CN115425288A - Electrolyte and lithium ion battery thereof - Google Patents

Electrolyte and lithium ion battery thereof Download PDF

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Publication number
CN115425288A
CN115425288A CN202211115602.2A CN202211115602A CN115425288A CN 115425288 A CN115425288 A CN 115425288A CN 202211115602 A CN202211115602 A CN 202211115602A CN 115425288 A CN115425288 A CN 115425288A
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electrolyte
additive
lithium
carbonate
group
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张昌明
段凯嘉
李枫
胡大林
廖兴群
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Huizhou Highpower 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
    • 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
    • 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 discloses an electrolyte and a lithium ion battery thereof, wherein the electrolyte comprises an organic solvent, lithium salt and an additive A, the additive A accounts for 0.01-3 wt% of the total mass of the electrolyte, and the structural general formula of the additive A is shown as the following formula I:
Figure DDA0003845403760000011
in the formula I, R 1 One selected from the group consisting of a methyl group, an ethyl group, a propyl group and a butyl group, R 2 、R 3 And R 4 Each independently selected from one of hydrogen, alkyl, fluoroalkyl, alkenyl, fluoroalkenyl, and alkynyl. The additive A contains unsaturated bond groups, can form a stable interfacial film on the surface of a negative electrode, contains Si-O bonds capable of combining hydrogen and metal ions, protects a positive electrode active substance and optimizes a positive electrode/electrolyte interface, and is characterized in thatThe organic electrolyte containing the additive can effectively improve the high-temperature cycle and high-temperature storage performance of the lithium ion battery under high voltage; and the interface film has good capability of conducting lithium ions, so that the low-temperature discharge performance of the lithium ion battery can be considered.

Description

Electrolyte and lithium ion battery thereof
Technical Field
The invention relates to the technical field of lithium ion batteries and electrolytes thereof, in particular to an electrolyte and a lithium ion battery thereof.
Background
Because of its many advantages, lithium ion batteries are widely used in the fields of portable electronic products, power automobiles, large-scale energy storage power grids, and the like. Since most of commercial organic electrolytes use carbonate or carboxylate as a solvent and lithium hexafluorophosphate as a lithium salt, they are decomposed at high voltage; especially under the voltage of 4.5V and higher, the conventional electrolyte is quickly oxidized and decomposed on the surface of the anode material, so that high-temperature cycle decay or high-temperature storage gas generation is serious.
The current strategy is mainly to add nitriles such as malononitrile, succinonitrile, adiponitrile, 1,3, 6-hexanetrinitrile and the like into the electrolyte to be complexed with the anode so as to prevent the metal of the active material of the anode from dissolving out and prevent the electrolyte from being further reacted with the anode to be consumed, thereby improving the high-temperature cycle and high-temperature storage performance of the lithium ion battery. However, addition of a large amount of nitriles leads to increase in viscosity of the electrolyte solution and deterioration of low-temperature cycle, and thus cannot satisfy various usage scenarios of lithium ion batteries.
Therefore, an electrolyte solution capable of improving high-temperature cycle and high-temperature storage performance of a lithium ion battery and simultaneously achieving low-temperature discharge performance of the lithium ion battery is needed.
Disclosure of Invention
The invention aims to provide an electrolyte and a lithium ion battery thereof, which can improve the high-temperature circulation and high-temperature storage performance of the lithium ion battery and also can give consideration to the low-temperature discharge performance of the lithium ion battery.
The invention discloses an electrolyte, which comprises an organic solvent, lithium salt and an additive A, wherein the additive A accounts for 0.01-3 wt% of the total mass of the electrolyte, and the structural general formula of the additive A is as follows:
Figure BDA0003845403750000021
in the formula I, R 1 One selected from the group consisting of a methyl group, an ethyl group, a propyl group and a butyl group, R 2 、R 3 And R 4 Each independently selected from one of hydrogen, alkyl, fluoroalkyl, alkenyl, fluoroalkenyl, and alkynyl.
Optionally, the electrolyte further comprises an additive B, wherein the additive B is one or more of vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, propylene sulfite, vinyl sulfate, vinylene sulfonate, biphenyl, trioctyl phosphate, succinonitrile, ethanedinitrile, 1,3, 6-hexanetrinitrile, ethylene glycol bis (propionitrile) ether and fluorosulfonyl isocyanate.
Optionally, the additive B accounts for 5-20 wt% of the total mass of the electrolyte.
Optionally, the organic solvent is a mixture of cyclic and chain esters.
Optionally, the cyclic ester is one or more of ethylene carbonate, propylene carbonate, fluoroethylene carbonate and gamma-butyrolactone.
Optionally, the chain ester is one or more of diethyl carbonate, ethyl methyl carbonate, methyl formate, ethyl acetate, ethyl propionate, propyl propionate, fluoro ethyl acetate, and fluoro ethyl propionate.
Optionally, the organic solvent accounts for 20-80 wt% of the total mass of the electrolyte, and the balance is lithium salt.
Optionally, the lithium salt is one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis (fluorosulfonyl) imide, lithium bis (trifluoromethanesulfonyl) imide, lithium difluorophosphate, lithium bis (oxalato) borate, lithium difluorooxalato phosphate, and lithium difluorobis (oxalato) borate.
Optionally, the lithium salt concentration is 1 to 1.5mol/L.
The invention also discloses a lithium ion battery which comprises a positive pole piece, a negative pole piece, an isolating membrane and the electrolyte.
According to the electrolyte, the additive A contains unsaturated bond groups, so that a stable interface film can be formed on the surface of a negative electrode, and simultaneously contains Si-O bonds which can combine hydrogen and metal ions to protect positive active substances and optimize a positive electrode/electrolyte interface, so that the organic electrolyte containing the additive can effectively improve the high-temperature cycle and high-temperature storage performance of a lithium ion battery under high voltage; and the interface film has good capability of conducting lithium ions, so that the low-temperature discharge performance of the lithium ion battery can be considered.
Detailed Description
It is to be understood that the terminology, the specific structural and functional details disclosed herein are for the purpose of describing particular embodiments only, and are representative, but that the present invention may be embodied in many alternate forms and should not be construed as limited to only the embodiments set forth herein.
The invention is described in detail below with reference to alternative embodiments.
The invention discloses an electrolyte, which comprises an organic solvent, lithium salt and an additive A, wherein the additive A accounts for 0.01-3 wt% of the total mass of the electrolyte, and the structural general formula of the additive A is shown as the following formula I:
Figure BDA0003845403750000041
in the formula I, R 1 One selected from the group consisting of a methyl group, an ethyl group, a propyl group and a butyl group, R 2 、R 3 And R 4 Each independently selected from one of hydrogen, alkyl, fluoroalkyl, alkenyl, fluoroalkenyl, and alkynyl.
According to the electrolyte, the additive A contains unsaturated bond groups, so that a stable interface film can be formed on the surface of a negative electrode, and simultaneously contains Si-O bonds which can combine hydrogen and metal ions to protect positive active substances and optimize a positive electrode/electrolyte interface, so that the organic electrolyte containing the additive can effectively improve the high-temperature cycle and high-temperature storage performance of a lithium ion battery under high voltage; and the interface film has good capability of conducting lithium ions, so that the low-temperature discharge performance of the lithium ion battery can be considered.
Specifically, the mass ratio of the additive a in the electrolyte solution may be 0.01wt%, 0.1wt%, 0.3wt%, 0.5wt%, 1wt%, 1.2wt%, 1.5wt%, 1.8wt%, 2wt%, 2.5wt%, 3wt%.
Specifically, the electrolyte also comprises an additive B, wherein the additive B is one or more of vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, propylene sulfite, ethylene sulfate, vinylene sulfonate, biphenyl, trioctyl phosphate, succinonitrile, ethanedinitrile, 1,3, 6-hexanetricarbonitrile, ethylene glycol bis (propionitrile) ether and fluorosulfonyl isocyanate. Specifically, the additive B accounts for 5-20 wt% of the total mass of the electrolyte. The mass ratio of the additive B in the electrolyte solution may be 5wt%, 7wt%, 10wt%, 12wt%, 15wt%, 17wt%, 20wt%. The combined use of the additive A and the additive B has better effect on improving the performance of the lithium ion battery. Specifically, the additive B accounts for 10-20 wt% of the total mass of the electrolyte.
Specifically, the organic solvent is a mixture of cyclic esters and chain esters. Specifically, the cyclic ester is one or more of ethylene carbonate, propylene carbonate, fluoroethylene carbonate and gamma-butyrolactone. Specifically, the chain ester is one or more of diethyl carbonate, ethyl methyl carbonate, methyl formate, ethyl acetate, ethyl propionate, propyl propionate, fluoro ethyl acetate, and fluoro ethyl propionate.
Specifically, the organic solvent accounts for 20-80 wt% of the total mass of the electrolyte, and the balance is lithium salt. The organic solvent may be present in the electrolyte in a mass ratio of 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, 75wt%, 80wt%. Specifically, the organic solvent accounts for 60-80 wt% of the total mass of the electrolyte.
Specifically, the lithium salt is one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis (fluorosulfonyl) imide, lithium bis (trifluoromethanesulfonyl) imide, lithium difluorophosphate, lithium bis (oxalato) borate, lithium difluorooxalato phosphate, and lithium difluorobis (oxalato) borate.
Specifically, the concentration of the lithium salt is 1 to 1.5mol/L.
The invention also discloses a lithium ion battery which comprises a positive pole piece, a negative pole piece, an isolating membrane and the electrolyte.
Specifically, the positive pole piece is composed of positive electrodeThe positive electrode comprises a positive electrode current collector and a positive electrode active substance layer coated on one side or two sides of the positive electrode current collector, wherein the positive electrode active substance layer comprises a positive electrode active substance, a positive electrode conductive agent and a positive electrode binder. Positive active materials include, but are not limited to, liCoO 2 、LiNiO 2 、LiVO 2 、LiCrO 2 、LiMn 2 O 4 、LiCoMnO 4 、Li2NiMn 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 negative pole piece consists of a negative pole current collector and a positive pole active substance layer coated on one side or two sides of the negative pole current collector, wherein the negative pole active substance layer comprises a negative pole active substance and a positive pole and negative pole binder. The negative active material includes, but is not limited to, 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.
The isolating membrane comprises various materials suitable for the lithium ion battery isolating membrane, including but not limited to one or more of polyethylene, polypropylene, polyvinylidene fluoride, aramid fiber, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, natural fiber and the like.
The electrolyte simultaneously contains the additive A and the additive B, and the additive A and the additive B have synergistic effect with other components in the electrolyte, so that the lithium ion battery containing the electrolyte has good high-temperature circulation and high-temperature storage performance under high voltage, and simultaneously has low-temperature discharge performance.
The following is further illustrated by specific examples and comparative examples.
Example 1
In a glove box filled with argon (H) 2 0≤0.1ppm，O 2 Less than or equal to 0.1 ppm), mixing Ethylene Carbonate (EC), propylene Carbonate (PC) and diethyl carbonate (DEC) serving as solvents: ethyl Acetate (EA) was uniformly mixed at a mass ratio of 21.2mol/L of lithium hexafluorophosphate (LiPF) was added to the resultant solvent 6 ) The electrolyte was prepared by adding 0.5wt% of vinyl sulfate as additive B and 0.3wt% of 3-isocyanatopropyltrimethoxysilane as additive A.
Example 2
In a glove box filled with argon (H) 2 0≤0.1ppm，O 2 Less than or equal to 0.1 ppm), mixing Ethylene Carbonate (EC), propylene Carbonate (PC) and diethyl carbonate (DEC) serving as solvents: ethyl Acetate (EA) was uniformly mixed at a mass ratio of 2 6 ) 1,3, 6-Hexanetricarbonitrile was added 2wt%, 3-isocyanatopropyltrimethoxysilane was added 0.3wt% to prepare an electrolyte solution.
Example 3
In a glove box filled with argon (H) 2 0≤0.1ppm，O 2 Less than or equal to 0.1 ppm), mixing Ethylene Carbonate (EC), propylene Carbonate (PC) and diethyl carbonate (DEC) as solvents: ethyl Acetate (EA) was uniformly mixed at a mass ratio of 2 6 ) 0.5% by weight of lithium difluorobis (oxalato) borate and 0.3% by weight of 3-isocyanatopropyltrimethoxysilane were added to prepare an electrolyte solution.
Example 4
In a glove box filled with argon (H) 2 0≤0.1ppm，O 2 Less than or equal to 0.1 ppm), mixing Ethylene Carbonate (EC), propylene Carbonate (PC) and diethyl carbonate (DEC) serving as solvents: ethyl Acetate (EA) was uniformly mixed at a mass ratio of 2 6 ) 0.5% by weight of vinyl sulfate, 2wt%1,3, 6-hexanetricarbonitrile, 0.5wt% lithium difluorobis (oxalato) borate, 0.3wt% of additive A, 3-isocyanatopropyltrimethoxysilane was added to prepare an electrolyte solution.
Example 5
In a glove box filled with argon (H) 2 0≤0.1ppm，O 2 Less than or equal to 0.1 ppm), mixing Ethylene Carbonate (EC), propylene Carbonate (PC) and diethyl carbonate (DEC) serving as solvents: ethyl Acetate (EA) was uniformly mixed at a mass ratio of 21.2mol/L lithium hexafluorophosphate (LiPF) was added to the agent 6 ) The electrolyte solution was prepared by adding 0.5wt% of vinyl sulfate as additive B and 0.5wt% of 3-isocyanatopropyltrimethoxysilane as additive A.
Example 6
In a glove box filled with argon (H) 2 0≤0.1ppm，O 2 Less than or equal to 0.1 ppm), mixing Ethylene Carbonate (EC), propylene Carbonate (PC) and diethyl carbonate (DEC) serving as solvents: ethyl Acetate (EA) was uniformly mixed at a mass ratio of 2 6 ) 1,3, 6-Hexanetricarbonitrile was added 2wt%, 3-isocyanatopropyltrimethoxysilane was added 0.5wt%.
Example 7
In a glove box filled with argon (H) 2 0≤0.1ppm，O 2 Less than or equal to 0.1 ppm), mixing Ethylene Carbonate (EC), propylene Carbonate (PC) and diethyl carbonate (DEC) serving as solvents: ethyl Acetate (EA) was uniformly mixed at a mass ratio of 2 6 ) The amount of the additive B added was 0.5% by weight of lithium difluorobis (oxalato) borate, and the amount of the additive A added was 0.5% by weight of 3-isocyanatopropyltrimethoxysilane, whereby an electrolyte solution was prepared.
Example 8
In a glove box filled with argon (H) 2 0≤0.1ppm，O 2 Less than or equal to 0.1 ppm), mixing Ethylene Carbonate (EC), propylene Carbonate (PC) and diethyl carbonate (DEC) as solvents: ethyl Acetate (EA) was uniformly mixed at a mass ratio of 2 6 ) The electrolyte solution was prepared by adding 1wt% of 3-isocyanatopropyltrimethoxysilane.
Example 9
In a glove box filled with argon (H) 2 0≤0.1ppm，O 2 Less than or equal to 0.1 ppm), mixing Ethylene Carbonate (EC), propylene Carbonate (PC) and diethyl carbonate (DEC) serving as solvents: ethyl Acetate (EA) was uniformly mixed at a mass ratio of 2 6 ) The additive B is 0.5wt% of vinyl sulfate and 2wt%1,3,6-Hexanetricarbonitrile, 0.5% by weight of lithium difluorobis (oxalato) borate, additive A amounted to 1wt.% of 3-isocyanatopropyltrimethoxysilane.
Example 10
In a glove box filled with argon (H) 2 0≤0.1ppm，O 2 Less than or equal to 0.1 ppm), mixing Ethylene Carbonate (EC), propylene Carbonate (PC) and diethyl carbonate (DEC) as solvents: ethyl Acetate (EA) was uniformly mixed at a mass ratio of 2 6 ) Adding 2wt% of 3-isocyanatopropyltrimethoxysilane to obtain an electrolyte solution.
Comparative example 1
In a glove box filled with argon (H) 2 0≤0.1ppm，O 2 Less than or equal to 0.1 ppm), mixing Ethylene Carbonate (EC), propylene Carbonate (PC) and diethyl carbonate (DEC) as solvents: ethyl Acetate (EA) was uniformly mixed at a mass ratio of 2 6 ) And preparing the electrolyte.
Comparative example 2
In a glove box filled with argon (H) 2 0≤0.1ppm，O 2 Less than or equal to 0.1 ppm), mixing Ethylene Carbonate (EC), propylene Carbonate (PC) and diethyl carbonate (DEC) serving as solvents: ethyl Acetate (EA) was uniformly mixed at a mass ratio of 2 6 ) And adding 0.5wt% of ethylene sulfate serving as an additive B to prepare the electrolyte.
Comparative example 3
In a glove box filled with argon (H) 2 0≤0.1ppm，O 2 Less than or equal to 0.1 ppm), mixing Ethylene Carbonate (EC), propylene Carbonate (PC) and diethyl carbonate (DEC) serving as solvents: ethyl Acetate (EA) was uniformly mixed at a mass ratio of 2 6 ) The electrolyte was prepared by adding 2wt% of 1,3,6-hexanetricarbonitrile as additive B.
Comparative example 4
In a glove box filled with argon (H) 2 0≤0.1ppm，O 2 Less than or equal to 0.1 ppm), adding solvents of Ethylene Carbonate (EC), propylene Carbonate (PC) and carbonic acid di-esterEthyl ester (DEC): ethyl Acetate (EA) was uniformly mixed at a mass ratio of 2 6 ) And the added additive B is 0.5wt% of lithium difluoro-bis (oxalato) borate to prepare the electrolyte.
Comparative example 5
In a glove box filled with argon (H) 2 0≤0.1ppm，O 2 Less than or equal to 0.1 ppm), mixing Ethylene Carbonate (EC), propylene Carbonate (PC) and diethyl carbonate (DEC) as solvents: ethyl Acetate (EA) was uniformly mixed at a mass ratio of 2 6 ) The electrolyte was prepared by adding 0.5wt% of vinyl sulfate, 2wt% of 1,3, 6-hexanetricarbonitrile and 0.5wt% of lithium difluorobis (oxalato) borate as additive A.
The electrolytes prepared in the above examples and comparative examples were prepared into corresponding lithium ion batteries according to the following methods.
Preparing a positive pole piece: the positive electrode active material lithium cobaltate, the conductive agent carbon black, the carbon nano tube and the binder polyvinylidene fluoride are mixed according to the mass ratio of 97.4%:1.4%:1.2 percent of the mixture is mixed, solvent N-methyl pyrrolidone is added, and the mixture is stirred evenly in a stirrer in a vacuum state to form uniform and flowable slurry; and then uniformly coating the slurry on two surfaces of an aluminum foil, and baking, rolling and slitting to obtain the positive pole piece.
Preparing a negative pole piece: the negative electrode active material graphite, the lithium carboxymethyl cellulose and the styrene butadiene rubber are mixed according to the mass ratio of 98%:1%:1 percent of the mixture is mixed, solvent deionized water is added, and the mixture is uniformly stirred in a stirrer in a vacuum state to form uniform and flowable slurry; and then uniformly coating the slurry on two surfaces of a copper foil, and baking, rolling and slitting to obtain the negative pole piece.
Preparing a battery: respectively welding the prepared positive pole piece and negative pole piece with a nickel lug and an aluminum lug, stacking the positive pole piece, the isolating film and the negative pole piece in sequence, and winding to obtain a battery cell; and putting the obtained winding battery core into an aluminum plastic shell, injecting the electrolyte of the embodiment or the comparative example, and carrying out vacuum packaging, standing at high temperature and normal temperature, formation and shaping for secondary packaging to obtain the lithium ion battery.
The electrolytes prepared in examples 1 to 10 and comparative examples 1 to 5 were formed into lithium ion batteries according to the above-described methods, respectively, and tested.
Cycle test at 45 ℃
The lithium ion battery is statically placed for 2 hours at the temperature of 45 +/-2 ℃, then 1C/0.5C charging and discharging are carried out, the charging and discharging voltage is 3.0-4.48V, the capacity retention rate of the battery after circulation is calculated, and the calculation formula is as follows: the nth cycle capacity retention (%) = (nth cycle discharge capacity)/(first cycle discharge capacity) × 100%.
10 ℃ cycle test
The lithium ion battery is statically placed for 2 hours at the temperature of 10 +/-2 ℃, then 0.7C/0.5C charging and discharging are carried out, the charging and discharging voltage is 3.0-4.48V, the capacity retention ratio of the battery after circulation is calculated, and the calculation formula is as follows: the nth cycle capacity retention ratio (%) = (nth cycle discharge capacity)/(first cycle discharge capacity) × 100%.
60 ℃ high temperature storage test
The lithium ion battery is placed still for 2 hours at the temperature of 25 +/-2 ℃ and then is charged and discharged at the temperature of 1C/0.5C, the charging and discharging voltage is 3.0-4.48V, the discharging capacity is the first discharging capacity, and then the battery is fully charged. And subsequently placing the battery for storage at 60 ℃, and calculating the remaining capacity retention rate of the stored battery, wherein the calculation formula is as follows: remaining capacity retention (%) on the nth day (= (remaining discharge capacity on the nth day)/(first-cycle discharge capacity) × 100%; and (3) calculating the thickness expansion rate of the stored battery, wherein the calculation formula is as follows: the thickness expansion rate (%) on the nth day = (cell thickness after storage on the nth day)/(initial cell thickness) × 100%.
The following table shows the cycling and storage test results for lithium ion batteries.
Figure BDA0003845403750000121
Figure BDA0003845403750000131
As can be seen from the results in the above table, the lithium ion batteries of examples 1 to 10 of the present invention have significantly improved high-temperature cycle, low-temperature cycle, and high-temperature storage properties as compared to the lithium ion batteries of comparative examples 1 to 5. This is because the electrolytes of the lithium ion batteries of examples 1 to 10 were added with additive a: the additive A contains-N = C = O bond functional groups and-Si-O bonds, groups with-N = C = O unsaturated bonds can form a stable interface film on the surface of a negative electrode, and the groups with-N = C = O unsaturated bonds can combine hydrogen and metal ions, so that the positive electrode active substance is protected, and simultaneously, the positive electrode/electrolyte interface is optimized, and therefore the organic electrolyte containing the additive with the general structural formula can effectively improve the high-temperature circulation and high-temperature storage performance of the lithium ion battery under high voltage; and the interface film has good capability of conducting lithium ions, so that the low-temperature discharge performance of the lithium ion battery can be considered.
From examples 1 to 10, it is clear that additive A: the 3-isocyanate propyl trimethoxy silane and the additive B are combined to be used, so that the effect of improving the performance of the lithium ion battery is better.
The foregoing is a further detailed description of the invention in connection with specific alternative embodiments and is not intended to limit the invention to the specific embodiments described herein. For those skilled in the art to which the invention pertains, several simple deductions or substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the invention.

Claims (10)

1. The electrolyte is characterized by comprising an organic solvent, a lithium salt and an additive A, wherein the additive A accounts for 0.01-3 wt% of the total mass of the electrolyte, and the structural general formula of the additive A is shown as the following formula I:
Figure FDA0003845403740000011
in the formula I, R 1 One selected from the group consisting of a methyl group, an ethyl group, a propyl group and a butyl group, R 2 、R 3 And R 4 Each independently selected from the group consisting of hydrogen, alkyl, fluoroalkyl,One of alkenyl, fluoroalkenyl and alkynyl.
2. The electrolyte according to claim 1, wherein the electrolyte further comprises an additive B, and the additive B is one or more of vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, propylene sulfite, vinyl sulfate, vinylene sulfonate, biphenyl, trioctyl phosphate, succinonitrile, ethanedinitrile, 1,3, 6-hexanetricarbonitrile, ethylene glycol bis (propionitrile) ether, and fluorosulfonyl isocyanate.
3. The electrolyte of claim 2, wherein the additive B comprises 5 to 20wt% of the total mass of the electrolyte.
4. The electrolyte of any one of claims 1 to 3, wherein the organic solvent is a mixture of cyclic and chain esters.
5. The electrolyte of claim 4, wherein the cyclic ester is one or more of ethylene carbonate, propylene carbonate, fluoroethylene carbonate, and γ -butyrolactone.
6. The electrolyte according to claim 5, wherein the chain ester is one or more of diethyl carbonate, ethyl methyl carbonate, methyl formate, ethyl acetate, ethyl propionate, propyl propionate, fluoroethyl acetate, and ethyl fluoropropionate.
7. The electrolyte of any one of claims 1 to 3, wherein the organic solvent accounts for 20 to 80wt% of the total mass of the electrolyte, and the lithium salt is the remainder.
8. The electrolyte of any one of claims 1 to 3, wherein the lithium salt is one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis (fluorosulfonyl) imide, lithium bis (trifluoromethanesulfonyl) imide, lithium difluorophosphate, lithium bis (oxalato) borate, lithium difluorooxalato phosphate, and lithium difluorobis (oxalato) borate.
9. The electrolyte of any one of claims 1 to 3, wherein the lithium salt concentration is 1 to 1.5mol/L.
10. A lithium ion battery comprising a positive electrode tab, a negative electrode tab, a separator and the electrolyte of any one of claims 1 to 9.
CN202211115602.2A 2022-09-14 2022-09-14 Electrolyte and lithium ion battery thereof Pending CN115425288A (en)

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