CN114976240A - Borate lithium salt electrolyte and lithium ion battery - Google Patents

Borate lithium salt electrolyte and lithium ion battery Download PDF

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CN114976240A
CN114976240A CN202210649058.3A CN202210649058A CN114976240A CN 114976240 A CN114976240 A CN 114976240A CN 202210649058 A CN202210649058 A CN 202210649058A CN 114976240 A CN114976240 A CN 114976240A
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lithium
borate
electrolyte
carbonate
lithium salt
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尚德华
王亚飞
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Aopu Shanghai New Energy 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
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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
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Abstract

The invention particularly relates to a borate lithium salt electrolyte and a lithium ion battery, wherein the electrolyte comprises borate lithium salt, a non-aqueous organic solvent and an additive, and the borate lithium salt has a structural general formula as follows:
Figure DDA0003685235660000011
wherein R is 1 、R 2 Is straight chain alkyl-C n . The borate lithium salt has good thermal stability and is insensitive to moisture, lithium hexafluorophosphate can be partially substituted in the electrolyte, the occurrence of side reactions in the battery caused by hydrolysis and thermal decomposition of lithium hexafluorophosphate is reduced, the capacity attenuation of the battery caused by moisture is further reduced, a water removing agent is not needed, and the cost is reduced. The borate lithium salt structure contains a large amount of groups with strong electron delocalization, such as fluorine, sulfonyl and the like,therefore, the borate lithium salt electrolyte has high conductivity, a cyclic carbonate and borate structure is introduced into the structure, a stable electrolyte membrane is formed on the surface of an electrode, the ion conductivity of the membrane is good, the high-temperature performance of the battery is improved, and the internal resistance of the battery is greatly reduced.

Description

Borate lithium salt electrolyte and lithium ion battery
Technical Field
The invention relates to the technical field of electrochemistry, in particular to borate lithium salt electrolyte and a lithium ion battery.
Background
The lithium ion battery has the obvious characteristics of high energy density, high voltage, good safety, low self-discharge rate, cleanness, no pollution and the like, so the lithium ion battery is widely researched and applied. The lithium ion battery is mainly applied to the fields of electric automobiles, energy storage, consumer electronics, war industry, aerospace, medical electronics and the like, and the lithium ion battery is required to have good cycle performance and safety performance. Currently, lithium ion battery technology is continuously advancing, and has made major breakthrough in some aspects, but the performance of some aspects of lithium ion batteries still needs to be improved.
The lithium ion battery has cylindrical, square, soft package and other packaging forms, but the lithium ion battery in any form consists of four core materials of an anode, a cathode, a diaphragm and electrolyte. The electrolyte is one of the most critical and high-technology materials in lithium ion battery materials. The commercial lithium ion battery electrolyte mainly comprises nonaqueous organic solvents such as carbonic ester and carboxylic ester, lithium salt mainly comprising lithium hexafluorophosphate, various functional additives and the like. Lithium hexafluorophosphate is very sensitive to moisture, can be hydrolyzed to generate hydrofluoric acid in the presence of trace water to corrode a current collector, and can also dissolve out transition metal elements in the positive electrode material to further catalyze the decomposition of electrolyte, so that the rapid attenuation of the battery capacity is caused; and lithium hexafluorophosphate has poor thermal stability, can be decomposed at about 60 ℃ to generate phosphorus pentafluoride gas, so that the battery expands, and the chemical property and the electrochemical property of the electrolyte are influenced, so that the performance of the battery is rapidly deteriorated.
In order to solve the above problems, the following solutions are generally proposed: firstly, adding a film additive into electrolyte to form a solid electrolyte film on the surface of a positive electrode, so that the dissolution of a positive electrode material at high temperature is avoided, the direct contact between the positive electrode material and the electrolyte is isolated, and the catalytic decomposition of a transition metal element in the positive electrode on the electrolyte is avoided; however, the use of the electrolyte additive increases the internal resistance of the battery, increases the polarization of the battery, decreases the cycle performance of the battery, and increases the manufacturing cost of the battery. Second, the water content of the electrolyte can be reduced by using a water removal means, thereby reducing hydrolysis of lithium hexafluorophosphate, and reducing the influence of moisture on the battery performance. However, the method uses a water removal agent, the price of the water removal agent special for the electrolyte is high, and the water removal process inevitably leads to new impurities introduced into the electrolyte. And thirdly, replacing lithium hexafluorophosphate with novel lithium salts which have high thermal stability and are insensitive to moisture, such as lithium bistrifluoromethylsulfonyl imide, lithium bistrifluorosulfonimide, lithium bisoxalato borate and lithium difluorooxalato borate. The synthesis of these new lithium salts is therefore still immature, resulting in insufficient purity and rather high price of the new lithium salts, some of which also corrode the aluminum foil.
Disclosure of Invention
In view of the above, it is desirable to provide a borate lithium salt electrolyte and a lithium ion battery, which are low in cost, improve the high-temperature performance of the battery, reduce the internal resistance of the battery, and reduce the damage of moisture to the battery capacity.
In order to achieve the above object, in a first aspect of the present invention, there is provided a borate lithium salt electrolyte comprising a borate lithium salt, a non-aqueous organic solvent and an additive, the borate lithium salt having a general structural formula:
Figure BDA0003685235650000021
wherein R is 1 、R 2 Is straight chain alkyl-C n Said straight chain alkyl-C n Wherein one or more hydrogen atoms are substituted with the following substituents to form the lithium borate salt: fluorine, trifluoromethyl, trifluoromethoxy, cyano, fluorosulfonyl, trifluoromethanesulfonyl, trifluoromethanesulfonic, fluoro (lithium sulfonimide) sulfonyl, trifluoromethyl (lithium sulfonimide) sulfonyl, lithium sulfonate, phenyl, fluorophenyl, trimethylsilyl, trifluoromethylsilyl, fluorocyclotriphosphazenyl, isocyanate.
Further, the borate lithium salt accounts for 0.01-20% of the weight of the electrolyte.
Further, said straight chain alkyl-C n Wherein n is an integer of 1 to 6.
Further, the lithium salt accounts for 2-20% of the weight of the electrolyte.
Further, the lithium salt is one or more of lithium hexafluorophosphate, lithium bis (oxalato) borate, lithium difluorophosphate, lithium difluoro (oxalato) borate, lithium bis (fluorosulfonyl) imide, lithium bis (trifluoromethanesulfonyl) imide, lithium trifluoromethanesulfonate, lithium tetrafluoroborate, lithium perchlorate, (fluorosulfonyl) trifluoromethanesulfonylimide, lithium tetrachloroaluminate and lithium hexafluoroarsenate.
Further, the nonaqueous organic solvent accounts for 70-90% of the weight of the electrolyte.
Further, the non-aqueous organic solvent is one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, vinylene carbonate, ethylene carbonate, fluoroethylene carbonate, methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, gamma-butyrolactone, dioxolane, tetrahydrofuran, dimethyl trifluoroacetamide and dimethyl sulfoxide.
Further, the additive accounts for 0.1-10% of the weight of the electrolyte.
Further, the additive is one or a combination of more of vinylene carbonate, ethylene carbonate, fluoroethylene carbonate, 1, 4-butane sultone, propylene sulfate, propylene sulfite, butylene sulfate and lithium difluorophosphate.
In a second aspect of the present invention, there is provided a lithium ion battery comprising a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator, the separator being disposed between the positive electrode sheet and the negative electrode sheet; the electrolyte is the borate lithium salt electrolyte according to the first aspect of the present invention.
The borate lithium salt electrolyte and the lithium ion battery are characterized in that the electrolyte consists of borate lithium salt, an additive and a non-aqueous organic solvent, and the structural general formula of the borate lithium salt is as follows:
Figure BDA0003685235650000031
the borate lithium salt has good thermal stability and is insensitive to moisture, and lithium hexafluorophosphate can be partially substituted in the electrolyte, so that the occurrence of side reactions in the battery caused by hydrolysis and thermal decomposition of lithium hexafluorophosphate is reduced, the capacity attenuation of the battery caused by moisture is reduced, a water removing agent is not required, and the cost is reduced. The borate lithium salt structure contains a large number of groups with strong electron delocalization such as fluorine and sulfonyl, so that the conductivity of the borate lithium salt electrolyte is high, a cyclic carbonate and borate structure is introduced into the structure, a stable solid electrolyte membrane can be formed on the surface of an electrode, the ion conductivity of the membrane is good, the high-temperature performance of the battery can be improved, the internal resistance of the battery can be greatly reduced, and the cycle performance and the rate capability of the battery can be improved.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the borate lithium salt electrolyte and the lithium ion battery according to the present invention are described below with reference to the embodiments, comparative examples, test procedures and test results. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
First, the borate ester lithium salt electrolyte of the first aspect of the invention is explained.
The borate lithium salt electrolyte consists of borate lithium salt, an additive and a non-aqueous organic solvent, wherein the borate lithium salt has a structural general formula as follows:
Figure BDA0003685235650000041
wherein R is 1 、R 2 Is straight chain alkyl-C n (wherein n is an integer of 1 to 6), the straight chain alkyl-C n One or more hydrogen atoms on (a) are substituted with the following substituents: fluorine, trifluoromethyl, trifluoromethoxy, cyano, fluorosulfonyl, trifluoromethanesulfonyl, trifluoromethyl, and the like,Trifluoromethanesulfonic acid group, fluorine (lithium sulfonyl imide group) sulfonyl group, trifluoromethyl (lithium sulfonyl imide group) sulfonic group, lithium sulfonate group, phenyl group, fluorophenyl group, trimethylsilyl group, trifluoromethyl silyl group, fluoro-cyclic triphosphonyl group and isocyanate group to generate borate lithium salt.
In the borate lithium salt electrolyte of the first aspect of the present invention, the borate lithium salt accounts for 0.01 to 20% by weight of the total weight of the electrolyte. The weight of the lithium salt accounts for 2-20% of the total weight of the electrolyte. The weight of the non-aqueous organic solvent accounts for 70-90% of the total weight of the electrolyte. The weight of the additive accounts for 0.1-10% of the total weight of the electrolyte.
In the borate ester lithium salt electrolyte according to the first aspect of the present invention, the lithium salt may be selected from at least one of lithium hexafluorophosphate, lithium bis (oxalato) borate, lithium difluorophosphate, lithium difluorooxalato borate, lithium bis (fluorosulfonyl) imide, lithium bis (trifluoromethylsulfonyl) imide, lithium trifluoromethanesulfonate, lithium tetrafluoroborate, lithium perchlorate, (fluorosulfonyl) trifluoromethylsulfonyl imide, lithium tetrachloroaluminate, and lithium hexafluoroarsenate.
In the borate lithium salt electrolyte according to the first aspect of the present invention, the non-aqueous organic solvent may be selected from at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, vinylene carbonate, ethylene carbonate, fluoroethylene carbonate, methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, γ -butyrolactone, dioxolane, tetrahydrofuran, dimethyl trifluoroacetamide, and dimethyl sulfoxide.
In the borate lithium salt electrolyte of the first aspect of the present invention, the additive may be at least one selected from the group consisting of vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, 1, 4-butane sultone, propylene sulfate, propylene sulfite, butylene sulfate, and lithium difluorophosphate.
Next, a lithium ion battery according to a second aspect of the present invention will be described.
A lithium ion battery comprises a positive plate, a negative plate, electrolyte and a diaphragm, wherein the diaphragm is arranged between the positive plate and the negative plate, and the electrolyte adopts the borate lithium salt electrolyte of the first aspect of the invention.
In the lithium ion battery of the second aspect of the invention, the positive electrode material of the positive electrode sheet includes lithium nickel cobalt manganese (LiNi) 0.5 Co 0.2 Mn 0.3 ) The conductive agent Super P, the carbon nano tube, the polyvinylidene fluoride and the aluminum foil.
In the lithium ion battery of the second aspect of the invention, the negative electrode material of the negative electrode sheet comprises graphite, a conductive agent Super P, carboxymethyl cellulose, styrene-butadiene rubber, deionized water and copper foil.
Next, examples and comparative examples of the borate ester lithium salt electrolyte of the present invention and a lithium ion battery will be described.
The first step is as follows: preparation of the electrolyte
The lithium borate salts used in the following examples and comparative examples have the following structural formula:
formula 1: lithium (1, 3-dioxolan-4-isocyanato-5-perfluoroisobutyl-2-one) oxalato borate ester
Figure BDA0003685235650000061
Formula 2: lithium (1, 3-dioxolane-4-fluorosulfonyl-5-cyano-2-one) oxalato borate ester
Figure BDA0003685235650000062
Formula 3: (1, 3-dioxolan-4-lithioxy-5-trifluoromethylsulfonyl-2-one) lithium oxalato borate ester
Figure BDA0003685235650000063
Formula 4: (1, 3-dioxolane-4-fluorosulfonyl-5-trifluoromethyl-2-one) oxalato borate lithium salt
Figure BDA0003685235650000064
Example 1:
uniformly mixing ethylene carbonate (EC, solvent), dimethyl carbonate (DMC, solvent) and methyl ethyl carbonate (EMC, solvent) according to the mass ratio of EC: DMC: EMC 2:3:5, adding (1, 3-dioxolan-4-isocyanate-5-perfluoroisobutyl-2-ketone) oxalic acid boric acid ester lithium with the concentration of 0.1mol/L and lithium hexafluorophosphate with the concentration of 0.9mol/L until the total concentration of lithium salts is 1mol/L, adding vinylene phosphate with the mass fraction of 2% and fluoroethylene carbonate with the mass fraction of 1%, and uniformly dissolving and stirring.
Example 2:
uniformly mixing ethylene carbonate (EC, solvent), dimethyl carbonate (DMC, solvent) and methyl ethyl carbonate (EMC, solvent) according to the mass ratio of EC: DMC: EMC 2:3:5, adding (1, 3-dioxolan-4-isocyanate-5-perfluoroisobutyl-2-ketone) oxalic acid boric acid ester lithium with the concentration of 0.3mol/L and lithium hexafluorophosphate with the concentration of 0.7mol/L until the total concentration of lithium salts is 1mol/L, adding vinylene phosphate with the mass fraction of 2% and fluoroethylene carbonate with the mass fraction of 1%, and uniformly dissolving and stirring.
Example 3:
uniformly mixing ethylene carbonate (EC, solvent), dimethyl carbonate (DMC, solvent) and methyl ethyl carbonate (EMC, solvent) according to the mass ratio of EC: DMC: EMC 2:3:5, adding (1, 3-dioxolan-4-isocyanate-5-perfluoroisobutyl-2-ketone) oxalic acid boric acid ester lithium with the concentration of 0.5mol/L and lithium hexafluorophosphate with the concentration of 0.5mol/L until the total concentration of lithium salts is 1mol/L, adding vinylene phosphate with the mass fraction of 2% and fluoroethylene carbonate with the mass fraction of 1%, and uniformly dissolving and stirring.
Example 4:
uniformly mixing ethylene carbonate (EC, solvent), dimethyl carbonate (DMC, solvent) and methyl ethyl carbonate (EMC, solvent) according to the mass ratio of EC: DMC: EMC 2:3:5, adding (1, 3-dioxolan-4-isocyanate-5-perfluoroisobutyl-2-ketone) lithium oxalate borate with the concentration of 0.7mol/L and lithium hexafluorophosphate with the concentration of 0.3mol/L until the total concentration of lithium salts is 1mol/L, adding vinylene phosphate with the mass fraction of 2% and fluoroethylene carbonate with the mass fraction of 1%, and uniformly dissolving and stirring.
Example 5:
uniformly mixing ethylene carbonate (EC, solvent), dimethyl carbonate (DMC, solvent) and methyl ethyl carbonate (EMC, solvent) according to the mass ratio of EC: DMC: EMC 2:3:5, adding (1, 3-dioxolan-4-isocyanate-5-perfluoroisobutyl-2-ketone) oxalic acid boric acid ester lithium with the concentration of 0.9mol/L and lithium hexafluorophosphate with the concentration of 0.1mol/L until the total concentration of lithium salts is 1mol/L, adding vinylene phosphate with the mass fraction of 2% and fluoroethylene carbonate with the mass fraction of 1%, and uniformly dissolving and stirring.
Example 6:
uniformly mixing ethylene carbonate (EC, solvent), dimethyl carbonate (DMC, solvent) and methyl ethyl carbonate (EMC, solvent) according to the mass ratio of EC: DMC: EMC 2:3:5, adding (1, 3-dioxolane-4-isocyanate-5-perfluoroisobutyl-2-ketone) oxalic acid boric acid ester lithium with the concentration of 0.5mol/L and lithium hexafluorophosphate with the concentration of 0.5mol/L until the total concentration of lithium salt is 1mol/L, and uniformly dissolving and stirring.
Example 7:
uniformly mixing ethylene carbonate (EC, solvent), dimethyl carbonate (DMC, solvent) and methyl ethyl carbonate (EMC, solvent) according to the mass ratio of EC: DMC: EMC 2:3:5, adding (1, 3-dioxolane-4-fluorosulfonyl-5-cyano-2-one) oxalic acid boric acid ester lithium with the concentration of 0.5mol/L and lithium hexafluorophosphate with the concentration of 0.5mol/L until the total concentration of lithium salts is 1mol/L, and uniformly dissolving and stirring.
Example 8:
uniformly mixing ethylene carbonate (EC, solvent), dimethyl carbonate (DMC, solvent) and methyl ethyl carbonate (EMC, solvent) according to the mass ratio of EC: DMC: EMC ═ 2:3:5, adding (1, 3-dioxolane-4-lithioxy-5-trifluoromethylsulfonyl-2-one) oxalic acid boric acid ester lithium with the concentration of 0.5mol/L and lithium hexafluorophosphate with the concentration of 0.5mol/L until the total concentration of lithium salts is 1mol/L, and uniformly dissolving and stirring.
Example 9:
uniformly mixing ethylene carbonate (EC, solvent), dimethyl carbonate (DMC, solvent) and methyl ethyl carbonate (EMC, solvent) according to the mass ratio of EC: DMC: EMC 2:3:5, adding (1, 3-dioxolane-4-fluorosulfonyl-5-trifluoromethyl-2-one) oxalic acid boric acid ester lithium with the concentration of 0.5mol/L and lithium hexafluorophosphate with the concentration of 0.5mol/L until the total concentration of lithium salts is 1mol/L, and uniformly dissolving and stirring.
Comparative example 1:
uniformly mixing ethylene carbonate (EC, solvent), dimethyl carbonate (DMC, solvent) and methyl ethyl carbonate (EMC, solvent) according to the mass ratio of EC to DMC to EMC of 2:3:5, adding lithium hexafluorophosphate (lithium salt) until the concentration of lithium salt is 1mol/L, and uniformly dissolving and stirring.
Comparative example 2:
uniformly mixing ethylene carbonate (EC, solvent), dimethyl carbonate (DMC, solvent) and methyl ethyl carbonate (EMC, solvent) according to a mass ratio of EC: DMC: EMC ═ 2:3:5, adding lithium hexafluorophosphate (lithium salt) until the concentration of lithium salt is 1mol/L, adding vinylene carbonate with the mass fraction of 2% and fluoroethylene carbonate with the mass fraction of 1%, and uniformly dissolving and stirring.
Comparative example 3:
uniformly mixing ethylene carbonate (EC, solvent), dimethyl carbonate (DMC, solvent) and methyl ethyl carbonate (EMC, solvent) according to a mass ratio of EC: DMC: EMC ═ 2:3:5, adding lithium hexafluorophosphate (lithium salt) until the concentration of lithium salt is 1mol/L, adding vinylene carbonate with the mass fraction of 2%, fluoroethylene carbonate with the mass fraction of 1% and 1, 3-propane sultone with the mass fraction of 2%, and uniformly dissolving and stirring.
Comparative example 4:
uniformly mixing ethylene carbonate (EC, solvent), dimethyl carbonate (DMC, solvent) and ethyl methyl carbonate (EMC, solvent) according to the mass ratio of EC: DMC: EMC ═ 2:3:5, adding lithium hexafluorophosphate (lithium salt) until the concentration of lithium salt is 1mol/L, adding vinylene carbonate with the mass fraction of 2%, fluoroethylene carbonate with the mass fraction of 1% and ethylene sulfate with the mass fraction of 2%.
Comparative example 5:
uniformly mixing ethylene carbonate (EC, solvent), dimethyl carbonate (DMC, solvent) and ethyl methyl carbonate (EMC, solvent) according to a mass ratio of EC: DMC: EMC ═ 2:3:5, adding lithium hexafluorophosphate (lithium salt) until the concentration of lithium salt is 1mol/L, adding vinylene carbonate with the mass fraction of 2%, fluoroethylene carbonate with the mass fraction of 1% and ethylene sulfite with the mass fraction of 2%.
The second step is that: preparation of lithium ion battery
(1) Preparing a positive plate:
the lithium nickel cobalt manganese oxide (LiNi) as the anode material 0.5 Co 0.2 Mn 0.3 ) The conductive agent Super P, the carbon nano tube and the polyvinylidene fluoride are uniformly dispersed in an N, N-dimethyl pyrrolidone solvent according to the mass ratio of 95.5:1.5:1.5:1.5 to prepare anode slurry. And uniformly coating the dispersed slurry on an aluminum foil with the thickness of 14 mu m, drying in a blast oven at 80 ℃, rolling and die-cutting to obtain the positive plate.
(2) Preparation of negative plate
Uniformly dispersing graphite, a conductive agent Super P, carboxymethyl cellulose and styrene butadiene rubber in deionized water according to a mass ratio of 94:3:2:1 to prepare negative electrode slurry. And coating the dispersed negative electrode slurry on a copper foil with the thickness of 10 mu m, drying in a blast oven at 80 ℃, rolling and die-cutting to prepare a negative electrode plate.
(3) Preparation of lithium batteries
And (3) preparing the positive plate, the negative plate and the diaphragm (the positive plate, the negative plate, the diaphragm and the electrolyte) into a pole core according to a lamination process, packaging the pole core into an aluminum-plastic film, and carrying out top side sealing, baking, liquid injection, formation and other processes to prepare the soft package battery.
And finally, giving a performance test and a test result of the lithium ion battery.
Testing I, high-temperature charge retention rate and recovery capability testing:
the lithium ion batteries of examples 1 to 9 and comparative examples 1 to 5 were charged at a constant current of 1C to a voltage of 4.3V, charged at a constant voltage of 4.3V to a current of 0.05C, and then discharged at a constant current of 1C to a voltage of 3V, respectively, at 25C, and the initial specific discharge capacity was recorded. And then carrying out high-temperature performance test, wherein the test steps are as follows:
(1) the battery was charged in a standard manner and the internal resistance was tested.
(2) Stored at 60 ℃ for 7 days.
(3) At room temperature, the cell was left to stand for 5h and tested for internal resistance, and discharged at a current of 1C to an end voltage of 3V.
(4) The battery is charged in a standard manner for charging.
(5) The test was stopped at room temperature when the cell was discharged to an end voltage of 3V at a current of 1C.
Wherein, the percentage of the charge retention capacity is actual specific discharge capacity/normal temperature 1C specific charge capacity before storage multiplied by 100%, and the capacity recovery rate is actual specific discharge capacity/normal temperature 1C specific charge capacity before storage multiplied by 100%.
And testing II, high-temperature cycle performance:
the lithium ion batteries of examples and comparative examples were respectively charged at 60 ℃ to a voltage of 4.3V at a constant current of 1C, charged at a constant voltage of 4.3V to a current of 0.05C, and then discharged at a constant current of 1C to a voltage of 3V, and cycled for 300 weeks.
The results of the performance tests of the lithium ion batteries prepared in examples 1 to 9 and comparative examples 1 to 5 are shown in Table 1.
TABLE 1
Figure BDA0003685235650000101
Figure BDA0003685235650000111
The borate lithium salt electrolyte and the lithium ion battery are characterized in that the electrolyte consists of borate lithium salt, an additive and a non-aqueous organic solvent, wherein the borate lithium salt has a structural general formula as follows:
Figure BDA0003685235650000112
the borate lithium salt has good thermal stability and is insensitive to moisture, and lithium hexafluorophosphate can be partially substituted in the electrolyte, so that the occurrence of side reactions in the battery caused by hydrolysis and thermal decomposition of lithium hexafluorophosphate is reduced, the capacity attenuation of the battery caused by moisture is reduced, a water removing agent is not required, and the cost is reduced. The borate lithium salt structure contains a large number of groups with strong electron delocalization such as fluorine and sulfonyl, so that the conductivity of the borate lithium salt electrolyte is high, a cyclic carbonate and borate structure is introduced into the structure, a stable solid electrolyte membrane can be formed on the surface of an electrode, the ion conductivity of the membrane is good, the high-temperature performance of the battery can be improved, the internal resistance of the battery can be greatly reduced, and the cycle performance and the rate capability of the battery can be improved.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims (10)

1. The borate lithium salt electrolyte is characterized by comprising a borate lithium salt, a non-aqueous organic solvent and an additive, wherein the borate lithium salt has a general structural formula:
Figure FDA0003685235640000011
wherein R is 1 、R 2 Is straight chain alkyl-C n Said straight chain alkyl-C n Wherein one or more hydrogen atoms are replaced with a substituent selected from the group consisting of: fluorine, trifluoromethyl, trifluoromethoxy, cyano, fluorosulfonyl, trifluoromethanesulfonyl, trifluoromethanesulfonic, fluoro (lithium sulfonimide) sulfonyl, trifluoromethyl (lithium sulfonimide) sulfonyl, lithium sulfonate, phenyl, fluorophenyl, trimethylsilyl, trifluoromethanesulfoniosilylFluoro-cyclotriphosphazene group and isocyanate group.
2. The borate lithium electrolyte of claim 1, wherein the borate lithium salt comprises 0.01% to 20% by weight of the electrolyte.
3. The lithium borate salt electrolyte of claim 1, wherein the linear alkyl-C is n Wherein n is an integer of 1 to 6.
4. The borate lithium electrolyte of claim 1, wherein the lithium salt is present in an amount of 2% to 20% by weight of the electrolyte.
5. The lithium borate salt electrolyte of claim 1, wherein the lithium salt is one or a combination of more of lithium hexafluorophosphate, lithium bis (oxalato) borate, lithium difluorophosphate, lithium difluoro (oxalato) borate, lithium bis (fluorosulfonyl) imide, lithium bis (trifluoromethylsulfonyl) imide, lithium triflate, lithium tetrafluoroborate, lithium perchlorate, lithium (fluorosulfonyl) trifluoromethylsulfonyl imide, lithium tetrachloroaluminate, lithium hexafluoroarsenate.
6. The borate lithium electrolyte of claim 1, wherein the non-aqueous organic solvent is present in an amount of 70% to 90% by weight of the electrolyte.
7. The lithium borate salt electrolyte of claim 1, wherein the non-aqueous organic solvent is one or a combination of more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene carbonate, fluoroethylene carbonate, methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, γ -butyrolactone, dioxolane, tetrahydrofuran, dimethyl trifluoroacetamide, dimethyl sulfoxide.
8. The borate lithium electrolyte of claim 1, wherein the additive comprises 0.1% to 10% by weight of the electrolyte.
9. The lithium borate salt electrolyte of claim 1, wherein the additive is one or a combination of more of vinylene carbonate, ethylene carbonate, fluoroethylene carbonate, 1, 4-butane sultone, propylene sulfate, propylene sulfite, butylene sulfate, lithium difluorophosphate.
10. The lithium ion battery is characterized by comprising a positive plate, a negative plate, electrolyte and a diaphragm, wherein the diaphragm is arranged between the positive plate and the negative plate; the electrolyte is the borate lithium salt electrolyte of any of claims 1 to 9.
CN202210649058.3A 2022-06-09 2022-06-09 Borate lithium salt electrolyte and lithium ion battery Pending CN114976240A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116315077A (en) * 2022-11-30 2023-06-23 九江天赐高新材料有限公司 Electrolyte combination, secondary injection method and lithium secondary battery
CN117096450A (en) * 2023-10-18 2023-11-21 瑞浦兰钧能源股份有限公司 Secondary battery electrolyte and battery thereof

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116315077A (en) * 2022-11-30 2023-06-23 九江天赐高新材料有限公司 Electrolyte combination, secondary injection method and lithium secondary battery
CN116315077B (en) * 2022-11-30 2024-06-04 九江天赐高新材料有限公司 Electrolyte combination, secondary injection method and lithium secondary battery
CN117096450A (en) * 2023-10-18 2023-11-21 瑞浦兰钧能源股份有限公司 Secondary battery electrolyte and battery thereof
CN117096450B (en) * 2023-10-18 2024-03-15 瑞浦兰钧能源股份有限公司 Secondary battery electrolyte and battery thereof

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