WO2022267757A1 - 一种锂离子电池 - Google Patents

一种锂离子电池 Download PDF

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Publication number
WO2022267757A1
WO2022267757A1 PCT/CN2022/093487 CN2022093487W WO2022267757A1 WO 2022267757 A1 WO2022267757 A1 WO 2022267757A1 CN 2022093487 W CN2022093487 W CN 2022093487W WO 2022267757 A1 WO2022267757 A1 WO 2022267757A1
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lithium
ion battery
active material
positive electrode
electrode active
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PCT/CN2022/093487
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English (en)
French (fr)
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樊亚楠
曾家江
于丽秋
童志强
李素丽
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珠海冠宇电池股份有限公司
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Publication of WO2022267757A1 publication Critical patent/WO2022267757A1/zh
Priority to US18/459,818 priority Critical patent/US20230411675A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—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
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—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
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
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    • 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
    • H01M10/0568—Liquid materials characterised by the solutes
    • 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
    • H01M4/13—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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
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    • 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
    • H01M4/50—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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/661—Metal or alloys, e.g. alloy coatings
    • 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
    • H01M2300/002—Inorganic electrolyte
    • 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 a lithium ion battery and relates to the technical field of secondary batteries.
  • lithium-ion batteries Since the commercialization of lithium-ion batteries, due to its high specific energy and good cycle performance, it has been widely used in digital fields such as notebooks and mobile phones. However, with the continuous improvement of human demand for electronic equipment, higher requirements are put forward for the energy density of lithium-ion batteries.
  • the energy density of lithium-ion batteries is related to the volume, discharge voltage platform and discharge capacity of lithium-ion batteries. Therefore, increasing the discharge voltage platform of lithium-ion batteries has become one of the effective means to increase energy density.
  • the present application provides a lithium ion battery, which is used to improve the cycle performance of the lithium ion battery under high voltage.
  • the present application provides a lithium ion battery
  • the lithium ion battery includes a positive electrode active material
  • the positive electrode active material includes doped with Al, Mg, Ti, Zr, Ni, Mn, Y, La, Sr, W, Sc Lithium cobaltate particles of one or more elements
  • the lithium ion battery is at 0% SOC
  • the molar ratio of lithium element to cobalt element in the positive electrode active material is A
  • the lithium ion battery is at 100% SOC
  • the molar ratio of lithium element to cobalt element in the positive electrode active material is B, 0.62 ⁇ A-B ⁇ 0.655.
  • the application provides a lithium ion battery, which includes a positive electrode active material, the positive electrode active material includes doped with one of Al, Mg, Ti, Zr, Ni, Mn, Y, La, Sr, W, Sc or Lithium cobaltate particles of various elements, doping lithium cobaltate particles with elements can help improve the structural stability of the positive active material, and at the same time, the structural stability of the positive active material is also affected by the charging and discharging system.
  • the lithium-ion battery including the positive active material has good cycle performance, otherwise, the cycle performance of the lithium-ion battery cannot meet the needs of use, and it is necessary to adjust the positive active material or the charging and discharging system accordingly to meet 0.62 ⁇ A-B ⁇ 0.655, the high voltage referred to in this application means that the charge cut-off voltage of the lithium ion battery is above 4.4V.
  • the present application provides a lithium-ion battery.
  • the lithium-ion battery is at 0% SOC
  • the molar ratio of the lithium element to the cobalt element in the positive electrode active material is A
  • the lithium-ion battery is at 100% SOC.
  • the molar ratio of lithium element to cobalt element in the positive electrode active material is B, 0.62 ⁇ A-B ⁇ 0.655, it means that the lithium ion battery has better cycle performance under high voltage.
  • the positive electrode active material in order to improve the structural stability of the positive electrode active material, can also be coated, specifically, the positive electrode active material also includes coating at least partially outside the lithium cobaltate particles.
  • a coating layer on the surface, the coating layer includes one or more of metal fluorides, metal oxides, metal borate compounds, and metal phosphate compounds.
  • the positive active material is prepared by the following preparation method:
  • the lithium cobaltate particles with M element, the M element being one or more of Al, Mg, Ti, Zr, Ni, Mn, Y, La, Sr, W, Sc;
  • the present application provides a method for preparing a positive electrode active material. Firstly, the lithium cobaltate particles are element-doped, and then a suitable coating material is selected to coat the lithium cobalt oxide particles doped with M element to obtain a positive electrode active material.
  • a suitable coating material is selected to coat the lithium cobalt oxide particles doped with M element to obtain a positive electrode active material.
  • Step 1 Doping the lithium cobaltate particles with M element specifically includes:
  • Step 1-1 dissolving a cobalt source, a complexing agent and a soluble base containing carbonate in a solvent, mixing and reacting to obtain a cobalt carbonate;
  • the cobalt source is selected from one or more of cobalt acetate, cobalt oxalate, cobalt nitrate, cobalt sulfate, cobalt chloride, cobalt hydroxide
  • the complexing agent can be ammonia water, the concentration of ammonia water is 20%- 25%
  • the soluble base containing carbonate is selected from one or more of Na 2 CO 3 , NH 4 HCO 3 , (NH 4 ) 2 CO 3
  • the solvent can be deionized water, and the above materials are dissolved in In the water, the concentration of the cobalt source is 0.8-3.8mol/L, and the concentration of the soluble base is 0.8-3.8mol/L.
  • the soluble base containing carbonate reacts with the cobalt source to form cobalt carbon Salt precipitation, the temperature of the reaction is 30-80°C, and the reaction time is 10-20 hours;
  • Step 1-2 calcining the cobalt carbonate to obtain a precursor
  • Cobalt carbonate is calcined at high temperature to obtain a precursor, the temperature of the calcining is 920-1000°C, and the calcining time is 8-12h.
  • Step 1-3 mixing and calcining the lithium source, the precursor, and the compound containing the M element;
  • the lithium source, the precursor, and the compound containing the M element are mixed and calcined to obtain lithium cobaltate particles doped with the M element, wherein the lithium source is selected from lithium hydroxide, lithium nitrate, lithium carbonate, lithium oxalate, acetic acid One or more of lithium, lithium oxide, lithium citrate; the compound containing M element is the oxide, chloride, hydroxide, carbonate, sulfate, nitrate, oxalate of M element , one or more of acetate;
  • the calcination temperature is 900-1050°C, and the calcination time is 8-12h.
  • Step 2 coating one or more of metal fluorides, metal oxides, metal borate compounds, and metal phosphate compounds on at least part of the surface of lithium cobaltate particles doped with M element to form a coating layer :
  • One or more of metal fluoride, metal oxide, metal borate compound, metal phosphate compound and lithium cobalt oxide particles doped with M element are mixed and calcined, so that the coating material is coated on the cobalt acid at least a part of the surface of the lithium particle to obtain the positive electrode active material.
  • the metal fluoride is selected from one or more of AlF 3 , Li 3 F, and MgF; the metal oxide is selected from one or more of Al 2 O 3 , TiO 2 , ZrO 2 , and MgO. species; the metal borate compound is AlBO 3 ; the metal phosphate compound is selected from one or both of AlPO 4 and Li 3 PO 4 .
  • the calcination temperature is 800-1000°C, and the calcination time is 6-9h.
  • the coating material and lithium cobaltate particles doped with M element can be physically mixed before calcination, and the physical mixing can be one of stirring, ball milling, grinding or Various, physical mixing time is 2-4h.
  • the thickness of the cladding layer is not easy to be too high, otherwise it will cause the transport of Li + to be blocked during the charging and discharging process, thereby affecting the rate performance and low temperature performance of the lithium-ion battery.
  • the thickness of the cladding layer is not greater than 50nm Those skilled in the art can control the amount of coating material added according to the requirements of the thickness of the coating layer, specifically, the mass of the coating layer is not greater than 1% of the total mass of the positive electrode active layer materials.
  • the positive electrode active material helps to improve the structural stability of the positive electrode active material. Therefore, in order to further improve the cycle performance of the lithium-ion battery, the positive electrode active material includes the Al element, and with the increase in the doping amount of the Al element The stability of the positive electrode active material is also improved, and A-B is reduced. Therefore, the doping amount of the Al element is not less than 3500ppm, that is, the content of the Al element/the total content of the positive electrode active material is greater than or equal to 3500ppm.
  • the compound containing Al element may be aluminum salt and/or aluminum oxide, for example, the compound containing Al element may be one or more of Al 2 (SO 4 ) 3 , AlCl 3 , Al 2 O 3 , which The addition amount can be adjusted according to the content of Al element.
  • the positive active material can be obtained by the above method. Since the final particle size distribution of the positive active material affects the compaction of the positive electrode sheet and the performance of the lithium-ion battery, the average particle size of the positive active material is 8.0-15.0 ⁇ m According to this, those skilled in the art can select the particle size of the raw material or grind the calcined positive electrode active material to meet the requirement of the particle size of the final active material.
  • the positive electrode active material can be obtained by grading large particles and small particles.
  • Large particles refer to particles with an average particle size of 8.0-18.0 ⁇ m
  • small particles refers to particles with an average particle size of 2.0-6.0 ⁇ m.
  • the positive electrode active material, the conductive agent and the binder are dispersed in the solvent to prepare the positive electrode active layer slurry, and evenly coated on the surface of the positive electrode current collector to obtain the positive electrode sheet, specifically, the positive electrode
  • the active layer slurry includes 70-99wt.% positive electrode active material, 0.5-15wt.% conductive agent and 0.5-15wt.% binder according to mass percentage; further, the positive electrode active layer slurry is based on mass percent
  • the component content includes 80-98wt.% positive electrode active material, 1-10wt.% conductive agent, and 1-10wt.% binder.
  • the conductive agent is selected from one or more of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotube, metal powder, and carbon fiber;
  • the binder is selected from polyvinylidene fluoride (PVDF ), polytetrafluoroethylene (PTFE), polyacrylate lithium (PAALi) in one or more.
  • Lithium-ion battery also includes negative electrode sheet, diaphragm and electrolyte, specifically, negative electrode sheet includes negative electrode current collector and negative electrode active layer, and negative electrode active layer includes negative electrode active material, conductive agent and binding agent, and the preparation method of negative electrode active layer and The preparation method of the positive electrode active layer is the same, and the negative electrode active layer slurry includes 70-99wt.% of the negative electrode active material, 0.5-15wt.% of the conductive agent, and 0.5-15wt.% of the binder according to the mass percentage, further The negative electrode active layer slurry includes 80-98wt.% negative electrode active material, 1-10wt.% conductive agent and 1-10wt.% binder according to mass percentage.
  • the choice of conductive agent and binder is the same as that of the positive electrode sheet, and the negative electrode active material is selected from one or more of artificial graphite, natural graphite, hard carbon, mesocarbon microspheres, lithium titanate, silicon carbon, and silicon oxide .
  • the electrolytic solution includes a non-aqueous solvent, a conductive lithium salt and an additive, and the non-aqueous solvent is a mixture of cyclic carbonates and at least one of linear carbonates and linear carboxylates mixed in any proportion;
  • the cyclic Carbonic acid ester is selected from ethylene carbonate and/or propylene carbonate, and described linear carbonate is selected from one or more in dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate, and described linear carboxylic acid ester One or more selected from ethyl propionate, propyl propionate and propyl acetate;
  • the conductive lithium salt is selected from lithium hexafluorophosphate, lithium bisfluorosulfonimide, lithium bistrifluoromethanesulfonylimide One or more of them;
  • the additives include one or more of nitrile compounds, vinylene carbonate, 1,3-propene sultone;
  • the volume fraction of the cyclic carbonate is 20-40vol%, and the volume fraction of the linear carbonate and/or linear carboxylate is 60-80vol%.
  • the diaphragm is a polypropylene film, or a polypropylene film with at least one surface coated with ceramic.
  • the positive electrode sheet, diaphragm, and negative electrode sheet are prepared by lamination process or winding process to obtain a battery cell, and after packaging, the electrolyte solution can be injected to obtain a lithium ion battery.
  • Those skilled in the art can carry out according to conventional technical means, and then the lithium ion battery can be processed.
  • the charge-discharge system of the ion battery is explored, and the inventor has found that in the process of charging and discharging the lithium-ion battery, the charge cut-off voltage, the charge cut-off current, and the charge-discharge temperature are important factors that affect A-B. For example, as the charge cut-off voltage As the charge and discharge temperature increases, A-B also increases gradually.
  • A-B With the increase of charge cut-off current, A-B gradually decreases. With the continuous increase of charge and discharge temperature, A-B continues to increase.
  • the charging cut-off voltage of the lithium-ion battery is less than 4.5V; the charging cut-off current of the lithium-ion battery is not less than 0.02C; the charge-discharge temperature of the lithium-ion battery is less than 45°C.
  • the lithium ion battery After determining the appropriate charging and discharging system, the lithium ion battery is charged and discharged according to the charging and discharging system.
  • the lithium ion battery When the lithium ion battery is at 0% SOC, the molar ratio of lithium element to cobalt element in the positive electrode active material is A, and the Lithium-ion battery is under 100% SOC, and the molar ratio of lithium element and cobalt element in positive electrode active material is B, and when 0.62 ⁇ A-B ⁇ 0.655, then shows that the lithium-ion battery comprising this positive electrode active material has comparatively good performance under this charging and discharging system. Good cycle performance, otherwise it is necessary to adjust the amount of doping and coating in the positive active material and/or the charging and discharging system to meet the requirements of 0.62 ⁇ A-B ⁇ 0.655.
  • the molar ratio of lithium element to cobalt element in the positive electrode active material can be obtained according to the ICP test.
  • the present application provides a lithium-ion battery.
  • the lithium-ion battery is at 0% SOC
  • the molar ratio of the lithium element to the cobalt element in the positive electrode active material is A
  • the lithium-ion battery is at 100% SOC.
  • the molar ratio of lithium element to cobalt element in the positive electrode active material is B, and 0.62 ⁇ A-B ⁇ 0.655
  • the lithium ion battery has better cycle performance.
  • This embodiment provides a lithium-ion battery, including a positive electrode sheet, a separator, a negative electrode sheet and an electrolyte, the positive electrode sheet includes an aluminum foil and a positive active layer, the positive active layer includes a positive active material, and the negative sheet includes a copper foil and a negative active layer.
  • the positive electrode active layer includes a positive electrode active material, the positive electrode active material includes lithium cobalt oxide particles doped with three elements of Al, Mg, and Ti, and a coating layer, and the coating layer includes magnesium oxide and titanium oxide.
  • Step 1-1 dissolving CoCl2 with an aqueous solution, preparing a salt solution with a concentration of Co2 + of 1.25mol/L, and preparing a complexing agent solution (with a concentration of 2- 2.5%), dissolving sodium carbonate in an aqueous solution to prepare a 1.2mol/L sodium carbonate solution; inject 1/3 of the sodium carbonate solution into the reactor, and use parallel flow to control the flow rate under strong stirring and inert gas protection
  • the method continues to inject the above-mentioned cobalt salt solution, complexing agent solution and the remaining 2/3 sodium carbonate solution into the reactor at the same time, and the flow rate of the parallel flow control is not more than 200L/h, while stirring, the stirring speed is not more than 200rpm, And control the pH value of the reaction system to 6-12, control the temperature of the reaction kettle at 70-80°C during the reaction process; monitor the liquid phase ion concentration of the Co element in the reaction system in real time during the reaction process, and repeat the crystallization three times after continuous reaction
  • Step 1-2 put the above-mentioned cobalt carbonate CoCO 3 in a muffle furnace for calcination, the calcination temperature is 930°C, and the time is 10h, and then the calcined product is pulverized to obtain a precursor Co 3 O with uniform particle distribution 4 ;
  • the average particle size of the positive electrode active material was 14.5 ⁇ m.
  • the positive electrode active material Disperse 97 parts by mass of the positive electrode active material, 1.5 parts by mass of the conductive agent Super-P and 1.5 parts by mass of the binder polyvinylidene fluoride (PVDF) in N-methylpyrrolidone (NMP) to prepare the positive electrode active layer Slurry, the slurry is evenly coated on the surface of the aluminum foil, and then rolled up after being baked in a five-stage oven.
  • the current collector coated with the positive electrode active layer slurry was baked in an oven at 100°C for 8 hours, and the solvent in the positive electrode active layer slurry was completely evaporated, and then rolled to obtain a compacted density of 4.1g/cm 3 .
  • Positive sheet Disperse 97 parts by mass of the positive electrode active material, 1.5 parts by mass of the conductive agent Super-P and 1.5 parts by mass of the binder polyvinylidene fluoride (PVDF) in N-methylpyrrolidone (NMP) to prepare the positive electrode active layer Slurry, the
  • negative electrode active material artificial graphite (average particle size: 13 ⁇ 1 ⁇ m, degree of graphitization 94 ⁇ 0.5%, secondary particles mixed with single particles, wherein the secondary particle mass accounts for 50%)
  • 1 mass Parts of superconducting carbon black (Super-P) 1.5 parts by mass of sodium carboxymethyl cellulose (CMC) and 1.5 parts by mass of styrene-butadiene rubber (SBR) are dispersed in a solvent to prepare negative electrode active layer slurry, and the negative electrode
  • the active layer slurry was coated on an 8 ⁇ m copper foil and dried at a temperature of 100°C. After baking for 4 hours, it was rolled and pressed to obtain a negative electrode sheet with a compacted density of 1.68 g/cm 3 .
  • the diaphragm is single-sided ceramic + double-sided oily LBG glued diaphragm;
  • Electrolyte comprises nonaqueous organic solvent, lithium salt and additive, and wherein, nonaqueous organic solvent comprises ethylene carbonate (EC), propylene carbonate (PC) and dimethyl carbonate (DMC) (mass ratio is 1:1:1 ), the lithium salt is LiPF 6 , the additives include 4wt.% 1,3-propene sultone, 6wt.% vinylene carbonate, 1wt.% succinonitrile, 2wt.% adiponitrile.
  • nonaqueous organic solvent comprises ethylene carbonate (EC), propylene carbonate (PC) and dimethyl carbonate (DMC) (mass ratio is 1:1:1 )
  • the lithium salt is LiPF 6
  • the additives include 4wt.% 1,3-propene sultone, 6wt.% vinylene carbonate, 1wt.% succinonitrile, 2wt.% adiponitrile.
  • the positive electrode sheet, negative electrode sheet, and separator are wound into batteries, packaged with aluminum-plastic film, in a nitrogen-protected oven, controlled at 120°C, baked for 36 hours, injected electrolyte, and carried out chemical separation and other processes. Finally, a soft pack lithium-ion battery with a capacity of 5Ah was obtained.
  • the lithium-ion battery is cycle tested with the above charging and discharging system, namely 0.7C/0.7C, 0.1C cut-off, voltage range 3.0-4.45V, temperature 25°C, and the capacity retention rate is tested after 500T cycle.
  • the ICP test was carried out on the positive electrode active material, and the test results showed that the total content of Al in the positive electrode active material was 4500 ppm, the total content of Mg was 1500 ppm, and the total content of Ti was 1500 ppm.
  • the ICP test method specifically includes the following steps:
  • the lithium-ion battery provided in this example is the same as that in Example 1, except that the charging and discharging system is different. Specifically, at 25°C, the battery is discharged to 3.0V at a rate of 0.7C, and the battery is disassembled to test its Li and the content of Co, calculate A; charge at a constant current rate of 0.7C to 4.45V, then carry out constant voltage charging, the cut-off current is 0.05C, disassemble the battery in this state to test its Li and Co content, calculate get B.
  • the lithium-ion battery is cycle tested with the above charging and discharging system, that is, 0.7C/0.7C, 0.05C cut-off, voltage range 3.0-4.45V, temperature 25°C, and the capacity retention rate is tested after 500T cycle.
  • the lithium-ion battery provided in this example is the same as that in Example 1, except that the charging and discharging system is different. Specifically, at 25°C, the battery is discharged to 3.0V at a rate of 0.7C, and the battery is disassembled to test its Li and the content of Co, calculate A; charge at a constant current rate of 0.7C to 4.45V, then charge at a constant voltage, with a cut-off current of 0.02C, disassemble the battery in this state to test its Li and Co content, and calculate get B.
  • the lithium-ion battery is cycle tested with the above charge and discharge system, namely 0.7C/0.7C, 0.02C cut-off, voltage range 3.0-4.45V, temperature 25°C, and the capacity retention rate is tested after a cycle of 500T.
  • the lithium-ion battery provided in this example is the same as that in Example 1, except that the charging and discharging system is different. Specifically, at 25°C, the battery is discharged to 3.0V at a rate of 0.7C, and the battery is disassembled to test its Li and the content of Co, calculate A; charge at a constant current rate of 0.7C to 4.4V, then charge at a constant voltage, with a cut-off current of 0.05C, disassemble the battery in this state to test its Li and Co content, and calculate get B.
  • the lithium-ion battery is cycle tested with the above charging and discharging system, that is, 0.7C/0.7C, 0.05C cut-off, voltage range 3.0-4.4V, temperature 25°C, and the capacity retention rate is tested after a cycle of 500T.
  • the lithium-ion battery provided in this example is the same as that in Example 1, except that the charging and discharging system is different. Specifically, at 25°C, the battery is discharged to 3.0V at a rate of 0.7C, and the battery is disassembled to test its Li and the content of Co, calculate A; charge at a constant current rate of 0.7C to 4.48V, then charge at a constant voltage, with a cut-off current of 0.05C, disassemble the battery in this state to test its Li and Co content, and calculate get B.
  • the lithium-ion battery is cycle tested with the above charging and discharging system, that is, 0.7C/0.7C, 0.05C cut-off, voltage range 3.0-4.48V, temperature 25°C, and the capacity retention rate is tested after 500T cycle.
  • the lithium-ion battery provided in this example is the same as that in Example 1, except that the charging and discharging system is different. Specifically, at 25°C, the battery is discharged to 3.0V at a rate of 0.7C, and the battery is disassembled to test its Li and the content of Co to calculate A; at 10°C, charge at a constant current rate of 0.7C to 4.45V, then charge at a constant voltage with a cut-off current of 0.05C, and disassemble the cell in this state to test its Li and Co content, calculated to get B.
  • the lithium-ion battery is cycle tested with the above charging and discharging system, that is, 0.7C/0.7C, 0.05C cut-off, voltage range 3.0-4.45V, temperature 10°C, and the capacity retention rate is tested after 500T cycle.
  • the lithium-ion battery provided in this example is the same as that in Example 1, except that the charging and discharging system is different. Specifically, at 25°C, the battery is discharged to 3.0V at a rate of 0.7C, and the battery is disassembled to test its Li and the content of Co to calculate A; at 35°C, charge at a constant current rate of 0.7C to 4.45V, then charge at a constant voltage with a cut-off current of 0.05C, and disassemble the cell in this state to test its Li and Co content, calculated to get B.
  • the lithium-ion battery is cycle tested with the above charging and discharging system, namely 0.7C/0.7C, 0.05C cut-off, voltage range 3.0-4.45V, temperature 35°C, and the capacity retention rate is tested after 500T cycle.
  • the lithium ion battery provided in this embodiment can refer to Embodiment 2, the difference is that the total content of Al in the positive electrode active material is 3500 ppm, the total content of Mg is 1500 ppm, and the total content of Ti is 1500 ppm.
  • the lithium-ion battery was charged and discharged using the charging and discharging system provided in Example 2, and the capacity retention rate was tested.
  • the lithium ion battery provided in this embodiment can refer to Embodiment 2, the difference is that the total content of Al in the positive electrode active material is 4000ppm, the total content of Mg is 1500ppm, and the total content of Ti is 1500ppm.
  • the lithium-ion battery was charged and discharged using the charging and discharging system provided in Example 2, and the capacity retention rate was tested.
  • the lithium ion battery provided in this embodiment can refer to Embodiment 2, the difference is that the total content of Al in the positive electrode active material is 5000 ppm, the total content of Mg is 1500 ppm, and the total content of Ti is 1500 ppm.
  • the lithium-ion battery was charged and discharged using the charging and discharging system provided in Example 2, and the capacity retention rate was tested.
  • the lithium ion battery provided in this embodiment can refer to Example 2, the difference is that the total content of Al in the positive electrode active material is 5500ppm, the total content of Mg is 1500ppm, and the total content of Ti is 1500ppm.
  • the lithium-ion battery was charged and discharged using the charging and discharging system provided in Example 2, and the capacity retention rate was tested.
  • the lithium-ion battery provided in this embodiment may refer to Embodiment 2, except that the total content of Al in the positive electrode active material is 6000 ppm, the total content of Mg is 1500 ppm, and the total content of Ti is 1500 ppm.
  • the lithium-ion battery was charged and discharged using the charging and discharging system provided in Example 2, and the capacity retention rate was tested.
  • the lithium ion battery provided in this embodiment can refer to Embodiment 2, the difference is that the total content of Al in the positive electrode active material is 7000ppm, the total content of Mg is 1500ppm, and the total content of Ti is 1500ppm.
  • the lithium-ion battery was charged and discharged using the charging and discharging system provided in Example 2, and the capacity retention rate was tested.
  • the positive electrode active material provided in this comparative example is lithium cobaltate, and the preparation and charging and discharging system of the lithium ion battery can refer to Example 2.
  • the preparation method of the positive electrode active material provided in this comparative example includes the following preparation steps:
  • Step 1 Dissolve CoCl2 in an aqueous solution to prepare a solution with a Co2 + concentration of 1.25mol/L, and add ammonia solution (concentrated ammonia water and distilled water are configured in a volume ratio of 1:10) and sodium carbonate solution (1.2mol/L L) carry out complex precipitation reaction after mixing, carry out centrifugation after continuous reaction repeats crystallization 3 times, obtain the carbonate CoCO of cobalt;
  • Step 2 Calcining cobalt carbonate in a muffle furnace at a temperature of 930° C. for 10 hours, and then pulverizing the calcined product to obtain a precursor Co 3 O 4 with uniform particle distribution;
  • the calcination temperature was 1035°C and the calcination time was 11 hours.
  • the calcined product is pulverized to obtain LiCoO 2 .
  • the lithium-ion battery provided in this comparative example is the same as that in Example 1, except that the charging and discharging system is different. Specifically, at 25°C, the battery is discharged to 3.0V at a rate of 0.7C, and the battery is disassembled to test its Li and the content of Co, calculate A; charge at a constant current rate of 0.7C to 4.45V, then charge at a constant voltage, with a cut-off current of 0.01C, disassemble the battery in this state to test its Li and Co content, and calculate get B.
  • the lithium-ion battery is cycle tested with the above charging and discharging system, that is, 0.7C/0.7C, 0.01C cut-off, voltage range 3.0-4.45V, temperature 25°C, and the capacity retention rate is tested after 500T cycle.
  • the lithium-ion battery provided in this comparative example is the same as that in Example 1, except that the charging and discharging system is different. Specifically, at 25°C, the battery is discharged to 3.0V at a rate of 0.7C, and the battery is disassembled to test its Li and the content of Co to calculate A; at the same time, charge the batteries of the same group to 4.5V at a rate of 0.7C, and then charge them at a constant voltage with a cut-off current of 0.05C, and disassemble the batteries in this state Test the content of Li and Co, and calculate B.
  • the lithium-ion battery is cycle tested with the above charging and discharging system, namely 0.7C/0.7C, 0.05C cut-off, voltage range 3.0-4.5V, temperature 25°C, and the capacity retention rate is tested after 500T cycle.
  • the lithium-ion battery provided in this comparative example is the same as that in Example 1, except that the charging and discharging system is different. Specifically, at 25°C, the battery is discharged to 3.0V at a rate of 0.7C, and the battery is disassembled to test its Li and the content of Co, calculate A; charge at a constant current rate of 0.7C to 4.55V, then charge at a constant voltage, with a cut-off current of 0.05C, disassemble the battery in this state to test its Li and Co content, and calculate get B.
  • the lithium-ion battery is cycle tested with the above charge and discharge system, that is, 0.7C/0.7C, 0.05C cut-off, voltage range 3.0-4.55V, temperature 25°C, and the capacity retention rate is tested after a cycle of 500T.
  • the lithium-ion battery provided in this comparative example is the same as that in Example 1, except that the charging and discharging system is different. Specifically, at 25°C, the battery is discharged to 3.0V at a rate of 0.7C, and the battery is disassembled to test its Li and the content of Co to calculate A; at 45°C, charge at a constant current rate of 0.7C to 4.45V, and then charge at a constant voltage with a cut-off current of 0.05C. Disassemble the battery in this state to test its Li and Co content, calculated to get B.
  • the lithium-ion battery is cycle tested with the above charging and discharging system, namely 0.7C/0.7C, 0.05C cut-off, voltage range 3.0-4.45V, temperature 45°C, and the capacity retention rate is tested after 500T cycle.
  • the lithium-ion battery provided in this comparative example is the same as that in Example 1, except that the charging and discharging system is different. Specifically, at 25°C, the battery is discharged to 3.0V at a rate of 0.7C, and the battery is disassembled to test its Li and the content of Co to calculate A; at 55°C, charge at a constant current rate of 0.7C to 4.45V, then charge at a constant voltage with a cut-off current of 0.05C, and disassemble the cell in this state to test its Li and Co content, calculated to get B.
  • the lithium-ion battery is cycle tested with the above charging and discharging system, that is, 0.7C/0.7C, 0.05C cut-off, voltage range 3.0-4.45V, temperature 55°C, and the capacity retention rate is tested after 500T cycle.
  • Table 2-5 lists the positive electrode active material and charge-discharge system provided by Examples 1-13 and Comparative Examples 1-6 respectively, and shows the lithium ions provided by Examples 1-13 and Comparative Examples 1-6.
  • the capacity retention rate of the battery is used to make the differences and effects of the embodiments provided in this application more intuitive.
  • Example 1 0.926 0.301 0.625 93.01% 0.1C
  • Example 2 0.926 0.287 0.639 91.46% 0.05C
  • Example 3 0.926 0.280 0.646 88.44% 0.02C
  • the lithium-ion battery is cycled within the voltage range of 3.0-4.45V at 25°C to ensure that its charge and discharge rate is consistent, and its charge cut-off current is adjusted to 0.1C, 0.05C, 0.02C, and 0.01C, according to Example 1- 3 and the data provided by Comparative Example 2, it can be seen that as the charging cut-off current becomes smaller, A-B becomes larger, the capacity retention rate decreases, and the cycle performance becomes worse.
  • the lithium-ion battery is charged and discharged at a rate of 0.7C/0.7C at 25°C, the charge cut-off current is 0.05C, and the cut-off voltage is adjusted to 4.4V, 4.45V, 4.48V, 4.5V, 4.55V, according to
  • Example 2 0.926 0.287 0.639 95.08% 25°C
  • Example 6 0.926 0.310 0.615 96.44% 10°C
  • Example 7 0.926 0.279 0.646 92.69% 35°C Comparative example 1 0.913 0.253 0.660 91.62% 25°C Comparative example 5 0.926 0.245 0.681 90.48% 45°C Comparative example 6 0.926 0.205 0.721 85.25% 55°C
  • Example 2 0.926 0.287 0.639 91.46% 4500
  • Example 8 0.921 0.266 0.655 88.22% 3500
  • Example 9 0.925 0.274 0.651 89.81% 4000
  • Example 10 0.929 0.302 0.627 92.12% 5000
  • Example 11 0.931 0.311 0.62 93.01% 5500
  • Example 12 0.934 0.317 0.617 94.98% 6000
  • Example 13 0.936 0.335 0.601 96.14% 7000 Comparative example 1 0.913 0.253 0.66 86.74% 0
  • the doping amount of Al element in the positive electrode active material is adjusted to 3500, 4000, 4500, 5000, 5500, 6000, 7000ppm, and the lithium ion battery including the above positive electrode active material is charged and discharged under the same conditions. According to the embodiment 2. From the data provided in 8-13, it can be seen that with the increase of the doping amount of Al element in the positive electrode active material, A-B decreases, the capacity retention rate increases, and the cycle performance becomes better.
  • the lithium-ion battery when the lithium-ion battery is at 0% SOC, the molar ratio of lithium element to cobalt element in the positive electrode active material is A, and at 100% SOC, the molar ratio of lithium element to cobalt element in the positive electrode active material is When B, 0.62 ⁇ A-B ⁇ 0.655, the lithium-ion battery has better cycle performance.

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Abstract

本申请提供一种锂离子电池，所述锂离子电池包括正极活性物质，所述正极活性物质包括掺杂有Al、Mg、Ti、Zr、Ni、Mn、Y、La、Sr、W、Sc中的一种或多种元素的钴酸锂颗粒，所述锂离子电池在0％SOC下，所述正极活性物质中锂元素与钴元素的摩尔比为A，所述锂离子电池在100％SOC下，所述正极活性物质中锂元素与钴元素的摩尔比为B，0.62≤A-B≤0.655。本申请提供的锂离子电池在高电压下具有较好的循环性能。

Description

一种锂离子电池
本申请要求于2021年06月21日提交中国专利局、申请号为202110687062.4、申请名称为“一种锂离子电池”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及一种锂离子电池，涉及二次电池技术领域。
背景技术
自锂离子电池从商业化以来，由于它的比能量高、循环性能好，被广泛用于笔记本、手机等数码领域。但是，随着人类对电子设备需求的不断提高，对锂离子电池的能量密度也随之提出了更高的要求，锂离子电池的能量密度与锂离子电池的体积、放电电压平台以及放电容量有很大的关系，因此提升锂离子电池的放电电压平台成为提升能量密度的有效手段之一。
然而，当锂离子电池充电到4.2V以上时，正极活性物质LiCoO 2中的锂离子脱出并形成Li 1-xCoO 2(0≤x≤0.5)，当充电电压提高至4.4V以上时，更多的锂离子从正极活性物质中脱出，脱出锂离子后的LiCoO 2也由六方晶系不断向单斜晶系转变，而转变后的单斜晶系的LiCoO 2将不再具有可逆的锂离子脱嵌能力，同时，当锂离子电池的充电电压达到4.4V及以上后，正极活性物质与电解液的副反应也会逐渐加剧，因此，随着充电电压的不断提高，正极活性物质的可逆容量不断降低，导致锂离子电池的循环性能变差，限制了锂离子电池的应用，这也是目前商业应用的正极活性物质钴酸锂的可逆容量远小于其理论容量(274mAh/g)的重要原因之一，因此，如何在高电压下提高锂离子电池的循环性能，成为了本领域技术人员亟待解决的技术问题。
发明内容
本申请提供一种锂离子电池，用于提高锂离子电池在高电压下的循环性能。
本申请提供一种锂离子电池，所述锂离子电池包括正极活性物质，所述正极活性物质包括掺杂有Al、Mg、Ti、Zr、Ni、Mn、Y、La、Sr、W、Sc中的一种或多种元素的钴酸锂颗粒，所述锂离子电池在0％SOC下，所述正极活性物质中锂元素与钴元素的摩尔比为A，所述锂离子电池在100％SOC下，所述正极活性物质中锂元素与钴元素的摩尔比为B，0.62≤A-B≤0.655。
本申请提供一种锂离子电池，其包括正极活性物质，所述正极活性物质包括掺杂有Al、Mg、Ti、Zr、Ni、Mn、Y、La、Sr、W、Sc中的一种或多种元素的钴酸锂颗粒，对钴酸锂颗粒进行元素掺杂有助于提高正极活性物质的结构稳定性，同时，正极活性物质的结构稳定性还受到充放电制度的影响，当使用一定的充放电制度对包括上述正极活性物质的锂离子电池进行充放电时，在0％SOC下，测试正极活性物质中锂元素与钴元素的摩尔比，记为A，在100％SOC下，测试正极活性物质中锂元素与钴元素的摩尔比，记为B，当0.62≤A-B≤0.655时，则表明包括该正极活性物质的锂离子电池在该充放电制度下，正极活性物质具有较好的结构稳定性，包括该正极活性物质的锂离子电池具备较好的循环性能，否则，锂离子电池的循环性能无法满足使用需求，需要对正极活性物质或者充放电制度进行相应的调整以满足0.62≤A-B≤0.655，本申请所指的高电压是指锂离子电池的充电截止电压在4.4V以上。综上，本申请提供一种锂离子电池，当所述锂离子电池在0％SOC下，所述正极活性物质中锂元素与钴元素的摩尔比为A，所述锂离子电池在100％SOC下，所述正极活性物质中锂元素与钴元素的摩尔比为B，0.62≤A-B≤0.655时，则说明该锂离子电池在高电压下具有较好的循环性能。
在一种具体实施方式中，为了提高正极活性物质的结构稳定性，还可以对正极活性物质进行包覆，具体地，所述正极活性物质还包括包覆在所述钴酸锂颗粒至少部分外表面的包覆层，所述包覆层包括金属氟化物、金属氧化物、金属硼酸盐化合物、金属磷酸盐化合物中的一种或多种。
在具体实施过程中，本领域技术人员可以选择对钴酸锂颗粒进行掺杂，或者同时进行掺杂和包覆，本申请主要以对钴酸锂颗粒进行掺杂包覆为例对正极活性物质进行详细阐述，具体地，所述正极活性物质通过如下制备方法制备得到：
对钴酸锂颗粒进行M元素的掺杂，所述M元素为Al、Mg、Ti、Zr、Ni、 Mn、Y、La、Sr、W、Sc中的一种或多种；
将金属氟化物、金属氧化物、金属硼酸盐化合物、金属磷酸盐化合物中的一种或多种包覆在掺杂有M元素的钴酸锂颗粒的至少部分表面形成包覆层，得到所述正极活性物质。
本申请提供了一种正极活性物质的制备方法，首先对钴酸锂颗粒进行元素掺杂，随后选择合适的包覆材料对掺杂有M元素的钴酸锂颗粒进行包覆得到正极活性物质，以下结合制备过程对正极活性物质进行详细阐述：
步骤1、对钴酸锂颗粒进行M元素的掺杂具体包括：
步骤1-1、将钴源、络合剂和含有碳酸根的可溶性碱溶于溶剂中混合并进行反应，得到钴的碳酸盐；
具体地，所述钴源选自乙酸钴、草酸钴、硝酸钴、硫酸钴、氯化钴、氢氧化钴中的一种或多种，络合剂可以为氨水，氨水的浓度为20％-25％，所述含有碳酸根的可溶性碱选自Na 2CO 3、NH 4HCO 3、(NH 4) 2CO 3中的一种或多种，溶剂可以为去离子水，将上述材料溶于水中，钴源的浓度为0.8-3.8mol/L，所述可溶性碱的浓度为0.8-3.8mol/L，在络合剂的作用下，含有碳酸根的可溶性碱与钴源反应生成钴的碳酸盐沉淀，所述反应的温度为30-80℃，所述反应的时间为10-20小时；
步骤1-2、煅烧所述钴的碳酸盐，得到前驱体；
将钴的碳酸盐在高温下煅烧，得到前驱体，所述煅烧的温度为920-1000℃，所述煅烧的时间为8-12h。
步骤1-3、将锂源、前驱体、含有M元素的化合物进行混合煅烧；
将锂源、前驱体、含有M元素的化合物进行混合煅烧，得到掺杂有M元素的钴酸锂颗粒，其中，所述锂源选自氢氧化锂、硝酸锂、碳酸锂、草酸锂、醋酸锂、氧化锂、柠檬酸锂中的一种或多种；所述含有M元素的化合物为M元素的氧化物、氯化物、氢氧化物、碳酸盐、硫酸盐、硝酸盐、草酸盐、醋酸盐中的一种或多种；
所述煅烧的温度为900-1050℃，所述煅烧的时间为8-12h。
步骤2、将金属氟化物、金属氧化物、金属硼酸盐化合物、金属磷酸盐化合物中的一种或多种包覆在掺杂有M元素的钴酸锂颗粒的至少部分表面形成包覆层：
将金属氟化物、金属氧化物、金属硼酸盐化合物、金属磷酸盐化合物中的一种或多种与掺杂有M元素的钴酸锂颗粒进行混合煅烧，使包覆材料包覆在钴酸锂颗粒的至少部分表面，得到所述正极活性物质。
其中，所述金属氟化物选自AlF 3、Li 3F、MgF中的一种或多种；所述金属氧化物选自Al 2O 3，TiO 2，ZrO 2、MgO中的一种或多种；所述金属硼酸盐化合物为AlBO 3；所述金属磷酸盐化合物选自AlPO 4、Li 3PO 4中的一种或两种。
所述煅烧的温度为800-1000℃，所述煅烧的时间为6-9h。
为了使包覆材料包覆的更加均匀，可在煅烧前对包覆材料和掺杂有M元素的钴酸锂颗粒进行物理混合，所述物理混合可以是搅拌、球磨、研磨中的一种或多种，物理混合的时间为2-4h。
包覆层的厚度不易过高，否则会导致在充放电过程中，Li +的输运受阻，从而影响锂离子电池的倍率性能和低温性能，具体地，所述包覆层的厚度不大于50nm，本领域技术人员可根据包覆层厚度的要求控制包覆材料的添加量，具体地，所述包覆层的质量不大于所述正极活性层物质总质量的1％。
经发明人研究发现，Al元素有助于提高正极活性物质的结构稳定性，因此，为了进一步提高锂离子电池的循环性能，所述正极活性物质包括Al元素，且随着Al元素掺杂量的提高，正极活性物质的稳定性也提高，A-B降低，因此，所述Al元素的掺杂量不低于3500ppm，即Al元素的含量/正极活性物质的总含量≥3500ppm。
含有Al元素的化合物可以为铝盐和/或铝的氧化物，例如，含有Al元素的化合物可以为Al 2(SO 4) 3、AlCl 3、Al 2O 3中的一种或多种，其添加量可以根据Al元素的含量进行调整。
通过以上方法即可得到正极活性物质，由于正极活性物质最终的粒径分布影响到正极极片的压实以及锂离子电池的性能，因此，所述正极活性物质的平均粒径为8.0-15.0μm，本领域技术人员可据此选择原材料的粒径或者对煅烧后的正极活性物质进行研磨，以满足最终活性物质粒径的要求。
此外，为了兼顾锂离子电池的高低温性能以及正极片的压实，所述正极活性物质可由大颗粒和小颗粒级配得到，大颗粒是指平均粒径为8.0-18.0μm的颗粒，小颗粒是指平均粒径为2.0-6.0μm的颗粒。
在制备得到正极活性物质的基础上，将正极活性物质、导电剂和粘结剂分散于溶剂中制备得到正极活性层浆料，并均匀涂布在正极集流体表面得到正极片，具体地，正极活性层浆料按照质量百分含量包括70-99wt.％的正极活性物质、0.5-15wt.％的导电剂以及0.5-15wt.％的粘结剂；进一步地，正极活性层浆料按照质量百分含量包括80-98wt.％的正极活性物质、1-10wt.％的导电剂、1-10wt.％的粘结剂。
其中，导电剂选自导电炭黑、乙炔黑、科琴黑、导电石墨、导电碳纤维、碳纳米管、金属粉、碳纤维中的一种或多种；粘结剂选自聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、聚丙烯酸锂(PAALi)中的一种或多种。
锂离子电池中还包括负极片、隔膜和电解液，具体地，负极片包括负极集流体和负极活性层，负极活性层包括负极活性物质、导电剂和粘结剂，负极活性层的制备方法与正极活性层的制备方法相同，负极活性层浆料按照质量百分含量包括70-99wt.％的负极活性物质、0.5-15wt.％的导电剂、0.5-15wt.％的粘结剂，进一步地，负极活性层浆料按照质量百分含量包括80-98wt.％的负极活性物质、1-10wt.％的导电剂、1-10wt.％的粘结剂。
导电剂与粘结剂的选择与正极片相同，负极活性物质选自人造石墨、天然石墨、硬炭、中间相碳微球、钛酸锂、硅碳、氧化亚硅中的一种或多种。
所述电解液包括非水溶剂、导电锂盐和添加剂，非水溶剂为环状碳酸酯类与线性碳酸酯和线性羧酸酯两者中的至少一种按任意比例混合的混合物；所述环状碳酸酯选自碳酸乙烯酯和/或碳酸丙烯酯，所述线性碳酸酯选自碳酸二甲酯、碳酸二乙酯和碳酸甲乙酯中的一种或多种，所述线性羧酸酯选自丙酸乙酯、丙酸丙酯和乙酸丙酯中的一种或多种；所述导电锂盐选自六氟磷酸锂、双氟磺酰亚胺锂盐、双三氟甲烷磺酰亚胺锂中的一种或多种；所述添加剂包括腈类化合物、碳酸亚乙烯酯、1,3-丙烯磺酸内酯中的一种或多种；
以非水有机溶剂的总体积为100vol％为计，所述环状碳酸酯的体积分数为20-40vol％，所述线性碳酸酯和/或线性羧酸酯的体积分数为60-80vol％。
隔膜为聚丙烯薄膜，或至少一个表面涂覆有陶瓷的聚丙烯薄膜。
将正极片、隔膜、负极片采用叠片工艺或卷绕工艺制备得到电芯，并封装后注入电解液即可得到锂离子电池，本领域技术人员可依据常规技术手段进行，随后即可对锂离子电池的充放电制度进行探索，发明人研究发现，在 对锂离子电池进行充放电过程中，充电截止电压、充电截止电流、充放电温度是影响A-B的重要因素，例如，随着充电截止电压的升高，A-B也逐渐提高，随着充电截止电流的增大，A-B逐渐降低，随着充放电温度的不断升高，A-B不断增大，因此，在对锂离子电池进行充放电时，所述锂离子电池的充电截止电压小于4.5V；所述锂离子电池的充电截止电流不小于0.02C；所述锂离子电池的充放电温度小于45℃。
在确定好合适的充放电制度后，按照该充放电制度对锂离子电池进行充放电，当锂离子电池在0％SOC下，正极活性物质中锂元素与钴元素的摩尔比为A，所述锂离子电池在100％SOC下，正极活性物质中锂元素与钴元素的摩尔比为B，0.62≤A-B≤0.655时，则表明包括该正极活性物质的锂离子电池在该充放电制度下具有较好的循环性能，否则需调整正极活性物质中掺杂包覆量和/或充放电制度，以满足0.62≤A-B≤0.655的需要。
锂离子电池在0％SOC和100％SOC下，正极活性物质中锂元素与钴元素的摩尔比可以根据ICP测试得到。
综上，本申请提供一种锂离子电池，当所述锂离子电池在0％SOC下，所述正极活性物质中锂元素与钴元素的摩尔比为A，所述锂离子电池在100％SOC下，所述正极活性物质中锂元素与钴元素的摩尔比为B，0.62≤A-B≤0.655时，锂离子电池具有较好的循环性能。
具体实施方式
为使本申请的目的、技术方案和优点更加清楚，下面将结合本申请的实施例，对本申请实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
实施例1
本实施例提供了一种锂离子电池，包括正极片、隔膜、负极片和电解液，正极片包括铝箔和正极活性层，正极活性层包括正极活性物质，负极片包括铜箔和负极活性层，具体地：
正极活性层包括正极活性物质，正极活性物质包括掺杂有Al、Mg、Ti三种元素的钴酸锂颗粒以及包覆层，包覆层包括氧化镁和氧化钛。
本实施例提供的正极活性物质的制备方法包括如下步骤：
步骤1-1、将CoCl 2用水溶液溶解，配制得到Co 2+的浓度为1.25mol/L的盐溶液，将浓氨水和蒸馏水按体积比1：10配制成络合剂溶液(浓度为2-2.5％)，将碳酸钠溶于水溶液中配制得到1.2mol/L的碳酸钠溶液；在反应釜中注入1/3的碳酸钠溶液，在强力搅拌作用和惰性气体保护下，采用并流控制流量方式继续向反应釜中同时注入上述钴的盐溶液、络合剂溶液和剩余2/3的碳酸钠溶液，并流控制流量的速度不超过200L/h，同时进行搅拌，搅拌速度不超过200rpm，并控制反应体系的pH值为6-12，反应过程中控制反应釜的温度在70-80℃；反应过程中实时监控反应体系中Co元素的液相离子浓度，连续反应重复结晶3次后进行离心过滤，得到钴的碳酸盐CoCO 3，
步骤1-2、将上述钴的碳酸盐CoCO 3置于马弗炉中煅烧，煅烧温度为930℃，时间为10h，然后对煅烧产物进行粉碎处理，得到颗粒分布均匀的前驱体Co 3O 4；
步骤1-3、将制备得到的前驱体Co 3O 4、Li 2CO 3、Al 2(SO 4) 3、MgSO 4、TiO 2混合，其中Co：Al：Mg：Ti＝0.9935：0.0045：0.001：0.001，Li与Co的摩尔比为100：99.6，将上述物质经过物理混合后，置于马弗炉中煅烧，煅烧温度为1035℃，煅烧时间为11h，然后对煅烧产物进行粉碎处理，得到颗粒分布均匀的掺杂有M元素的钴酸锂颗粒；
步骤2、按照摩尔比例Mg：Ti：掺杂有M元素的钴酸锂颗粒＝0.5：0.5：99.5称取氧化镁、氧化钛与掺杂有M元素的钴酸锂颗粒进行搅拌，混合均匀后置于马弗炉中煅烧，煅烧温度为950℃，煅烧时间为8h，然后对煅烧产物进行粉碎处理，得到正极活性物质。
正极活性物质的平均粒径为14.5μm。
将97质量份的正极活性物质、1.5质量份的导电剂Super-P以及1.5质量份的粘结剂聚偏四氟乙烯(PVDF)分散在N-甲基吡咯烷酮(NMP)中制备得到正极活性层浆料，将所述浆料均匀涂覆在铝箔表面，经过五段烘箱烘烤后收卷，五段烘箱的温度设置分别为70℃、80℃、95℃、120℃、120℃，再将涂覆有正极活性层浆料的集流体置于100℃的烘箱中烘烤8h，将正极活性 层浆料中的溶剂挥发完全后进行辊压，压实密度为4.1g/cm 3，制得正极片。
将96质量份的负极活性物料人造石墨(粒径平均粒径：13±1μm，石墨化度94±0.5％，二次颗粒与单颗粒混合，其中二次颗粒质量占比50％)、1质量份的超导炭黑(Super-P)、1.5质量份的羧甲基纤维素钠(CMC)和1.5质量份的丁苯橡胶(SBR)分散于溶剂中制备得到负极活性层浆料，将负极活性层浆料涂布在8μm的铜箔上烘干，烘烤温度为100℃，烘烤4h后辊压得到压实密度为1.68g/cm 3的负极片。
隔膜为单面陶瓷+双面油性LBG涂胶隔膜；
电解液包括非水有机溶剂、锂盐和添加剂，其中，非水有机溶剂包括碳酸乙烯酯(EC)、碳酸丙烯酯(PC)和碳酸二甲酯(DMC)(质量比为1:1:1)，锂盐为LiPF 6，添加剂包括4wt.％的1,3-丙烯磺酸内酯、6wt.％的碳酸亚乙烯酯、1wt.％的丁二腈、2wt.％的己二腈。
将正极片、负极片、隔膜通过卷绕制成电芯，用铝塑膜封装，在氮气保护的烘箱中，控制温度为120℃，烘烤36h，注入电解液，进行化成分选等工序，最终得到容量为5Ah的软包锂离子电池。
将上述制备的电池在25℃下进行充放电，在0.7C的倍率下放电到3.0V，拆解电芯测试其Li和Co的含量，并计算得到A；以0.7C的倍率恒流充电至4.45V，随后进行恒压充电，截止电流为0.1C，拆解该状态下的电芯测试其Li和Co的含量，计算得到B。
以上述充放电制度对锂离子电池进行循环测试，即0.7C/0.7C，0.1C截止，电压范围3.0-4.45V，温度25℃，循环500T后测试容量保持率。
对正极活性物质进行ICP测试，测试结果表明正极活性物质中Al的总含量为4500ppm，Mg的总含量为1500ppm，Ti的总含量为1500ppm。
ICP测试方法具体包括如下步骤：
1、对上述制备得到的锂离子电池进行拆解，拆解后的正极片保留，将正极片置于碳酸二甲酯(DMC)的溶液中浸泡，浸泡30min后，将其取出，放入120℃烘箱中干燥6H；
2、将干燥后的正极片置于管式炉中，对其进行高温烧结，设定管式炉烧结温度为300℃，烧结时间设定为4H，烧结结束后自然冷却后，将其置于密封的玻璃瓶中；
3、将有正极片的玻璃瓶置于超声机中超声，超声15min后取出，轻轻搓粉，即可得到正极极粉；
4、将上述的正极极粉使用原子吸收光谱(ICP)进行测试，得到各元素的含量值，其中各元素谱线如表1所示：
表1正极活性物质中各元素谱线
元素 Li Co Al Mg Ti
谱线(nm) 670.784 228.616 396.15 279.553 323.5
STD1 0 0 0 0 0
STD2 1 10 1 1 1
STD3 3 30 2 2 2
STD4 10 100 5 5 5
实施例2
本实施例提供的锂离子电池与实施例1相同，不同在于充放电制度不同，具体地，在25℃下，将电芯在0.7C的倍率下放电到3.0V，拆解电芯测试其Li和Co的含量，计算得到A；以0.7C的倍率恒流充电至4.45V，随后进行恒压充电，截止电流为0.05C，拆解该状态下的电芯测试其Li和Co的含量，计算得到B。
以上述充放电制度对锂离子电池进行循环测试，即0.7C/0.7C，0.05C截止，电压范围3.0-4.45V，温度25℃，循环500T后测试容量保持率。
实施例3
本实施例提供的锂离子电池与实施例1相同，不同在于充放电制度不同，具体地，在25℃下，将电芯在0.7C的倍率下放电到3.0V，拆解电芯测试其Li和Co的含量，计算得到A；以0.7C的倍率恒流充电至4.45V，随后进行恒压充电，截止电流为0.02C，拆解该状态下的电芯测试其Li和Co的含量，计算得到B。
以上述充放电制度对锂离子电池进行循环测试，即0.7C/0.7C，0.02C截止，电压范围3.0-4.45V，温度25℃，循环500T后测试容量保持率。
实施例4
本实施例提供的锂离子电池与实施例1相同，不同在于充放电制度不同，具体地，在25℃下，将电芯在0.7C的倍率下放电到3.0V，拆解电芯测试其Li和Co的含量，计算得到A；以0.7C的倍率恒流充电至4.4V，随后进行恒压充电，截止电流为0.05C，拆解该状态下的电芯测试其Li和Co的含量，计算得到B。
以上述充放电制度对锂离子电池进行循环测试，即0.7C/0.7C，0.05C截止，电压范围3.0-4.4V，温度25℃，循环500T后测试容量保持率。
实施例5
本实施例提供的锂离子电池与实施例1相同，不同在于充放电制度不同，具体地，在25℃下，将电芯在0.7C的倍率下放电到3.0V，拆解电芯测试其Li和Co的含量，计算得到A；以0.7C的倍率恒流充电至4.48V，随后进行恒压充电，截止电流为0.05C，拆解该状态下的电芯测试其Li和Co的含量，计算得到B。
以上述充放电制度对锂离子电池进行循环测试，即0.7C/0.7C，0.05C截止，电压范围3.0-4.48V，温度25℃，循环500T后测试容量保持率。
实施例6
本实施例提供的锂离子电池与实施例1相同，不同在于充放电制度不同，具体地，在25℃下，将电芯在0.7C的倍率下放电到3.0V，拆解电芯测试其Li和Co的含量，计算得到A；在10℃下，以0.7C的倍率恒流充电至4.45V，随后进行恒压充电，截止电流为0.05C，拆解该状态下的电芯测试其Li和Co的含量，计算得到B。
以上述充放电制度对锂离子电池进行循环测试，即0.7C/0.7C，0.05C截止，电压范围3.0-4.45V，温度10℃，循环500T后测试容量保持率。
实施例7
本实施例提供的锂离子电池与实施例1相同，不同在于充放电制度不同， 具体地，在25℃下，将电芯在0.7C的倍率下放电到3.0V，拆解电芯测试其Li和Co的含量，计算得到A；在35℃下，以0.7C的倍率恒流充电至4.45V，随后进行恒压充电，截止电流为0.05C，拆解该状态下的电芯测试其Li和Co的含量，计算得到B。
以上述充放电制度对锂离子电池进行循环测试，即0.7C/0.7C，0.05C截止，电压范围3.0-4.45V，温度35℃，循环500T后测试容量保持率。
实施例8
本实施例提供的锂离子电池可参考实施例2，不同之处在于，正极活性物质中Al的总含量为3500ppm，Mg的总含量为1500ppm，Ti的总含量为1500ppm。
采用实施例2提供的充放电制度对锂离子电池进行充放电，并测试容量保持率。
实施例9
本实施例提供的锂离子电池可参考实施例2，不同之处在于，正极活性物质中Al的总含量为4000ppm，Mg的总含量为1500ppm，Ti的总含量为1500ppm。
采用实施例2提供的充放电制度对锂离子电池进行充放电，并测试容量保持率。
实施例10
本实施例提供的锂离子电池可参考实施例2，不同之处在于，正极活性物质中Al的总含量为5000ppm，Mg的总含量为1500ppm，Ti的总含量为1500ppm。
采用实施例2提供的充放电制度对锂离子电池进行充放电，并测试容量保持率。
实施例11
本实施例提供的锂离子电池可参考实施例2，不同之处在于，正极活性 物质中Al的总含量为5500ppm，Mg的总含量为1500ppm，Ti的总含量为1500ppm。
采用实施例2提供的充放电制度对锂离子电池进行充放电，并测试容量保持率。
实施例12
本实施例提供的锂离子电池可参考实施例2，不同之处在于，正极活性物质中Al的总含量为6000ppm，Mg的总含量为1500ppm，Ti的总含量为1500ppm。
采用实施例2提供的充放电制度对锂离子电池进行充放电，并测试容量保持率。
实施例13
本实施例提供的锂离子电池可参考实施例2，不同之处在于，正极活性物质中Al的总含量为7000ppm，Mg的总含量为1500ppm，Ti的总含量为1500ppm。
采用实施例2提供的充放电制度对锂离子电池进行充放电，并测试容量保持率。
对比例1
本对比例提供的正极活性物质为钴酸锂，锂离子电池的制备以及充放电制度可参考实施例2。
本对比例提供的正极活性物质的制备方法包括如下制备步骤：
步骤1、将CoCl 2用水溶液溶解，配制得到Co 2+的浓度为1.25mol/L的溶液，将加入氨水溶液(浓氨水和蒸馏水按体积比1：10配置)和碳酸钠溶液(1.2mol/L)混合后进行络合沉淀反应，连续反应重复结晶3次后进行离心过滤，得到钴的碳酸盐CoCO 3；
步骤2、将钴的碳酸盐置于马弗炉进行煅烧，煅烧温度为930℃，时间为10h，然后对煅烧产物进行粉碎处理，得到颗粒分布均匀的前驱体Co 3O 4；
步骤3、将制备得到的前驱体Co 3O 4、Li 2CO 3按照Li：Co＝100：99.6进 行高速球磨混合，置于马弗炉中煅烧，煅烧温度为1035℃，煅烧时间为11h，然后对煅烧产物进行粉碎处理，得到LiCoO 2。
对比例2
本对比例提供的锂离子电池与实施例1相同，不同在于充放电制度不同，具体地，在25℃下，将电芯在0.7C的倍率下放电到3.0V，拆解电芯测试其Li和Co的含量，计算得到A；以0.7C的倍率恒流充电至4.45V，随后进行恒压充电，截止电流为0.01C，拆解该状态下的电芯测试其Li和Co的含量，计算得到B。
以上述充放电制度对锂离子电池进行循环测试，即0.7C/0.7C，0.01C截止，电压范围3.0-4.45V，温度25℃，循环500T后测试容量保持率。
对比例3
本对比例提供的锂离子电池与实施例1相同，不同在于充放电制度不同，具体地，在25℃下，将电芯在0.7C的倍率下放电到3.0V，拆解电芯测试其Li和Co的含量，计算得到A；同时，将同组方案的电芯以0.7C的倍率恒流充电至4.5V，随后进行恒压充电，截止电流为0.05C，拆解该状态下的电芯测试其Li和Co的含量，计算得到B。
以上述充放电制度对锂离子电池进行循环测试，即0.7C/0.7C，0.05C截止，电压范围3.0-4.5V，温度25℃，循环500T后测试容量保持率。
对比例4
本对比例提供的锂离子电池与实施例1相同，不同在于充放电制度不同，具体地，在25℃下，将电芯在0.7C的倍率下放电到3.0V，拆解电芯测试其Li和Co的含量，计算得到A；以0.7C的倍率恒流充电至4.55V，随后进行恒压充电，截止电流为0.05C，拆解该状态下的电芯测试其Li和Co的含量，计算得到B。
以上述充放电制度对锂离子电池进行循环测试，即0.7C/0.7C，0.05C截止，电压范围3.0-4.55V，温度25℃，循环500T后测试容量保持率。
对比例5
本对比例提供的锂离子电池与实施例1相同，不同在于充放电制度不同，具体地，在25℃下，将电芯在0.7C的倍率下放电到3.0V，拆解电芯测试其Li和Co的含量，计算得到A；在45℃下，以0.7C的倍率恒流充电至4.45V，随后进行恒压充电，截止电流为0.05C，拆解该状态下的电芯测试其Li和Co的含量，计算得到B。
以上述充放电制度对锂离子电池进行循环测试，即0.7C/0.7C，0.05C截止，电压范围3.0-4.45V，温度45℃，循环500T后测试容量保持率。
对比例6
本对比例提供的锂离子电池与实施例1相同，不同在于充放电制度不同，具体地，在25℃下，将电芯在0.7C的倍率下放电到3.0V，拆解电芯测试其Li和Co的含量，计算得到A；在55℃下，以0.7C的倍率恒流充电至4.45V，随后进行恒压充电，截止电流为0.05C，拆解该状态下的电芯测试其Li和Co的含量，计算得到B。
以上述充放电制度对锂离子电池进行循环测试，即0.7C/0.7C，0.05C截止，电压范围3.0-4.45V，温度55℃，循环500T后测试容量保持率。
表2-5对实施例1-13及对比例1-6提供的正极活性物质、充放电制度分别进行了列表说明，并示出了实施例1-13以及对比例1-6提供的锂离子电池的容量保持率，以使本申请提供的实施例的区别和效果更加直观。
表2实施例1-3以及对比例1-2提供的锂离子电池的A-B以及容量保持率
  A B A-B 容量保持率 充电截止电流
实施例1 0.926 0.301 0.625 93.01％ 0.1C
实施例2 0.926 0.287 0.639 91.46％ 0.05C
实施例3 0.926 0.280 0.646 88.44％ 0.02C
对比例1 0.913 0.253 0.660 86.74％ 0.05C
对比例2 0.926 0.269 0.657 87.76％ 0.01C
将锂离子电池在25℃下，进行3.0-4.45V电压范围内的循环，保证其充 放电倍率一致，调整其充电截止电流为0.1C、0.05C、0.02C、0.01C，根据实施例1-3以及对比例2提供的数据可知，随着充电截止电流的变小，A-B变大，容量保持率降低，循环性能变差。
表3实施例2、4、5以及对比例1-4提供的锂离子电池的A-B以及容量保持率
Figure PCTCN2022093487-appb-000001
将锂离子电池在25℃下，以0.7C/0.7C倍率进行充放电，充电截止电流均为0.05C，调整截止电压分别为4.4V、4.45V、4.48V、4.5V、4.55V，根据
实施例2、4-5以及对比例3-4提供的数据可知，随着充电截止电压的升高，A-B变大，容量保持率降低，循环性能变差。
表4实施例2、6-7以及对比例1、5、6提供的锂离子电池的A-B以及容量保持率
  A B A-B 容量保持率 循环温度
实施例2 0.926 0.287 0.639 95.08％ 25℃
实施例6 0.926 0.310 0.615 96.44％ 10℃
实施例7 0.926 0.279 0.646 92.69％ 35℃
对比例1 0.913 0.253 0.660 91.62％ 25℃
对比例5 0.926 0.245 0.681 90.48％ 45℃
对比例6 0.926 0.205 0.721 85.25％ 55℃
将锂离子电池在10、25、35、45、55℃下，以3.0-4.45V，0.7C/0.7C，截止电流0.05C进行充放电，根据实施例2、6-7以及对比例5-6提供的数据可知，随着循环温度的升高，A-B变大，容量保持率降低，循环性能变差。
表5实施例2、8-13以及对比例1提供的锂离子电池的A-B以及容量保持率
  A B A-B 容量保持率 Al含量/ppm
实施例2 0.926 0.287 0.639 91.46％ 4500
实施例8 0.921 0.266 0.655 88.22％ 3500
实施例9 0.925 0.274 0.651 89.81％ 4000
实施例10 0.929 0.302 0.627 92.12％ 5000
实施例11 0.931 0.311 0.62 93.01％ 5500
实施例12 0.934 0.317 0.617 94.98％ 6000
实施例13 0.936 0.335 0.601 96.14％ 7000
对比例1 0.913 0.253 0.66 86.74％ 0
将正极活性物质中Al元素的掺杂量调整为3500、4000、4500、5000、5500、6000、7000ppm，并将包括上述正极活性物质的锂离子电池在相同条件下进行充放电循环，根据实施例2、8-13提供的数据可知，随着正极活性物质中Al元素掺杂量的提高，A-B降低，容量保持率提高，循环性能变好。
综上，当锂离子电池在0％SOC下，所述正极活性物质中锂元素与钴元素的摩尔比为A，在100％SOC下，所述正极活性物质中锂元素与钴元素的摩尔比为B，0.62≤A-B≤0.655时，锂离子电池具有较好的循环性能。
最后应说明的是：以上各实施例仅用以说明本申请的技术方案，而非对其限制；尽管参照前述各实施例对本申请进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分或者全部技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本申请各实施例技术方案的范围。

Claims (10)

  1. 一种锂离子电池，其中，所述锂离子电池包括正极活性物质，所述正极活性物质包括掺杂有Al、Mg、Ti、Zr、Ni、Mn、Y、La、Sr、W、Sc中的一种或多种元素的钴酸锂颗粒，所述锂离子电池在0％SOC下，所述正极活性物质中锂元素与钴元素的摩尔比为A，所述锂离子电池在100％SOC下，所述正极活性物质中锂元素与钴元素的摩尔比为B，0.62≤A-B≤0.655。
  2. 根据权利要求1所述的锂离子电池，其中，所述正极活性物质还包括包覆在所述钴酸锂颗粒至少部分外表面的包覆层，所述包覆层包括金属氟化物、金属氧化物、金属硼酸盐化合物、金属磷酸盐化合物中的一种或多种。
  3. 根据权利要求2所述的锂离子电池，其中，所述金属氟化物选自AlF 3、Li 3F、MgF中的一种或多种；
    和/或，所述金属氧化物选自Al 2O 3、TiO 2、ZrO 2、MgO中的一种或多种；
    和/或，所述金属硼酸盐化合物为AlBO 3；
    和/或，所述金属磷酸盐化合物选自AlPO 4、Li 3PO 4中的一种或两种。
  4. 根据权利要求2所述的锂离子电池，其中，所述正极活性物质包括Al元素，且所述Al元素的含量不低于3500ppm。
  5. 根据权利要求2所述的锂离子电池，其中，所述包覆层的质量不大于所述正极活性物质总质量的1％。
  6. 根据权利要求2所述的锂离子电池，其中，所述正极活性物质通过如下制备方法制备得到：
    对钴酸锂颗粒进行M元素的掺杂，所述M元素为Al、Mg、Ti、Zr、Ni、Mn、Y、La、Sr、W、Sc中的一种或多种；
    将金属氟化物、金属氧化物、金属硼酸盐化合物、金属磷酸盐化合物中的一种或多种包覆在掺杂有M元素的钴酸锂颗粒的至少部分表面形成包覆层，得到所述正极活性物质。
  7. 根据权利要求1-6任一项所述的锂离子电池，其中，所述正极活性物质的平均粒径为8.0-15.0μm。
  8. 根据权利要求1-7任一项所述的锂离子电池，其中，所述锂离子电池的充电截止电压小于4.5V。
  9. 根据权利要求1-7任一项所述的锂离子电池，其中，所述锂离子电池 的充电截止电流不小于0.02C。
  10. 根据权利要求1-7任一项所述的锂离子电池，其中，所述锂离子电池的充放电温度小于45℃。
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