，然后使用DMC溶液浸泡24小时，真空烘干后密封备用。
DEMS测试中电池的工作条件：使用上述处理过的正极，装在DEMS测试系统的原位电池中，电解液成分由30％EC和70％DEC(质量百分比)以及1mol LiPF 6组成，电解液添加量在3g/Ah至4g/Ah，然后调节电池的环境温度为85℃并进行存储，同时实时检测在0至500000s时间段内的CO 2气体信号。
2.电感耦合等离子体光谱仪(ICP)测试
基本原理为：根据不同元素的原子或离子在热激发下，发射特征谱线而进行的定性和定量分析。由于待测元素原子的能级结构不同，因此发射谱线 的特征不同，据此可以进行定性分析，而根据待测元素原子的浓度不同，因此发射强度不同，可实现元素的定量测定。
测试方法为：将待测试的极片取6个平行样，分别称重、消解、稀释，然后使用Thermo ICAP6300型号的电感耦合等离子体发射光谱仪测试Li元素的质量含量求平均值，其Li元素的质量含量为极片扣除基材后活性材料中的质量百分比。
3.容量测试
将实施例和对比例中的锂离子电池各组取4支，在约25℃的环境中，0.5C(即2h内完全放掉理论容量的电流值)的充电电流下进行恒流和恒压充电，直到上限电压为约4.2V，然后在0.2C的放电电流下进行恒流放电，直到最终电压为约2.8V，计算首次的放电容量作为电池的容量。
4.循环性能及循环产气测试
将实施例和对比例中的锂离子电池各组取4支，通过以下步骤对锂离子电池重复进行充电和放电，并计算锂离子电池的放电容量保持率。
首先，在约45℃的环境中，进行第一次充电和放电，在2C的充电电流下进行恒流和恒压充电，直到上限电压为约4.2V，然后在6C的放电电流下进行恒流放电，直到最终电压为约2.8V，记录首次循环的放电容量和此时的厚度(初始厚度)；而后进行400次的充电和放电循环，记录第400次循环的放电容量和第400次循环后的厚度。
400圈循环容量保持率＝(第400次循环的放电容量/首次循环的放电容量)×100％。
循环产气情况：400圈循环膨胀率＝((第400次循环后厚度-初始厚度)/初始厚度))×100％
5.高温存储测试
将实施例和对比例中的锂离子电池各组取4支，在约25℃的环境中，以0.5C倍率恒定电流充电至电压高于约4.2V，在约4.2V恒定电压下充电至电流低于0.05C，使电池处于4.2V满充状态。测试存储前的满充电池厚度(初始满冲厚度)。将满充状态的电池置于约85℃烘箱存储约24h后，测试其存储后的厚度。
85℃存储24h厚度膨胀率＝((85℃存储24h厚度-初始满冲厚度)/初始满充厚度)×100％。
6.压实密度(PD)的测试方法：
取冷压后的正极，用1540.25mm 2模具冲取6片正极材料层和6片正极集流体，使用分析天平(上海精科天美电子天平FA2004B)称量6片正极材料层的总重Mc g和6片集流体的总重为Mb g，用千分尺测量6片正极材料层的平均厚度为Dc mm，6片集流体的平均厚度为Db mm。PD＝[(Mc-Mb)/6]/(Dc-Db)/1540.25×1000，单位为g/ml。
7.10C放电容量保持率测试
将锂离子电池在25℃的环境中静置30分钟，然后以0.5C倍率恒流充电至4.2V，以4.2V恒压充电至0.05C，静置30分钟，接着以0.2C倍率放电至2.8V，记录此时的放电容量为锂离子电池的实际容量C1；静置30分钟后再以0.5C倍率恒流充电至4.2V，以4.2V恒压充电至0.05C，静置30分钟，接着以10C倍率放电至2.8V，记录此时的放电容量为锂离子电池的实际容量C2。通过下式计算10C放电容量保持率：
10C放电容量保持率＝C2/C1×100％。
8.N计算方法
按照循环性能的测试方法获得45℃循环过程中第N圈的循环保持率P(N)和第N周电化学装置的膨胀率，然后按照满足第N周(N>400)前后的第N-3周和第N+3周循环保持率P的差异P(N-3)-P(N+3)>10％，且第N周电化学装置的膨胀率小于10％的条件获的最小的N即为N值。
9.正极材料延伸率测试
获取活性材料：将满放态的电芯拆解，得到满放正极，使用DMC溶剂浸泡48h进行清洗，烘干后刮粉，并在500℃的氧气气氛下烧结约6h除去导电剂和粘结剂，得到正极材料。
特定条件下的延伸率计算：将正极材料和乙炔黑(导电剂)、聚偏二氟乙烯(粘结剂)按照96.0：2.0：2.0的比例混合均匀，添加适量的N-甲基吡咯烷酮充分搅拌配制成均匀的浆料，以90g/m2的面密度涂覆于10um Al箔(集 流体)上，经过烘干后取长度为1m极片，控制冷压压密为3.5g/cm 3进行冷压，得到冷压后的极片长度为L，则正极材料的延伸率为：(L-1)/1。
表1示出了实施例1至13和对比例1的各个参数和评估结果。
表1
Figure PCTCN2021079807-appb-000001
表1展示了通过控制正极材料在一定Li含量下的CO 2积分强度，对高温存储性能，高温循环保持率及高温循环产气性能的影响，包括正极材料组分、掺杂元素和掺杂量的影响。表1中，实施例和对比例的B元素含量均为0ppm，且一次颗粒的平均粒径均为1.8μm，涂覆质量均为1.2g/cm 2，压实密度均为3.5g/cm 3，1g正极材料所含1,3,6-己三甲腈量为0g。
从实施例1至13和对比例1的测试结果可以看出，实施例1至13的N值，10C放电容量保持率和400圈循环保持率均高于对比例1，且85℃存储24h膨胀率和400圈循环膨胀率均低于对比例1，由此可见，在使用电感耦合等离子体光谱仪(ICP)测试正极的Li元素在正极活性物质层的质量含量在1.45％至1.55％范围，使用差分电化学质谱测试正极得到的CO 2的积分强度 Q≤2000nmol/mg的条件的情况下，可以提高锂离子电池的高温循环性能并减少高温产气，改善电池的安全可靠性。
对比实施例1至4可以看出，实施例1至4中采用了不同组分的正极材料，随着正极材料中Ni含量的降低，CO 2积分强度明显减少，表明正极材料在高温条件下的释氧量减少，氧化电解液产生的CO 2气体降低，因此能够明显改善电化学装置在高温条件下存储性能和循环性能。
对比实施例1和实施例3可以看出，实施例3的高温存储产气和高温循环产气均少于实施例1，这是因为实施例3中使用Al元素替换了实施例1中的Mn元素，从而能够更好的稳定结构中的氧，减少CO 2积分强度，改善高温性能。
对比实施例1、实施例5至7和对比例1可以看出，实施例1、实施例5至7与对比例1的正极材料组分相同，实施例1、实施例5至7通过调控烧结后的冷却参数，使得CO 2的积分强度降低到1200nmol/mg至2000nmol/mg，极大降低了正极材料在高脱锂态下的释氧量，抑制了正极材料与电解液之间的界面反应，使得锂离子电池85℃存储性能和高温循环性能显著改善。
相比对比例1，实施例1和实施例5至7在45℃循环过程中存在第N圈循环(N>400)，第N-3周循环容量保持率P(N-3)和第N+3周循环保持率P(N+3)的差异P(N-3)-P(N+3)>10％，且第N周电化学装置的膨胀率小于10％。例如实施例1在第497圈和第503圈的循环保持率相差大于10％，且其第500周循环的膨胀率小于10％，表明实施例1的电化学装置在500圈循环前后发生功能型失效，即在达到一定循环寿命后循环保持率发生快速衰减，避免继续工作所带来的安全风险。而对比例1不存在这样的特征，其高温循环性能较差(400圈循环保持率53％)且存在较大的安全风险(400周循膨胀率达到29％)。
实施例8至13展示了不同的掺杂元素及掺杂量对CO 2积分强度的影响，及通过对其调控改善高温存储和高温循环性能。相比实施例1，实施例8至11分别通过Zr、Al、Sr、W的掺杂实现了CO 2积分强度的降低，并对锂离子电池的高温性能进一步改善。不同的掺杂元素实现效果接近，其中Al和W元素较优，但Al的引入会导致克容量的降低。对比实施例8和实施例12至 13可以看出，随掺杂量的增加，CO 2积分强度进一步降低，但过高的掺杂量会导致克容量的降低。
表2示出了实施例8、14至17的各个参数和评估结果。
表2
Figure PCTCN2021079807-appb-000002
表2展示了B元素的含量及一次颗粒平均粒径对高温存储性能，高温循环保持率及高温循环产气性能的影响，表2中，掺杂元素为Zr，且掺杂量3000ppm，正极的涂覆质量1.2g/cm 2，压实密度为3.5g/cm 3，1,3,6-己三甲腈的添加量为0g。
从实施例8和实施例14至15可以看出，可以通过一定B含量的包覆能够改善材料表面稳定性，减少正极CO 2积分强度，改善锂离子电池高温存储和高温循环性能。但当B元素含量过高超过Zr元素含量时，由于过量的B的存在会带来倍率性能显著降低，同时也影响高温产气，所以优选正极材料中Zr元素的质量含量大于或等于B元素的质量含量。
从实施例8和实施例16至17可以看出，通过调整烧结温度使正极材料一次颗粒的平均粒径增大，能够改善锂离子电池的高温循环性能能和高温存储性能，这是因为一次颗粒的粒径增大减小了正极材料表面与电解液的接触和副反应，从而降低了CO 2的积分强度，改善了高温性能。一次粒子平均粒径过大时，Li +传输路径减少，影响克容量，当一次粒子平均粒径过小时会增加颗粒表面副反应，影响高温产气及循环性能，因此，一次颗粒的平均粒径为1.5μm至2.5μm时，能兼顾高温产气及循环性能。
表3示出了实施例1、18至19的各个参数和评估结果。
Figure PCTCN2021079807-appb-000003
表3展示了在正极中采用一次颗粒与二次颗粒混用的设计对高温存储性能，高温循环保持率及高温循环产气性能的影响，表3中，无掺杂元素，一次颗粒Dv50为3.5μm，一次颗粒FWHM2为0.15°，正极的涂覆质量1.2g/cm 2，压实密度为3.5g/cm 3，1,3,6-己三甲腈的添加量为0g。
从对比例2，实施例1和实施例18至19可以看出，相比实施例1中的单一颗粒设计，其在实施例19中采用一次颗粒和二次颗粒混用，其中二者的粒径满足一定的大小关系能够实现更大的堆积密度，使极片冷压制作过程中能够在较小的压力下实现同样的压实密度，减少颗粒破裂，改善高温存储和高温循环性能。同时，由于对烧结温度及颗粒尺寸的控制，使一次颗粒和二次颗粒的X射线衍射图谱中(003)面的衍射峰半高宽FWHM1分别在一定范围，其二次颗粒具有优异的容量发挥，一次颗粒具有更加稳定的结构及更少的反应界面，二者搭配实现高温性能。相比实施例19，实施例18在满足一次颗粒和二次颗粒大小关系的条件下通过增加二次颗粒的Dv50，可进一步减少一次颗粒的暴露表面，抑制表面副反应，改善循环和存储性能。同比之下，对比例2同样采用了一次颗粒与二次颗粒的混合设计，但由于二者的颗粒Dv50不满足二次颗粒Dv50大于一次颗粒的Dv50的1.5倍的范围，导致大小颗粒不能实现最优的级配，循环性能和高温性能发挥有限。
表4示出了实施例8、20至23的各个参数和评估结果。
表4
Figure PCTCN2021079807-appb-000004
Figure PCTCN2021079807-appb-000005
表4展示了正极涂覆质量和压实密度对高温循环保持率及高温循环产气性能的影响，表4中，掺杂元素为Zr，且掺杂量3000ppm，实施例B元素含量均为0，1,3,6-己三甲腈的添加量为0g，克容量为199mAh/g，一次颗粒平均粒径为1.8μm。
实施例8和实施例20至实施例21可以看出，通过减少正极的涂覆质量，能够提高锂离子电池的高温循环性能，这是因为通过减少正极的涂覆质量能够减小锂离子在正极中的传输路径，降低循环过程中的温升，从而改善高温循环性能。
实施例22至23可以看出，压实密度过大，锂离子电池的高温循环性能明显降低，导致正极材料的颗粒破碎，增加了与电解液的接触面积，导致副反应增加，实施例22和实施例23通过选取合适的压实密度，减少了正极材料的颗粒之间的挤压和破裂，减小材料中新鲜表面的暴露，降低CO 2积分强度，从而改善了锂离子电池的高温循环。
表5示出了实施例8、24至26的各个参数和评估结果。
表5
Figure PCTCN2021079807-appb-000006
表5展示了电解液中多腈化合物相对于正极材料的质量比对锂离子电池的正极克容量、高温循环性能、高温存储性能和倍率性能的影响，表5中实 施例的掺杂元素均为Zr，且掺杂量均为3000ppm，实施例的B元素含量均为0，一次颗粒平均粒径均为1.8μm，涂覆质量均为1.2g/cm 2，压实密度均为3.5g/cm 3，克容量均为199mAh/g。
从实施例8、24至26可以看出，当基于每1g正极材料，电解液包含0.001g至0.005g多腈化合物时，可进一步改善锂离子电池的高温存储性能和高温循环性能。当电解液中多腈化合物含量过高时，对高温存储无进一步改善，但会严重影响倍率性能，进而影响循环性能。因此，限定正极材料与所述多腈化合物的质量比为1：(0.001至0.005)时具有较好的高温存储性能和高温循环性能。
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。

Claims (10)

  1. 一种正极，其特征在于，包括：
    正极集流体和正极活性物质层；
    所述正极活性物质层位于所述正极集流体一面或两面的至少部分区域上，所述正极活性物质层包括正极材料，所述正极材料中包括Li元素；
    使用电感耦合等离子体光谱仪(ICP)测试所述正极的Li元素在正极活性物质层的质量含量为1.45％至1.55％时，使用差分电化学质谱测试所述正极得到的CO 2的积分强度Q≤2000nmol/mg。
  2. 根据权利要求1所述的正极，其特征在于，
    所述正极材料包括：LiNi xCo yM1 1-x-y-zM2 zO 2；
    其中0.5≤x<1，0≤y<0.5，0≤z≤0.005，M1包括Mn或Al中的至少一种，M2包括Mg、Ti、Zr、Ce、Sr、Y、Hf、Ba、Nb、V、Al、Ge、Sn、W、Mo、Si或B中的至少一种。
  3. 根据权利要求1所述的正极，其特征在于，
    所述正极材料中含有Zr元素和B元素，且所述正极材料中Zr元素的质量含量大于或等于B元素的质量含量。
  4. 根据权利要求1所述的正极，其特征在于，
    所述正极材料包括一次颗粒和二次颗粒，二次颗粒Dv50大于一次颗粒的Dv50的1.5倍；
    所述二次颗粒的X射线衍射图谱中(003)面的衍射峰的半高宽FWHM1满足：0.140°≤FWHM1≤0.25°；
    所述一次颗粒的X射线衍射图谱中(003)面的衍射峰的半高宽FWHM2满足：0.12°≤FWHM2≤0.19°。
  5. 根据权利要求1所述的正极，其特征在于，
    所述正极材料包括一次颗粒；
    所述一次颗粒的平均粒径为1.5μm至2.5μm。
  6. 根据权利要求1所述的正极，其特征在于，
    所述正极活性物质层的涂覆质量为0.78g/m 2至1.62g/m 2,压实密度为3.1g/cm 3至3.55g/cm 3。
  7. 根据权利要求1所述的正极，其特征在于，
    所述正极材料的延伸率≤1％。
  8. 一种电化学装置，其特征在于，包括：如权利要求1至7任一项所述的正极、电解液、负极和隔离膜，所述隔离膜位于所述正极和所述负极之间。
  9. 根据权利要求8所述的电化学装置，其特征在于，满足以下条件(a)至(b)中至少一者：
    (a)所述电化学装置在45℃循环过程中存在第N圈循环，其中N>400，且第N-3圈循环的容量保持率P(N-3)和第N+3圈循环的容量保持率P(N+3)满足：P(N-3)-P(N+3)>10％，且所述电化学装置第N圈循环的体积膨胀率小于10％；
    (b)所述电解液包括有多腈化合物；所述多腈化合物包括：1,3,6-己三甲腈、1,2,6-己三甲腈、1,3,5-戊三甲腈、1,2,3-三(2-氰氧基)丙烷、丁二腈或己二腈中的至少一种；其中，所述正极材料与所述多腈化合物的质量比为1：(0.001至0.005)。
  10. 一种电子装置，其特征在于，包括如权利要求8至9任一项所述的电化学装置。
PCT/CN2021/079807 2021-03-09 2021-03-09 正极、电化学装置和电子装置 WO2022188037A1 (zh)

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CN101777653A (zh) * 2005-03-31 2010-07-14 东洋炭素株式会社 正极活性物质及其制备方法
US20120280172A1 (en) * 2007-11-13 2012-11-08 Sanyo Electric Co., Ltd. Method for producing positive electrode for non-aqueous electrolyte secondary cell and method for producing non-aqueous electrolyte secondary cell
CN104282903A (zh) * 2013-07-08 2015-01-14 三星Sdi株式会社 正极活性物质、其制备方法、含其的正极和锂二次电池
CN111864196A (zh) * 2019-04-30 2020-10-30 Sk新技术株式会社 锂二次电池

Patent Citations (4)

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CN101777653A (zh) * 2005-03-31 2010-07-14 东洋炭素株式会社 正极活性物质及其制备方法
US20120280172A1 (en) * 2007-11-13 2012-11-08 Sanyo Electric Co., Ltd. Method for producing positive electrode for non-aqueous electrolyte secondary cell and method for producing non-aqueous electrolyte secondary cell
CN104282903A (zh) * 2013-07-08 2015-01-14 三星Sdi株式会社 正极活性物质、其制备方法、含其的正极和锂二次电池
CN111864196A (zh) * 2019-04-30 2020-10-30 Sk新技术株式会社 锂二次电池

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