CN114843606A - Additive for battery electrolyte, electrolyte and lithium ion battery - Google Patents

Additive for battery electrolyte, electrolyte and lithium ion battery Download PDF

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CN114843606A
CN114843606A CN202210439173.8A CN202210439173A CN114843606A CN 114843606 A CN114843606 A CN 114843606A CN 202210439173 A CN202210439173 A CN 202210439173A CN 114843606 A CN114843606 A CN 114843606A
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additive
electrolyte
lithium
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battery
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李江蓝
熊伟
马斌
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Huizhou Liwinon Energy Technology Co Ltd
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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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • 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

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Abstract

The invention provides an additive for battery electrolyte, the electrolyte and a lithium ion battery, which comprise a first additive and a second additive; the first additive has the structure of C m H n X p COOLi, wherein C m H n X p Is at least one of chain or cyclic alkyl, chain or cyclic alkenyl, chain or cyclic alkynyl and aryl, X is at least one halogen atom, N is more than or equal to 0 and less than 2m +1, p is more than 0 and less than or equal to 2m +1, m is more than or equal to 4 and less than or equal to 18, p/(p + N) is more than or equal to 20 percent, and m, N and p are respectively equal to N; the second additive is a compound with a structure shown in a formula I. Compared with the prior art, the additive provided by the invention can efficiently capture active oxygen free radicals and oxygen, effectively reduce side reactions of the product on the surface of a negative electrode at high temperature and high pressure, and protect an electrode material from oxidation, thereby effectively improving the high temperature and high pressure of a lithium ion batteryTemperature cycle performance and storage performance, and safety performance.

Description

Additive for battery electrolyte, electrolyte and lithium ion battery
Technical Field
The invention relates to the field of lithium batteries, in particular to an additive for a battery electrolyte, the electrolyte and a lithium ion battery.
Background
The lithium ion battery has the characteristics of high energy density, long cycle life, high working voltage, low self-discharge rate and the like, so that the lithium ion battery is widely applied to the fields of intelligent wearing, computers, smart phones, electric automobiles and the like. The electrolyte is used as blood vessels of the lithium ion battery, is one of important composition raw materials of the lithium ion battery, is responsible for transmission capacity between a positive electrode and a negative electrode, plays a vital role in the performance of the lithium ion battery, and the contained solvent, lithium salt and additive play an important role in the low temperature, circulation, storage and safety performance of the lithium ion battery. However, the conventional electrolyte cannot effectively improve the side reaction on the surface of the electrode under high voltage, so that great challenges are brought to the cycle performance and the storage performance of the lithium ion battery, and the development of the lithium ion battery under high voltage is severely restricted.
In view of the above, it is necessary to provide a technical solution to solve the above problems.
Disclosure of Invention
One of the objects of the present invention is: aiming at the defects of the prior art, the additive for the battery electrolyte is provided to solve the problem that the prior electrolyte can not improve the serious side reaction on the surface of the electrode under high temperature and high pressure, and the side reaction on the surface of the electrode under high temperature and high pressure is reduced, so that the high-temperature cycle life and the storage capacity of the lithium ion battery are effectively improved.
In order to achieve the purpose, the invention adopts the following technical scheme:
an additive for battery electrolytes, comprising a first additive and a second additive; the first additive has the structure of C m H n X p COOLi, wherein C m H n X p Is at least one of chain or cyclic alkyl, chain or cyclic alkenyl, chain or cyclic alkynyl and aryl, X is at least one halogen atom, N is more than or equal to 0 and less than 2m +1, p is more than 0 and less than or equal to 2m +1, m is more than or equal to 4 and less than or equal to 18, p/(p + N) is more than or equal to 20 percent, and m, N and p are respectively equal to N; the second additive is a compound with a structure shown in a formula I,
Figure BDA0003614369400000021
wherein R is 1 ～R 7 Each independently selected from hydrogen, alkyl with 1-10 carbon atoms and alkyl with 1-10 carbon atomsAlkenyl, alkynyl with 1-10 carbon atoms, aryl, halogenated group, amido, nitro and sulfo.
Preferably, the first additive further satisfies the following condition: n is less than p.
Preferably, the first additive further satisfies the following condition: n is more than or equal to 0 and less than m, and m is more than or equal to 6 and less than or equal to 18.
Preferably, the first additive is at least one of the following structural formulas:
Figure BDA0003614369400000022
Figure BDA0003614369400000031
preferably, the second additive is at least one of the following structural formulas:
Figure BDA0003614369400000032
preferably, the additive further comprises a third additive, wherein the third additive is at least one of vinylene carbonate, fluoroethylene carbonate, 1, 3-propane sultone, vinyl sulfate, succinonitrile, adiponitrile, 1,3, 6-hexane trinitrile, 1,2, 3-tris (2-cyanato) propane, propylene sultone, methylene methanedisulfonate and ethylene glycol bis (propionitrile) ether.
Another object of the present invention is to provide an electrolyte solution, including a lithium salt, an organic solvent, and an additive, wherein the additive is the additive for a battery electrolyte solution described in any one of the above.
Preferably, the mass of the first additive is 0.1-10 wt% of the total mass of the electrolyte; the mass of the second additive accounts for 0.1-10 wt% of the total mass of the electrolyte; the mass of the third additive accounts for 0.5-20 wt% of the total mass of the electrolyte.
Preferably, the lithium salt is at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium difluorobis (oxalate) phosphate, lithium tetrafluoro (oxalate) phosphate, lithium oxalate phosphate, lithium bis (oxalate) borate, lithium difluorooxalate borate, lithium tetrafluoroborate, lithium bis (trifluoromethanesulfonyl) imide and lithium bis (fluorosulfonyl) imide, and the mass of the lithium salt is 8-20 wt% of the total mass of the electrolyte; the organic solvent comprises one or more of ethylene carbonate, propylene carbonate, diethyl carbonate, methyl ethyl carbonate, ethyl propionate, propyl propionate, ethyl acetate, ethyl n-butyrate and gamma-butyrolactone, and the mass of the organic solvent is 50-85 wt% of the total mass of the electrolyte.
The invention also provides a lithium ion battery, which comprises a positive plate, a negative plate, a diaphragm and electrolyte, wherein the diaphragm is arranged between the positive plate and the negative plate, and the electrolyte is any one of the electrolytes.
Compared with the prior art, the invention has the beneficial effects that: the additive comprises a first additive and a second additive, wherein the first additive can form a supermolecule assembly body through hydrogen bond interaction with a solvent or the first additive in an electrolyte, the supermolecule assembly body has higher surface energy and enrichment action and can be preferentially adsorbed on active oxygen free radicals and oxygen generated after a positive electrode material is damaged at high temperature and high pressure, meanwhile, the second additive can also react with the active oxygen free radicals and the oxygen, and under the enrichment action of the supermolecule assembly body, the synergistic action of the active oxygen free radicals and the oxygen can be more efficiently combined with each other through reaction, so that the side reaction of the product on the surface of a negative electrode at high temperature and high pressure is effectively reduced, the electrode material is protected from being oxidized, and the high-temperature cycle performance, the storage performance and the safety performance of a lithium ion battery are effectively improved.
Detailed Description
1. Additive for battery electrolyte
The first aspect of the present invention is directed to an additive for a battery electrolyte, comprising a first additive and a second additive; the first additive has the structure of C m H n X p COOLi, wherein C m H n X p Is at least one of chain or cyclic alkyl, chain or cyclic alkenyl, chain or cyclic alkynyl and aryl, and X is at least oneA halogen atom is planted, N is more than or equal to 0 and less than 2m +1, p is more than 0 and less than or equal to 2m +1, m is more than or equal to 4 and less than or equal to 18, p/(p + N) is more than or equal to 20 percent, and m, N and p are belonged to N; the second additive is a compound with a structure shown in a formula I,
Figure BDA0003614369400000051
wherein R is 1 ～R 7 Each independently selected from at least one of hydrogen, alkyl with 1-10 carbon atoms, alkenyl with 1-10 carbon atoms, alkynyl with 1-10 carbon atoms, aryl, halogenated group, amido, nitryl and sulfo.
For the first additive, which forms a supramolecular assembly comprising an external portion and an internal portion, the structure of the COOLi dissociates to form COO - Forming an outer portion of the assembly by mutual repulsion of electrostatic forces; c m H n X p The structure is defined as an inner portion containing a halogen atom with a high substitution degree, and the halogen atom and the hydrogen atom are bonded to each other through a hydrogen bond formed between the halogen atom and the hydrogen atom (not limited to C) m H n X p Itself, some solvent molecules may also participate in the binding), and finally form a supramolecular assembly with a structure such as a sphere, a rod, or a double-layer membrane.
The supermolecule assembly has higher surface energy and enrichment function, active oxygen free radicals, oxygen and a second additive generated after the positive electrode material is damaged can be enriched, and a reaction site for avoiding the electrode material is provided, so that under the enrichment function of the supermolecule assembly, the first additive and the second additive can be more efficiently combined with oxygen in a reaction manner, the electrode material is protected from being oxidized, and the high-temperature cycle performance, the storage performance and the safety performance of the lithium ion battery are improved.
Specifically, m can be 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18, n can be 0, 1,2,3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, etc., and p can be 1,2,3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, etc.The amount of substitution X is chosen according to the carbon atom m and can be in particular Cl or F, preferably X is substituted with F, the number of substitutions n < p, more preferably n is 0 and p is fully substituted. The inventors have found that for C in the first additive m H n X p The more the carbon atom number and the halogen atom number are, the stronger the hydrogen bonding capacity among molecules is, the easier the supermolecule assembly is formed, the stronger the capacity of adsorbing active oxygen free radicals and oxygen under high temperature and high pressure is, the side reaction of the active oxygen free radicals and the oxygen on the surface of the negative electrode can be effectively reduced, and the cycle performance under high voltage is further improved. Preferably, 6. ltoreq. m. ltoreq.18, C m H n X p Is a chain alkyl or aryl.
Compared with other compounds containing halogen atoms or compounds containing less halogen atoms and carbon atoms, the first additive can form a supermolecular assembly and has synergistic effect with the second additive, so that the problem of serious side reaction on the surface of the electrode at high temperature and high pressure can be effectively solved.
In some embodiments, the first additive is at least one of the formulas in table 1.
TABLE 1
Figure BDA0003614369400000061
Figure BDA0003614369400000071
Wherein, the first additive can be prepared by dissolving the corresponding precursor in a solvent, and the solvent can be hexafluoroisopropanol: adding water into a mixed solvent of 1:1, then adding the mixed solvent into a lithium hydroxide aqueous solution according to the mol ratio of 1:1, mixing, removing the solvent by rotary evaporation, and drying to obtain the lithium ion battery. As described above A 4 Compound, using hexafluoroisopropanol: dissolving perfluorooctanoic acid in a solvent of water to 1:1, adding the solution into a lithium hydroxide aqueous solution according to a molar ratio of 1:1, mixing, removing the solvent by rotary evaporation, and drying to obtain the perfluorooctanoic acid. As above A 5 Compound, using hexafluoroisopropanol: solvent of water 1:1 dissolves 2,4, 6-trifluoroBenzoic acid, then adding the benzoic acid into a lithium hydroxide aqueous solution according to the molar ratio of 1:1, mixing, removing the solvent by rotary evaporation, and drying to obtain the compound.
Preferably, the second additive is at least one of the following structural formulas in table 2 below.
TABLE 2
Figure BDA0003614369400000072
Figure BDA0003614369400000081
Preferably, the additive further comprises a third additive, wherein the third additive is at least one of Vinylene Carbonate (VC), fluoroethylene carbonate (FEC), 1, 3-Propane Sultone (PS), vinyl sulfate (DTD), Succinonitrile (SN), Adiponitrile (ADN), 1,3, 6-Hexane Trinitrile (HTCN), 1,2, 3-tris (2-cyanato) propane, Propylene Sultone (PST), Methylene Methane Disulfonate (MMDS), ethylene glycol bis (propionitrile) ether (EGBE). Preferably, the third additive is at least two of the above additives. More than two third additives are adopted to be used together with the first additive and the second additive, so that the effect of the third additive can be exerted, the effects of the first additive and the second additive can be further promoted, and the cycle performance, the storage performance and the safety performance can be better improved. Preferably, the third additive is a mixture of 1, 3-Propane Sultone (PS), fluoroethylene carbonate (FEC), 1,2, 3-tris (2-cyanato) propane.
2. Electrolyte solution
A second aspect of the present invention is directed to an electrolyte including a lithium salt, an organic solvent, and an additive for a battery electrolyte as described in any one of the above.
In some embodiments, the mass of the first additive is 0.1 to 10 wt% of the total mass of the electrolyte. Specifically, the amount of the electrolyte is 0.1 to 0.5 wt%, 0.5 to 1 wt%, 1 to 2 wt%, 2 to 3 wt%, 3 to 4 wt%, 4 to 5 wt%, 5 to 6 wt%, 6 to 7 wt%, 7 to 8 wt%, 8 to 9 wt%, or 9 to 10 wt% based on the total mass of the electrolyte. Preferably, the mass of the first additive is 0.5-5.0 wt% of the total mass of the electrolyte. In the electrolyte, a proper amount of first additive can preferentially capture active oxygen free radicals and oxygen generated after the anode material is damaged at high temperature and high pressure, so that the side reaction of the active oxygen free radicals and the oxygen on the surface of the cathode is effectively reduced.
In some embodiments, the second additive is 0.1 to 10 wt% of the total mass of the electrolyte. Specifically, the amount of the electrolyte is 0.1 to 0.5 wt%, 0.5 to 1 wt%, 1 to 2 wt%, 2 to 3 wt%, 3 to 4 wt%, 4 to 5 wt%, 5 to 6 wt%, 6 to 7 wt%, 7 to 8 wt%, 8 to 9 wt%, or 9 to 10 wt% based on the total mass of the electrolyte. Preferably, the mass of the second additive is 0.5-3.0 wt% of the total mass of the electrolyte. Under the condition that the first additive is added in a proper amount, the second additive is also added in a proper amount, and the synergistic effect of the first additive and the second additive can effectively capture generated oxygen, effectively reduce the side reaction of the active material at high temperature and high pressure, and improve the cycle performance, the storage performance and the safety performance of the lithium ion battery at high temperature and high pressure.
In some embodiments, the mass of the third additive is 0.5 to 20 wt% of the total mass of the electrolyte. Preferably, the mass of the third additive is 5-13 wt% of the total mass of the electrolyte, and specifically may be 5-6 wt%, 6-7 wt%, 7-8 wt%, 8-9 wt%, 9-10 wt%, 10-11 wt%, 11-12 wt%, or 12-13 wt%. More preferably, the mass of the third additive is 5-10 wt% of the total mass of the electrolyte.
In some embodiments, the lithium salt is lithium hexafluorophosphate (LiPF) 6 ) Lithium difluorophosphate (LiPF) 2 O 2 ) Lithium difluorobis (oxalato) phosphate (LiPF) 2 (C 2 O 4 ) 2 ) Lithium tetrafluoro oxalate phosphate (LiPF) 4 C 2 O 4 ) Lithium oxalate phosphate (LiPO) 2 C 2 O 4 ) Lithium bis (oxalato) borate (LiBOB), lithium difluoro (oxalato) borate (LiODFB), lithium tetrafluoroborate (LiBF) 4 ) Lithium bis (trifluoromethanesulfonylimide) (LiTFSI) and lithium bis (fluorosulfonylimide) (LiFSI). The mass of the lithium salt is 8-20 wt% of the total mass of the electrolyte.
In some embodiments, the organic solvent comprises one or more of Ethylene Carbonate (EC), Propylene Carbonate (PC), diethyl carbonate (DEC), Ethyl Methyl Carbonate (EMC), Ethyl Propionate (EP), Propyl Propionate (PP), Ethyl Acetate (EA), ethyl n-butyrate (EB), and gamma-butyrolactone (GBL); the mass of the organic solvent is 50-85 wt% of the total mass of the electrolyte.
3. Lithium ion battery
The third aspect of the invention aims to provide a lithium ion battery, which comprises a positive plate, a negative plate, a diaphragm and electrolyte, wherein the diaphragm is arranged between the positive plate and the negative plate, and the electrolyte is any one of the above electrolytes. Compared with other conventional electrolyte additives, the electrolyte is particularly suitable for being applied at high pressure and high temperature of 4.4-4.5V due to the addition of the first additive and the second additive.
The positive plate comprises a positive current collector and a positive active substance layer coated on the positive current collector, wherein the positive active substance layer comprises a positive active substance, a positive conductive agent and a positive binder. The positive active material may be of a chemical formula including but not limited to Li a Ni x Co y M z O 2-b N b (wherein a is more than or equal to 0.95 and less than or equal to 1.2, x>0, y is more than or equal to 0, z is more than or equal to 0, and x + y + z is 1,0 is more than or equal to b and less than or equal to 1, M is selected from one or more of Mn and Al, N is selected from one or more of F, P and S), and the positive electrode active material can also be selected from one or more of LiCoO (lithium LiCoO), but not limited to 2 、LiNiO 2 、LiVO 2 、LiCrO 2 、LiMn 2 O 4 、LiCoMnO 4 、Li 2 NiMn 3 O 8 、LiNi 0.5 Mn 1.5 O 4 、LiCoPO 4 、LiMnPO 4 、LiFePO 4 、LiNiPO 4 、LiCoFSO 4 、CuS 2 、FeS 2 、MoS 2 、NiS、TiS 2 And the like. The positive electrode active material may be further subjected to a modification treatment, and a method for modifying the positive electrode active material is known to those skilled in the art, and for example, a coating method, and the like can be used,Doping and the like are used for modifying the positive electrode active substance, and the material used in the modification treatment can be one or more of Al, B, P, Zr, Si, Ti, Ge, Sn, Mg, Ce, W and the like. The positive electrode current collector is generally a structure or a part for collecting current, and may be any material suitable for use as a positive electrode current collector of a lithium ion battery in the art, for example, the positive electrode current collector may include, but is not limited to, a metal foil, and the like, and more specifically, may include, but is not limited to, an aluminum foil, and the like.
The negative plate comprises a negative current collector and a negative active material layer coated on the negative current collector, wherein the negative active material layer comprises a negative active material, a negative conductive agent and a negative binder. The negative active material may be one or more of graphite, soft carbon, hard carbon, carbon fiber, mesocarbon microbeads, silicon-based materials, tin-based materials, lithium titanate, or other metals capable of forming an alloy with lithium. Wherein, the graphite can be selected from one or more of artificial graphite, natural graphite and modified graphite; the silicon-based material can be one or more selected from simple substance silicon, silicon-oxygen compound, silicon-carbon compound and silicon alloy; the tin-based material can be one or more selected from simple substance tin, tin oxide compound and tin alloy. The negative electrode current collector is generally a structure or a part for collecting current, and the negative electrode current collector may be any material suitable for use as a negative electrode current collector of a lithium ion battery in the art, for example, the negative electrode current collector may include, but is not limited to, a metal foil, and the like, and more specifically, may include, but is not limited to, a copper foil, and the like.
And the separator may be various materials suitable for lithium ion battery separators in the art, and for example, may be one or a combination of more of polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, natural fiber, and the like, including but not limited thereto.
In order to make the technical solutions and advantages of the present invention clearer, the present invention and its advantageous effects will be described in further detail with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.
Example 1
A lithium ion battery comprises a positive plate, a negative plate, a diaphragm and electrolyte, wherein the diaphragm and the electrolyte are arranged between the positive plate and the negative plate at intervals, and the positive plate adopts LiCoO 2 As the positive electrode active substance, graphite is adopted as the negative electrode active substance in the negative electrode sheet, and the diaphragm is a polypropylene diaphragm.
Preparing an electrolyte: in a glove box filled with argon, the moisture content was < 5ppm and the oxygen content was < 5ppm, Ethylene Carbonate (EC), Propylene Carbonate (PC), ethyl methyl carbonate (DEC), Propyl Propionate (PP), Ethyl Propionate (EP) were mixed in a mass ratio of EC: PC: DEC: PP: EP ═ 1:1:1:1:1 to obtain an organic solvent, and then 13.7 wt% of lithium hexafluorophosphate (LiPF) based on the total weight of the electrolyte was slowly added to the organic solvent 6 ) To obtain a mixture of an organic solvent and a lithium salt, and finally adding 0.5 wt% of a first additive A based on the total weight of the electrolyte 4 0.5 wt% of a second additive B 1 3 wt% of Propane Sultone (PS), 3 wt% of fluoroethylene carbonate (FEC), and 3 wt% of 1,2, 3-tris (2-cyanato) propane, and the mixture was uniformly stirred to obtain an electrolyte solution of example 1.
Wherein the first additive A 4 The preparation method comprises the following steps: using hexafluoroisopropanol: dissolving perfluorooctanoic acid in a solvent of water to 1:1, adding the solution into a lithium hydroxide aqueous solution according to a molar ratio of 1:1, mixing, removing the solvent by rotary evaporation, and drying to obtain the perfluorooctanoic acid.
Preparing a soft package battery: stacking the prepared positive plate, the diaphragm and the negative plate in sequence, enabling the diaphragm to be positioned between the positive plate and the negative plate, and winding to obtain a bare cell; and (2) placing the bare cell in an aluminum plastic film outer package, drying at 80 ℃ in vacuum, injecting the prepared electrolyte into the dried battery after the moisture reaches the standard, packaging, standing, carrying out hot cold pressing, forming, shaping and grading to finish the preparation of the lithium ion battery.
Examples 2 to 37 and comparative examples 1 to 6 were prepared according to the above-described preparation method, and different from example 1, the contents of the respective substances of the electrolyte, and the specific substances and contents thereof are as shown in table 3 below.
TABLE 3
Figure BDA0003614369400000121
Figure BDA0003614369400000131
Figure BDA0003614369400000141
Figure BDA0003614369400000151
Performance testing
The lithium ion batteries and the electrolytes thereof obtained in the above examples 1 to 37 and comparative examples 1 to 6 were subjected to a relevant performance test.
(1) Lithium ion battery cycle performance test
And respectively placing the lithium ion batteries in a constant temperature room at 45 ℃, and standing for 30 minutes to keep the temperature of the lithium ion batteries constant. The lithium ion battery reaching a constant temperature is charged with a constant current of 0.5C to a voltage of 4.4V, then charged with a constant voltage of 4.4V to a current of 0.05C, and then discharged with a constant current of 0.5C to a voltage of 3.0V, which is a charge-discharge cycle. Thus, the charge and discharge were repeated, and the capacity retention ratio of the lithium ion battery was calculated for 500 cycles, respectively.
(2) High temperature storage volume expansion test
The lithium ion battery is charged to 4.4V at a constant current of 0.5C, and then charged at a constant voltage until the current is 0.05C, until the battery is in a full charge state. Testing the thickness THK of a lithium ion battery in a fully charged state 1 . Placing the fully charged battery core in a high-temperature furnace at 60 ℃ for storage for 14D, and thermally testing the thickness THK of the battery core 2 . The expansion ratio of the lithium ion battery was calculated as follows:
swelling ratio (THK) 2 -THK 1 )/THK 1 。
The test results are shown in table 4 below.
TABLE 4
Figure BDA0003614369400000152
Figure BDA0003614369400000161
Figure BDA0003614369400000171
As can be seen from the test results of the above examples 1 to 22 and comparative examples 1 to 4, the cycle performance and the storage performance of the lithium ion battery at high temperature and high pressure can be effectively improved after the first additive and the second additive of the present invention are added. Under the same conditions as the second additive, in particular with A 4 The first additive with the structure contains more carbon atoms and halogen atoms, has stronger intermolecular hydrogen bonding capacity, is easier to form a supramolecular assembly, has large surface energy of the formed supramolecular assembly, can effectively adsorb active oxygen free radicals and oxygen at high temperature and high pressure, reduces side reactions of the active oxygen free radicals and the oxygen on the surface of a negative electrode, and further improves the cycle performance and the storage performance at high temperature and high pressure. And under the same conditions as the first additive, especially B 5 The second additive of the structure is more likely to act synergistically with the first additive, mainly because both of them contain halogen atoms and are more compatible, and the first additive also has a better enriching effect on the second additive, so that the second additive can also react with oxygen more efficiently.
In addition, as can be seen from the comparison of examples 1 to 16, when the content of the second additive is not changed, the effect of suppressing the high-temperature swelling is more remarkable as the content of the first additive is increased, but the excessive amount of the first additive adversely affects the cycle performance at high temperature. In addition, as can be seen from the comparison of examples 1 to 37, the cycle and storage performance of the lithium ion battery using more than two first additives is better than that of the lithium ion battery using only one first additiveThe improvement is better, particularly adopting A 4 The combination of the lithium ion battery and other first additives can more effectively improve the cycle performance and the storage performance of the lithium ion battery under high temperature and high pressure. In particular, when the third additive is a mixture of 1 wt% Propane Sultone (PS), 5 wt% fluoroethylene carbonate (FEC), and 3 wt% 1,2, 3-tris (2-cyanato) propane, the two first and second additives are used, the synergistic effect between the additives can significantly improve the cycle performance at high temperature and high pressure, as can be seen from the comparison of examples 23 to 37.
In conclusion, the first additive, the second additive and the third additive are used as the additives for the lithium ion electrolyte together, so that active oxygen free radicals and oxygen can be efficiently captured, side reactions of the product on the surface of a negative electrode at high temperature and high pressure are effectively reduced, an electrode material is protected from being oxidized, and the high-temperature cycle performance, the storage performance and the safety performance of the lithium ion battery are effectively improved.
Variations and modifications to the above-described embodiments may also occur to those skilled in the art, which fall within the scope of the invention as disclosed and taught herein. Therefore, the present invention is not limited to the above-mentioned embodiments, and any obvious improvement, replacement or modification made by those skilled in the art based on the present invention is within the protection scope of the present invention. Furthermore, although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims (10)

1. An additive for a battery electrolyte, comprising a first additive and a second additive; the first additive has the structure of C m H n X p COOLi, wherein C m H n X p Is at least one of chain or cyclic alkyl, chain or cyclic alkenyl, chain or cyclic alkynyl and aryl, X is at least one halogen atom, N is more than or equal to 0 and less than 2m +1, p is more than 0 and less than or equal to 2m +1, m is more than or equal to 4 and less than or equal to 18, p/(p + N) is more than or equal to 20 percent, and m, N and p are respectively equal to N; the second additive is a compound with a structure shown in a formula I,
Figure FDA0003614369390000011
wherein R is 1 ～R 7 Each independently selected from at least one of hydrogen, alkyl with 1-10 carbon atoms, alkenyl with 1-10 carbon atoms, alkynyl with 1-10 carbon atoms, aryl, halogenated group, amido, nitryl and sulfo.
2. The additive for battery electrolytes according to claim 1, wherein the first additive further satisfies the following condition: n is less than p.
3. The additive for battery electrolytes according to claim 2, wherein the first additive further satisfies the following condition: n is more than or equal to 0 and less than m, and m is more than or equal to 6 and less than or equal to 18.
4. The additive for battery electrolytes according to claim 1, wherein the first additive is at least one of the following structural formulas:
Figure FDA0003614369390000012
Figure FDA0003614369390000021
5. the additive for battery electrolytes according to claim 1, wherein the second additive is at least one of the following structural formulas:
Figure FDA0003614369390000022
6. the additive for battery electrolytes according to claim 1, further comprising a third additive, wherein the third additive is at least one of vinylene carbonate, fluoroethylene carbonate, 1, 3-propane sultone, vinyl sulfate, succinonitrile, adiponitrile, 1,3, 6-hexane trinitrile, 1,2, 3-tris (2-cyanato) propane, propylene sultone, methylene methanedisulfonate, ethylene glycol bis (propionitrile) ether.
7. An electrolyte comprising a lithium salt, an organic solvent and an additive, wherein the additive is the additive for a battery electrolyte according to any one of claims 1 to 6.
8. The electrolyte according to claim 7, wherein the mass of the first additive is 0.1-10 wt% of the total mass of the electrolyte; the mass of the second additive accounts for 0.1-10 wt% of the total mass of the electrolyte; the mass of the third additive accounts for 0.5-20 wt% of the total mass of the electrolyte.
9. The electrolyte of claim 7, wherein the lithium salt is at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium difluorobis (oxalato) phosphate, lithium tetrafluorooxalato phosphate, lithium oxalato phosphate, lithium bis (oxalato) borate, lithium difluorooxalato borate, lithium tetrafluoroborate, lithium bis (trifluoromethanesulfonyl) imide and lithium bis (fluorosulfonyl) imide, and the mass of the lithium salt is 8-20 wt% of the total mass of the electrolyte; the organic solvent comprises one or more of ethylene carbonate, propylene carbonate, diethyl carbonate, methyl ethyl carbonate, ethyl propionate, propyl propionate, ethyl acetate, ethyl n-butyrate and gamma-butyrolactone, and the mass of the organic solvent is 50-85 wt% of the total mass of the electrolyte.
10. A lithium ion battery comprising a positive plate, a negative plate, a separator and an electrolyte, wherein the separator is arranged between the positive plate and the negative plate, and the electrolyte is the electrolyte according to any one of claims 7 to 9.
CN202210439173.8A 2022-04-25 2022-04-25 Additive for battery electrolyte, electrolyte and lithium ion battery Pending CN114843606A (en)

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