WO2022042373A1 - 锂离子电池 - Google Patents

锂离子电池 Download PDF

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WO2022042373A1
WO2022042373A1 PCT/CN2021/113011 CN2021113011W WO2022042373A1 WO 2022042373 A1 WO2022042373 A1 WO 2022042373A1 CN 2021113011 W CN2021113011 W CN 2021113011W WO 2022042373 A1 WO2022042373 A1 WO 2022042373A1
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carbonate
ion battery
lithium ion
lithium
negative electrode
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PCT/CN2021/113011
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French (fr)
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WO2022042373A8 (zh
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钱韫娴
胡时光
孙桂岩
林雄贵
邓永红
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深圳新宙邦科技股份有限公司
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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
    • 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
    • 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
    • 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
    • H01M10/0568—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
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • 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 invention relates to a lithium ion battery, in particular to a lithium ion battery with artificial graphite and/or natural graphite as a negative electrode and the electrolyte quality: battery capacity within a specific range.
  • lithium-ion batteries have advantages of high operating voltage, high energy density, no memory effect and long cycle life of lithium-ion batteries make them widely used not only in mobile phones, cameras, notebook computers and other digital products, but also in power storage devices, such as new energy power Automotive and other fields are becoming more and more popular.
  • the negative electrode materials used in commercial lithium-ion batteries are mainly carbon materials with good conductivity. Negative materials such as artificial graphite and mesocarbon microspheres have good performance but high cost, while natural graphite has abundant reserves, low cost, and reversible desorption.
  • the present invention provides a lithium ion battery with a high capacity retention rate during a long cycle.
  • the present invention provides a lithium ion battery, wherein the lithium ion battery includes: a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, a separator placed between the positive electrode and the negative electrode, and a non-aqueous electrolysis
  • the negative electrode active material includes artificial graphite and/or natural graphite; the electrolyte quality of the non-aqueous electrolyte of the lithium ion battery: the battery capacity is 1.2-4g/Ah.
  • the non-aqueous electrolyte includes a lithium salt, an organic solvent, and one or more of compounds represented by the following formulae (1) to (3),
  • formula (1) formula (2), and formula (3), A 1 , A 6 , and A 11 are each:
  • a 2 , A 3 , A 4 , A 5 , A 7 , A 8 , A 9 , A 10 , A 12 , A 13 , A 14 , A 15 are each a single bond or methylene Base, m, n and p are all integers from 0 to 6, -* indicates that it is related to A 2 , A 3 , A 4 , A 5 , A 7 , A 8 , A 9 , A 10 , A 12 , A 13 , A 14 , the position of A 15 binding.
  • the electrolyte quality of the non-aqueous electrolyte of the lithium ion battery is 2-3.5 g/Ah.
  • the compounds represented by formula (1) to formula (3) are selected from one or more of the following compounds 1-15:
  • the content of the cyclic sulfate compound is 0.01-5 mass % of the total mass of the non-aqueous electrolyte of the lithium ion battery; more preferably, the content of the cyclic sulfate compound is the non-aqueous lithium ion battery. 0.05-3 mass% of the total mass of the electrolyte.
  • the lithium salt is selected from LiPF6, LiPO2F2 , LiBF4 , LiBOB, LiClO4 , LiCF3SO3 , LiDFOB , LiN ( SO2CF3 )2 , LiN ( SO2C2F5 ) 2 , one or more of LiC(SO 2 CF 3 ) 3 , LiN(SO 2 F) 2 , LiTFSI and LiDFOB; more preferably, the lithium salt is LiPF 6 and/or LiPO 2 F 2 ;
  • the concentration of the lithium salt is 0.5-2 mol/L.
  • the organic solvent is a carbonate compound
  • the carbonate compound is a cyclic carbonate and/or a chain carbonate.
  • the cyclic carbonate is one or more of ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate and fluoroethylene carbonate.
  • the chain carbonate is one or more of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate and propyl methyl carbonate.
  • the organic solvent is a mixture of ethylene carbonate, diethyl carbonate and ethyl methyl carbonate.
  • the content of the natural graphite is 0-80% by mass of the total mass of the negative electrode active material
  • the content of the natural graphite is 20-50 mass % of the total mass of the negative electrode active material.
  • the positive active material is one or more of lithium cobaltate, lithium manganate, lithium nickelate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate and lithium iron phosphate;
  • the positive electrode active material is nickel cobalt lithium manganate and/or lithium iron phosphate.
  • the non-aqueous electrolyte further comprises an additive selected from the group consisting of unsaturated cyclic carbonates, fluorinated cyclic carbonates, cyclic sultones, cyclic sulfates, phosphates and borates one or more of.
  • an additive selected from the group consisting of unsaturated cyclic carbonates, fluorinated cyclic carbonates, cyclic sultones, cyclic sulfates, phosphates and borates one or more of.
  • the unsaturated cyclic carbonate is selected from one or more of vinylene carbonate, ethylene ethylene carbonate and methylene ethylene carbonate.
  • the fluorocyclic carbonate is selected from one or more of fluoroethylene carbonate, trifluoromethyl ethylene carbonate and difluoroethylene carbonate.
  • the cyclic sultone is selected from one or more of 1,3-propane sultone, 1,4-butane sultone and propenyl-1,3-sultone .
  • the cyclic sulfate is selected from one or more of vinyl sulfate, vinyl 4-methyl sulfate and propylene sulfate.
  • the phosphate is tris(trimethylsilane) phosphate and/or tripropynyl phosphate.
  • the borate is tris(trimethylsilane)borate and/or tris(triethylsilane)borate.
  • the content of the additive is 0.1-8% by mass of the total amount of the non-aqueous electrolyte.
  • the lithium ion battery uses artificial graphite and/or natural graphite as the negative electrode, the non-aqueous electrolyte contains specific cyclic sulfate compounds and/or cyclic sulfite compounds, and the electrolyte quality: battery
  • the capacity is in a specific range, and the battery has a high capacity retention rate during long cycles.
  • the present invention also provides a lithium ion battery with a specific proportion of natural graphite and artificial graphite as the negative electrode, and the battery exhibits excellent performance better than the lithium ion battery with artificial graphite as an electrode,
  • FIG. 1 is a photograph of the negative electrode piece disassembled after the lithium ion battery of Example 1 is cycled at 45° C. for 1000 times.
  • FIG. 2 is a photograph of the disassembled negative pole piece of the lithium ion battery of Comparative Example 1 after being cycled for 1000 times at 45°C.
  • the present invention provides a lithium ion battery, the lithium ion battery comprises: a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, a separator placed between the positive electrode and the negative electrode, and a non-aqueous electrolyte, the negative electrode active material Including artificial graphite and/or natural graphite, the electrolyte quality of the non-aqueous electrolyte of the lithium ion battery: the battery capacity is 1.2-4g/Ah; the non-aqueous electrolyte includes a lithium salt, an organic solvent and is composed of the following formula (1 ) to one or more of the compounds represented by formula (3),
  • formula (1) formula (2), and formula (3), A 1 , A 6 , and A 11 are each:
  • a 2 , A 3 , A 4 , A 5 , A 7 , A 8 , A 9 , A 10 , A 12 , A 13 , A 14 , A 15 are each a single bond or methylene Base, m, n and p are all integers from 0 to 6, -* indicates that it is related to A 2 , A 3 , A 4 , A 5 , A 7 , A 8 , A 9 , A 10 , A 12 , A 13 , A 14 , the position of A 15 binding.
  • 1, 2, 3, 4, 5, or 6 may be sufficient, for example.
  • 1, 2, 3, 4, 5, or 6 may be sufficient, for example.
  • 1, 2, 3, 4, 5, or 6 may be sufficient, for example.
  • the inventors of the present invention have unexpectedly found that when the negative electrode active material of a lithium ion battery is artificial graphite and/or natural graphite, and the non-aqueous electrolyte contains compounds represented by formulas (1) to (3), even if the electrolysis Liquid quality: the battery capacity is as low as 1.2 g/Ah, and the performance of the resulting lithium-ion battery is still excellent, showing better performance than electrolyte quality: lithium-ion battery with higher battery capacity.
  • the inventors of the present invention speculate that this is because the SEI film generated when the compounds represented by the formulas (1) to (3) are formed into a specific bond on the graphite negative electrode. The consumption of the water electrolyte during the cycle is much lower than that of the electrolyte without the addition of such compounds, so the lithium-ion battery with low electrolyte quality: battery capacity shows better performance.
  • the lithium ion battery of the present invention when the electrolyte quality: the battery capacity is low, the lithium ion battery of the present invention exhibits excellent performance, specifically, the electrolyte quality of the non-aqueous electrolyte of the lithium ion battery: the battery capacity is 1.2-4g /Ah; preferably, the electrolyte quality of the non-aqueous electrolyte of the lithium ion battery: the battery capacity is 2-3.5g/Ah.
  • the compounds represented by formula (1) to formula (3) are selected from one or more of the following compounds 1-15:
  • the content of the compounds represented by the formulas (1) to (3) is 0.01-5 mass % of the total mass of the non-aqueous electrolyte of the lithium ion battery; more preferably, formula (1)
  • the content of the compound represented by the formula (3) is 0.05-3 mass % of the total mass of the non-aqueous electrolyte solution of the lithium ion battery.
  • the lithium salt in the non-aqueous electrolyte of the lithium ion battery can use various lithium salts commonly used in the preparation of lithium ion batteries in the art, without special limitation , for example, LiPF 6 , LiPO 2 F 2 , LiBF can be selected 4 , LiBOB, LiClO 4 , LiCF 3 SO 3 , LiDFOB, LiN(SO 2 CF 3 ) 2 , LiN(SO 2 C 2 F 5 ) 2 , LiC(SO 2 CF 3 ) 3 , LiN(SO 2 F) 2 One or more of , LiTFSI and LiDFOB, etc.; preferably, the lithium salt is selected from one of LiPF 6 , LiBF 4 , LiPO 2 F 2 , LiTFSI, LiBOB, LiDFOB and LiN(SO 2 F) 2 or more; more preferably, the lithium salt is selected from LiPF 6 and/or LiPO 2 F 2 .
  • the content of the lithium salt can be the usual content in lithium ion batteries in the art, and is not particularly limited.
  • the concentration of the lithium salt is 0.5-2 mol/L.
  • the content of the lithium salt is within this range, it can ensure that the electrical conductivity of the non-aqueous electrolyte is high and the overall performance of the battery is excellent.
  • the organic solvent in the non-aqueous electrolyte of the lithium ion battery can be various organic solvents commonly used in the field to prepare non-aqueous electrolytes, and is not particularly limited. Carbonates, carboxylates, ethers, etc. are used as organic solvents.
  • the organic solvent is a carbonate compound, and the carbonate compound is a cyclic carbonate and/or a chain carbonate.
  • the cyclic carbonate is one or more of ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate and fluoroethylene carbonate.
  • the chain carbonate is one or more of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate and propyl methyl carbonate.
  • the organic solvent is a mixture of ethylene carbonate, diethyl carbonate and ethyl methyl carbonate.
  • the organic solvent is a mixture of ethylene carbonate, diethyl carbonate and ethyl methyl carbonate, and the mass ratio of ethylene carbonate, diethyl carbonate and ethyl methyl carbonate is 30:50:20.
  • the positive electrode active material may be various positive electrode active materials used in lithium batteries.
  • the positive electrode active material for example, it can be one or more of lithium cobaltate, lithium manganate, lithium nickelate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate and lithium iron phosphate; preferably, the positive electrode The active material is lithium nickel cobalt manganate and/or lithium iron phosphate.
  • the positive electrode active material is LiNi 0.5 Co 0.2 Mn 0.3 O 2 .
  • the natural graphite content is 0-80 mass % of the total mass of the negative electrode active material; preferably, the natural graphite content is 20-50 mass % of the total mass of the negative electrode active material.
  • the inventors of the present invention unexpectedly found that when the negative electrode active material of a lithium ion battery contains natural graphite and artificial graphite, and the content of natural graphite is 20-50 mass % of the total mass of the negative electrode active material, the specific cyclic sulfate is contained.
  • the performance of the lithium-ion battery of the compound-like compound is particularly excellent, which is better than that of the lithium-ion battery with artificial graphite as the electrode.
  • the inventors of the present invention speculate that this may be because when the negative electrode active material contains a specific proportion of natural graphite, the compounds represented by formulas (1) to (3) are more stable in combination with the graphite negative electrode and have a protective effect on the negative electrode. better.
  • the lithium ion battery may further contain various additives commonly used in the art to improve the performance of lithium ion batteries.
  • additives can be selected from Self-unsaturated cyclic carbonates, fluorinated cyclic carbonates, cyclic sultones, cyclic sulfates, phosphates and boronic esters, and the like.
  • the unsaturated cyclic carbonate is selected from vinylene carbonate (CAS: 872-36-6), vinyl ethylene carbonate (CAS: 4427-96-7) and methylene carbonate One or more of ethylene carbonate (CAS: 124222-05-5).
  • the fluorinated cyclic carbonate is selected from fluoroethylene carbonate (CAS: 114435-02-8), trifluoromethyl ethylene carbonate (CAS: 167951-80-6), and difluoroethylene carbonate (CAS: 167951-80-6).
  • fluoroethylene carbonate CAS: 311810-76-1
  • the cyclic sultone is selected from 1,3-propane sultone (CAS: 1120-71-4), 1,4-butane sultone (CAS: 1633-83) -6) and one or more of propenyl-1,3-sultone (CAS: 21806-61-1).
  • the cyclic sulfate is selected from vinyl sulfate (CAS: 1072-53-3), 4-methyl vinyl sulfate (CAS: 5689-83-8) and propylene sulfate one or more.
  • the phosphate is tris(trimethylsilane) phosphate and/or tripropynyl phosphate.
  • the borate is tris(trimethylsilane)borate and/or tris(triethylsilane)borate.
  • the additive is one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), 1,3-propane sultone (PS) and vinyl sulfate (DTD) one or more.
  • VC vinylene carbonate
  • FEC fluoroethylene carbonate
  • PS 1,3-propane sultone
  • DTD vinyl sulfate
  • the content of the additive can be the conventional content of various additives in the lithium ion battery in the art.
  • the content of the additive may be 0.1-8% by mass of the total amount of the non-aqueous electrolyte; preferably, the content of the additive may be 0.1-5% by mass of the total amount of the non-aqueous electrolyte.
  • the preparation of the positive electrode and the negative electrode of the lithium ion battery can be carried out according to the method commonly used in the art for preparing the positive electrode and the negative electrode of the lithium ion battery, and there is no particular limitation.
  • the active materials of the positive and negative electrodes can be mixed with a conductive agent and a binder, and the mixture can be dispersed in a solvent to prepare a slurry, and then the obtained slurry can be coated on a current collector and subjected to drying and rolling treatments.
  • the conductive agent, adhesive, organic solvent, current collector, etc. used can all adopt materials and substances commonly used in the art, and will not be repeated here.
  • the preparation of the lithium ion battery can adopt the method commonly used in the art, for example, it can be as follows: the positive electrode/negative electrode active material, the conductive material, and the binder are mixed and coated on the metal to prepare the positive electrode/negative electrode pole piece, The positive pole piece, the separator and the negative pole piece are stacked or wound in sequence to form a bare cell, the bare cell is placed in a casing to obtain a cell, and the electrolyte is injected into the obtained cell and sealed to obtain the lithium ion battery.
  • the separator placed between the positive electrode and the negative electrode can be various materials commonly used as separators in the field, without particular limitation, for example, can be polyolefin separators, polyamide separators, polysulfone separators , one or more of polyphosphazene diaphragms, polyethersulfone diaphragms, polyetheretherketone diaphragms, polyetheramide diaphragms and polyacrylonitrile diaphragms; preferably, the diaphragms are selected from polyolefins One or more of separators and polyacrylonitrile.
  • the housing is not particularly limited, and can be various housings commonly used in the field, such as stainless steel housing, aluminum housing, and aluminum-plastic film housing; preferably, the housing is aluminum-plastic Membrane housing.
  • EC Ethylene carbonate
  • DEC diethyl carbonate
  • EMC ethyl methyl carbonate
  • the binder PVDF Dissolve the binder PVDF in N-methylpyrrolidone, add the positive electrode active material LiNi 0.5 Co 0.2 Mn 0.3 O 2 and the conductive agent carbon black, and mix thoroughly to obtain the positive electrode slurry (positive electrode active material, conductive agent and The mass ratio of the binder was 96:2:2, and the amount of N-methylpyrrolidone was such that the solid content of the positive electrode slurry was 70% by mass).
  • the obtained positive electrode slurry was coated on a 20 ⁇ m thick positive electrode aluminum foil (15 ⁇ m coating thickness), then air-dried at 85° C. for 24 h, rolled up by cold pressing, and welded with tabs to obtain a lithium ion battery positive electrode sheet.
  • the negative electrode active material artificial graphite and natural graphite (calculated by the total mass of artificial graphite and natural graphite, artificial graphite 70 mass %, natural graphite 30 mass %), conductive agent carbon black, thickener sodium carboxymethyl cellulose, bonding SBR is dissolved in water to obtain negative electrode slurry (the mass ratio of negative electrode active material, conductive agent, thickener and binder is 95:1:1.5:2.5, and the amount of water is such that the solid content of the negative electrode slurry is 45 quality%).
  • the negative electrode slurry was coated on the negative electrode copper foil with a thickness of 12 ⁇ m (the coating thickness was 9 ⁇ m), and then air-dried at 85° C. for 24 h, rolled up by cold pressing, and welded the tabs to obtain the negative electrode pole piece.
  • a 20 ⁇ m polyethylene separator was placed between the positive electrode and the negative electrode obtained in steps (2) and (3), and then the sandwich structure composed of the positive electrode, the separator and the negative electrode was wound to obtain a bare cell. After the cell is flattened, it is put into the aluminum-plastic film as the casing, and the tabs of the positive and negative electrodes are drawn out respectively, and the aluminum-plastic film is hot-pressed and sealed to obtain the cell to be injected.
  • the non-aqueous electrolyte obtained in the above step (1) is injected into the cell to be injected according to the electrolyte quality: battery capacity shown in Table 1, vacuum-sealed, and allowed to stand. 24h. Then the formation is carried out according to the following steps: 0.05C rate constant current charging for 180min, 0.1C rate constant current charging for 180min, and 0.2C rate constant current charging for 120min. After resting for 24 hours, shaping and secondary sealing were carried out, and then it was further charged to 4.2V with a constant current of 0.2C rate.
  • the lithium-ion battery was prepared as in Example 1, except that the ratio of natural graphite to the negative electrode active material, the electrolyte mass of the non-aqueous electrolyte: the battery capacity ratio, and the types of compounds represented by formulas (1) to (3) and contents, and the types and contents of other additives are the values shown in Table 1 below.
  • VC vinylene carbonate
  • DTD vinyl sulfate
  • FEC fluoroethylene carbonate
  • PS 1,3-propane sultone
  • the initial volume of the lithium-ion batteries prepared in Examples 1-19 and Comparative Examples 1-7 was measured by the drainage method. After the water was dried, the batteries were placed in a high-temperature oven with a constant temperature of 45°C, at a rate of 0.5°C. The battery is charged to 4.2V at a constant current, and then charged at a constant voltage until the current drops to a rate of 0.05C. After leaving it for 5 minutes, it is discharged to a constant current of 3V at a rate of 1C, which is the first cycle. Carry out 1000 cycles of charging/discharging according to the above conditions, respectively calculate the discharge capacity and internal resistance of the battery after 1000 cycles at 45°C. After the battery cycle is completed, take it out of the oven and leave it at room temperature for 8 hours. The volume of the battery after the cycle was determined by the method.
  • the capacity retention rate for high temperature cycling is calculated as follows:
  • Battery capacity retention rate after cycle (%) (discharge capacity after 1000th cycle-discharge capacity of first cycle)/discharge capacity of first cycle ⁇ 100%
  • the growth rate (%) of the internal resistance of the battery after the cycle (the internal resistance after the 1000th cycle - the internal resistance of the first cycle)/the internal resistance of the first cycle.
  • the volume growth rate (%) of the battery after the cycle (the volume after the 1000th cycle - the volume of the first cycle)/the volume of the first cycle.
  • Example number Capacity retention rate (%) Initial internal resistance ( ⁇ ) Internal resistance growth rate (%) Volume growth rate (%)
  • Example 1 90.1 twenty four 54.4 20.1
  • Example 3 89.2 twenty four 55.0 22.3
  • Example 4 87.4 25.5 60.7 23.5
  • Example 5 84.5 26.1 62.4 26.4
  • Example 6 87.1 25.6 70.3 43.5
  • Example 7 87 24.2 55.1 35.2
  • Example 10 87.6 23.5 63.2 27.4
  • Example 11 90.2 26.9 47.1 20.9
  • Example 12 87.7 40.6 70.3 31.4
  • Example 13 86 27 67.4 25.1
  • Example 14 86.3 27.1 59.8 23.7
  • Example 15 89.9 23.4 48.1 17.6
  • Example 16 92.1 35.6 40.9 23.0
  • Example 17 92.5 36.4 53.1 22.1
  • Example 18 89.3 32.7 60.2 26.5
  • Example 19 90.8 26.3 54.8 19.2
  • Comparative Example 1 56.3 22.5 84.1 60.3
  • Comparative Example 2 78.6 28.0 68.4 31.1 Comparative Example 3 69.9 50.4 61.1 21.6
  • Comparative Example 4 89.4 30.1 58.7 26.7
  • Comparative Example 5 90 25.2 60.5 20.4
  • Comparative Example 6 87.3 28.4 63.4 23.9
  • Comparative Example 7 88.5 23.9 66.2 50.1
  • Comparative analysis of Example 1, Examples 8-12 and Comparative Example 1 shows that the cycle performance of lithium ion batteries added with compounds represented by formula (1) to formula (3) is better than that without cyclic sulfate/cyclic sulfite. Compound lithium-ion batteries.
  • Comparative analysis of Example 1, Examples 13-15 and Comparative Example 2 shows that when the liquid injection coefficient of the non-aqueous electrolyte electrolyte quality: battery capacity is lower than 1.2g/Ah, the cycle performance of the lithium ion battery is significantly reduced.
  • Example 1 Comparative analysis of Example 1, Examples 13-15 and Comparative Example 3, when the electrolyte quality of the non-aqueous electrolyte: the battery capacity is higher than the preferred range of the present invention, the initial internal resistance of the lithium ion battery is too high, which also leads to Cycling performance is reduced.
  • Example 1-4 Comparative analysis of Example 1-4 and Example 5-8 shows that when the content of natural graphite in the negative electrode active material is within the preferred range of the present invention, the compounds represented by formulas (1) to (3) have a better protective effect on the graphite negative electrode. Good, the battery has low internal resistance and good capacity retention.
  • Example 1 Comparative analysis of Example 1 and Examples 8-12 shows that when the content of the compounds represented by formula (1) to formula (3) is within the preferred range of the present invention, the protection effect is better, the internal resistance of the battery is low, and the capacity retention rate is Okay.
  • the cyclic ester compound used in the present invention can effectively reduce the electrolyte consumption during the cycle, so the electrolyte quality: when the battery capacity range is 1.2-4g/Ah, the cycle performance is significantly better than the electrolyte without the cyclic ester compound , while effectively improving the energy density.
  • Example 13 in the absence of a cyclic sulfate compound (Comparative Example 1), although the electrolyte quality: the battery capacity reaches 4g/Ah, its cycle performance is still not as good as the compound of the present invention (1).
  • battery of battery capacity Example 13
  • the quality of the electrolyte is low: under the battery capacity, the cyclic sulfate compound represented by compound (1) can effectively protect the electrode material and optimize the cycle performance.
  • FIG. 1 is a photograph of the negative electrode piece disassembled after the lithium ion battery of Example 1 was cycled 1000 times at 45°C.
  • FIG. 2 is a photograph of the disassembled negative pole piece of the lithium ion battery of Comparative Example 1 after being cycled at 45° C. for 1000 times. Comparative analysis of Figure 1 and Figure 2 shows that the compounds represented by formulas (1) to (3) have a great effect on improving the cycle performance of lithium-ion batteries whose negative electrodes contain natural graphite, and the by-products generated by the reaction can effectively cover natural stones. The active sites on the ink surface prevent the subsequent large consumption of solvent and lithium salt, and the non-aqueous electrolyte is still sufficient after 1000 cycles.

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Abstract

本发明涉及锂电池领域，公开了一种锂离子电池，所述锂离子电池包括：包含正极活性物质的正极、包含负极活性物质的负极、置于正极和负极之间的隔膜以及非水电解液，所述负极活性物质包括人造石墨和/或天然石墨；所述非水电解液包括锂盐、有机溶剂和环硫酸酯/环亚硫酸酯类化合物；所述非水电解液的电解液质量：电池容量为1.2g～4/Ah。本发明的锂离子电池的循环性能较好，循环过程中容量保持率高。

Description

锂离子电池 技术领域
本发明涉及锂离子电池，具体涉及一种以人造石墨和/或天然石墨为负极且电解液质量：电池容量在特定范围内的锂离子电池。
背景技术
锂离子电池的高工作电压、高能量密度、无记忆效应和长循环寿命等优点使得其不仅在手机、相机、笔记本电脑等数码产品中广泛应用，而且也在动力储能设备，如新能源动力汽车等领域越来越受到青睐。随着锂离子电池的应用范围越来越广，锂离子电池的“血液”非水电解液的应用也得以飞速发展。目前商用锂离子电池所用负极材料主要以导电性良好的碳材料为主，人造石墨与中间相碳微球等负极材料，性能良好但成本较高，而天然石墨具有储量丰富、成本低廉、可逆脱嵌电位低等优点，也是非常具有发展潜力的负极材料之一。但是天然石墨较大的比较面积和较多的活性位点在反复充放电过程中会持续消耗大量的溶剂和锂盐，从而导致电解液在循环过程中极易干涸，同时副产物二氧化碳等气体也会导致循环性能迅速劣化；另外，天然石墨微观晶形结排列杂乱，宏观各向异性的结构特征，使得充放电过程中锂离子的嵌脱非常困难，导致以天然石墨为负极的锂离子电池循环性能较差。
因此，有必要提供一种锂离子电池，该电池有效降低锂离子电池负极的生产成本，同时可以达到人造石墨的优良电化学性能。
发明内容
本发明为了克服以上问题，提供一种锂离子电池，该锂离子电池长循环过程中容量保持率高。
为了实现上述目的，本发明提供一种锂离子电池，其中，所述锂离子电池包括：包含正极活性物质的正极、包含负极活性物质的负极、置于正极和负极之间的隔膜以及非水电解液，所述负极活性物质包括人造石墨和/或天然石墨；所述锂离子电池非水电解液的电解液质量：电池容量为1.2-4g/Ah。所述非水电解液包括锂盐、有机溶剂和由以下式(1)～式(3)表示的化合物中的一种或多种，
Figure PCTCN2021113011-appb-000001
式(1)、式(2)、式(3)中，A 1、A 6、A 11各自为：
Figure PCTCN2021113011-appb-000002
中的一种或多种，A 2、A 3、A 4、A 5、A 7、A 8、A 9、A 10、A 12、A 13、A 14、A 15各自为单键或亚甲基，m、n和p均为0到6的整数，—*表示与A 2、A 3、A 4、A 5、A 7、A 8、A 9、A 10、A 12、A 13、A 14、A 15结合的位置。
优选地，所述锂离子电池非水电解液的电解液质量：电池容量为2-3.5g/Ah。
优选地，由式(1)～式(3)表示的化合物选自以下化合物1-15中的一种或多种：
Figure PCTCN2021113011-appb-000003
Figure PCTCN2021113011-appb-000004
Figure PCTCN2021113011-appb-000005
优选地，所述环硫酸酯类化合物含量为所述锂离子电池非水电解液总质量的0.01-5质量％；更优选地，所述环硫酸酯类化合物含量为所述锂离子电池非水电解液总质量的0.05-3质量％。
优选地，所述锂盐为选自LiPF 6、LiPO 2F 2、LiBF 4、LiBOB、LiClO 4、LiCF 3SO 3、LiDFOB、LiN(SO 2CF 3) 2、LiN(SO 2C 2F 5) 2、LiC(SO 2CF 3) 3、LiN(SO 2F) 2、LiTFSI和LiDFOB中的一种或多种；更优选地，所述锂盐为LiPF 6和/或LiPO 2F 2；
优选地，所述锂盐的浓度为0.5-2mol/L。
优选地，所述有机溶剂为碳酸酯类化合物，所述碳酸酯类化合物为环状碳酸酯和/或链状碳酸酯。
优选地，所述环状碳酸酯为碳酸乙烯酯、碳酸丙烯酯、碳酸丁烯酯、碳酸亚乙烯酯和氟代碳酸乙烯酯中的一种或多种。
优选地，所述链状碳酸酯为碳酸二甲酯、碳酸二乙酯、碳酸二丙酯、碳酸甲乙酯和碳酸甲丙酯中的一种或多种。
优选地，所述有机溶剂为碳酸乙烯酯、碳酸二乙酯和碳酸甲乙酯的混合物。
优选地，所述天然石墨含量为所述负极活性物质总质量的0-80质量％；
更优选地，所述天然石墨含量为所述负极活性物质总质量的20-50质量％。
优选地，所述正极活性物质为钴酸锂、锰酸锂、镍酸锂、镍钴锰酸锂、镍钴铝酸锂和磷酸铁锂中的一种或多种；
更优选地，所述正极活性物质为镍钴锰酸锂和/或磷酸铁锂。
优选地，所述非水电解液进一步包含添加剂，所述添加剂选自不饱和环状碳酸酯、氟代环状碳酸酯、环状磺酸内酯、环状硫酸酯、磷酸酯和硼酸酯中的一种或多种。
优选地，所述不饱和环状碳酸酯选自碳酸亚乙烯酯、碳酸乙烯亚乙酯和亚甲基碳酸乙烯酯中的一种或多种。
优选地，所述氟代环状碳酸酯选自氟代碳酸乙烯酯、三氟甲基碳酸乙烯酯和双氟代碳酸乙烯酯中的一种或多种。
优选地，所述环状磺酸内酯选自1,3-丙烷磺内酯、1,4-丁烷磺内酯和丙烯基-1,3-磺酸内酯中的一种或多种。
优选地，所述环状硫酸酯选自硫酸乙烯酯、4-甲基硫酸乙烯酯和硫酸丙烯酯中的一种或多种。
优选地，所述磷酸酯为三(三甲基硅烷)磷酸酯和/或三丙炔基磷酸酯。
优选地，所述硼酸酯为三(三甲基硅烷)硼酸酯和/或三(三乙基硅烷)硼酸酯。
优选地，所述添加剂的含量为所述非水电解液总量的0.1-8质量％。
通过上述技术方案，所述锂离子电池以人造石墨和/或天然石墨为负极，非水电解液中含有特定的环硫酸酯类化合物和/或环亚硫酸酯类化合物，且电解液质量：电池容量为特定范围，该电池长循环过程中容量保持率高。
进而，本发明还提供以特定比例的天然石墨和人造石墨为负极的锂离子电池，该电池表现出优于以人造石墨为电极的锂离子电池的优良性能，
附图说明
图1是实施例1的锂离子电池在45℃下循环1000次后拆解出的负极极片的照片。
图2是对比例1的锂离子电池在45℃下循环1000次后拆解出的负极极片的照片。
具体实施方式
在本文中所披露的范围的端点和任何值都不限于该精确的范围或值，这些范围或值应当理解为包含接近这些范围或值的值。对于数值范围来说，各个范围的端点值之间、各个范围的端点值和单独的点值之间，以及单独的点值之间可以彼此组合而得到一个或多个新的数值范围，这些数值范围应被视为在本文中具体公开。
本发明提供一种锂离子电池，所述锂离子电池包括：包含正极活性物质的正极、包含负极活性物质的负极、置于正极和负极之间的隔膜以及非水电解液，所述负极活性物质包括人造石墨和/或天然石墨，所述锂离子电池非水 电解液的电解液质量：电池容量为1.2-4g/Ah；所述非水电解液包括锂盐、有机溶剂和由以下式(1)～式(3)表示的化合物中的一种或多种，
Figure PCTCN2021113011-appb-000006
式(1)、式(2)、式(3)中，A 1、A 6、A 11各自为：
Figure PCTCN2021113011-appb-000007
中的一种或多种，A 2、A 3、A 4、A 5、A 7、A 8、A 9、A 10、A 12、A 13、A 14、A 15各自为单键或亚甲基，m、n和p均为0到6的整数，—*表示与A 2、A 3、A 4、A 5、A 7、A 8、A 9、A 10、A 12、A 13、A 14、A 15结合的位置。
作为上述m例如可以为1、2、3、4、5或6。
作为上述n例如可以为1、2、3、4、5或6。
作为上述p例如可以为1、2、3、4、5或6。
本发明的发明人意外地发现，当锂离子电池的负极活性物质为人造石墨和/或天然石墨，且其非水电解液中含有式(1)～式(3)表示的化合物时，即使电解液质量：电池容量低至1.2g/Ah，所得锂离子电池的性能仍优秀，表现出优于电解液质量：电池容量更高的锂离子电池的性能。本发明的发明人推测，这是由于式(1)～式(3)表示的化合物化成时生成的SEI膜在石墨负极上形成特定结合，该结合化学性质稳定且锂离子传输性能优异，使得非水电解液在循环过程中的消耗远低于未添加该类化合物的电解液，因此低电解液质量：电池容量的锂离子电池表现出更优异的性能。
根据本发明，当电解液质量：电池容量较低时，本发明的锂离子电池表现出优异的性能，具体地，所述锂离子电池非水电解液的电解液质量：电池容量为1.2-4g/Ah；优选地，所述锂离子电池非水电解液的电解液质量：电池容量为2-3.5g/Ah。
根据本发明，优选地，由式(1)～式(3)表示的化合物选自以下化合 物1-15中的一种或多种：
Figure PCTCN2021113011-appb-000008
Figure PCTCN2021113011-appb-000009
根据本发明，提高式(1)～式(3)表示的化合物含量可提高锂离子电池性能，但所述式(1)～式(3)表示的化合物含量过高时，所得锂离子电池初始阻抗偏大，电池倍率性能降低。为了得到性能良好的锂离子电池，优选地，式(1)～式(3)表示的化合物含量为锂离子电池非水电解液总质量的0.01-5质量％；更优选地，式(1)～式(3)表示的化合物含量为所述锂离子电池非水电解液总质量的0.05-3质量％。
根据本发明，所述锂离子电池非水电解液中的锂盐可以使用本领域常用于制备锂离子电池的各种锂盐，没有特别的限定 ，例如可以选择LiPF 6、LiPO 2F 2、LiBF 4、LiBOB、LiClO 4、LiCF 3SO 3、LiDFOB、LiN(SO 2CF 3) 2、LiN(SO 2C 2F 5) 2、LiC(SO 2CF 3) 3、LiN(SO 2F) 2、LiTFSI和LiDFOB等中的一种或多种；优选地，所述锂盐选自LiPF 6、LiBF 4、LiPO 2F 2、LiTFSI、LiBOB、LiDFOB和LiN(SO 2F) 2中的一种或多种；更优选地，所述锂盐选自LiPF 6和/或LiPO 2F 2。当使用上述锂盐时，可以显著提高非水电解液的电导率，提升锂离子电池的性能，降低生产成本。
本发明中，所述锂盐的含量可以为本领域锂离子电池中的通常含量，没 有特别的限定。优选地，所述锂盐的浓度为0.5-2mol/L。当所述锂盐的含量在此范围内时，可以保证非水电解液的电导率较高，电池综合性能优良。
根据本发明，所述锂离子电池非水电解液中的有机溶剂可以为本领域常用于制备非水电解液的各种有机溶剂，没有特别地限定，例如，可以使用环状碳酸酯、链状碳酸酯、羧酸酯和醚类等作为有机溶剂。优选地，所述有机溶剂为碳酸酯类化合物，所述碳酸酯类化合物为环状碳酸酯和/或链状碳酸酯。
优选地，所述环状碳酸酯为碳酸乙烯酯、碳酸丙烯酯、碳酸丁烯酯、碳酸亚乙烯酯和氟代碳酸乙烯酯中的一种或多种。
优选地，所述链状碳酸酯为碳酸二甲酯、碳酸二乙酯、碳酸二丙酯、碳酸甲乙酯和碳酸甲丙酯中的一种或多种。
更优选地，所述有机溶剂为碳酸乙烯酯、碳酸二乙酯和碳酸甲乙酯的混合物。
在本发明一个特别优选的实施方式中，所述有机溶剂为碳酸乙烯酯、碳酸二乙酯和碳酸甲乙酯的混合物，且碳酸乙烯酯、碳酸二乙酯和碳酸甲乙酯的质量比为30：50：20。通过使用在上述比例范围内的上述三种化合物作为有机溶剂，可以使非水电解液获得较高的电导率，有利于提高电池的综合性能。
根据本发明，所述正极活性物质可以为用于锂电池中的各种正极活性物质。作为所述正极活性物质例如可以为钴酸锂、锰酸锂、镍酸锂、镍钴锰酸锂、镍钴铝酸锂和磷酸铁锂中的一种或多种；优选地，所述正极活性物质为镍钴锰酸锂和/或磷酸铁锂。
在本发明的一个特别优选的实施方式中，所述正极活性物质为LiNi 0.5Co 0.2Mn 0.3O 2。
根据本发明，所述天然石墨含量为所述负极活性物质总质量的0-80质量％；优选地，所述天然石墨含量为所述负极活性物质总质量的20-50质量％。
本发明的发明人意外地发现，当锂离子电池负极活性物质包含天然石墨和人造石墨，且天然石墨的含量为负极活性物质总质量的20-50质量％时，含有所述特定的环硫酸酯类化合物的锂离子电池的性能特别优异，表现出优于以人造石墨为电极的锂离子电池的性能。本发明的发明人推测，这可能是因为当负极活性物质中含有特定比例的天然石墨时，式(1)～式(3)表示的化合物与石墨负极产生的结合更加稳定，对负极的保护效果更好。
根据本发明，除了式(1)～式(3)表示的化合物以外，所述锂离子电池还可以进一步含有本领域常用于提高锂离子电池性能的各种添加剂，例如，作为这样的添加剂可以选自不饱和环状碳酸酯、氟代环状碳酸酯、环状磺酸内酯、环状硫酸酯、磷酸酯和硼酸酯等。
本发明中，优选地，所述不饱和环状碳酸酯为选自碳酸亚乙烯酯(CAS：872-36-6)、碳酸乙烯亚乙酯(CAS：4427-96-7)和亚甲基碳酸乙烯酯(CAS：124222-05-5)中的一种或多种。
本发明中，优选地，所述氟代环状碳酸酯选自氟代碳酸乙烯酯(CAS：114435-02-8)、三氟甲基碳酸乙烯酯(CAS：167951-80-6)和双氟代碳酸乙烯酯(CAS：311810-76-1)中的一种或多种。
本发明中，优选地，所述环状磺酸内酯选自1,3-丙烷磺内酯(CAS：1120-71-4)、1,4-丁烷磺内酯(CAS：1633-83-6)和丙烯基-1,3-磺酸内酯(CAS：21806-61-1)中的一种或多种。
本发明中，优选地，所述环状硫酸酯选自硫酸乙烯酯(CAS：1072-53-3)、4-甲基硫酸乙烯酯(CAS：5689-83-8)和硫酸丙烯酯中的一种或多种。
本发明中，优选地，所述磷酸酯为三(三甲基硅烷)磷酸酯和/或三丙炔基磷酸酯。
本发明中，优选地，所述硼酸酯为三(三甲基硅烷)硼酸酯和/或三(三乙基硅烷)硼酸酯。
本发明中，更优选地，所述添加剂为碳酸亚乙烯酯(VC)、氟代碳酸乙烯酯(FEC)、1,3-丙烷磺内酯(PS)和硫酸乙烯酯(DTD)中的一种或多种。本发明的发明人发现，当在锂离子电池中进一步添加上述添加剂时，可以与式(1)～式(3)表示的化合物发挥协同作用，提升锂离子电池的综合性能。
本发明中，所述添加剂的含量可以为本领域各种添加剂在锂离子电池中的常规含量。例如，所述添加剂的含量可以为所述非水电解液总量的0.1-8质量％；优选地，所述添加剂的含量为所述非水电解液总量的0.1-5质量％。
本发明中，所述锂离子电池正极和负极的制备可以按照本领域常用于制备锂离子电池正极和负极的方法进行，没有特别的限制。例如，可以将正负极的活性材料与导电剂和粘接剂混合，并将混合物分散于溶剂，制得浆料，之后将所得浆料涂覆于集流体上并进行干燥和延压等处理。所用导电剂、粘 接剂、有机溶剂和集流体等均可采用本领域常用的材料和物质，此处不再赘述。根据本发明，所述锂离子电池的制备可以采用本领域通常使用的方式，例如可以为：将正极/负极活性物质，导电材料，粘结剂混合涂布在金属上制备正极/负极极片，将正极极片、隔膜、负极极片依次层叠或卷绕成裸电芯，将裸电芯置于壳体中得到电芯，向所得电芯中注入所述电解液并封口，得到所述锂离子电池。
根据本发明，所述置于正极和负极之间的隔膜可以为本领域常用作隔膜的各种材料，没有特别的限定，例如，可以为聚烯烃类隔膜、聚酰胺类隔膜、聚砜类隔膜、聚磷腈类隔膜、聚醚砜类隔膜、聚醚醚酮类隔膜、聚醚酰胺类隔膜和聚丙烯腈类隔膜中的一种或多种；优选地，所述隔膜选自聚烯烃类隔膜和聚丙烯腈类中的一种或多种。
根据本发明，所述壳体没有特别限定，可以为本领域常用的各种壳体，例如可以为不锈钢壳体、铝壳体、铝塑膜壳体；优选地，所述壳体为铝塑膜壳体。
以下将通过实施例对本发明进行详细描述，但本发明并不仅限于下述实施例。
以下实施例和对比例中，化合物1、3、11购于上海阿拉丁生化科技有限公司，化合物10、15购于上海麦克林生化科技有限公司。
实施例1
(1)电解液的制备
在水氧含量均小于10ppm的手套箱中，将碳酸乙烯酯(EC)、碳酸二乙酯(DEC)、碳酸甲乙酯(EMC)按照质量比＝3:5:2进行混合。-20℃冷冻后加入六氟磷酸锂(LiPF 6)浓度为1mol/L，按照表1所示含量加入化合物1和其他添加剂得到非水电解液。
(2)正极极片的制备
将将粘结剂PVDF溶于N-甲基吡咯烷酮中，向其中加入正极活性材料LiNi 0.5Co 0.2Mn 0.3O 2和导电剂炭黑，充分混合后得到正极浆料(正极活性材料、导电剂和粘结剂的质量比为96：2：2，N-甲基吡咯烷酮的用量使得正极浆料的固含量为70质量％)。将得到的正极浆料涂覆于20μm厚的正极铝箔上(涂覆厚度为15μm)，然后在85℃下鼓风干燥24h，冷压卷起，焊接极耳， 得到锂离子电池正极极片。
(3)负极极片的制备
将负极活性材料人造石墨和天然石墨(以人造石墨和天然石墨总质量计，人造石墨70质量％，天然石墨30质量％)，导电剂炭黑，增稠剂羧甲基纤维素钠，粘结剂丁苯橡胶溶于水中得到负极浆料(负极活性材料、导电剂、增稠剂和粘结剂的质量比为95：1：1.5：2.5，水的用量使得负极浆料的固含量为45质量％)。将负极浆料涂覆于12μm厚的负极铜箔上(涂覆厚度为9μm)，然后85℃下鼓风干燥24h，冷压卷起，焊接极耳，得到负极极片。
(4)电芯的制备
在步骤(2)和(3)所得正极极片和负极极片之间放置20μm聚乙烯隔膜，然后将正极极片、隔膜和负极极片组成的三明治结构进行卷绕得到裸电芯，再将电芯压扁后放入作为壳体的铝塑膜中，将正负极的极耳分别引出后，热压封口铝塑膜，得到待注液的电芯。
(5)电芯的注液和化成
在露点控制在-40℃以下的手套箱中，将上述步骤(1)得到的非水电解液按表1所示电解液质量：电池容量注入待注液的电芯中，真空封装、静置24h。然后按以下步骤进行化成：0.05C倍率恒流充电180min，0.1C倍率恒流充电180min，0.2C倍率恒流充电120min。搁置24h后进行整形和二次封口，然后进一步以0.2C倍率的电流恒流充电至4.2V，常温搁置5min后，以0.2C倍率的电流恒流放电至3.0V。
实施例2-19，对比例1-7：
按照实施例1的方式制备锂离子电池，不同之处在于，天然石墨占负极活性物质比例、非水电解液的电解液质量：电池容量比例、式(1)～式(3)表示的化合物种类及含量、其他添加剂的种类与含量为下述表1所示的值。
表1
Figure PCTCN2021113011-appb-000010
Figure PCTCN2021113011-appb-000011
注：VC指碳酸亚乙烯酯，DTD指硫酸乙烯酯，FEC指氟代碳酸乙烯酯，PS指1，3-丙烷磺内酯
测试例1
在45℃下，使用排水法测定实施例1-19及对比例1-7制备的锂离子电池的初始体积，水分晾干后，将电池置于恒温45℃的高温烘箱中，以0.5C倍率的电流恒流充电至4.2V，再恒压充电至电流下降至0.05C倍率，搁置5分钟后，以1C倍率的电流恒流放电至3V，即为首次循环。按照上述条件分别进行1000次循环充电/放电，分别计算得出电池在45℃下循环1000次后的放电容量和内阻，电池循环结束后从烘箱中取出，在常温下搁置8h，同样使用排水法测定循环后的电池体积。
按下式计算高温循环的容量保持率：
循环后的电池容量保持率(％)＝(第1000次循环后的放电容量-首次循环的放电容量)/首次循环的放电容量×100％，
按下式计算高温循环的内阻增长率：
循环后的电池内阻增长率(％)＝(第1000次循环后的内阻-首次循环的内阻)/首次循环的内阻。
按下式计算高温循环的体积增长率：
循环后的电池体积增长率(％)＝(第1000次循环后的体积-首次循环的体积)/首次循环的体积。
结果见表2所示。
表2
实施例编号 容量保持率(％) 初始内阻(Ω) 内阻增长率(％) 体积增长率(％)
实施例1 90.1 24 54.4 20.1
实施例2 88.9 25.1 58.3 21.8
实施例3 89.2 24 55.0 22.3
实施例4 87.4 25.5 60.7 23.5
实施例5 84.5 26.1 62.4 26.4
实施例6 87.1 25.6 70.3 43.5
实施例7 87 24.2 55.1 35.2
实施例8 83.9 22.6 70.2 42.3
实施例9 85.8 23.2 68.8 36.5
实施例10 87.6 23.5 63.2 27.4
实施例11 90.2 26.9 47.1 20.9
实施例12 87.7 40.6 70.3 31.4
实施例13 86 27 67.4 25.1
实施例14 86.3 27.1 59.8 23.7
实施例15 89.9 23.4 48.1 17.6
实施例16 92.1 35.6 40.9 23.0
实施例17 92.5 36.4 53.1 22.1
实施例18 89.3 32.7 60.2 26.5
实施例19 90.8 26.3 54.8 19.2
对比例1 56.3 22.5 84.1 60.3
对比例2 78.6 28.0 68.4 31.1
对比例3 69.9 50.4 61.1 21.6
对比例4 89.4 30.1 58.7 26.7
对比例5 90 25.2 60.5 20.4
对比例6 87.3 28.4 63.4 23.9
对比例7 88.5 23.9 66.2 50.1
对比分析实施例1、实施例8-12和对比例1，说明添加了式(1)～式(3)表示的化合物的锂离子电池循环性能优于未添加环硫酸酯/环亚硫酸酯类化合物的锂离子电池。
对比分析实施例1、实施例13-15和对比例2，说明当非水电解液的注液系数电解液质量：电池容量低于1.2g/Ah时，锂离子电池的循环性能显著降低。
对比分析实施例1、实施例13-15和对比例3，当非水电解液的电解液质量：电池容量高于本发明的优选范围时，锂离子电池的初始内阻过高，同时也导致循环性能降低。
对比分析实施例1-4和实施例5-8，说明负极活性物质中天然石墨含量在本发明的优选范围内时，式(1)～式(3)表示的化合物对石墨负极的保护效果更好，电池内阻低，容量保持率好。
对比分析实施例1与实施例8-12，说明当式(1)～式(3)表示的化合物的含量在本发明的优选范围内时，保护效果更好，电池内阻低，容量保持率好。
对比实施例1-3、实施例13-15和对比例1，在权利要求范围内，电解液质量：电池容量比例越高，对电池循环性能越有利。由于天然石墨材料表面活性位点多，循环过程中会消耗大量电解液，容易导致界面干涸从而循环跳水。为保证电池正常循环性能，该电池体系常规使用的电解液质量：电池容量需要≥4g/Ah，但该比例越高，其质量能量密度越低，成本越高。本发明中使用的环状酯化合物可有效降低循环过程的电解液消耗，所以电解液质量：电池容量范围为1.2-4g/Ah时，循环性能显著优于不使用该环状酯化合物的电解液，同时有效提高了能量密度。进一步对比实施例13与对比例1，在没有环状硫酸酯化合物的情况下(对比例1)，尽管电解液质量：电池容量达到4g/Ah，其循环性能仍不如本发明所述化合物(1)存在情况下低电解液质量：电池容量的电池(实施例13)。说明低电解液质量：电池容量下，化合物(1)代表的环状硫酸酯类化合物可以有效保护电极材料，优化循环性能。
对比实施例16-19与对比例4-7，在有其他添加剂存在的情况下，式(1)～式(3)表示的化合物(实施例16-19)对电池的循环性能有进一步的改善作用，比没有该类化合物的电池(对比例4-7)高温循环结果更好。
另外，图1是实施例1的锂离子电池在45℃下循环1000次后拆解出的负极极片的照片。图2是对比例1的锂离子电池在45℃下循环1000次后拆解出的负极极片的照片。对比分析图1和图2，说明式(1)～式(3)表示的化合物对负极包含天然石墨的锂离子电池的循环性能有很大的改善作用，其反应生成的副产物可有效覆盖天然石墨表面活性位点，阻止后续溶剂和锂盐的大量消耗，1000次循环过后非水电解液仍足量。
以上详细描述了本发明的优选实施方式，但是，本发明并不限于此。在本发明的技术构思范围内，可以对本发明的技术方案进行多种简单变型，包括各个技术特征以任何其它的合适方式进行组合，这些简单变型和组合同样应当视为本发明所公开的内容，均属于本发明的保护范围。

Claims (9)

  1. 一种锂离子电池，其特征在于，所述锂离子电池包括：包含正极活性物质的正极、包含负极活性物质的负极、置于正极和负极之间的隔膜以及非水电解液，
    所述负极活性物质包括人造石墨和/或天然石墨；
    所述锂离子电池非水电解液的电解液质量：电池容量为1.2-4g/Ah；
    所述非水电解液包括锂盐、有机溶剂和由以下式(1)～式(3)表示的化合物中的一种或多种，
    Figure PCTCN2021113011-appb-100001
    式(1)、式(2)、式(3)中，A 1、A 6、A 11各自为：
    Figure PCTCN2021113011-appb-100002
    中的一种或多种，A 2、A 3、A 4、A 5、A 7、A 8、A 9、A 10、A 12、A 13、A 14、A 15各自为单键或亚甲基，m、n和p均为0到6的整数，—*表示与A 2、A 3、A 4、A 5、A 7、A 8、A 9、A 10、A 12、A 13、A 14、A 15结合的位置。
  2. 根据权利要求1所述的锂离子电池，所述锂离子电池非水电解液的电解液质量：电池容量为2-3.5g/Ah。
  3. 根据权利要求1或2的锂离子电池，其中，由式(1)～式(3)表示的化合物选自以下化合物1-15中的一种或多种：
    Figure PCTCN2021113011-appb-100003
    Figure PCTCN2021113011-appb-100004
    Figure PCTCN2021113011-appb-100005
  4. 根据权利要求1-3中任意一项所述的锂离子电池，其中，式(1)～式(3)表示的化合物的含量为所述锂离子电池非水电解液总质量的0.01-5质量％；
    优选地，式(1)～式(3)表示的化合物的含量为所述锂离子电池非水电解液总质量的0.05-3质量％。
  5. 根据权利要求1-3中任意一项所述的锂离子电池，其中，所述锂盐为选自LiPF 6、LiPO 2F 2、LiBF 4、LiBOB、LiClO 4、LiCF 3SO 3、LiDFOB、LiN(SO 2CF 3) 2、LiN(SO 2C 2F 5) 2、LiC(SO 2CF 3) 3、LiN(SO 2F) 2、LiTFSI和LiDFOB中的一种或多种；
    优选地，所述锂盐为LiPF 6和/或LiPO 2F 2；
    优选地，所述锂盐的浓度为0.5-2mol/L。
  6. 根据权利要求1-3中任意一项所述的锂离子电池，其中，所述有机溶剂为碳酸酯类化合物，所述碳酸酯类化合物为环状碳酸酯和/或链状碳酸酯；
    优选地，所述环状碳酸酯为碳酸乙烯酯、碳酸丙烯酯、碳酸丁烯酯、碳酸亚乙烯酯和氟代碳酸乙烯酯中的一种或多种；
    优选地，所述链状碳酸酯为碳酸二甲酯、碳酸二乙酯、碳酸二丙酯、碳 酸甲乙酯和碳酸甲丙酯中的一种或多种；
    优选地，所述有机溶剂为碳酸乙烯酯、碳酸二乙酯和碳酸甲乙酯的混合物。
  7. 根据权利要求1-3中任意一项所述的锂离子电池，所述天然石墨含量为所述负极活性物质总质量的0-80质量％；
    优选地，所述天然石墨含量为所述负极活性物质总质量的20-50质量％。
  8. 根据权利要求1-3中任意一项所述的锂离子电池，所述正极活性物质为钴酸锂、锰酸锂、镍酸锂、镍钴锰酸锂、镍钴铝酸锂和磷酸铁锂中的一种或多种；
    优选地，所述正极活性物质为镍钴锰酸锂和/或磷酸铁锂。
  9. 根据权利要求1-3中任意一项所述的锂离子电池，其中，所述非水电解液进一步包含添加剂，所述添加剂选自不饱和环状碳酸酯、氟代环状碳酸酯、环状磺酸内酯、环状硫酸酯、磷酸酯和硼酸酯中的一种或多种；
    优选地，所述不饱和环状碳酸酯选自碳酸亚乙烯酯、碳酸乙烯亚乙酯和亚甲基碳酸乙烯酯中的一种或多种；
    优选地，所述氟代环状碳酸酯选自氟代碳酸乙烯酯、三氟甲基碳酸乙烯酯和双氟代碳酸乙烯酯中的一种或多种；
    优选地，所述环状磺酸内酯选自1,3-丙烷磺内酯、1,4-丁烷磺内酯和丙烯基-1,3-磺酸内酯中的一种或多种；
    优选地，所述环状硫酸酯选自硫酸乙烯酯、4-甲基硫酸乙烯酯和硫酸丙烯酯中的一种或多种；
    优选地，所述磷酸酯为三(三甲基硅烷)磷酸酯和/或三丙炔基磷酸酯；
    优选地，所述硼酸酯为三(三甲基硅烷)硼酸酯和/或三(三乙基硅烷)硼酸酯；
    优选地，所述添加剂的含量为所述非水电解液总量的0.1-8质量％。
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CN115312856A (zh) * 2022-09-13 2022-11-08 武汉大学 一种锂电池非燃电解液及其应用
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