WO2021110165A1 - Lithium secondary battery electrolyte with low internal resistance and lithium secondary battery - Google Patents

Lithium secondary battery electrolyte with low internal resistance and lithium secondary battery Download PDF

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WO2021110165A1
WO2021110165A1 PCT/CN2020/134175 CN2020134175W WO2021110165A1 WO 2021110165 A1 WO2021110165 A1 WO 2021110165A1 CN 2020134175 W CN2020134175 W CN 2020134175W WO 2021110165 A1 WO2021110165 A1 WO 2021110165A1
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lithium
electrolyte
secondary battery
lithium secondary
carbonate
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PCT/CN2020/134175
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French (fr)
Chinese (zh)
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范伟贞
刘念滔
范超君
赵经纬
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广州天赐高新材料股份有限公司
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Publication of WO2021110165A1 publication Critical patent/WO2021110165A1/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
    • 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
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • This application belongs to the field of lithium secondary battery electrolytes, and relates to an electrolyte containing specific fluorophosphate additives.
  • Electrolyte is the medium for lithium ions to migrate between the positive and negative electrodes in the lithium secondary battery, and it has an important impact on the lithium battery capacity, operating temperature, cycle efficiency and safety. It is generally prepared from raw materials such as high-purity organic solvents, electrolyte lithium salts, and main additives under certain conditions. In order to improve the performance of lithium batteries, the improvement of electrolyte is a current research hotspot.
  • LiPF 6 has outstanding comprehensive properties such as ion mobility, ion dissociation rate, solubility, surface chemistry and passivation ability to current collectors, and is considered to be the "best" conductive salt in the market. Although it has achieved commercial success, LiPF 6 is chemically and thermally unstable, and is prone to decomposition and positive and negative reactions. Therefore, it is necessary to add additives to improve the stability of LiPF 6 in the electrolyte and improve battery performance. .
  • the electrolyte is prepared by mixing lithium hexafluorophosphate, lithium tetrafluorophosphate, ethyl propionate, ethyl acetate, sodium chloride, potassium chloride, dibutyl carbonate, additives and deionized water; the prepared electrolyte can make lithium Ion batteries can be charged and discharged quickly under high-rate current conditions and can be effectively discharged under low-temperature environments.
  • the electrolyte is charged and discharged at a rate of 8C at 25°C, and the discharge capacity reaches more than 95% of the rated capacity, and the 1C charge and 5C discharge cycles are 2000 times, and the capacity retention rate is more than 90%; at -20°C, 5C rate current discharge, the discharge capacity reaches more than 80% of the rated capacity.
  • electrolytes such as sodium chloride and potassium chloride are also added to the application. Due to the presence of chloride ions, it is easy to corrode the Al current collector and reduce the service life of the battery.
  • CN109148951A additives include boron phosphorous lithium oxalate; lithium fluorophosphate; and one or two of vinylene carbonate and fluoroethylene carbonate.
  • Lithium fluorophosphate can passivate the positive electrode, inhibit the side reaction of the positive electrode and dimethyl carbonate, etc., and cooperate with the boron phosphorus lithium oxalate salt to improve the normal temperature and high temperature fast charge cycle performance and high temperature storage performance of lithium ion batteries, while reducing lithium ion batteries The impedance at low temperature improves the low-temperature power performance of lithium-ion batteries.
  • lithium-ion batteries have normal temperature and high temperature fast charge cycle performance, normal temperature and low temperature power performance, and high temperature storage
  • the performance is relatively good, meeting the fast charging requirements of lithium-ion batteries, while taking into account the requirements of high energy density and high power performance.
  • the fluorolithium phosphate used in the invention has poor solubility in non-aqueous solvents, which will significantly reduce the conductivity of the electrolyte, resulting in poor normal temperature power performance of the lithium ion battery.
  • the lithium salt of oxalic acid is easy to decompose to produce oxalate, which is easy to cause battery flatulence in the battery, which affects the safety and service life of the battery.
  • the additives in CN108123172A include fluoroborate and lithium difluorophosphate.
  • Lithium difluorophosphate can improve the high-temperature cycle performance, high-temperature storage performance, and low-temperature discharge performance of secondary lithium batteries.
  • the role of lithium difluorophosphate with the positive electrode is beneficial to reduce the electrochemical reaction impedance of the positive electrode, improve the kinetic performance of the positive electrode, and improve the low-temperature discharge performance of the secondary lithium battery.
  • lithium difluorophosphate will undergo reductive decomposition in the negative electrode, and the decomposition product will cover the surface of the negative electrode, resulting in an increase in the lithium insertion resistance of the negative electrode, which is not conducive to the high-rate charging performance of the negative electrode.
  • Fluorinated boronic acid esters are easily hydrolyzed to produce boric acid in the presence of trace amounts of water, and boric acid is not conducive to the cycle performance of the battery.
  • CN108232296A and CN108232297A use fluorophosphate in combination with fluorophosphate and/or cyclophosphazene compound to significantly reduce the negative electrode SEI film interface impedance of lithium ion batteries, reduce the low-temperature internal resistance of lithium ion batteries, and improve the Power performance, while significantly inhibiting the production of gas during the cycle and storage of lithium-ion batteries, so as to well improve the cycle performance, high-temperature storage performance and safety performance of lithium-ion batteries.
  • the purpose of this application is to provide a lithium secondary battery electrolyte containing LiPF 6 electrolyte lithium salt.
  • the lithium secondary battery using the electrolyte has good thermal and chemical stability during high-rate charging and discharging. At the same time, it has low internal resistance, good low temperature performance and cycle life. At the same time, this application also discloses a lithium ion battery using the electrolyte.
  • the key means to solve the problem is: when the polyfluorophosphate shown in the following formula (1) is added to the lithium secondary battery electrolyte containing LiPF 6 electrolyte lithium salt, the electrolyte has good heat Stability and chemical stability, while having low internal resistance, good low temperature performance and cycle life.
  • M is selected from any one or a combination of Li, Na, and K.
  • M is selected from any one of Li, Na, and K, and R 1 , R 2 , R 3 , R 4 , R 5 , and R 6 are each independently selected from methyl or ethyl.
  • the compound of formula (1) improves the thermal and chemical stability of lithium hexafluorophosphate
  • the applicant can reasonably speculate that the oxygen in the anion part of the compound of formula (1) can complex with the transition metal element in the positive electrode active material It can improve the stability of the positive electrode active material, thereby reducing the oxidation activity of LiPF 6 lithium salt in the electrolyte, thereby effectively improving the high temperature cycle performance of the secondary lithium battery and inhibiting the volume expansion of the secondary lithium battery at high temperatures.
  • the SEI film formed on the surface of the negative electrode forms a diffusion channel that is conducive to lithium ion transmission, and then forms an SEI film with lower impedance, which can improve the battery performance at low temperatures.
  • the charging performance prevents LiPF 6 from forming high-impedance reduction decomposition products covering the surface of the negative electrode.
  • the solubility of the compound of formula (1) is better than the solubility of lithium monofluorophosphate and lithium difluorophosphate in non-aqueous organic solvents, it has better interface wettability, which provides a better solution for reducing the electrolytic resistance of the electrolyte. Excellent choice.
  • this application proposes a lithium secondary battery electrolyte, which contains: 1) LiPF 6 electrolyte lithium salt, 2) non-aqueous organic solvent; 3) additives, the additives are as shown in the following formula (1) structural formula Fluorophosphate:
  • M is selected from any one or a combination of Li, Na, and K.
  • the electrolyte optionally contains other lithium salts, selected from lithium bis(trifluoromethylsulfonyl)imide, lithium bisfluorosulfonimide (LiFSI), and tetrafluoroethylene At least one of lithium borate (LiBF 4 ) and lithium bisoxalate borate (LiBOB).
  • the non-aqueous organic solvent is dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene carbonate, ethyl acetate, methyl propyl carbonate, fluoroethylene carbonate, 2,2-difluoroethyl ethyl At least one of acid ester, trifluoroethyl propionate, difluoroethyl propionate, fluoropropylene carbonate, methyl propyl carbonate, ⁇ -butyrolactone, and ⁇ -valerolactone.
  • the lithium secondary battery electrolyte of the present application may also contain selected from vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, lithium difluorodioxalate phosphate, vinyl sulfate, triallyl phosphate, tripropylene
  • One or more of the second additives of alkynyl phosphate, tris(trimethylsilane) phosphate, and hexamethylene diisocyanate is electrolytic
  • the liquid additive is used in combination with the second additive, it can achieve better cycle performance than when they are used alone. It is assumed that there is a synergistic effect between them, that is, when used with the compound of formula (1), it can further reduce the electrolyte at room temperature. Under the impedance.
  • This application also proposes a lithium secondary battery electrolyte containing the lithium secondary battery electrolyte additive of formula (1), including a lithium salt, a non-aqueous solvent, the formula (1) lithium secondary battery electrolyte additive, and the LiPF 6
  • the mass percentage of lithium salt is 10%-25%; the mass percentage of the non-aqueous solvent is 60%-89.99%; the mass percentage of the formula (1) lithium secondary battery electrolyte additive is 0.01%- 5%, the mass percentage of the second additive is 0%-10%.
  • This application also proposes the application of the electrolyte additive of the formula (1) lithium secondary battery for use in the non-aqueous system lithium secondary battery electrolyte containing the LiPF 6 electrolyte lithium salt.
  • the formula (1) lithium secondary battery electrolyte The weight percentage of the battery electrolyte additive in the lithium ion battery electrolyte is 0.01% to 5%.
  • the present application adds 0.01% to 5% of the total mass of the electrolyte as an additive to the electrolyte of a lithium secondary battery containing LiPF 6 electrolyte lithium salt, which can reduce the internal resistance of the battery while having more Good low temperature performance, high temperature performance, rate performance and cycle life.
  • the positive electrode active material, lithium nickel cobalt manganese oxide (LiNi 1/3 Co 1/3 Mn 1/3 O 2 ), the conductive agent Super-P, and the adhesive PVDF are dissolved in the solvent N-form at a mass ratio of 96:2.0:2.0.
  • the negative electrode active material graphite, conductive agent Super-P, thickener CMC, and binder SBR are dissolved in the solvent deionized water at a mass ratio of 96.5:1.0:1.0:1.5 and mixed uniformly to make a negative electrode slurry, and then the negative electrode slurry Coat evenly on the current collector copper foil with a coating amount of 0.0089g/cm 2 , then dry at 85°C, then perform cold pressing, trimming, cutting, and slitting, and then dry at 110°C under vacuum for 4h , Weld the tabs to make the negative electrode sheet of the lithium secondary battery that meets the requirements.
  • the electrolyte of the lithium secondary battery uses lithium hexafluorophosphate which accounts for 12.5% of the total mass of the electrolyte as the lithium salt, and uses a mixture of ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate as the non-aqueous organic solvent, which accounts for 86.39 of the total mass of the electrolyte. %, where the mass ratio of ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate is 3:5:2.
  • the lithium secondary electrolyte also contains additives, and the first additive is lithium tetrafluorophosphate accounting for 0.01% of the total mass of the lithium secondary battery electrolyte.
  • the second additives are vinylene carbonate and fluoroethylene carbonate, which respectively account for 0.1% and 1.0% of the total mass of the electrolyte.
  • the positive electrode sheet, the negative electrode sheet and the separator of the lithium secondary battery prepared according to the foregoing process are made into a battery with a thickness of 8mm, a width of 60mm, and a length of 130mm through a winding process, and vacuum-baked at 75°C 10h, inject electrolyte, stand for 24h, then charge to 4.2V with a constant current of 0.1C (160mA), then charge with a constant voltage of 4.2V until the current drops to 0.05C (80mA), and then charge at 0.1C (160mA) Discharge with constant current to 3.0V, repeat the charge and discharge twice, and finally charge to 3.8V with a constant current of 0.1C (160mA) to complete the preparation of the lithium ion battery.
  • the lithium secondary battery was prepared according to the method of Example 1. The difference is that the electrolyte of the lithium secondary battery uses 10.0% of the total mass of the electrolyte as the lithium salt, and the non-aqueous organic solvent is ethylene carbonate and ethyl methyl carbonate. It accounts for 85.5% of the total mass of the electrolyte, and the mass ratio is 1:2. Add sodium tetrafluorophosphate, which accounts for 0.5% of the total mass of the electrolyte. The second additives are fluoroethylene carbonate and lithium difluorophosphate, which respectively account for 3.0% and 1.0% of the total mass of the electrolyte.
  • the cathode material used in the lithium secondary battery is LiNi 0.8 Co 0.1 Mn 0.1 O 2 .
  • the lithium secondary battery was prepared according to the method of Example 1. The difference is that the electrolyte of the lithium secondary battery uses 13.0% of the total mass of the electrolyte as the lithium salt, and the non-aqueous organic solvent is ethylene carbonate and ethyl methyl carbonate. It accounts for 85.0% of the total mass of the electrolyte, and the mass ratio is 1:3. Potassium tetrafluorophosphate is added to account for 0.5% of the total mass of the electrolyte. The second additive is fluoroethylene carbonate, which accounts for 1.5% of the total mass of the electrolyte.
  • the cathode material used in the lithium secondary battery is LiNi 0.8 Co 0.15 Al 0.05 O 2 .
  • the lithium secondary battery was prepared according to the method of Example 1. The difference is that the electrolyte of the lithium secondary battery uses 10.0% of the total mass of the electrolyte as the lithium salt, and the non-aqueous organic solvent is ethylene carbonate and diethyl carbonate. It accounts for 77.5% of the total mass of the electrolyte, and the mass ratio is 1:2. Add lithium tetrafluorophosphate, which accounts for 2.5% of the total mass of the electrolyte. The second additive is fluoroethylene carbonate, and vinyl sulfate accounts for 8.0% and 2.0% of the total mass of the electrolyte, respectively.
  • the positive electrode material used in the lithium secondary battery is LiCoO 2
  • the negative electrode material is a silicon-carbon composite material.
  • the lithium secondary battery was prepared according to the method of Example 1. The difference is that the electrolyte of the lithium secondary battery uses 15% of the total mass of the electrolyte as the lithium salt, and the non-aqueous organic solvent is ethylene carbonate, propylene carbonate, and carbonic acid. Diethyl ester accounts for 81.0% of the total mass of the electrolyte, and the mass ratio is 4:1:5. Add sodium tetrafluorophosphate, accounting for 1.5% of the total mass of the electrolyte. The second additives are tripropynyl phosphate and vinyl sulfate, which respectively account for 0.5% and 2.0% of the total mass of the electrolyte.
  • the positive electrode material used in the lithium secondary battery is LiNi 0.8 Co 0.15 Al 0.05 O 2
  • the negative electrode material is lithium titanate.
  • the charge cut-off voltage of the lithium secondary battery is 2.7V.
  • the lithium secondary battery was prepared according to the method of Example 1. The difference is that the electrolyte of the lithium secondary battery uses 15% of the total mass of the electrolyte as the lithium salt, and uses ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate.
  • the mixture is a non-aqueous organic solvent, accounting for 84.5% of the total mass of the electrolyte, and the mass ratio is 3:5:2.
  • Potassium tetrafluorophosphate is added, which accounts for 1.0% of the total mass of the electrolyte.
  • the second additives are lithium difluorodioxalate phosphate and triallyl phosphate, which respectively account for 1.0% and 0.5% of the total mass of the electrolyte.
  • the cathode material used in lithium secondary batteries is LiCoO 2 .
  • the lithium secondary battery was prepared according to the method of Example 1. The difference is that the electrolyte of the lithium secondary battery uses 17.5% of the total mass of the electrolyte as the lithium salt, and uses ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate.
  • the mixture is a non-aqueous organic solvent, accounting for 77.0% of the total mass of the electrolyte, and the mass ratio is 3:5:2.
  • Lithium tetrafluorophosphate and sodium tetrafluorophosphate are added, accounting for 1.5% and 2.5 of the total mass of the electrolyte, respectively. %.
  • the second additives are fluoroethylene carbonate, lithium difluorooxalate phosphate, and tris(trimethylsilane) phosphate, which account for 3.0%, 0.5%, and 1.0% of the total mass of the electrolyte.
  • the positive electrode material used in the lithium secondary battery is LiMn 2 O 4
  • the negative electrode material is lithium titanate.
  • the lithium secondary battery was prepared according to the method of Example 1. The difference is that the electrolyte of the lithium secondary battery uses 17.5% of the total mass of the electrolyte as the lithium salt, and uses ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate.
  • the mixture is a non-aqueous organic solvent, accounting for 75.5% of the total mass of the electrolyte, and the mass ratio is 3:5:2.
  • Potassium tetrafluorophosphate and sodium tetrafluorophosphate are added to account for 1.0% and 1.0% of the total mass of the electrolyte, respectively.
  • the second additive is ethylene ethylene carbonate, lithium difluorophosphate, tripropynyl phosphate, and tris(trimethylsilane) phosphate, which account for 1.0%, 3.0%, 0.5%, and 0.5% of the total mass of the electrolyte.
  • the cathode material used in the lithium secondary battery is LiMnO 2 .
  • the lithium secondary battery was prepared according to the method of Example 1, the difference is that the electrolyte of the lithium secondary battery uses 20.0% of the total mass of the electrolyte as the lithium salt, and the non-aqueous organic solvent is ethylene carbonate and fluoroethylene carbonate. , Trifluoroethyl propionate, accounting for 70.0% of the total mass of the electrolyte, with a mass ratio of 4:1:5. Lithium tetrafluorophosphate and potassium tetrafluorophosphate are added, which respectively account for 2.5% and 2.5% of the total mass of the electrolyte.
  • the second additives are vinylene carbonate, lithium bisoxalate borate, vinyl sulfate, and hexamethylene diisocyanate, which respectively account for 1.0%, 1.5%, 1.0%, and 1.5% of the total mass of the electrolyte.
  • the positive electrode material used in the lithium secondary battery is LiNi 0.8 Co 0.15 Al 0.05 O 2
  • the negative electrode material is lithium titanate.
  • the charge cut-off voltage of the lithium secondary battery is 2.7V.
  • the lithium secondary battery was prepared according to the method of Example 1, except that in addition to 12.5% of the total mass of the electrolyte, LiPF 6 was added, and 2.5% of lithium trifluoromethanesulfonimide was added as the lithium salt.
  • the organic solvents are dimethyl carbonate and methyl propyl carbonate, which account for 84.5% of the total mass of the electrolyte, and the mass ratio is 1:3.
  • Add lithium tetrafluorophosphate which accounts for 0.5% of the total mass of the electrolyte.
  • the cathode material used in the lithium secondary battery is LiNi 0.8 Co 0.15 Al 0.05 O 2 .
  • the lithium secondary battery was prepared according to the method of Example 1, except that in addition to 12.5% of the total mass of the electrolyte, LiPF 6 was added, and 6.5% of lithium bisfluorosulfonimide (LiFSI) was added as the lithium salt.
  • the non-aqueous organic solvents are ethylene carbonate and diethyl carbonate, accounting for 72.5% of the total mass of the electrolyte, and the mass ratio is 1:2.
  • Lithium tetrafluorophosphate and sodium tetrafluorophosphate are added, which respectively account for 3.0% and 2.0% of the total mass of the electrolyte.
  • the second additive is fluoroethylene carbonate, lithium difluorophosphate, and tris(trimethylsilane) phosphate, which respectively account for 2.0%, 0.5%, and 1.0% of the total mass of the electrolyte.
  • the positive electrode material used in the lithium secondary battery is LiCoO 2
  • the negative electrode material is a silicon-carbon composite material.
  • the lithium secondary battery was prepared according to the method of Example 1, except that the electrolyte of the lithium secondary battery uses 25% of the total mass of the electrolyte as the lithium salt, and the non-aqueous organic solvent is propylene carbonate, diethyl carbonate and ⁇ -butyrolactone accounts for 63.0% of the total mass of the electrolyte, and the mass ratio is 4:1:5. Potassium tetrafluorophosphate is added, which accounts for 4.0% of the total mass of the electrolyte.
  • the second additives are vinylene carbonate, lithium difluorobisoxalate phosphate, and hexamethylene diisocyanate, which respectively account for 2.0%, 3.5%, and 2.5% of the total mass of the electrolyte.
  • the positive electrode material used in the lithium secondary battery is LiNi 0.8 Co 0.15 Al 0.05 O 2
  • the negative electrode material is lithium titanate.
  • the charge cut-off voltage of the lithium secondary battery is 2.7V.
  • the lithium secondary battery was prepared according to the method of Example 1, except that the electrolyte of the lithium secondary battery uses 15% lithium hexafluorophosphate and 5% lithium bisoxalate borate, which account for the total mass of the electrolyte, as the lithium salt, and the non-aqueous organic solvent is carbonic acid. Methyl propyl ester and trifluoroethyl propionate account for 70% of the total mass of the electrolyte, and the mass ratio is 2:1. Lithium tetrafluorophosphate, potassium tetrafluorophosphate and sodium tetrafluorophosphate are added, each accounting for 1.5%, 1.5% and 2.0% of the total mass of the electrolyte.
  • the second additives are vinylene carbonate, vinyl sulfate, and triallyl phosphate, which respectively account for 2.0%, 1.5%, and 1.5% of the total mass of the electrolyte.
  • the positive electrode material used in the lithium secondary battery is LiNi 0.8 Co 0.15 Al 0.05 O 2
  • the negative electrode material is lithium titanate.
  • the charge cut-off voltage of the lithium secondary battery is 2.7V.
  • the lithium secondary battery was prepared according to the method of Example 1, except that lithium tetrafluorophosphate was not added to the electrolyte of the lithium secondary battery, and the remaining components retained their original content ratios.
  • the lithium secondary battery was prepared according to the method of Example 2, except that sodium tetrafluorophosphate was not added to the electrolyte of the lithium secondary battery, and the remaining components retained their original content ratios. .
  • the lithium secondary battery was prepared according to the method of Example 3, except that potassium tetrafluorophosphate was not added to the electrolyte of the lithium secondary battery, and the remaining components retained their original content ratios.
  • the lithium secondary battery was prepared according to the method of Example 4, the difference is that the electrolyte of the lithium secondary battery uses 8.0% of the total mass of the electrolyte as the lithium salt, and the non-aqueous organic solvent is ethylene carbonate and diethyl carbonate. , Accounting for 75.5% of the total mass of the electrolyte, with a mass ratio of 1:2. Add lithium tetrafluorophosphate, which accounts for 2.5% of the total mass of the electrolyte. The second additive is fluoroethylene carbonate, and vinyl sulfate accounts for 10.0% and 4.0% of the total mass of the electrolyte, respectively.
  • the lithium secondary battery was prepared according to the method of Example 5, except that LiPF 6 was replaced with lithium bisfluorosulfonimide in the electrolyte of the lithium secondary battery.
  • the lithium secondary battery was prepared according to the method of Example 6, the difference is that the electrolyte of the lithium secondary battery uses 8% of the total mass of the electrolyte as the lithium salt, and uses ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate.
  • the mixture is a non-aqueous organic solvent, accounting for 84.5% of the total mass of the electrolyte, and the mass ratio is 3:5:2.
  • Potassium tetrafluorophosphate is added, which accounts for 2.0% of the total mass of the electrolyte.
  • the second additives are lithium difluorobisoxalate phosphate and triallyl phosphate, which respectively account for 2.0% and 3.5% of the total mass of the electrolyte.
  • the lithium secondary battery was prepared according to the method of Example 7. The difference is that the electrolyte of the lithium secondary battery uses lithium hexafluorophosphate, which accounts for 27% of the total mass of the electrolyte, as the lithium salt, and uses ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate.
  • the mixture is a non-aqueous organic solvent, accounting for 64.5% of the total mass of the electrolyte, and the mass ratio is 3:5:2.
  • Lithium tetrafluorophosphate and sodium tetrafluorophosphate are added to account for 1.5% and 2.5 of the total electrolyte mass, respectively. %.
  • the second additives are fluoroethylene carbonate, lithium difluorooxalate phosphate, and tris(trimethylsilane) phosphate, which account for 3.0%, 0.5%, and 1.0% of the total mass of the electrolyte.
  • the lithium secondary battery was prepared according to the method of Example 8. The difference is that the electrolyte of the lithium secondary battery uses 5% of the total mass of the electrolyte as the lithium salt, and uses ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate.
  • the mixture of is a non-aqueous organic solvent, accounting for 92.5% of the total mass of the electrolyte, and the mass ratio is 3:5:2.
  • Potassium tetrafluorophosphate and sodium tetrafluorophosphate are added to account for 0.25% and 0.25% of the total mass of the electrolyte, respectively.
  • the second additive is ethylene ethylene carbonate, lithium difluorophosphate, tripropynyl phosphate, and tris(trimethylsilane) phosphate, which account for 0.5%, 0.5%, 0.5%, and 0.5% of the total mass of the electrolyte.
  • the lithium secondary battery was prepared according to the method of Example 9. The difference is that the electrolyte of the lithium secondary battery uses 25.0% of the total mass of the electrolyte as the lithium salt, and the non-aqueous organic solvent is ethylene carbonate and fluoroethylene carbonate. , Trifluoroethyl propionate, accounting for 57% of the total mass of the electrolyte, with a mass ratio of 4:1:5. Lithium tetrafluorophosphate and potassium tetrafluorophosphate are added, which respectively account for 2.5% and 2.5% of the total mass of the electrolyte.
  • the second additives are vinylene carbonate, lithium bisoxalate borate, vinyl sulfate, and hexamethylene diisocyanate, which respectively account for 3.0%, 3.0%, 3.0%, and 4.0% of the total mass of the electrolyte.
  • the lithium secondary battery was prepared according to the method of Example 10, except that lithium tetrafluorophosphate was replaced with lithium difluorophosphate.
  • the lithium secondary battery was prepared according to the method of Example 11. The difference was that in addition to 12.5% of the total mass of the electrolyte, LiPF 6 was added, and 6.5% of lithium bisfluorosulfonimide (LiFSI) was added as the lithium salt.
  • the non-aqueous organic solvents are ethylene carbonate and diethyl carbonate, accounting for 72.5% of the total mass of the electrolyte, and the mass ratio is 1:2.
  • Lithium tetrafluorophosphate and sodium tetrafluorophosphate are added, which respectively account for 3.0% and 3.0% of the total mass of the electrolyte.
  • the second additive is fluoroethylene carbonate, lithium difluorophosphate, and tris(trimethylsilane) phosphate, which respectively account for 1.0%, 0.5%, and 1.0% of the total mass of the electrolyte.
  • the lithium secondary battery was prepared according to the method of Example 12, except that the second additives, vinylene carbonate, lithium difluorobisoxalate, and hexamethylene diisocyanate, respectively accounted for 2.0% and 3.5% of the total mass of the electrolyte. , 2.5% was replaced by lithium chloride, sodium chloride and potassium chloride.
  • Cycle experiment test the internal resistance of the batteries obtained in Comparative Examples 1-12 and Examples 1-13 at room temperature and 25°C; charge and discharge at a rate of 2CC/0.5CD at 25°C; and at a low temperature of -10°C Perform charge and discharge at a rate of 0.5CC/0.2CD; perform a charge-discharge cycle test at a high temperature of 55°C at a charge-discharge rate of 0.5CC/0.5CD. Record the discharge capacity of the last cycle and divide it by the discharge capacity of the first cycle. Obtain the capacity retention rate, and record the results as shown in Table 1.

Abstract

Disclosed is a lithium secondary battery electrolyte. The electrolyte is obtained by adding a polyfluorophosphate of a specific structure and a non-aqueous solvent to a LiPF6 electrolyte lithium salt and reasonably compounding same. A lithium secondary battery using the electrolyte can have a good thermal stability and chemical stability during high-rate charging and discharging, and also has a low internal resistance and a better low temperature performance and cycle life.

Description

一种低内阻的锂二次电池电解液及锂二次电池Low internal resistance lithium secondary battery electrolyte and lithium secondary battery 技术领域Technical field
本申请属于锂二次电池电解液领域，涉及一种含特定氟代磷酸盐添加剂的电解液。This application belongs to the field of lithium secondary battery electrolytes, and relates to an electrolyte containing specific fluorophosphate additives.
背景技术Background technique
电解液是锂二次电池中实现锂离子在正负极迁移的媒介，对锂电容量、工作温度、循环效率以及安全性都有重要的影响。一般由高纯度有机溶剂、电解质锂盐、主要添加剂等原料，在一定条件下配制而成。为了改善锂电池电池的各项性能，对于电解液的改进是目前的研究热点。Electrolyte is the medium for lithium ions to migrate between the positive and negative electrodes in the lithium secondary battery, and it has an important impact on the lithium battery capacity, operating temperature, cycle efficiency and safety. It is generally prepared from raw materials such as high-purity organic solvents, electrolyte lithium salts, and main additives under certain conditions. In order to improve the performance of lithium batteries, the improvement of electrolyte is a current research hotspot.
作为电解液中的锂盐，必须满足的基本要求是：高纯度、低分子量、低毒性、在非水溶剂可以完全溶解和解离、较好的热稳定性、在溶剂中强的化学稳定性、具有宽的电化学稳定性、溶剂化离子(特别是溶剂化的锂离子)的迁移率高、有效形成SEI和CEI、对Al集流体的钝化以避免正极Al溶解，以及低成本。LiPF 6因为离子迁移率、离子解离率、溶解度、表面化学和对集流体的钝化能力等综合性能突出，其被认为是市售中的“最佳”导电盐。尽管取得了商业上的成功，但LiPF 6的化学和热不稳定性，容易发生分解和正负极的反应，因此也需要另外加入添加剂，来改善LiPF 6在电解液中的稳定性，进而提升电池性能。 As the lithium salt in the electrolyte, the basic requirements that must be met are: high purity, low molecular weight, low toxicity, complete dissolution and dissociation in non-aqueous solvents, good thermal stability, strong chemical stability in solvents, It has wide electrochemical stability, high mobility of solvated ions (especially solvated lithium ions), effective formation of SEI and CEI, passivation of Al current collectors to avoid Al dissolution in the positive electrode, and low cost. LiPF 6 has outstanding comprehensive properties such as ion mobility, ion dissociation rate, solubility, surface chemistry and passivation ability to current collectors, and is considered to be the "best" conductive salt in the market. Although it has achieved commercial success, LiPF 6 is chemically and thermally unstable, and is prone to decomposition and positive and negative reactions. Therefore, it is necessary to add additives to improve the stability of LiPF 6 in the electrolyte and improve battery performance. .
CN108520975A将六氟磷酸锂、四氟磷酸锂、丙酸乙酯、乙酸乙酯、氯化钠、氯化钾、碳酸二丁酯、添加剂和去离子水混合制得电解液；制得的电解液能够使得锂离子电池在大倍率电流情况下快速充放电以及低温环境下有效放电。该电解液在25℃的环境下，8C倍率电流充放电，放电容量达额定容量的 95％以上，且1C充电5C放电循环2000次，容量保持率在90％以上；在-20℃下，以5C倍率电流放电，放电容量达额定容量的80％以上。但是该申请中还加入了氯化钠、氯化钾等电解质，由于氯离子的存在，容易腐蚀Al集流体，降低电池使用寿命。CN108520975A The electrolyte is prepared by mixing lithium hexafluorophosphate, lithium tetrafluorophosphate, ethyl propionate, ethyl acetate, sodium chloride, potassium chloride, dibutyl carbonate, additives and deionized water; the prepared electrolyte can make lithium Ion batteries can be charged and discharged quickly under high-rate current conditions and can be effectively discharged under low-temperature environments. The electrolyte is charged and discharged at a rate of 8C at 25°C, and the discharge capacity reaches more than 95% of the rated capacity, and the 1C charge and 5C discharge cycles are 2000 times, and the capacity retention rate is more than 90%; at -20°C, 5C rate current discharge, the discharge capacity reaches more than 80% of the rated capacity. However, electrolytes such as sodium chloride and potassium chloride are also added to the application. Due to the presence of chloride ions, it is easy to corrode the Al current collector and reduce the service life of the battery.
CN109148951A添加剂包括硼磷类草酸锂盐；氟代磷酸锂；以及碳酸亚乙烯酯、氟代碳酸乙烯酯中的一种或两种。氟代磷酸锂能钝化正极，抑制正极与碳酸二甲酯等的副反应，协同硼磷类草酸锂盐改善锂离子电池的常温和高温快充循环性能和高温存储性能，同时降低锂离子电池低温下的阻抗，改善锂离子电池的低温功率性能。将碳酸亚乙烯酯和/或氟代碳酸乙烯酯与硼磷类草酸锂盐和氟代磷酸锂配合使用，可以使锂离子电池的常温和高温快充循环性能、常温和低温功率性能以及高温存储性能均较优，满足锂离子电池的快充需求，同时兼顾高能量密度以及高功率性能需求。但是该发明所选用的氟代磷酸锂在非水溶剂中的溶解性不佳，会明显降低电解液电导率，造成锂离子电池的常温功率性能较差。且草酸类的锂盐容易分解产生草酸根，草酸根在电池内容易导致电池胀气，影响电池的安全性和使用寿命。CN109148951A additives include boron phosphorous lithium oxalate; lithium fluorophosphate; and one or two of vinylene carbonate and fluoroethylene carbonate. Lithium fluorophosphate can passivate the positive electrode, inhibit the side reaction of the positive electrode and dimethyl carbonate, etc., and cooperate with the boron phosphorus lithium oxalate salt to improve the normal temperature and high temperature fast charge cycle performance and high temperature storage performance of lithium ion batteries, while reducing lithium ion batteries The impedance at low temperature improves the low-temperature power performance of lithium-ion batteries. Using vinylene carbonate and/or fluoroethylene carbonate in combination with boron-phosphorus lithium oxalate and lithium fluorophosphate can make lithium-ion batteries have normal temperature and high temperature fast charge cycle performance, normal temperature and low temperature power performance, and high temperature storage The performance is relatively good, meeting the fast charging requirements of lithium-ion batteries, while taking into account the requirements of high energy density and high power performance. However, the fluorolithium phosphate used in the invention has poor solubility in non-aqueous solvents, which will significantly reduce the conductivity of the electrolyte, resulting in poor normal temperature power performance of the lithium ion battery. In addition, the lithium salt of oxalic acid is easy to decompose to produce oxalate, which is easy to cause battery flatulence in the battery, which affects the safety and service life of the battery.
CN108123172A中的添加剂包括氟代硼酸酯以及二氟磷酸锂。二氟磷酸锂能够改善二次锂电池的高温循环性能、高温存储性能以及低温放电性能。同时，二氟磷酸锂与正极的作用有利于降低正极电化学反应阻抗，改善正极的动力学性能，提高二次锂电池的低温放电性能。然而，二氟磷酸锂会在负极发生还原分解，分解产物覆盖负极表面，造成负极嵌锂阻抗增大，不利于负极的大倍率充电性能。因而需要额外加入氟代硼酸酯，在负极表面形成离子电导率高的SEI膜，来有效改善二次锂电池的低温充电性能和大倍率充电性能。氟代硼酸酯在 微量水存在的情况下容易水解产生硼酸，硼酸不利于电池的循环性能。The additives in CN108123172A include fluoroborate and lithium difluorophosphate. Lithium difluorophosphate can improve the high-temperature cycle performance, high-temperature storage performance, and low-temperature discharge performance of secondary lithium batteries. At the same time, the role of lithium difluorophosphate with the positive electrode is beneficial to reduce the electrochemical reaction impedance of the positive electrode, improve the kinetic performance of the positive electrode, and improve the low-temperature discharge performance of the secondary lithium battery. However, lithium difluorophosphate will undergo reductive decomposition in the negative electrode, and the decomposition product will cover the surface of the negative electrode, resulting in an increase in the lithium insertion resistance of the negative electrode, which is not conducive to the high-rate charging performance of the negative electrode. Therefore, it is necessary to additionally add fluoroborate to form an SEI film with high ionic conductivity on the surface of the negative electrode to effectively improve the low-temperature charging performance and high-rate charging performance of the secondary lithium battery. Fluorinated boronic acid esters are easily hydrolyzed to produce boric acid in the presence of trace amounts of water, and boric acid is not conducive to the cycle performance of the battery.
CN108232296A和CN108232297A将氟代磷酸盐与氟代磷酸盐和/或环磷腈化合物进行配合使用，显著降低锂离子电池的负极SEI膜界面阻抗，降低锂离子电池的低温内阻，提高锂离子电池的功率性能，同时可明显抑制锂离子电池循环和存储过程中的产气，从而很好地改善锂离子电池的循环性能、高温存储性能以及安全性能。CN108232296A and CN108232297A use fluorophosphate in combination with fluorophosphate and/or cyclophosphazene compound to significantly reduce the negative electrode SEI film interface impedance of lithium ion batteries, reduce the low-temperature internal resistance of lithium ion batteries, and improve the Power performance, while significantly inhibiting the production of gas during the cycle and storage of lithium-ion batteries, so as to well improve the cycle performance, high-temperature storage performance and safety performance of lithium-ion batteries.
由此可见，在包含有LiPF 6电解质锂盐的电解液中，由于含有LiPF 6的解液在高温下容易发生不可避免地热分解，导致HF的形成，同时各种挥发性和潜在毒性的有机磷酸酯化合物将直接影响电池的整体性能，而现有的改善锂离子电池性能的方法由需要借助大量非氟代磷酸盐添加剂，例如环磷腈，卤代苯，硼磷类草酸锂盐，氟代硼酸酯等，而上述添加剂的引入会导致形成的SEI膜组成与形态复杂，导致电池循环中不稳定，存在安全隐患。因此需要获得一种组成简单，能够使LiPF 6电解质在大倍率充放电过程中有良好的热稳定性和化学稳定性，同时具有低的内阻、较好的低温性能以及循环寿命。 It can be seen that in the electrolyte containing LiPF 6 electrolyte lithium salt, the solution containing LiPF 6 is prone to inevitably thermally decompose at high temperatures, leading to the formation of HF, and various volatile and potentially toxic organic phosphoric acids Ester compounds will directly affect the overall performance of the battery, and the existing methods to improve the performance of lithium-ion batteries require the use of a large number of non-fluorinated phosphate additives, such as cyclophosphazene, halogenated benzene, boron phosphorous lithium oxalate, and fluoro Borate esters, etc., and the introduction of the above additives will cause the composition and morphology of the formed SEI film to be complex, leading to instability in the battery cycle and posing safety risks. Therefore, it is necessary to obtain a simple composition that can enable the LiPF 6 electrolyte to have good thermal and chemical stability during high-rate charging and discharging, as well as low internal resistance, good low-temperature performance and cycle life.
发明内容Summary of the invention
本申请的目的是提供一种包含有LiPF 6电解质锂盐的锂二次电池电解液，使用该电解液的锂二次电池在大倍率充放电过程中有良好的热稳定性和化学稳定性，同时具有低的内阻、较好的低温性能以及循环寿命。同时，本申请还公开了采用该电解液的锂离子电池。 The purpose of this application is to provide a lithium secondary battery electrolyte containing LiPF 6 electrolyte lithium salt. The lithium secondary battery using the electrolyte has good thermal and chemical stability during high-rate charging and discharging. At the same time, it has low internal resistance, good low temperature performance and cycle life. At the same time, this application also discloses a lithium ion battery using the electrolyte.
申请人发现，解决问题的关键手段在于：当包含有LiPF 6电解质锂盐的锂二次电池电解液中添加如下式(1)结构式所示的多氟代磷酸盐时，电解液具有良好的热稳定性和化学稳定性，同时具有低的内阻、较好的低温性能以及循环 寿命。 The applicant found that the key means to solve the problem is: when the polyfluorophosphate shown in the following formula (1) is added to the lithium secondary battery electrolyte containing LiPF 6 electrolyte lithium salt, the electrolyte has good heat Stability and chemical stability, while having low internal resistance, good low temperature performance and cycle life.
Figure PCTCN2020134175-appb-000001
Figure PCTCN2020134175-appb-000001
其中，M选自Li，Na，K中的任一种或多种的组合。Wherein, M is selected from any one or a combination of Li, Na, and K.
式(I)化合物的合成路线如下：The synthetic route of the compound of formula (I) is as follows:
Figure PCTCN2020134175-appb-000002
Figure PCTCN2020134175-appb-000002
其中M选自Li，Na，K中的任一种，R 1，R 2，R 3，R 4，R 5，R 6各自独立地选自甲基或乙基。 Wherein M is selected from any one of Li, Na, and K, and R 1 , R 2 , R 3 , R 4 , R 5 , and R 6 are each independently selected from methyl or ethyl.
具体而言，在150～300重量份的碳酸甲乙酯中加入80～120重量份MPF 6，充分溶解后，通入氮气，升高温度至100～105℃，缓慢滴加115～130重量份硅氧烷，搅拌反应4小时。反应停止后冷却至室温，往圆底烧瓶中加入200重量份二氯甲烷，使MPOF 4析出来，过滤，获得固体MPOF 4。 Specifically, add 80-120 parts by weight of MPF 6 to 150-300 parts by weight of ethyl methyl carbonate, and after it is fully dissolved, blow in nitrogen, raise the temperature to 100-105°C, and slowly add 115-130 parts by weight. Siloxane, stirred and reacted for 4 hours. After the reaction was stopped, it was cooled to room temperature, and 200 parts by weight of dichloromethane was added to the round bottom flask to precipitate MPOF 4 and filtered to obtain solid MPOF 4 .
虽然目前没有理论证明式(1)化合物改善六氟磷酸锂热稳定性和化学稳定性的机理，申请人可以合理推测：式(1)化合物阴离子部分的氧能够与正极活性材料中的过渡金属元素产生络合作用，改善正极活性材料的稳定性，从而降低对电解液中LiPF 6锂盐的氧化活性，从而有效改善二次锂电池的高温循环性能并抑制二次锂电池在高温下的体积膨胀。同时，式(1)化合物与负极发生还原分解反应后，在负极表面形成的SEI膜形成了有利于锂离子传输的扩散通道， 进而形成了阻抗较低的SEI膜，可以在低温下改善电池的充电性能，避免了LiPF 6形成高阻抗的还原分解产物覆盖在负极表面。并且由于式(1)化合物的溶解性优于一氟磷酸锂和二氟磷酸锂在非水有机溶剂中的溶解性，因此具有更好的界面浸润性，为降低电解液的电解阻抗提供了更优的选择。 Although there is currently no theoretical proof that the compound of formula (1) improves the thermal and chemical stability of lithium hexafluorophosphate, the applicant can reasonably speculate that the oxygen in the anion part of the compound of formula (1) can complex with the transition metal element in the positive electrode active material It can improve the stability of the positive electrode active material, thereby reducing the oxidation activity of LiPF 6 lithium salt in the electrolyte, thereby effectively improving the high temperature cycle performance of the secondary lithium battery and inhibiting the volume expansion of the secondary lithium battery at high temperatures. At the same time, after the compound of formula (1) and the negative electrode undergo a reduction and decomposition reaction, the SEI film formed on the surface of the negative electrode forms a diffusion channel that is conducive to lithium ion transmission, and then forms an SEI film with lower impedance, which can improve the battery performance at low temperatures. The charging performance prevents LiPF 6 from forming high-impedance reduction decomposition products covering the surface of the negative electrode. And because the solubility of the compound of formula (1) is better than the solubility of lithium monofluorophosphate and lithium difluorophosphate in non-aqueous organic solvents, it has better interface wettability, which provides a better solution for reducing the electrolytic resistance of the electrolyte. Excellent choice.
由此本申请提出一种锂二次电池电解液，其中包含：1)LiPF 6电解质锂盐，2)非水有机溶剂；3)添加剂，所述添加剂为如下式(1)结构式所示的多氟代磷酸盐： Therefore, this application proposes a lithium secondary battery electrolyte, which contains: 1) LiPF 6 electrolyte lithium salt, 2) non-aqueous organic solvent; 3) additives, the additives are as shown in the following formula (1) structural formula Fluorophosphate:
Figure PCTCN2020134175-appb-000003
Figure PCTCN2020134175-appb-000003
其中，M选自Li，Na，K中的任一种或多种的组合。Wherein, M is selected from any one or a combination of Li, Na, and K.
除必须存在的LiPF 6电解质锂盐外，电解液中任选地含有其他锂盐，选自双(三氟甲基磺酰)亚胺锂、双氟磺酰亚胺锂(LiFSI)、四氟硼酸锂(LiBF 4)、双草酸硼酸锂(LiBOB)中的至少一种。 In addition to the necessary LiPF 6 electrolyte lithium salt, the electrolyte optionally contains other lithium salts, selected from lithium bis(trifluoromethylsulfonyl)imide, lithium bisfluorosulfonimide (LiFSI), and tetrafluoroethylene At least one of lithium borate (LiBF 4 ) and lithium bisoxalate borate (LiBOB).
所述非水有机溶剂为碳酸二甲酯、碳酸二乙酯、碳酸甲乙酯、碳酸乙烯酯、乙酸乙酯、碳酸甲丙酯、氟代碳酸乙烯酯、2，2-二氟乙基乙酸酯、丙酸三氟乙基酯、丙酸二氟乙基酯、氟代碳酸丙烯酯、碳酸甲丙酯、γ-丁内酯和γ-戊内酯中的至少一种。The non-aqueous organic solvent is dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene carbonate, ethyl acetate, methyl propyl carbonate, fluoroethylene carbonate, 2,2-difluoroethyl ethyl At least one of acid ester, trifluoroethyl propionate, difluoroethyl propionate, fluoropropylene carbonate, methyl propyl carbonate, γ-butyrolactone, and γ-valerolactone.
本申请的锂二次电池电解液还可以含有选自碳酸亚乙烯酯、氟代碳酸乙烯酯、二氟磷酸锂、二氟二草酸磷酸锂、硫酸乙烯酯、三烯丙基磷酸酯、三丙炔基磷酸酯、三(三甲基硅烷)磷酸酯、六亚甲基二异氰酸酯中一种或多种的第 二添加剂，通过大量实验发现，本申请提供的式(1)锂二次电池电解液添加剂在与第二添加剂联合使用时，能够取得比它们单独使用时更优异的循环性能推测它们之间有协同作用，即在与式(1)化合物一起使用时，能进一步降低电解液在常温下的阻抗。The lithium secondary battery electrolyte of the present application may also contain selected from vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, lithium difluorodioxalate phosphate, vinyl sulfate, triallyl phosphate, tripropylene One or more of the second additives of alkynyl phosphate, tris(trimethylsilane) phosphate, and hexamethylene diisocyanate. Through a large number of experiments, it has been found that the formula (1) lithium secondary battery provided by this application is electrolytic When the liquid additive is used in combination with the second additive, it can achieve better cycle performance than when they are used alone. It is assumed that there is a synergistic effect between them, that is, when used with the compound of formula (1), it can further reduce the electrolyte at room temperature. Under the impedance.
本申请还提出含有式(1)的锂二次电池电解液添加剂的锂二次电池电解液，包括锂盐，非水溶剂、所述式(1)锂二次电池电解液添加剂，所述LiPF 6锂盐的质量百分数为10％-25％；所述的非水溶剂的质量百分数为60％-89.99％；所述的式(1)锂二次电池电解液添加剂的质量百分数为0.01％-5％，所述第二添加剂的质量百分数为0％-10％。 This application also proposes a lithium secondary battery electrolyte containing the lithium secondary battery electrolyte additive of formula (1), including a lithium salt, a non-aqueous solvent, the formula (1) lithium secondary battery electrolyte additive, and the LiPF 6 The mass percentage of lithium salt is 10%-25%; the mass percentage of the non-aqueous solvent is 60%-89.99%; the mass percentage of the formula (1) lithium secondary battery electrolyte additive is 0.01%- 5%, the mass percentage of the second additive is 0%-10%.
本申请还提出具有式(1)锂二次电池电解液添加剂的应用，用于包含有LiPF 6电解质锂盐的非水体系锂二次电池电解液中，所述的式(1)锂二次电池电解液添加剂在锂离子电池电解液中所占的重量百分比为0.01％-5％。 This application also proposes the application of the electrolyte additive of the formula (1) lithium secondary battery for use in the non-aqueous system lithium secondary battery electrolyte containing the LiPF 6 electrolyte lithium salt. The formula (1) lithium secondary battery electrolyte The weight percentage of the battery electrolyte additive in the lithium ion battery electrolyte is 0.01% to 5%.
本申请的有益效果包括：The beneficial effects of this application include:
本申请通过在包含有LiPF 6电解质锂盐的锂二次电池的电解液中添加占电解液总质量0.01％-5％的式(1)化合物作为添加剂，可以降低电池的内阻，同时具备更好的低温性能、高温性能、倍率性能和循环寿命。 The present application adds 0.01% to 5% of the total mass of the electrolyte as an additive to the electrolyte of a lithium secondary battery containing LiPF 6 electrolyte lithium salt, which can reduce the internal resistance of the battery while having more Good low temperature performance, high temperature performance, rate performance and cycle life.
具体实施方式Detailed ways
下面结合具体实施方式，对本申请的技术方案作进一步的详细说明，但不构成对本申请的任何限制。The technical solutions of this application will be further described in detail below in conjunction with specific implementations, but this does not constitute any limitation to this application.
实施例1Example 1
(1)锂二次电池的正极片的制备(1) Preparation of positive electrode sheet for lithium secondary battery
将正极活性材料镍钴锰酸锂(LiNi 1/3Co 1/3Mn 1/3O 2)、导电剂Super-P、粘接 剂PVDF按质量比96:2.0:2.0溶于溶剂N-甲基吡咯烷酮中混合均匀制成正极浆料，之后将正极浆料均匀涂布在集流体铝箔上，涂布量为0.018g/cm 2，随后在85℃下烘干后进行冷压、切边、裁片、分条，之后在85℃真空条件下干燥4h，焊接极耳，制成满足要求的锂二次电池的正极片。 The positive electrode active material, lithium nickel cobalt manganese oxide (LiNi 1/3 Co 1/3 Mn 1/3 O 2 ), the conductive agent Super-P, and the adhesive PVDF are dissolved in the solvent N-form at a mass ratio of 96:2.0:2.0. Mix the base pyrrolidone uniformly to make the positive electrode slurry, and then uniformly coat the positive electrode slurry on the aluminum foil of the current collector, the coating amount is 0.018g/cm 2 , and then dry at 85 ℃, then carry out cold pressing, trimming, After cutting and slitting, they were dried for 4 hours under vacuum at 85°C, and the tabs were welded to form a positive electrode sheet for a lithium secondary battery that satisfies the requirements.
(2)锂二次电池的负极片的制备(2) Preparation of negative electrode sheet for lithium secondary battery
将负极活性材料石墨、导电剂Super-P、增稠剂CMC、粘接剂SBR按质量比96.5:1.0:1.0:1.5溶于溶剂去离子水中混合均匀制成负极浆料，之后将负极浆料均匀涂布在集流体铜箔上，涂布量为0.0089g/cm 2，随后在85℃下烘干后进行冷压、切边、裁片、分条，之后在110℃真空条件下干燥4h，焊接极耳，制成满足要求的锂二次电池的负极片。 The negative electrode active material graphite, conductive agent Super-P, thickener CMC, and binder SBR are dissolved in the solvent deionized water at a mass ratio of 96.5:1.0:1.0:1.5 and mixed uniformly to make a negative electrode slurry, and then the negative electrode slurry Coat evenly on the current collector copper foil with a coating amount of 0.0089g/cm 2 , then dry at 85°C, then perform cold pressing, trimming, cutting, and slitting, and then dry at 110°C under vacuum for 4h , Weld the tabs to make the negative electrode sheet of the lithium secondary battery that meets the requirements.
(3)锂二次电池的电解液的制备(3) Preparation of electrolyte for lithium secondary battery
锂二次电池的电解液以占电解液总质量12.5％的六氟磷酸锂为锂盐，以碳酸乙烯酯、碳酸甲乙酯、碳酸二乙酯的混合物为非水有机溶剂，占电解液总质量的86.39％，其中以碳酸乙烯酯、碳酸甲乙酯、碳酸二乙酯的质量比为3:5:2。此外，锂二次电解液中还含有添加剂，第一添加剂为占锂二次电池电解液总质量0.01％的四氟代磷酸锂。第二添加剂为碳酸亚乙烯酯、氟代碳酸乙烯酯，分别占电解液总质量的0.1％、1.0％。The electrolyte of the lithium secondary battery uses lithium hexafluorophosphate which accounts for 12.5% of the total mass of the electrolyte as the lithium salt, and uses a mixture of ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate as the non-aqueous organic solvent, which accounts for 86.39 of the total mass of the electrolyte. %, where the mass ratio of ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate is 3:5:2. In addition, the lithium secondary electrolyte also contains additives, and the first additive is lithium tetrafluorophosphate accounting for 0.01% of the total mass of the lithium secondary battery electrolyte. The second additives are vinylene carbonate and fluoroethylene carbonate, which respectively account for 0.1% and 1.0% of the total mass of the electrolyte.
(4)锂二次电池的制备(4) Preparation of lithium secondary battery
将根据前述工艺制备的锂二次二次电池的正极片、负极片以及隔离膜经过卷绕工艺制作成厚度为8mm、宽度为60mm、长度为130mm的电芯，并在75℃下真空烘烤10h、注入电解液、静置24h，之后用0.1C(160mA)的恒定电流充电至4.2V，然后以4.2V恒压充电至电流下降到0.05C(80mA)，然后以0.1C (160mA)的恒定电流放电至3.0V，重复2次充放电，最后以0.1C(160mA)的恒定电流充电至3.8V，完成锂离电池的制备。The positive electrode sheet, the negative electrode sheet and the separator of the lithium secondary battery prepared according to the foregoing process are made into a battery with a thickness of 8mm, a width of 60mm, and a length of 130mm through a winding process, and vacuum-baked at 75°C 10h, inject electrolyte, stand for 24h, then charge to 4.2V with a constant current of 0.1C (160mA), then charge with a constant voltage of 4.2V until the current drops to 0.05C (80mA), and then charge at 0.1C (160mA) Discharge with constant current to 3.0V, repeat the charge and discharge twice, and finally charge to 3.8V with a constant current of 0.1C (160mA) to complete the preparation of the lithium ion battery.
实施例2Example 2
依照实施例1的方法制备锂二次电池，不同的是锂二次电池的电解液以占电解液总质量10.0％的六氟磷酸锂为锂盐，非水有机溶剂为碳酸乙烯酯、碳酸甲乙酯，占电解液总质量的85.5％，质量比为1:2。添加四氟代磷酸钠，占电解液总质量的0.5％。第二添加剂为氟代碳酸乙烯酯、二氟磷酸锂，分别占电解液总质量的3.0％、1.0％。锂二次电池所用的正极材料为LiNi 0.8Co 0.1Mn 0.1O 2。 The lithium secondary battery was prepared according to the method of Example 1. The difference is that the electrolyte of the lithium secondary battery uses 10.0% of the total mass of the electrolyte as the lithium salt, and the non-aqueous organic solvent is ethylene carbonate and ethyl methyl carbonate. It accounts for 85.5% of the total mass of the electrolyte, and the mass ratio is 1:2. Add sodium tetrafluorophosphate, which accounts for 0.5% of the total mass of the electrolyte. The second additives are fluoroethylene carbonate and lithium difluorophosphate, which respectively account for 3.0% and 1.0% of the total mass of the electrolyte. The cathode material used in the lithium secondary battery is LiNi 0.8 Co 0.1 Mn 0.1 O 2 .
实施例3Example 3
依照实施例1的方法制备锂二次电池，不同的是锂二次电池的电解液以占电解液总质量13.0％的六氟磷酸锂为锂盐，非水有机溶剂为碳酸乙烯酯、碳酸甲乙酯，占电解液总质量的85.0％，质量比为1:3。添加四氟代磷酸钾，占电解液总质量的0.5％。第二添加剂为氟代碳酸乙烯酯，占电解液总质量的1.5％。锂二次电池所用的正极材料为LiNi 0.8Co 0.15Al 0.05O 2。 The lithium secondary battery was prepared according to the method of Example 1. The difference is that the electrolyte of the lithium secondary battery uses 13.0% of the total mass of the electrolyte as the lithium salt, and the non-aqueous organic solvent is ethylene carbonate and ethyl methyl carbonate. It accounts for 85.0% of the total mass of the electrolyte, and the mass ratio is 1:3. Potassium tetrafluorophosphate is added to account for 0.5% of the total mass of the electrolyte. The second additive is fluoroethylene carbonate, which accounts for 1.5% of the total mass of the electrolyte. The cathode material used in the lithium secondary battery is LiNi 0.8 Co 0.15 Al 0.05 O 2 .
实施例4Example 4
依照实施例1的方法制备锂二次电池，不同的是锂二次电池的电解液以占电解液总质量10.0％的六氟磷酸锂为锂盐，非水有机溶剂为碳酸乙烯酯、碳酸二乙酯，占电解液总质量的77.5％，质量比为1:2。添加四氟代磷酸锂，占电解液总质量的2.5％。第二添加剂为氟代碳酸乙烯酯，硫酸乙烯酯分别占电解液总质量的8.0％、2.0％。锂二次电池所用的正极材料为LiCoO 2，负极材料为硅碳复合材料。 The lithium secondary battery was prepared according to the method of Example 1. The difference is that the electrolyte of the lithium secondary battery uses 10.0% of the total mass of the electrolyte as the lithium salt, and the non-aqueous organic solvent is ethylene carbonate and diethyl carbonate. It accounts for 77.5% of the total mass of the electrolyte, and the mass ratio is 1:2. Add lithium tetrafluorophosphate, which accounts for 2.5% of the total mass of the electrolyte. The second additive is fluoroethylene carbonate, and vinyl sulfate accounts for 8.0% and 2.0% of the total mass of the electrolyte, respectively. The positive electrode material used in the lithium secondary battery is LiCoO 2 , and the negative electrode material is a silicon-carbon composite material.
实施例5Example 5
依照实施例1的方法制备锂二次电池，不同的是锂二次电池的电解液以占电解液总质量15％的六氟磷酸锂为锂盐，非水有机溶剂为碳酸乙烯酯、碳酸丙烯酯、碳酸二乙酯，占电解液总质量的81.0％，质量比为4:1:5。添加四氟代磷酸钠，占电解液总质量的1.5％。第二添加剂为三丙炔基磷酸酯、硫酸乙烯酯，分别占电解液总质量的0.5％、2.0％。锂二次电池所用的正极材料为LiNi 0.8Co 0.15Al 0.05O 2，负极材料为钛酸锂。锂二次电池的充电截止电压为2.7V。 The lithium secondary battery was prepared according to the method of Example 1. The difference is that the electrolyte of the lithium secondary battery uses 15% of the total mass of the electrolyte as the lithium salt, and the non-aqueous organic solvent is ethylene carbonate, propylene carbonate, and carbonic acid. Diethyl ester accounts for 81.0% of the total mass of the electrolyte, and the mass ratio is 4:1:5. Add sodium tetrafluorophosphate, accounting for 1.5% of the total mass of the electrolyte. The second additives are tripropynyl phosphate and vinyl sulfate, which respectively account for 0.5% and 2.0% of the total mass of the electrolyte. The positive electrode material used in the lithium secondary battery is LiNi 0.8 Co 0.15 Al 0.05 O 2 , and the negative electrode material is lithium titanate. The charge cut-off voltage of the lithium secondary battery is 2.7V.
实施例6Example 6
依照实施例1的方法制备锂二次电池，不同的是锂二次电池的电解液以占电解液总质量15％的六氟磷酸锂为锂盐，以碳酸乙烯酯、碳酸甲乙酯、碳酸二乙酯的混合物为非水有机溶剂，占电解液总质量的84.5％，质量比为3:5:2。添加四氟代磷酸钾，占电解液总质量的1.0％。第二添加剂为二氟二草酸磷酸锂、三烯丙基磷酸酯，分别占电解液总质量的1.0％、0.5％。锂二次电池所用的正极材料为LiCoO 2。 The lithium secondary battery was prepared according to the method of Example 1. The difference is that the electrolyte of the lithium secondary battery uses 15% of the total mass of the electrolyte as the lithium salt, and uses ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate. The mixture is a non-aqueous organic solvent, accounting for 84.5% of the total mass of the electrolyte, and the mass ratio is 3:5:2. Potassium tetrafluorophosphate is added, which accounts for 1.0% of the total mass of the electrolyte. The second additives are lithium difluorodioxalate phosphate and triallyl phosphate, which respectively account for 1.0% and 0.5% of the total mass of the electrolyte. The cathode material used in lithium secondary batteries is LiCoO 2 .
实施例7Example 7
依照实施例1的方法制备锂二次电池，不同的是锂二次电池的电解液以占电解液总质量17.5％的六氟磷酸锂为锂盐，以碳酸乙烯酯、碳酸甲乙酯、碳酸二乙酯的混合物为非水有机溶剂，占电解液总质量的77.0％，质量比为3:5:2，添加四氟代磷酸锂和四氟代磷酸钠，分别占电解液总质量的1.5％和2.5％。第二添加剂为氟代碳酸乙烯酯、二氟草酸磷酸锂、三(三甲基硅烷)磷酸酯，占电解液总质量的3.0％、0.5％、1.0％。锂二次电池所用的正极材料为LiMn 2O 4，负极材料为钛酸锂。 The lithium secondary battery was prepared according to the method of Example 1. The difference is that the electrolyte of the lithium secondary battery uses 17.5% of the total mass of the electrolyte as the lithium salt, and uses ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate. The mixture is a non-aqueous organic solvent, accounting for 77.0% of the total mass of the electrolyte, and the mass ratio is 3:5:2. Lithium tetrafluorophosphate and sodium tetrafluorophosphate are added, accounting for 1.5% and 2.5 of the total mass of the electrolyte, respectively. %. The second additives are fluoroethylene carbonate, lithium difluorooxalate phosphate, and tris(trimethylsilane) phosphate, which account for 3.0%, 0.5%, and 1.0% of the total mass of the electrolyte. The positive electrode material used in the lithium secondary battery is LiMn 2 O 4 , and the negative electrode material is lithium titanate.
实施例8Example 8
依照实施例1的方法制备锂二次电池，不同的是锂二次电池的电解液以占电解液总质量17.5％的六氟磷酸锂为锂盐，以碳酸乙烯酯、碳酸甲乙酯、碳酸二乙酯的混合物为非水有机溶剂，占电解液总质量的75.5％，质量比为3:5:2，添加四氟磷酸钾和四氟磷酸钠，分别占电解液总质量的1.0％和1.0％，第二添加剂为碳酸乙烯亚乙酯、二氟磷酸锂、三丙炔基磷酸酯、三(三甲基硅烷)磷酸酯，占电解液总质量的1.0％、3.0％、0.5％、0.5％。锂二次电池所用的正极材料为LiMnO 2。 The lithium secondary battery was prepared according to the method of Example 1. The difference is that the electrolyte of the lithium secondary battery uses 17.5% of the total mass of the electrolyte as the lithium salt, and uses ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate. The mixture is a non-aqueous organic solvent, accounting for 75.5% of the total mass of the electrolyte, and the mass ratio is 3:5:2. Potassium tetrafluorophosphate and sodium tetrafluorophosphate are added to account for 1.0% and 1.0% of the total mass of the electrolyte, respectively. The second additive is ethylene ethylene carbonate, lithium difluorophosphate, tripropynyl phosphate, and tris(trimethylsilane) phosphate, which account for 1.0%, 3.0%, 0.5%, and 0.5% of the total mass of the electrolyte. The cathode material used in the lithium secondary battery is LiMnO 2 .
实施例9Example 9
依照实施例1的方法制备锂二次电池，不同的是锂二次电池的电解液以占电解液总质量20.0％的六氟磷酸锂为锂盐，非水有机溶剂为碳酸乙烯酯、氟代碳酸乙烯酯、丙酸三氟乙基酯，占电解液总质量的70.0％，质量比为4:1:5。添加四氟磷酸锂和四氟磷酸钾，分别占电解液总质量的2.5％和2.5％。第二添加剂为碳酸亚乙烯酯、双草酸硼酸锂、硫酸乙烯酯、六亚甲基二异氰酸酯，分别占电解液总质量的1.0％、1.5％、1.0％、1.5％。锂二次电池所用的正极材料为LiNi 0.8Co 0.15Al 0.05O 2，负极材料为钛酸锂。锂二次电池的充电截止电压为2.7V。 The lithium secondary battery was prepared according to the method of Example 1, the difference is that the electrolyte of the lithium secondary battery uses 20.0% of the total mass of the electrolyte as the lithium salt, and the non-aqueous organic solvent is ethylene carbonate and fluoroethylene carbonate. , Trifluoroethyl propionate, accounting for 70.0% of the total mass of the electrolyte, with a mass ratio of 4:1:5. Lithium tetrafluorophosphate and potassium tetrafluorophosphate are added, which respectively account for 2.5% and 2.5% of the total mass of the electrolyte. The second additives are vinylene carbonate, lithium bisoxalate borate, vinyl sulfate, and hexamethylene diisocyanate, which respectively account for 1.0%, 1.5%, 1.0%, and 1.5% of the total mass of the electrolyte. The positive electrode material used in the lithium secondary battery is LiNi 0.8 Co 0.15 Al 0.05 O 2 , and the negative electrode material is lithium titanate. The charge cut-off voltage of the lithium secondary battery is 2.7V.
实施例10Example 10
依照实施例1的方法制备锂二次电池，不同的是除了加入占电解液总质量的12.5％的LiPF 6外，还加入了2.5％的三氟甲烷磺酰亚胺锂作为锂盐，非水有机溶剂为碳酸二甲酯、碳酸甲丙酯，占电解液总质量的84.5％，质量比为1:3。添加四氟代磷酸锂，占电解液总质量的0.5％。锂二次电池所用的正极材料为LiNi 0.8Co 0.15Al 0.05O 2。 The lithium secondary battery was prepared according to the method of Example 1, except that in addition to 12.5% of the total mass of the electrolyte, LiPF 6 was added, and 2.5% of lithium trifluoromethanesulfonimide was added as the lithium salt. The organic solvents are dimethyl carbonate and methyl propyl carbonate, which account for 84.5% of the total mass of the electrolyte, and the mass ratio is 1:3. Add lithium tetrafluorophosphate, which accounts for 0.5% of the total mass of the electrolyte. The cathode material used in the lithium secondary battery is LiNi 0.8 Co 0.15 Al 0.05 O 2 .
实施例11Example 11
依照实施例1的方法制备锂二次电池，不同的是除了加入占电解液总质量的12.5％的LiPF 6外，还加入了6.5％的双氟磺酰亚胺锂(LiFSI)作为锂盐，非水有机溶剂为碳酸乙烯酯、碳酸二乙酯，占电解液总质量的72.5％，质量比为1:2。添加四氟代磷酸锂和四氟代磷酸钠，分别占电解液总质量的3.0％和2.0％。第二添加剂为氟代碳酸乙烯酯、二氟磷酸锂、三(三甲基硅烷)磷酸酯，分别占电解液总质量的2.0％、0.5％、1.0％。锂二次电池所用的正极材料为LiCoO 2，负极材料为硅碳复合材料。 The lithium secondary battery was prepared according to the method of Example 1, except that in addition to 12.5% of the total mass of the electrolyte, LiPF 6 was added, and 6.5% of lithium bisfluorosulfonimide (LiFSI) was added as the lithium salt. The non-aqueous organic solvents are ethylene carbonate and diethyl carbonate, accounting for 72.5% of the total mass of the electrolyte, and the mass ratio is 1:2. Lithium tetrafluorophosphate and sodium tetrafluorophosphate are added, which respectively account for 3.0% and 2.0% of the total mass of the electrolyte. The second additive is fluoroethylene carbonate, lithium difluorophosphate, and tris(trimethylsilane) phosphate, which respectively account for 2.0%, 0.5%, and 1.0% of the total mass of the electrolyte. The positive electrode material used in the lithium secondary battery is LiCoO 2 , and the negative electrode material is a silicon-carbon composite material.
实施例12Example 12
依照实施例1的方法制备锂二次电池，不同的是锂二次电池的电解液以占电解液总质量25％的六氟磷酸锂为锂盐，非水有机溶剂为碳酸丙烯酯、碳酸二乙酯和γ-丁内酯，占电解液总质量的63.0％，质量比为4:1:5。添加四氟代磷酸钾，占电解液总质量的4.0％。第二添加剂为碳酸亚乙烯酯、二氟二草酸磷酸锂、六亚甲基二异氰酸酯，分别占电解液总质量的2.0％、3.5％、2.5％。锂二次电池所用的正极材料为LiNi 0.8Co 0.15Al 0.05O 2，负极材料为钛酸锂。锂二次电池的充电截止电压为2.7V。 The lithium secondary battery was prepared according to the method of Example 1, except that the electrolyte of the lithium secondary battery uses 25% of the total mass of the electrolyte as the lithium salt, and the non-aqueous organic solvent is propylene carbonate, diethyl carbonate and γ-butyrolactone accounts for 63.0% of the total mass of the electrolyte, and the mass ratio is 4:1:5. Potassium tetrafluorophosphate is added, which accounts for 4.0% of the total mass of the electrolyte. The second additives are vinylene carbonate, lithium difluorobisoxalate phosphate, and hexamethylene diisocyanate, which respectively account for 2.0%, 3.5%, and 2.5% of the total mass of the electrolyte. The positive electrode material used in the lithium secondary battery is LiNi 0.8 Co 0.15 Al 0.05 O 2 , and the negative electrode material is lithium titanate. The charge cut-off voltage of the lithium secondary battery is 2.7V.
实施例13Example 13
依照实施例1的方法制备锂二次电池，不同的是锂二次电池的电解液以占电解液总质量15％的六氟磷酸锂和5％的双草酸硼酸锂为锂盐，非水有机溶剂为碳酸甲丙酯、丙酸三氟乙基酯，占电解液总质量的70％，质量比为2:1。添加四氟代磷酸锂、四氟代磷酸钾和四氟代磷酸钠，各占电解液总质量的1.5、1.5％和2.0％。第二添加剂为碳酸亚乙烯酯、硫酸乙烯酯、三烯丙基磷酸酯，分别占电解液总质量的2.0％、1.5％、1.5％。锂二次电池所用的正极材料为 LiNi 0.8Co 0.15Al 0.05O 2，负极材料为钛酸锂。锂二次电池的充电截止电压为2.7V。 The lithium secondary battery was prepared according to the method of Example 1, except that the electrolyte of the lithium secondary battery uses 15% lithium hexafluorophosphate and 5% lithium bisoxalate borate, which account for the total mass of the electrolyte, as the lithium salt, and the non-aqueous organic solvent is carbonic acid. Methyl propyl ester and trifluoroethyl propionate account for 70% of the total mass of the electrolyte, and the mass ratio is 2:1. Lithium tetrafluorophosphate, potassium tetrafluorophosphate and sodium tetrafluorophosphate are added, each accounting for 1.5%, 1.5% and 2.0% of the total mass of the electrolyte. The second additives are vinylene carbonate, vinyl sulfate, and triallyl phosphate, which respectively account for 2.0%, 1.5%, and 1.5% of the total mass of the electrolyte. The positive electrode material used in the lithium secondary battery is LiNi 0.8 Co 0.15 Al 0.05 O 2 , and the negative electrode material is lithium titanate. The charge cut-off voltage of the lithium secondary battery is 2.7V.
对比例1Comparative example 1
依照实施例1的方法制备锂二次电池，只是在锂二次电池电解液中不添加四氟代磷酸锂，其余组分保留其原有含量比例。The lithium secondary battery was prepared according to the method of Example 1, except that lithium tetrafluorophosphate was not added to the electrolyte of the lithium secondary battery, and the remaining components retained their original content ratios.
对比例2Comparative example 2
依照实施例2的方法制备锂二次电池，只是在锂二次电池电解液中不添加四氟代磷酸钠，其余组分保留其原有含量比例。。The lithium secondary battery was prepared according to the method of Example 2, except that sodium tetrafluorophosphate was not added to the electrolyte of the lithium secondary battery, and the remaining components retained their original content ratios. .
对比例3Comparative example 3
依照实施例3的方法制备锂二次电池，只是在锂二次电池电解液中不添加四氟磷酸钾，其余组分保留其原有含量比例。The lithium secondary battery was prepared according to the method of Example 3, except that potassium tetrafluorophosphate was not added to the electrolyte of the lithium secondary battery, and the remaining components retained their original content ratios.
对比例4Comparative example 4
依照实施例4的方法制备锂二次电池，不同之处在于锂二次电池的电解液以占电解液总质量8.0％的六氟磷酸锂为锂盐，非水有机溶剂为碳酸乙烯酯、碳酸二乙酯，占电解液总质量的75.5％，质量比为1:2。添加四氟代磷酸锂，占电解液总质量的2.5％。第二添加剂为氟代碳酸乙烯酯，硫酸乙烯酯分别占电解液总质量的10.0％、4.0％。The lithium secondary battery was prepared according to the method of Example 4, the difference is that the electrolyte of the lithium secondary battery uses 8.0% of the total mass of the electrolyte as the lithium salt, and the non-aqueous organic solvent is ethylene carbonate and diethyl carbonate. , Accounting for 75.5% of the total mass of the electrolyte, with a mass ratio of 1:2. Add lithium tetrafluorophosphate, which accounts for 2.5% of the total mass of the electrolyte. The second additive is fluoroethylene carbonate, and vinyl sulfate accounts for 10.0% and 4.0% of the total mass of the electrolyte, respectively.
对比例5Comparative example 5
依照实施例5的方法制备锂二次电池，只是在锂二次电池电解液中将LiPF 6换成双氟磺酰亚胺锂。 The lithium secondary battery was prepared according to the method of Example 5, except that LiPF 6 was replaced with lithium bisfluorosulfonimide in the electrolyte of the lithium secondary battery.
对比例6Comparative example 6
依照实施例6的方法制备锂二次电池，不同的是锂二次电池的电解液以占电解液总质量8％的六氟磷酸锂为锂盐，以碳酸乙烯酯、碳酸甲乙酯、碳酸二乙 酯的混合物为非水有机溶剂，占电解液总质量的84.5％，质量比为3:5:2。添加四氟代磷酸钾，占电解液总质量的2.0％。第二添加剂为二氟二草酸磷酸锂、三烯丙基磷酸酯，分别占电解液总质量的2.0％、3.5％。The lithium secondary battery was prepared according to the method of Example 6, the difference is that the electrolyte of the lithium secondary battery uses 8% of the total mass of the electrolyte as the lithium salt, and uses ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate. The mixture is a non-aqueous organic solvent, accounting for 84.5% of the total mass of the electrolyte, and the mass ratio is 3:5:2. Potassium tetrafluorophosphate is added, which accounts for 2.0% of the total mass of the electrolyte. The second additives are lithium difluorobisoxalate phosphate and triallyl phosphate, which respectively account for 2.0% and 3.5% of the total mass of the electrolyte.
对比例7Comparative example 7
依照实施例7的方法制备锂二次电池，不同的是锂二次电池的电解液以占电解液总质量27％的六氟磷酸锂为锂盐，以碳酸乙烯酯、碳酸甲乙酯、碳酸二乙酯的混合物为非水有机溶剂，占电解液总质量的64.5％，质量比为3:5:2，添加四氟代磷酸锂和四氟代磷酸钠，分别占电解液总质量的1.5％和2.5％。第二添加剂为氟代碳酸乙烯酯、二氟草酸磷酸锂、三(三甲基硅烷)磷酸酯，占电解液总质量的3.0％、0.5％、1.0％。The lithium secondary battery was prepared according to the method of Example 7. The difference is that the electrolyte of the lithium secondary battery uses lithium hexafluorophosphate, which accounts for 27% of the total mass of the electrolyte, as the lithium salt, and uses ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate. The mixture is a non-aqueous organic solvent, accounting for 64.5% of the total mass of the electrolyte, and the mass ratio is 3:5:2. Lithium tetrafluorophosphate and sodium tetrafluorophosphate are added to account for 1.5% and 2.5 of the total electrolyte mass, respectively. %. The second additives are fluoroethylene carbonate, lithium difluorooxalate phosphate, and tris(trimethylsilane) phosphate, which account for 3.0%, 0.5%, and 1.0% of the total mass of the electrolyte.
对比例8Comparative example 8
依照实施例8的方法制备锂二次电池，不同的是锂二次电池的电解液以占电解液总质量5％的六氟磷酸锂为锂盐，以碳酸乙烯酯、碳酸甲乙酯、碳酸二乙酯的混合物为非水有机溶剂，占电解液总质量的92.5％，质量比为3:5:2，添加四氟磷酸钾和四氟磷酸钠，分别占电解液总质量的0.25％和0.25％，第二添加剂为碳酸乙烯亚乙酯、二氟磷酸锂、三丙炔基磷酸酯、三(三甲基硅烷)磷酸酯，占电解液总质量的0.5％、0.5％、0.5％、0.5％。The lithium secondary battery was prepared according to the method of Example 8. The difference is that the electrolyte of the lithium secondary battery uses 5% of the total mass of the electrolyte as the lithium salt, and uses ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate. The mixture of is a non-aqueous organic solvent, accounting for 92.5% of the total mass of the electrolyte, and the mass ratio is 3:5:2. Potassium tetrafluorophosphate and sodium tetrafluorophosphate are added to account for 0.25% and 0.25% of the total mass of the electrolyte, respectively. The second additive is ethylene ethylene carbonate, lithium difluorophosphate, tripropynyl phosphate, and tris(trimethylsilane) phosphate, which account for 0.5%, 0.5%, 0.5%, and 0.5% of the total mass of the electrolyte.
对比例9Comparative example 9
依照实施例9的方法制备锂二次电池，不同的是锂二次电池的电解液以占电解液总质量25.0％的六氟磷酸锂为锂盐，非水有机溶剂为碳酸乙烯酯、氟代碳酸乙烯酯、丙酸三氟乙基酯，占电解液总质量的57％，质量比为4:1:5。添加四氟磷酸锂和四氟磷酸钾，分别占电解液总质量的2.5％和2.5％。第二添加剂为 碳酸亚乙烯酯、双草酸硼酸锂、硫酸乙烯酯、六亚甲基二异氰酸酯，分别占电解液总质量的3.0％、3.0％、3.0％、4.0％。The lithium secondary battery was prepared according to the method of Example 9. The difference is that the electrolyte of the lithium secondary battery uses 25.0% of the total mass of the electrolyte as the lithium salt, and the non-aqueous organic solvent is ethylene carbonate and fluoroethylene carbonate. , Trifluoroethyl propionate, accounting for 57% of the total mass of the electrolyte, with a mass ratio of 4:1:5. Lithium tetrafluorophosphate and potassium tetrafluorophosphate are added, which respectively account for 2.5% and 2.5% of the total mass of the electrolyte. The second additives are vinylene carbonate, lithium bisoxalate borate, vinyl sulfate, and hexamethylene diisocyanate, which respectively account for 3.0%, 3.0%, 3.0%, and 4.0% of the total mass of the electrolyte.
对比例10Comparative example 10
依照实施例10的方法制备锂二次电池，只是将四氟代磷酸锂换成了二氟代磷酸锂。The lithium secondary battery was prepared according to the method of Example 10, except that lithium tetrafluorophosphate was replaced with lithium difluorophosphate.
对比例11Comparative example 11
依照实施例11的方法制备锂二次电池，不同的是除了加入占电解液总质量的12.5％的LiPF 6外，还加入了6.5％的双氟磺酰亚胺锂(LiFSI)作为锂盐，非水有机溶剂为碳酸乙烯酯、碳酸二乙酯，占电解液总质量的72.5％，质量比为1:2。添加四氟代磷酸锂和四氟代磷酸钠，分别占电解液总质量的3.0％和3.0％。第二添加剂为氟代碳酸乙烯酯、二氟磷酸锂、三(三甲基硅烷)磷酸酯，分别占电解液总质量的1.0％、0.5％、1.0％。 The lithium secondary battery was prepared according to the method of Example 11. The difference was that in addition to 12.5% of the total mass of the electrolyte, LiPF 6 was added, and 6.5% of lithium bisfluorosulfonimide (LiFSI) was added as the lithium salt. The non-aqueous organic solvents are ethylene carbonate and diethyl carbonate, accounting for 72.5% of the total mass of the electrolyte, and the mass ratio is 1:2. Lithium tetrafluorophosphate and sodium tetrafluorophosphate are added, which respectively account for 3.0% and 3.0% of the total mass of the electrolyte. The second additive is fluoroethylene carbonate, lithium difluorophosphate, and tris(trimethylsilane) phosphate, which respectively account for 1.0%, 0.5%, and 1.0% of the total mass of the electrolyte.
对比例12Comparative example 12
依照实施例12的方法制备锂二次电池，不同的是将第二添加剂碳酸亚乙烯酯、二氟二草酸磷酸锂、六亚甲基二异氰酸酯，分别占电解液总质量的2.0％、3.5％、2.5％相应替换为氯化锂、氯化钠和氯化钾。The lithium secondary battery was prepared according to the method of Example 12, except that the second additives, vinylene carbonate, lithium difluorobisoxalate, and hexamethylene diisocyanate, respectively accounted for 2.0% and 3.5% of the total mass of the electrolyte. , 2.5% was replaced by lithium chloride, sodium chloride and potassium chloride.
对所有对比例1～12和所有实施例1～13所得电池进行如下实验：The following experiments were performed on the batteries obtained in all Comparative Examples 1-12 and all Examples 1-13:
循环实验：将对比例1～12和实施例1～13所得电池在分别在室温25℃测试电池的内阻；在25℃下以2CC/0.5CD的倍率进行充放电；在低温-10℃下以0.5CC/0.2CD的倍率进行充放电；在高温55℃下以0.5CC/0.5CD的充放电倍率进行充放电循环测试，分别记录最后一次循环放电容量并除以第1次循环放电 容量即得容量保持率，记录结果如表1。Cycle experiment: test the internal resistance of the batteries obtained in Comparative Examples 1-12 and Examples 1-13 at room temperature and 25°C; charge and discharge at a rate of 2CC/0.5CD at 25°C; and at a low temperature of -10°C Perform charge and discharge at a rate of 0.5CC/0.2CD; perform a charge-discharge cycle test at a high temperature of 55℃ at a charge-discharge rate of 0.5CC/0.5CD. Record the discharge capacity of the last cycle and divide it by the discharge capacity of the first cycle. Obtain the capacity retention rate, and record the results as shown in Table 1.
高温存储实验：将对比例1～12和实施例1～13的电池先在室温下以0.5C/0.5C的充放电倍率在3.0～4.2V充放电3次，再以0.5C充电至4.2V，记录电池的厚度。将电池放置在60℃烘箱中存储15天，记录电池的厚度。第二次记录电池的厚度除以第一次记录电池的厚度即为电池膨胀率。结果记录如表1。High-temperature storage experiment: The batteries of Comparative Examples 1-12 and Examples 1-13 were first charged and discharged at room temperature at a charge-discharge rate of 0.5C/0.5C at 3.0-4.2V for 3 times, and then charged at 0.5C to 4.2V , Record the thickness of the battery. The battery was stored in a 60°C oven for 15 days, and the thickness of the battery was recorded. The thickness of the second recording battery divided by the thickness of the first recording battery is the battery expansion rate. The results are recorded in Table 1.
表1 实施例和对比例的测试结果：Table 1 Test results of Examples and Comparative Examples:
Figure PCTCN2020134175-appb-000004
Figure PCTCN2020134175-appb-000004
Figure PCTCN2020134175-appb-000005
Figure PCTCN2020134175-appb-000005
通过以上数据可以明显看出，当六氟磷酸锂中加入四氟磷酸盐后，在内阻、低温、室温和高温循环性、以及高温膨胀性上均比不加入四氟磷酸盐时整体效果更佳，同时各添加剂的含量经过反复试验后，能够达到令人满意的效果。From the above data, it can be clearly seen that when tetrafluorophosphate is added to lithium hexafluorophosphate, the overall effect is better in terms of internal resistance, low temperature, room temperature and high temperature cyclability, and high temperature expansion than when tetrafluorophosphate is not added. After repeated tests, the content of each additive can achieve satisfactory results.
以上所述的仅为本申请的较佳实施例，不作为对本申请保护范围的具体限定。本申请的保护范围以权利要求书为准。The foregoing descriptions are only preferred embodiments of the present application, and are not intended to specifically limit the scope of protection of the present application. The scope of protection of this application is subject to the claims.

Claims (10)

  1. 式(1)所示的锂二次电池电解液添加剂：The lithium secondary battery electrolyte additive shown in formula (1):
    Figure PCTCN2020134175-appb-100001
    Figure PCTCN2020134175-appb-100001
    其中，M选自Li，Na，K中的任一种或多种的组合。Wherein, M is selected from any one or a combination of Li, Na, and K.
  2. 一种锂二次电池电解液，其中包含：1)至少含有六氟磷酸锂的电解质锂盐，2)非水有机溶剂；3)添加剂，所述添加剂为如下式(1)结构式所示的多氟代磷酸盐：An electrolyte for a lithium secondary battery, comprising: 1) an electrolyte lithium salt containing at least lithium hexafluorophosphate; 2) a non-aqueous organic solvent; 3) an additive, the additive being a polyfluorophosphoric acid represented by the following formula (1) structural formula salt:
    Figure PCTCN2020134175-appb-100002
    Figure PCTCN2020134175-appb-100002
    其中，M选自Li，Na，K中的任一种或多种的组合。Wherein, M is selected from any one or a combination of Li, Na, and K.
  3. 根据权利要求2所述的锂二次电池电解液，其中，所述的式(1)锂二次电池电解液添加剂在锂二次电池电解液中所占的重量百分数为0.01％-5％。The lithium secondary battery electrolyte according to claim 2, wherein the weight percentage of the lithium secondary battery electrolyte additive of formula (1) in the lithium secondary battery electrolyte is 0.01% to 5%.
  4. 根据权利要求2所述的锂二次电池电解液，其中，所述锂盐在锂二次电池电解液中重量百分数为10％-25％；所述的非水溶剂的重量百分数为60％-89.99％；所述的式(1)锂二次电池电解液添加剂的重量百分数为0.01％-5％。The lithium secondary battery electrolyte according to claim 2, wherein the weight percentage of the lithium salt in the lithium secondary battery electrolyte is 10%-25%; the weight percentage of the non-aqueous solvent is 60%- 89.99%; the weight percentage of the electrolyte additive of the formula (1) lithium secondary battery is 0.01%-5%.
  5. 根据权利要求2到4之一所述的锂二次电池电解液，其中，除六氟磷酸锂外，还包含选自双(三氟甲基磺酰)亚胺锂、双氟磺酰亚胺锂、四氟硼酸锂、 双草酸硼酸锂中的至少一种锂盐。The electrolyte for a lithium secondary battery according to any one of claims 2 to 4, wherein in addition to lithium hexafluorophosphate, it further contains lithium bis(trifluoromethylsulfonyl)imide, lithium bisfluorosulfonimide, and lithium hexafluorophosphate. At least one lithium salt of lithium fluoroborate and lithium bisoxalate borate.
  6. 根据权利要求2到4之一所述的锂二次电池电解液，其中，所述非水溶剂为碳酸二甲酯、碳酸二乙酯、碳酸甲乙酯、碳酸乙烯酯、乙酸乙酯、碳酸甲丙酯、氟代碳酸乙烯酯、2，2-二氟乙基乙酸酯、丙酸三氟乙基酯、丙酸二氟乙基酯、氟代碳酸丙烯酯、碳酸甲丙酯、γ-丁内酯和γ-戊内酯中的至少一种。The lithium secondary battery electrolyte according to any one of claims 2 to 4, wherein the non-aqueous solvent is dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene carbonate, ethyl acetate, carbonic acid Methyl propyl, fluoroethylene carbonate, 2,2-difluoroethyl acetate, trifluoroethyl propionate, difluoroethyl propionate, fluoropropylene carbonate, methyl propyl carbonate, γ -At least one of butyrolactone and γ-valerolactone.
  7. 根据权利要求2到4之一所述的锂二次电池电解液，其还包括第二添加剂，占电解液的质量百分数为0-10％，所述第二添加剂选自碳酸亚乙烯酯、氟代碳酸乙烯酯、二氟磷酸锂、二氟二草酸磷酸锂、硫酸乙烯酯、三烯丙基磷酸酯、三丙炔基磷酸酯、三(三甲基硅烷)磷酸酯、六亚甲基二异氰酸酯中的至少一种。The lithium secondary battery electrolyte according to any one of claims 2 to 4, further comprising a second additive, which accounts for 0-10% by mass of the electrolyte, and the second additive is selected from vinylene carbonate, fluorine Ethylene carbonate, lithium difluorophosphate, lithium difluorodioxalate, vinyl sulfate, triallyl phosphate, tripropynyl phosphate, tris(trimethylsilane) phosphate, hexamethylene bis At least one of isocyanates.
  8. 一种锂二次电池，其包括权利要求2-7之一所述的锂二次电池电解液。A lithium secondary battery comprising the lithium secondary battery electrolyte according to any one of claims 2-7.
  9. 权利要求1所述的具有式(1)的锂二次电池电解液添加剂在含有LiPF 6电解质锂盐的锂二次电池中降低阻抗的用途。 The use of the lithium secondary battery electrolyte additive having formula (1) according to claim 1 for reducing impedance in a lithium secondary battery containing LiPF 6 electrolyte lithium salt.
  10. 根据权利要求9所述的用途，其中所述的具有式(1)的锂二次电池电解液添加剂与第二添加剂配合在常温下使用，所述第二添加剂包括选自碳酸亚乙烯酯、氟代碳酸乙烯酯、二氟磷酸锂、二氟二草酸磷酸锂、硫酸乙烯酯、三烯丙基磷酸酯、三丙炔基磷酸酯、三(三甲基硅烷)磷酸酯、六亚甲基二异氰酸酯中的至少一种。The use according to claim 9, wherein the lithium secondary battery electrolyte additive of formula (1) is used in combination with a second additive at room temperature, and the second additive includes a compound selected from the group consisting of vinylene carbonate and fluorine. Ethylene carbonate, lithium difluorophosphate, lithium difluorodioxalate phosphate, vinyl sulfate, triallyl phosphate, tripropynyl phosphate, tris(trimethylsilane) phosphate, hexamethylene bis At least one of isocyanates.
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