WO2021243953A1 - 锂离子电池用电解液功能添加剂、锂离子电池电解液及锂离子电池 - Google Patents

锂离子电池用电解液功能添加剂、锂离子电池电解液及锂离子电池 Download PDF

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WO2021243953A1
WO2021243953A1 PCT/CN2020/127182 CN2020127182W WO2021243953A1 WO 2021243953 A1 WO2021243953 A1 WO 2021243953A1 CN 2020127182 W CN2020127182 W CN 2020127182W WO 2021243953 A1 WO2021243953 A1 WO 2021243953A1
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lithium
electrolyte
ion battery
lithium ion
functional additive
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French (fr)
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支岩辉
刘颖
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Svolt Energy Technology Co Ltd
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Svolt Energy Technology Co Ltd
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Priority to KR1020227027191A priority Critical patent/KR102849131B1/ko
Priority to US17/788,286 priority patent/US12230758B2/en
Priority to JP2022538275A priority patent/JP7416955B2/ja
Priority to EP20939302.4A priority patent/EP4068454A4/en
Publication of WO2021243953A1 publication Critical patent/WO2021243953A1/zh
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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
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0569—Liquid materials characterised by the solvents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • H01M2300/0037—Mixture of solvents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • H01M2300/0037—Mixture of solvents
    • H01M2300/004—Three solvents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • H01M2300/0037—Mixture of solvents
    • H01M2300/0042—Four or more solvents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H01M50/417—Polyolefins
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/431—Inorganic material
    • H01M50/434—Ceramics
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • H01M50/451—Separators, membranes or diaphragms characterised by the material having a layered structure comprising layers of only organic material and layers containing inorganic material
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to the technical field of power battery materials, and in particular to an electrolyte functional additive for lithium ion batteries, lithium ion battery electrolyte and lithium ion batteries.
  • the cost and safety of power batteries are the industry pain points that need to be solved urgently at the moment of automobile electrification. Safety is the bottom line of the development of electric vehicles, and it is also the top priority for consumers. Whether the cost can be reduced directly affects whether electric vehicles can truly be compared with fuel vehicles PK in the market. The high pressure of safety and cost makes power battery and industry chain companies continue to explore new directions on the basis of existing material systems. As a strategic resource, the price fluctuation of cobalt will directly affect the cost of the final battery cell. Therefore, international mainstream power battery companies are taking underestimated and cobalt-free batteries as the research and development direction of next-generation power batteries.
  • the cobalt content of the positive electrode material decreases, the ionic and electronic conductivity of the material deteriorates, and the overall DC internal resistance of the battery increases; at the same time, the removal of cobalt makes the stability of the layered structure of the positive electrode material worse, and the metal ions especially manganese
  • the precipitation of ions increases and deposits on the negative electrode, destroying the negative electrode SEI film, and affecting the cycle life of the battery.
  • the metal ions on the surface of the material can also easily catalyze the electrolyte, causing it to oxidize and decompose on the surface of the positive electrode, consume the electrolyte, and affect the cycle life of the battery.
  • the main purpose of the present invention is to provide an electrolyte functional additive for lithium-ion batteries, lithium-ion battery electrolytes and lithium-ion batteries, so as to solve the problem that the electrolyte in the prior art is applied to lithium-ion batteries with no cobalt or low cobalt content. Causes the problem of reduced battery cycle life.
  • a functional additive for electrolyte for lithium ion batteries there is provided a functional additive for electrolyte for lithium ion batteries. And 0.2 to 2 parts of vinylene carbonate.
  • the weight ratio of the above-mentioned lithium tetrafluoroborate and lithium bisoxalate borate satisfies the range of 1:2 to 1:4.
  • the above functional additive further includes 0.2 to 1 part of pyridine trifluoroborate.
  • an electrolyte for a lithium ion battery including an organic solvent, an electrolyte lithium salt, and a functional additive.
  • the functional additive is any one of the above functional additives.
  • the mass content of the functional additive in the electrolyte of the lithium ion battery is 2.5 to 5%.
  • the concentration of the electrolyte lithium salt in the electrolyte of the lithium ion battery is 0.8-2.0 mol/L.
  • the electrolyte lithium salt includes lithium hexafluorophosphate and lithium bisfluorosulfonimide, and more preferably lithium hexafluorophosphate and bisfluorosulfonimide.
  • the molar ratio of imide lithium is 6-10:1.
  • the above-mentioned organic solvent includes at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, and ethyl methyl carbonate.
  • the organic solvent is selected from the group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, and methyl carbonate.
  • a mixture of any three or more of ethyl esters, and it is further preferred that the mass ratio of ethylene carbonate, propylene carbonate, diethyl carbonate and ethyl methyl carbonate in the organic solvent is 2 to 3: 0.3 to 0.8: 1.5 ⁇ 3:4 ⁇ 7.
  • a lithium ion battery includes a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte, and the electrolyte is any one of the foregoing electrolytes.
  • the above-mentioned positive electrode sheet includes a positive electrode active material
  • the above-mentioned diaphragm is a ceramic diaphragm.
  • the electrolyte functional additives for lithium ion batteries of the present invention include vinylene carbonate, lithium tetrafluoroborate, and lithium bisoxalate borate.
  • the combined use of multiple additives ensures that a dense, dense layer is formed on the surface of the negative electrode.
  • the stable SEI film improves the high temperature storage performance and high temperature cycle performance of the battery.
  • lithium tetrafluoroborate and lithium bisoxalate borate will react to a certain extent, and the formed intermediate product, lithium difluorooxalate borate, on the one hand can oxidize and form a film on the surface of the positive electrode, effectively preventing the direct contact between the electrolyte and the positive electrode material.
  • the lithium ion battery electrolyte with the functional additives of the present application contains lithium tetrafluoroborate, lithium bisoxalate and lithium difluorooxalate at the same time during use, and can take advantage of their respective advantages and can still maintain high levels in low temperature or high temperature environments. Electrical properties.
  • a functional additive for electrolyte for lithium ion batteries In parts by weight, the functional additive includes 0.1 to 0.5 parts of lithium tetrafluoroborate and 0.3 to 1.5 parts of lithium bisoxalate borate. And 0.2 to 2 parts of vinylene carbonate.
  • the electrolyte functional additives for lithium-ion batteries of the present invention include vinylene carbonate, lithium tetrafluoroborate, and lithium bisoxalate borate.
  • the combined use of multiple additives ensures that a dense and stable SEI film is formed on the surface of the negative electrode and improves the battery High temperature storage performance and high temperature cycle performance.
  • lithium tetrafluoroborate and lithium bisoxalate borate will react to a certain extent, and the formed intermediate product, lithium difluorooxalate borate, on the one hand can oxidize and form a film on the surface of the positive electrode, effectively preventing the direct contact between the electrolyte and the positive electrode material.
  • the lithium ion battery electrolyte with the functional additives of the present application contains lithium tetrafluoroborate, lithium bisoxalate and lithium difluorooxalate at the same time during use, and can take advantage of their respective advantages and can still maintain high levels in low temperature or high temperature environments. Electrical properties.
  • the weight ratio of the above lithium tetrafluoroborate and lithium bisoxalate borate satisfies the range of 1:2 to 1:4.
  • the above functional additive further includes 0.2 to 1 part of pyridine trifluoroborate.
  • the trifluoroboric acid group in trifluoroboric acid pyridine can complex the acidic substances in the electrolyte, reduce its damage to the negative electrode SEI film and the dissolution of positive electrode metal ions, on the other hand, it can dissolve the positive and negative electrode interface film Lithium fluoride reduces the interface impedance of the positive and negative electrodes, thereby reducing the DC internal resistance of the battery; at the same time, the pyridine group can complex the manganese ions dissolved in the positive electrode, reducing its damage to the negative electrode, and further improving the cycle performance of the battery.
  • a lithium ion battery electrolyte which includes an organic solvent, an electrolyte lithium salt, and a functional additive, and the functional additive is the above functional additive.
  • the AC impedance of the electrolyte is significantly reduced, which is beneficial to improve rate performance and low temperature performance.
  • the SEI film formed on the surface of the negative electrode is dense and stable.
  • a protective film is formed on the surface of the positive electrode, which can significantly improve the high-temperature performance and cycle performance of the battery.
  • the mass content of the functional additive in the electrolyte of the ion battery is 2.5-5. So that the function of the additive can be brought into full play.
  • the electrolyte lithium salt used in the electrolyte of the lithium ion battery of the present application can adopt the electrolyte lithium salt commonly used in the prior art. In order to ensure the overall excellent performance of the lithium ion battery, it is preferably calculated in terms of lithium ion.
  • the concentration of salt is 0.5 to 2.0 mol/L.
  • the above-mentioned electrolyte lithium salt includes lithium hexafluorophosphate and lithium bisfluorosulfonimide, and it is further preferable that the molar ratio of lithium hexafluorophosphate and lithium bisfluorosulfonimide is 6-10:1.
  • lithium bisfluorosulfonimide can significantly increase the conductivity of the electrolyte, improve the rate performance and low-temperature performance of the battery, and its high-temperature stability can also significantly improve the high-temperature performance of the electrolyte; It can be deposited on the surface of the positive electrode to protect the positive electrode to a certain extent.
  • the organic solvent in the electrolyte of the lithium ion battery is used to fully dissolve and disperse the electrolyte lithium salt and functional additives therein, so that their respective functions can be fully exerted.
  • the organic solvent used in this application can be a solvent commonly used in the field, such as an organic solvent Including at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, and ethyl methyl carbonate.
  • the organic solvent is selected from any three of ethylene carbonate, propylene carbonate, dimethyl carbonate, and ethyl methyl carbonate.
  • the combination of the above organic solvents can better take into account the high and low temperature performance of the battery on the basis of ensuring that the electrolyte meets a certain electrical conductivity.
  • a lithium ion battery in another exemplary embodiment of the present application, includes a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte, and the electrolyte is any one of the foregoing electrolytes.
  • the AC impedance of the electrolyte is significantly reduced, which is beneficial to improve rate performance and low temperature performance.
  • the SEI film formed on the surface of the negative electrode is dense and stable, and at the same time, a layer is formed on the surface of the positive electrode.
  • the protective film can significantly improve the high temperature performance and cycle performance of the battery.
  • the lithium-ion battery electrolyte of the present application is suitable for current conventional lithium-ion batteries. When it is applied to a cobalt-free lithium-ion battery or a low-cobalt-ion battery, the battery can still maintain high cycle performance.
  • the above-mentioned positive electrode sheet includes a positive electrode active material
  • the above-mentioned nickel-manganese binary layered material does not contain cobalt, which further reduces the cost of raw materials and has a certain strategic significance. When used in conjunction with the electrolyte, it can make up for the shortcomings of the material itself and maximize the satisfaction of the battery Various performance requirements.
  • the above-mentioned diaphragm is a ceramic diaphragm.
  • the ceramic diaphragm includes a polyolefin diaphragm substrate and a ceramic coating coated on the polyolefin diaphragm.
  • the ceramic coating may be an alumina coating.
  • the polyolefin diaphragm base is made of PE, and the thickness of the ceramic coating is 2 to 3 ⁇ m.
  • the electrolyte functional additive for lithium ion batteries of this embodiment is composed of the following components in parts by weight: 0.3 parts of lithium tetrafluoroborate, 1.0 part of lithium bisoxalate borate, 0.5 part of pyridine trifluoroborate, and 1 part of vinylene carbonate .
  • the lithium ion battery electrolyte of this embodiment is composed of an organic solvent, electrolyte lithium salt and functional additives;
  • the organic solvent is composed of ethylene carbonate, propylene carbonate, diethyl carbonate and ethyl methyl carbonate, and ethylene carbonate, carbonic acid
  • the mass ratio of propylene ester, diethyl carbonate and ethyl methyl carbonate is 2.5:0.5:2:5;
  • the electrolyte lithium salt is composed of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide, and lithium hexafluorophosphate and bisfluorosulfonimide
  • the molar ratio of lithium is 6:1, the total molar concentration of the electrolyte lithium salt in the electrolyte is 1.2 mol/L; the amount of functional additives in the electrolyte is 4%.
  • Example 2 The difference from Example 1 is that the electrolyte functional additive for lithium ion batteries of this example is composed of the following components by weight: 0.25 parts of lithium tetrafluoroborate, 1.0 part of lithium bisoxalate borate, and pyridine trifluoroborate. 0.5 part, 1 part of vinylene carbonate.
  • the electrolyte functional additive for lithium ion batteries of this example is composed of the following components in parts by weight: 0.5 parts of lithium tetrafluoroborate, 1.0 part of lithium bisoxalate borate, and pyridine trifluoroborate. 0.5 part, 1 part of vinylene carbonate.
  • the functional additive for electrolyte for lithium ion batteries of this embodiment consists of the following components in parts by weight: 0.1 part of lithium tetrafluoroborate, 1.0 part of lithium bisoxalate borate, and pyridine trifluoroborate. 0.5 part, 1 part of vinylene carbonate.
  • Example 2 The difference from Example 1 is that the electrolyte functional additive for lithium ion batteries of this example is composed of the following components in parts by weight: 0.3 parts of lithium tetrafluoroborate, 1.5 parts of lithium bisoxalate borate, and pyridine trifluoroborate. 0.5 part, 1 part of vinylene carbonate.
  • Example 2 The difference from Example 1 is that the electrolyte functional additive for lithium ion batteries of this example is composed of the following components in parts by weight: 0.3 parts of lithium tetrafluoroborate, 0.3 parts of lithium bisoxalate borate, and pyridine trifluoroborate. 0.5 part, 1 part of vinylene carbonate.
  • the electrolyte functional additive for lithium ion batteries of this example is composed of the following components by weight: 0.3 parts of lithium tetrafluoroborate, 1.0 part of lithium bisoxalate borate, and pyridine trifluoroborate. 0.5 part, 0.2 part of vinylene carbonate.
  • the electrolyte functional additive for lithium ion batteries of this example is composed of the following components by weight: 0.3 parts of lithium tetrafluoroborate, 1.0 part of lithium bisoxalate borate, and pyridine trifluoroborate. 0.5 part, 2 parts of vinylene carbonate.
  • the electrolyte functional additive for lithium ion batteries of this example is composed of the following components by weight: 0.3 parts of lithium tetrafluoroborate, 1.0 part of lithium bisoxalate borate, and pyridine trifluoroborate. 0.2 part, 1 part of vinylene carbonate.
  • Example 2 The difference from Example 1 is that the electrolyte functional additive for lithium ion batteries of this example is composed of the following components by weight: 0.3 parts of lithium tetrafluoroborate, 1.0 part of lithium bisoxalate borate, and pyridine trifluoroborate. 1 part, 1 part of vinylene carbonate.
  • Example 1 The difference from Example 1 is that the electrolyte functional additive for lithium ion batteries of this example is composed of the following components in parts by weight: 0.3 parts of lithium tetrafluoroborate, 1.0 part of lithium bisoxalate borate, and vinylene carbonate 1 serving.
  • Example 2 The difference from Example 1 is that the total molar concentration of the electrolyte lithium salt in the electrolyte is 0.8 mol/L.
  • Example 2 The difference from Example 1 is that the total molar concentration of the electrolyte lithium salt in the electrolyte is 2.0 mol/L.
  • Example 2 The difference from Example 1 is that the total molar concentration of the electrolyte lithium salt in the electrolyte is 2.5 mol/L.
  • Example 1 The difference from Example 1 is that the electrolyte lithium salt is composed of lithium hexafluorophosphate and lithium bisfluorosulfonimide, and the molar ratio of lithium hexafluorophosphate and lithium bisfluorosulfonimide is 10:1.
  • Example 1 The difference from Example 1 is that the electrolyte lithium salt is composed of lithium hexafluorophosphate and lithium bisfluorosulfonimide, and the molar ratio of lithium hexafluorophosphate and lithium bisfluorosulfonimide is 4:1.
  • Example 2 The difference from Example 1 is that the mass ratio of ethylene carbonate, propylene carbonate, diethyl carbonate and ethyl methyl carbonate is 2:0.8:1.5:7.
  • Example 2 The difference from Example 1 is that the mass ratio of ethylene carbonate, propylene carbonate, diethyl carbonate and ethyl methyl carbonate is 3:0.3:3:4.
  • Example 2 The difference from Example 1 is that the organic solvent is composed of ethylene carbonate, propylene carbonate and ethyl methyl carbonate, and the mass ratio of ethylene carbonate, propylene carbonate and ethyl methyl carbonate is 2.5:0.5:7.
  • Example 2 The difference from Example 1 is that the organic solvent is composed of ethylene carbonate, diethyl carbonate and ethyl methyl carbonate, and the mass ratio of ethylene carbonate, diethyl carbonate and ethyl methyl carbonate is 3:2:5 .
  • Example 2 The difference from Example 1 is that the mass content of the functional additive in the electrolyte is 2%.
  • Example 2 The difference from Example 1 is that the mass content of the functional additive in the electrolyte is 5%.
  • Example 1 The difference from Example 1 is that the mass content of the functional additive in the electrolyte is 1.5%.
  • the comparative lithium ion battery electrolyte is composed of organic solvent, electrolyte lithium salt and functional additives;
  • the organic solvent is composed of ethylene carbonate, propylene carbonate, diethyl carbonate and ethyl methyl carbonate, ethylene carbonate, propylene carbonate
  • the mass ratio of diethyl carbonate and ethyl methyl carbonate is 2.5:0.5:2:5;
  • the electrolyte lithium salt is lithium hexafluorophosphate, and the total molar concentration of the electrolyte lithium salt in the electrolyte is 1.1 mol/L;
  • the functional additives are composed of the following weights
  • the component composition of parts 1 part of vinylene carbonate and 1 part of lithium difluorophosphate; the mass percentage of vinylene carbonate in the electrolyte of the lithium ion battery is 1%.
  • Example 2 The difference from Example 1 is that the electrolyte functional additive for lithium ion batteries of this example is composed of the following parts by weight: 1 part of lithium difluorooxalate borate, 0.5 part of pyridine trifluoroborate, and vinylene carbonate. 1 part of ester.
  • Example 1 The difference from Example 1 is that the electrolyte functional additive for lithium ion batteries of this example is composed of the following components in parts by weight: 0.3 parts of lithium tetrafluoroborate, 2.0 parts of lithium bisoxalate borate, and vinylene carbonate 1 serving.
  • Example 2 The difference from Example 1 is that the electrolyte functional additive for lithium ion batteries of this example is composed of the following components in parts by weight: 0.3 parts of lithium tetrafluoroborate, 1.0 part of lithium bisoxalate borate, and vinylene carbonate 2.5 copies.
  • Lithium-ion batteries were prepared with the lithium-ion battery electrolytes of the examples and comparative examples respectively, and the cycle performance of the obtained lithium-ion batteries was tested.
  • artificial graphite is used as the negative electrode active material to make the negative electrode sheet
  • LiNi 0.75 Mn 0.25 O 2 is used as the positive electrode active material to make the positive electrode sheet.
  • a 5Ah lithium-ion battery is made using a conventional lithium-ion battery assembly method; the ceramic diaphragm used includes a PE diaphragm substrate and an alumina coating coated on the diaphragm substrate. The thickness of the alumina coating is 2 to 3 ⁇ m.
  • the cycle performance of the lithium-ion battery prepared above was tested, and each battery was cycled 500 times, and the battery capacity retention rate before and after the cycle was calculated.
  • the test conditions are as follows,
  • High temperature performance test 1.0C rate discharge, 1.0C rate charge, voltage range 2.8 ⁇ 4.3V, temperature 45 ⁇ 5°C;
  • Example 1 500 99.4% 95.0% 55.0%
  • Example 2 500 99.3% 95.4% 51.0%
  • Example 3 500 98.9% 94.3% 58.0%
  • Example 4 500 98.1% 93.7% 48.0%
  • Example 5 500 98.3% 94.1% 47.0%
  • Example 6 500 98.1% 93.5% 48.0%
  • Example 7 500 98.3% 93.4% 57.0%
  • Example 8 500 99.1% 94.5% 51.0%
  • Example 9 500 98.2% 93.5% 52.0%
  • Example 10 500 99.0% 95.2% 50.0%
  • Example 11 500 97.5% 92.8% 53.0%
  • Example 12 500 98.9% 94.8% 47.0%
  • Example 13 500 99.2% 95.4% 57.0%
  • Example 14 500 98.5% 94.1% 45.0%
  • Example 15 500 99.2% 95.3% 53.0%
  • Example 16 500 99.4% 95.3% 58.0%
  • Example 17 500 99.5%
  • the electrolyte functional additives for lithium-ion batteries of the present invention include vinylene carbonate, lithium tetrafluoroborate, and lithium bisoxalate borate.
  • the combined use of multiple additives ensures that a dense and stable SEI film is formed on the surface of the negative electrode and improves the battery High temperature storage performance and high temperature cycle performance.
  • lithium tetrafluoroborate and lithium bisoxalate borate will react to a certain extent, and the formed intermediate product, lithium difluorooxalate borate, on the one hand can oxidize and form a film on the surface of the positive electrode, effectively preventing the direct contact between the electrolyte and the positive electrode material.
  • the lithium ion battery electrolyte with the functional additives of the present application contains lithium tetrafluoroborate, lithium bisoxalate and lithium difluorooxalate at the same time during use, and can take advantage of their respective advantages and can still maintain high levels in low temperature or high temperature environments. Electrical properties.

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Abstract

一种锂离子电池用电解液功能添加剂、锂离子电池电解液及锂离子电池。以重量份计，该功能添加剂包括0.1～0.5份四氟硼酸锂、0.3～1.5份双草酸硼酸锂和0.2～2份碳酸亚乙烯酯。该功能添加剂保证在负极表面形成一层致密、稳定的SEI膜，提高电池的高温存储性能和高温循环性能。其中，四氟硼酸锂和双草酸硼酸锂会形成中间产物二氟草酸硼酸锂，该物质可以避免电解液在正极表面的催化氧化，而且可以减少电解液的氧化分解，提升电池的循环性能，具有功能添加剂的锂离子电池电解液在使用时同时含有四氟硼酸锂、双草酸硼酸锂和二氟草酸硼酸锂，可以利用各自的优势，在低温或高温环境下仍然可以保持较高的电性能。

Description

锂离子电池用电解液功能添加剂、锂离子电池电解液及锂离子电池 技术领域
本发明涉及动力电池材料技术领域，具体而言，涉及一种锂离子电池用电解液功能添加剂、锂离子电池电解液及锂离子电池。
背景技术
动力电池的成本和安全是汽车电动化当下亟待解决的产业痛点，安全是电动汽车发展的底线，也是消费者关切的头等大事，而成本能否下降，直接影响着电动汽车能否真正与燃油汽车在市场上PK。安全与成本的高压倒使得动力电池及产业链企业在现有材料体系的基础上不断探寻新的方向。作为战略性的资源，钴的价格波动将会直接影响到最终电芯的成本，因此国际主流动力电池企业都在将低估及无钴化电池作为下一代动力电池的研发方向。
随正极材料钴含量的降低，材料的离子和电子电导性变差，电池整体直流内阻有所增加；同时，钴元素的去除使得正极材料层状结构的稳定性变差，金属离子尤其是锰离子析出增加，并向负极沉积，破坏负极SEI膜，影响电池的循环寿命。同时，材料表面的金属离子也极易对电解液起到一定的催化作用，使其在正极表面发生氧化分解，消耗电解液，影响电池的循环寿命。目前市场上还没有专门针对无钴层状材料的电解液来满足无钴电池的各项性能需求。
发明内容
本发明的主要目的在于提供一种锂离子电池用电解液功能添加剂、锂离子电池电解液及锂离子电池，以解决现有技术中电解液在应用至无钴或低钴含量的锂离子电池时导致电池循环寿命降低的问题。
为了实现上述目的，根据本发明的一个方面，提供了一种锂离子电池用电解液功能添加剂，以重量份计，功能添加剂包括0.1～0.5份四氟硼酸锂、0.3～1.5份双草酸硼酸锂和0.2～2份碳酸亚乙烯酯。
进一步地，上述四氟硼酸锂和双草酸硼酸锂的重量比例满足1:2～1:4的范围。
进一步地，以重量份计，上述功能添加剂还包括0.2～1份三氟硼酸吡啶。
根据本发明的另一方面，提供了一种锂离子电池电解液，包括有机溶剂、电解质锂盐和功能添加剂，该功能添加剂为上述任一种的功能添加剂。
进一步地，上述锂离子电池电解液中功能添加剂的质量含量为2.5～5％。
进一步地，以锂离子计，上述锂离子电池电解液中电解质锂盐的浓度为0.8～2.0mol/L，优选电解质锂盐包括六氟磷酸锂和双氟磺酰亚胺锂，进一步优选六氟磷酸锂和双氟磺酰亚胺锂的摩尔比为6～10:1。
进一步地，上述有机溶剂包括碳酸乙烯酯、碳酸丙烯酯、碳酸二乙酯、碳酸甲乙酯中的至少一种，优选有机溶剂选自碳酸乙烯酯、碳酸丙烯酯、碳酸二甲酯、碳酸甲乙酯中的任意三种或三种以上组成的混合物，进一步优选有机溶剂中碳酸乙烯酯、碳酸丙烯酯、碳酸二乙酯和碳酸甲乙酯的质量比为2～3:0.3～0.8:1.5～3:4～7。
根据本发明的另一方面，提供了一种锂离子电池，锂离子电池包括正极片、隔膜、负极片和电解液，该电解液为上述任一种的电解液。
进一步地，上述正极片包括正极活性物质，正极活性物质包括镍锰二元层状材料LiNi xMn yO 2，其中，0.5<x≤0.8，0.1<y≤0.5且x+y＝1。
进一步地，上述隔膜为陶瓷隔膜。
应用本发明的技术方案，本发明的锂离子电池用电解液功能添加剂包括碳酸亚乙烯酯、四氟硼酸锂、双草酸硼酸锂，多种添加剂的配合使用，保证在负极表面形成一层致密、稳定的SEI膜，提高电池的高温存储性能和高温循环性能。其中，四氟硼酸锂和双草酸硼酸锂会发生一定程度的反应，所形成的中间产物二氟草酸硼酸锂，一方面可在正极表面氧化成膜，有效阻止电解液与正极材料的直接接触，避免电解液在正极表面的催化氧化；另一方面正极材料M-O表面O空穴中心与ODFB －反应,生成路易斯酸F 2BOC·O自由基随后与M-O表面的O配位，同时相互之间通过两个自由电子结合成键，并稳定地存在于M-O表面，从而抑制该活性位的活性，减少电解液的氧化分解，提升电池的循环性能；而且还能够减少金属离子的溶出，避免金属离子对负极SEI膜的破坏，进而改善电池的循环性能。具有本申请的功能添加剂的锂离子电池电解液在使用时同时含有四氟硼酸锂、双草酸硼酸锂和二氟草酸硼酸锂，可以利用各自的优势，在低温或高温环境下仍然可以保持较高的电性能。
具体实施方式
需要说明的是，在不冲突的情况下，本申请中的实施例及实施例中的特征可以相互组合。下面将结合实施例来详细说明本发明。
在本申请一种典型的实施方式中，提供了一种锂离子电池用电解液功能添加剂，以重量份计，该功能添加剂包括0.1～0.5份四氟硼酸锂、0.3～1.5份双草酸硼酸锂和0.2～2份碳酸亚乙烯酯。
本发明的锂离子电池用电解液功能添加剂包括碳酸亚乙烯酯、四氟硼酸锂、双草酸硼酸锂，多种添加剂的配合使用，保证在负极表面形成一层致密、稳定的SEI膜，提高电池的高温存储性能和高温循环性能。其中，四氟硼酸锂和双草酸硼酸锂会发生一定程度的反应，所 形成的中间产物二氟草酸硼酸锂，一方面可在正极表面氧化成膜，有效阻止电解液与正极材料的直接接触，避免电解液在正极表面的催化氧化；另一方面正极材料M-O表面O空穴中心与ODFB －反应,生成路易斯酸F 2BOC·O自由基随后与M-O表面的O配位，同时相互之间通过两个自由电子结合成键，并稳定地存在于M-O表面，从而抑制该活性位的活性，减少电解液的氧化分解，提升电池的循环性能；而且还能够减少金属离子的溶出，避免金属离子对负极SEI膜的破坏，进而改善电池的循环性能。具有本申请的功能添加剂的锂离子电池电解液在使用时同时含有四氟硼酸锂、双草酸硼酸锂和二氟草酸硼酸锂，可以利用各自的优势，在低温或高温环境下仍然可以保持较高的电性能。
为了进一步使得四氟硼酸锂、双草酸硼酸锂和二氟草酸硼酸锂实现更好地协同作用，优选上述四氟硼酸锂和双草酸硼酸锂的重量比例满足1:2～1:4的范围。
在本申请一种实施例中，以重量份计，上述功能添加剂还包括0.2～1份三氟硼酸吡啶。三氟硼酸吡啶中的三氟硼酸基团，一方面可以络合电解液中的酸性物质，减少其对负极SEI膜和破坏和正极金属离子的溶解，另一方面可溶解正负极界面膜中的氟化锂，降低正负极界面阻抗，进而降低电池直流内阻；同时，吡啶基团可以络合正极溶出的锰离子，减少其对负极的破坏，进而进一步提升电池的循环性能。
在本申请又一种典型的实施方式中，提供了一种锂离子电池电解液，包括有机溶剂、电解质锂盐和功能添加剂，该功能添加剂为上述功能添加剂。
将本申请的功能添加剂应用至锂离子电池电解液中时，电解液交流阻抗明显降低，有利于提升倍率性能和低温性能，应用至锂离子电池时，在负极表面生成的SEI膜致密且稳定，同时在正极表面形成一层保护膜，能明显提升电池的高温性能和循环性能。
在本申请一种优选的实施例中，上述离子电池电解液中功能添加剂的质量含量为2.5～5。使得功能添加剂的作用得到充分发挥。
用于本申请的锂离子电池电解液的电解质锂盐可以采用现有技术中常用的电解质锂盐，为了保证锂离子电池的整体优异性能，优选以锂离子计，锂离子电池电解液中电解质锂盐的浓度为0.5～2.0mol/L。经过试验，优选上述电解质锂盐包括六氟磷酸锂和双氟磺酰亚胺锂，进一步优选六氟磷酸锂和双氟磺酰亚胺锂的摩尔比为6～10:1。双氟磺酰亚胺锂的加入能够明显提升电解液的电导率，改善电池的倍率性能和低温性能，同时其高温稳定性也能明显提升电解液的高温性能；双氟磺酰亚胺锂还可以在正极表面沉积，对正极起到一定的保护作用。
锂离子电池电解液中的有机溶剂用于将其中的电解质锂盐和功能添加剂充分溶解分散，使得各自的功能得到充分发挥，用于本申请的有机溶剂可以采用本领域常用的溶剂，比如有机溶剂包括碳酸乙烯酯、碳酸丙烯酯、碳酸二乙酯、碳酸甲乙酯中的至少一种，优选有机溶剂选自碳酸乙烯酯、碳酸丙烯酯、碳酸二甲酯、碳酸甲乙酯中的任意三种或三种以上组成的混合物，进一步优选有机溶剂中碳酸乙烯酯、碳酸丙烯酯、碳酸二乙酯和碳酸甲乙酯的质量 比为2～3:0.3～0.8:1.5～3:4～7。上述有机溶剂的组合在保证电解液满足一定的电导率的基础上，更好地兼顾电池的高低温性能。
在本申请又一种典型的实施方式中，提供了一种锂离子电池，锂离子电池包括正极片、隔膜、负极片和电解液，该电解液为上述任一种的电解液。
具有本申请的锂离子电池电解液的锂离子电池，其中的电解液交流阻抗明显降低，有利于提升倍率性能和低温性能，在负极表面生成的SEI膜致密且稳定，同时在正极表面形成一层保护膜，能明显提升电池的高温性能和循环性能。
本申请的锂离子电池电解液适用于目前常规的锂离子电池，当其应用于无钴锂离子电池或低钴离子电池时，仍然可以使电池保持高的循环性能。在一种实施例中，上述正极片包括正极活性物质，正极活性物质包括镍锰二元层状材料LiNi xMn yO 2，其中，0.5<x≤0.8，0.1<y≤0.5且x+y＝1。上述镍锰二元层状材料，不含钴元素，进一步降低了原材料成本，且具备一定的战略意义，与该电解液配合使用，能很好地弥补材料本身存在的缺点，最大限度地满足电池的各项性能需求。
在一种实施例中，上述隔膜为陶瓷隔膜。该陶瓷隔膜包括聚烯烃隔膜基体和聚烯烃隔膜上涂覆的陶瓷涂层。该陶瓷涂层可以为氧化铝涂层。聚烯烃隔膜基体为PE材质，陶瓷涂层的厚度为2～3μm。
以下将结合实施例和对比例进一步说明本申请的有益效果。
实施例1
本实施例的锂离子电池用电解液功能添加剂，由以下重量份数的组分组成：四氟硼酸锂0.3份、双草酸硼酸锂1.0份、三氟硼酸吡啶0.5份、碳酸亚乙烯酯1份。
本实施例的锂离子电池电解液，由有机溶剂、电解质锂盐和功能添加剂组成；有机溶剂由碳酸乙烯酯、碳酸丙烯酯、碳酸二乙酯和碳酸甲乙酯组成，且碳酸乙烯酯、碳酸丙烯酯、碳酸二乙酯和碳酸甲乙酯的质量比为2.5:0.5:2:5；电解质锂盐由六氟磷酸锂和双(氟磺酰)亚胺锂组成，且六氟磷酸锂和双氟磺酰亚胺锂的摩尔比为6:1，电解质锂盐在电解液中的总摩尔浓度为1.2mol/L；功能添加剂在电解液中的用量4％。
实施例2
与实施例1不同之处在于，本实施例的锂离子电池用电解液功能添加剂，由以下重量份数的组分组成：四氟硼酸锂0.25份、双草酸硼酸锂1.0份、三氟硼酸吡啶0.5份、碳酸亚乙烯酯1份。
实施例3
与实施例1不同之处在于，本实施例的锂离子电池用电解液功能添加剂，由以下重量份数的组分组成：四氟硼酸锂0.5份、双草酸硼酸锂1.0份、三氟硼酸吡啶0.5份、碳酸亚乙烯酯1份。
实施例4
与实施例1不同之处在于，本实施例的锂离子电池用电解液功能添加剂，由以下重量份数的组分组成：四氟硼酸锂0.1份、双草酸硼酸锂1.0份、三氟硼酸吡啶0.5份、碳酸亚乙烯酯1份。
实施例5
与实施例1不同之处在于，本实施例的锂离子电池用电解液功能添加剂，由以下重量份数的组分组成：四氟硼酸锂0.3份、双草酸硼酸锂1.5份、三氟硼酸吡啶0.5份、碳酸亚乙烯酯1份。
实施例6
与实施例1不同之处在于，本实施例的锂离子电池用电解液功能添加剂，由以下重量份数的组分组成：四氟硼酸锂0.3份、双草酸硼酸锂0.3份、三氟硼酸吡啶0.5份、碳酸亚乙烯酯1份。
实施例7
与实施例1不同之处在于，本实施例的锂离子电池用电解液功能添加剂，由以下重量份数的组分组成：四氟硼酸锂0.3份、双草酸硼酸锂1.0份、三氟硼酸吡啶0.5份、碳酸亚乙烯酯0.2份。
实施例8
与实施例1不同之处在于，本实施例的锂离子电池用电解液功能添加剂，由以下重量份数的组分组成：四氟硼酸锂0.3份、双草酸硼酸锂1.0份、三氟硼酸吡啶0.5份、碳酸亚乙烯酯2份。
实施例9
与实施例1不同之处在于，本实施例的锂离子电池用电解液功能添加剂，由以下重量份数的组分组成：四氟硼酸锂0.3份、双草酸硼酸锂1.0份、三氟硼酸吡啶0.2份、碳酸亚乙烯酯1份。
实施例10
与实施例1不同之处在于，本实施例的锂离子电池用电解液功能添加剂，由以下重量份数的组分组成：四氟硼酸锂0.3份、双草酸硼酸锂1.0份、三氟硼酸吡啶1份、碳酸亚乙烯酯1份。
实施例11
与实施例1不同之处在于，本实施例的锂离子电池用电解液功能添加剂，由以下重量份数的组分组成：四氟硼酸锂0.3份、双草酸硼酸锂1.0份、碳酸亚乙烯酯1份。
实施例12
与实施例1不同之处在于，电解质锂盐在电解液中的总摩尔浓度为0.8mol/L。
实施例13
与实施例1不同之处在于，电解质锂盐在电解液中的总摩尔浓度为2.0mol/L。
实施例14
与实施例1不同之处在于，电解质锂盐在电解液中的总摩尔浓度为2.5mol/L。
实施例15
与实施例1不同之处在于，电解质锂盐由六氟磷酸锂和双氟磺酰亚胺锂组成，且六氟磷酸锂和双氟磺酰亚胺锂的摩尔比为10:1。
实施例16
与实施例1不同之处在于，电解质锂盐由六氟磷酸锂和双氟磺酰亚胺锂组成，且六氟磷酸锂和双氟磺酰亚胺锂的摩尔比为4:1。
实施例17
与实施例1不同之处在于，碳酸乙烯酯、碳酸丙烯酯、碳酸二乙酯和碳酸甲乙酯的质量比为2:0.8:1.5:7。
实施例18
与实施例1不同之处在于，碳酸乙烯酯、碳酸丙烯酯、碳酸二乙酯和碳酸甲乙酯的质量比为3:0.3:3:4。
实施例19
与实施例1不同之处在于，有机溶剂由碳酸乙烯酯、碳酸丙烯酯和碳酸甲乙酯组成，且碳酸乙烯酯、碳酸丙烯酯和碳酸甲乙酯的质量比为2.5:0.5:7。
实施例20
与实施例1不同之处在于，有机溶剂由碳酸乙烯酯、碳酸二乙酯和碳酸甲乙酯组成，且碳酸乙烯酯、碳酸二乙酯和碳酸甲乙酯的质量比为3:2:5。
实施例21
与实施例1不同之处在于，功能添加剂在电解液中的质量含量为2％。
实施例22
与实施例1不同之处在于，功能添加剂在电解液中的质量含量为5％。
实施例23
与实施例1不同之处在于，功能添加剂在电解液中的质量含量为1.5％。
对比例1
对比例的锂离子电池电解液，由有机溶剂、电解质锂盐和功能添加剂组成；有机溶剂由碳酸乙烯酯、碳酸丙烯酯、碳酸二乙酯和碳酸甲乙酯组成，碳酸乙烯酯、碳酸丙烯酯、碳酸二乙酯和碳酸甲乙酯的质量比为2.5:0.5:2:5；电解质锂盐为六氟磷酸锂，电解质锂盐在电解液中的总摩尔浓度为1.1mol/L；功能添加剂由以下重量份数的组分组成：碳酸亚乙烯酯1份、二氟磷酸锂1份；碳酸亚乙烯酯在锂离子电池电解液中的质量百分比为1％。
对比例2
与实施例1不同之处在于，本实施例的锂离子电池用电解液功能添加剂，由以下重量份数的组分组成：二氟草酸硼酸锂1份、三氟硼酸吡啶0.5份、碳酸亚乙烯酯1份。
对比例3
与实施例1不同之处在于，本实施例的锂离子电池用电解液功能添加剂，由以下重量份数的组分组成：四氟硼酸锂0.3份、双草酸硼酸锂2.0份、碳酸亚乙烯酯1份。
对比例4
与实施例1不同之处在于，本实施例的锂离子电池用电解液功能添加剂，由以下重量份数的组分组成：四氟硼酸锂0.3份、双草酸硼酸锂1.0份、碳酸亚乙烯酯2.5份。
测试
分别以实施例以及对比例的锂离子电池电解液制备锂离子电池，对所得锂离子电池的循环性能进行测试。锂离子电池在制备时，以人造石墨为负极活性物质制作负极片，以LiNi 0.75Mn 0.25O 2为正极活性物质制作正极片，采用陶瓷隔膜，并分别采用实施例及对比例的锂离子电池电解液，采用常规锂离子电池的组装方法制作5Ah的锂离子电池；所采用的陶瓷隔膜包括PE隔膜基体和涂覆在隔膜基体上的氧化铝涂层，氧化铝涂层的厚度为2～3μm。
对上述制得的锂离子电池的循环性能进行测试，将各电池分别循环500次，计算循环前后的电池容量保持率。测试条件如下，
常温性能测试：1.0C倍率放电，1.0C倍率充电，电压范围2.8～4.3V，温度25±5℃；
高温性能测试：1.0C倍率放电，1.0C倍率充电，电压范围2.8～4.3V，温度45±5℃；
低温性能测试：25±5℃下充满电，-20℃条件下，1.0C放电，电压范围2.8～4.3V。测试结果如表1所示。
表1
  循环次数 常温循环容量保持率 高温循环容量保持率 低温放电容量保持率
实施例1 500 99.4％ 95.0％ 55.0％
实施例2 500 99.3％ 95.4％ 51.0％
实施例3 500 98.9％ 94.3％ 58.0％
实施例4 500 98.1％ 93.7％ 48.0％
实施例5 500 98.3％ 94.1％ 47.0％
实施例6 500 98.1％ 93.5％ 48.0％
实施例7 500 98.3％ 93.4％ 57.0％
实施例8 500 99.1％ 94.5％ 51.0％
实施例9 500 98.2％ 93.5％ 52.0％
实施例10 500 99.0％ 95.2％ 50.0％
实施例11 500 97.5％ 92.8％ 53.0％
实施例12 500 98.9％ 94.8％ 47.0％
实施例13 500 99.2％ 95.4％ 57.0％
实施例14 500 98.5％ 94.1％ 45.0％
实施例15 500 99.2％ 95.3％ 53.0％
实施例16 500 99.4％ 95.3％ 58.0％
实施例17 500 99.5％ 94.9％ 58.0％
实施例18 500 99.4％ 95.0％ 50.0％
实施例19 500 99.4％ 94.0％ 56.0％
实施例20 500 98.0％ 95.1％ 48.0％
实施例21 500 97.9％ 93.8％ 60.0％
实施例22 500 99.4％ 95.0％ 46.0％
实施例23 500 95.0％ 91.3％ 56.0％
对比例1 500 95.3％ 90％ 54％
对比例2 500 96.1％ 91％ 52％
对比例3 500 96％ 92.5％ 43％
对比例4 500 96.3％ 93％ 45％
从以上的描述中，可以看出，本发明上述的实施例实现了如下技术效果：
本发明的锂离子电池用电解液功能添加剂包括碳酸亚乙烯酯、四氟硼酸锂、双草酸硼酸锂，多种添加剂的配合使用，保证在负极表面形成一层致密、稳定的SEI膜，提高电池的高温存储性能和高温循环性能。其中，四氟硼酸锂和双草酸硼酸锂会发生一定程度的反应，所 形成的中间产物二氟草酸硼酸锂，一方面可在正极表面氧化成膜，有效阻止电解液与正极材料的直接接触，避免电解液在正极表面的催化氧化；另一方面正极材料M-O表面O空穴中心与ODFB －反应,生成路易斯酸F 2BOC·O自由基随后与M-O表面的O配位，同时相互之间通过两个自由电子结合成键，并稳定地存在于M-O表面，从而抑制该活性位的活性，减少电解液的氧化分解，提升电池的循环性能；而且还能够减少金属离子的溶出，避免金属离子对负极SEI膜的破坏，进而改善电池的循环性能。具有本申请的功能添加剂的锂离子电池电解液在使用时同时含有四氟硼酸锂、双草酸硼酸锂和二氟草酸硼酸锂，可以利用各自的优势，在低温或高温环境下仍然可以保持较高的电性能。
以上所述仅为本发明的优选实施例而已，并不用于限制本发明，对于本领域的技术人员来说，本发明可以有各种更改和变化。凡在本发明的精神和原则之内，所作的任何修改、等同替换、改进等，均应包含在本发明的保护范围之内。

Claims (10)

  1. 一种锂离子电池用电解液功能添加剂，其特征在于，以重量份计，所述功能添加剂包括0.1～0.5份四氟硼酸锂、0.3～1.5份双草酸硼酸锂和0.2～2份碳酸亚乙烯酯。
  2. 根据权利要求1所述的功能添加剂，其特征在于，所述四氟硼酸锂和所述双草酸硼酸锂的重量比例满足1:2～1:4的范围。
  3. 根据权利要求1所述的功能添加剂，其特征在于，以所述重量份计，所述功能添加剂还包括0.2～1份三氟硼酸吡啶。
  4. 一种锂离子电池电解液，包括有机溶剂、电解质锂盐和功能添加剂，其特征在于，所述功能添加剂为权利要求1至3中任一项所述的功能添加剂。
  5. 根据权利要求4所述的锂离子电池电解液，其特征在于，所述锂离子电池电解液中所述功能添加剂的质量含量为2.5～5％。
  6. 根据权利要求4所述的锂离子电池电解液，其特征在于，以锂离子计，所述锂离子电池电解液中所述电解质锂盐的浓度为0.8～2.0mol/L，优选所述电解质锂盐包括六氟磷酸锂和双氟磺酰亚胺锂，进一步优选所述六氟磷酸锂和双氟磺酰亚胺锂的摩尔比为6～10:1。
  7. 根据权利要求4所述的锂离子电池电解液，其特征在于，所述有机溶剂包括碳酸乙烯酯、碳酸丙烯酯、碳酸二乙酯、碳酸甲乙酯中的至少一种，优选所述有机溶剂选自碳酸乙烯酯、碳酸丙烯酯、碳酸二甲酯、碳酸甲乙酯中的任意三种或三种以上组成的混合物，进一步优选所述有机溶剂中所述碳酸乙烯酯、所述碳酸丙烯酯、所述碳酸二乙酯和所述碳酸甲乙酯的质量比为2～3:0.3～0.8:1.5～3:4～7。
  8. 一种锂离子电池，所述锂离子电池包括正极片、隔膜、负极片和电解液，其特征在于，所述电解液为权利要求4至7中任一项所述的电解液。
  9. 根据权利要求8所述的锂离子电池，其特征在于，所述正极片包括正极活性物质，所述正极活性物质包括镍锰二元层状材料LiNi xMn yO 2，其中，0.5<x≤0.8，0.1<y≤0.5且x+y＝1。
  10. 根据权利要求8所述的锂离子电池，其特征在于，所述隔膜为陶瓷隔膜。
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