CN114976251A - Lithium battery electrolyte and secondary battery - Google Patents

Lithium battery electrolyte and secondary battery Download PDF

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Publication number
CN114976251A
CN114976251A CN202210764322.8A CN202210764322A CN114976251A CN 114976251 A CN114976251 A CN 114976251A CN 202210764322 A CN202210764322 A CN 202210764322A CN 114976251 A CN114976251 A CN 114976251A
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lithium
electrolyte
carbonate
low
methyl
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冯志强
刘静
杨红新
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Svolt Energy Technology Co Ltd
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Svolt 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
    • 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
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Inorganic Chemistry (AREA)
  • Secondary Cells (AREA)

Abstract

The invention provides a lithium battery electrolyte and a secondary battery. The electrolyte comprises an organic solvent, lithium salt, ionic liquid and a low-impedance additive, wherein the ionic liquid is 1-methyl-3-ethoxymethyl imidazole bis (trifluoromethanesulfonyl) imide salt and/or 1-methyl-3-butylimidazole bis (trifluoromethanesulfonyl) imide salt, and the low-impedance additive is vinylene carbonate and/or methylene methanedisulfonate. According to the invention, the stability and the conductivity of the electrolyte can be improved by adding the ionic liquid into the lithium battery electrolyte, and the electrochemical window is obviously widened, so that the high-low temperature discharge performance and the cycle performance of the lithium battery are obviously improved; meanwhile, the low-impedance additive is added to further reduce the internal resistance of the battery, and the low-impedance additive and the ionic liquid are synergistic to improve the cycle performance of the lithium battery in a wide temperature range of high temperature, normal temperature and low temperature.

Description

Lithium battery electrolyte and secondary battery
Technical Field
The invention relates to the technical field of lithium batteries, in particular to a lithium battery electrolyte and a secondary battery.
Background
The lithium ion battery has the excellent characteristics of high voltage, long storage and cycle life, strong charge retention capacity, no environmental pollution, wide working range and the like, and is widely applied to the field of new energy electric automobiles at present. However, in the lithium ion power battery of the conventional electrolyte system, under a low temperature condition, the viscosity of the electrolyte is increased, the conductivity is reduced, the interfacial impedance of the electrode is increased, and the phenomena of low charge and discharge capacity, lithium precipitation and the like of the battery often occur, so that the electrode reaction polarization, the discharge platform reduction and the energy attenuation of the lithium ion battery are caused. While electricityAt high temperature in the cell, by LiPF 6 The conventional electrolyte with the composition is easy to oxidize and decompose, the generated HF can corrode a positive electrode material to cause partial metal ions to be dissolved out and deposited on a negative electrode, the composition and the structure of a negative electrode electrolyte interface film are changed, the electrolyte interface is unstable, the impedance of an SEI (solid electrolyte interface) film is increased, and further the battery is inflated, the performance is deteriorated, and even potential safety hazards are brought. Moreover, the electrolyte of the existing lithium ion battery can not reach the state of high and low temperature performance, the low temperature performance is deteriorated if the high temperature performance is satisfied, and the high temperature performance is deteriorated if the low temperature performance is satisfied.
Disclosure of Invention
The invention mainly aims to provide a lithium battery electrolyte and a secondary battery, and aims to solve the problem that the lithium battery electrolyte in the prior art cannot give consideration to high and low temperature performances.
In order to achieve the above object, according to one aspect of the present invention, there is provided a lithium battery electrolyte including an organic solvent, a lithium salt, an ionic liquid and a low resistance additive, the ionic liquid being 1-methyl-3-ethoxymethylimidazolium bistrifluoromethylsulfonyl imide salt and/or 1-methyl-3-butylimidazolium bistrifluoromethylsulfonyl imide salt, and the low resistance additive being vinylene carbonate and/or methylene methanedisulfonate.
Further, the mass of the ionic liquid accounts for 3-10% of the total mass of the electrolyte, and the mass of the low-impedance additive accounts for the total mass of the electrolyte
Further, the low impedance additives are vinylene carbonate and methylene methanedisulfonate; preferably, the mass ratio of the vinylene carbonate to the methylene methanedisulfonate is (0.5-2): 1.
Further, the mass of the organic solvent accounts for 89-96% of the total mass of the electrolyte; preferably, the organic solvent is a cyclic ester and/or a chain ester.
Further, the cyclic ester is selected from one or more of ethylene carbonate, propylene carbonate and gamma-butyrolactone; the chain ester is selected from one or more of dimethyl carbonate, butylene carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate and propyl propionate.
Further, the lithium salt is selected from one or more of lithium hexafluorophosphate, lithium difluorophosphate, lithium difluorobis (oxalato) phosphate, lithium tetrafluorooxalato phosphate, lithium oxalato phosphate, lithium bis (oxalato) borate, lithium difluorooxalato borate, lithium tetrafluoroborate, and lithium bis (fluorosulfonylimide).
According to another aspect of the present invention, there is provided a secondary battery including a positive electrode, a negative electrode, a separator, and an electrolytic solution, the electrolytic solution being the electrolytic solution of the present invention.
Further, the positive electrode includes a positive active material selected from the group consisting of LiCoO 2 、LiMn 2 O 4 、LiMnO 2 、Li 2 MnO 4 、LiFePO 4 、Li 1+a Mn 1-x M x O 2 、LiCo 1-x M x O 2 、LiFe 1-x M x PO 4 、LiMn 2-y M y O 4 、Li 2 Mn 1-x O 4 Wherein M is selected from one or more of Ni, Co, Mn, Al, Cr, Mg, Zr, Mo, V, Ti, B, F and Y, a is more than or equal to 0 and less than 0.2, x is less than 1, and Y is less than 2.
Further, the negative electrode comprises a negative electrode active material, and the negative electrode active material is selected from one or more of natural graphite, artificial graphite, soft carbon, hard carbon, lithium titanate, silicon and silicon-carbon alloy; wherein the soft carbon is one or more of petroleum coke, needle coke, carbon fiber and carbon microspheres, and the hard carbon is one or more of resin carbon, organic polymer pyrolytic carbon and carbon black.
Further, the diaphragm is a PE film and/or a PP-PE-PP film; preferably, the separator is a PE film and/or a PP-PE-PP film with a ceramic or PVDF coated surface.
By applying the technical scheme of the invention, the ionic liquid 1-methyl-3-ethoxymethylimidazole bistrifluoromethylsulfonyl imide salt and/or 1-methyl-3-butylimidazole bistrifluoromethylsulfonyl imide salt is added into the lithium battery electrolyte, so that the stability and the conductivity of the electrolyte can be well improved, the electrochemical window is obviously widened, and the high and low temperature discharge performance and the cycle performance of the lithium battery are obviously improved. And meanwhile, a low-impedance additive vinylene carbonate and/or methylene methanedisulfonate is added, so that the internal resistance of the battery can be further reduced, and the cycling performance of the lithium battery in a wide temperature range of high temperature, normal temperature and low temperature can be improved under the synergistic effect of the vinylene carbonate and/or methylene methanedisulfonate and the ionic liquid.
Detailed Description
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail with reference to examples.
As described in the background of the invention, the problem that the electrolyte of the lithium ion battery cannot give consideration to high and low temperature performance exists in the prior art. In order to solve the above problems, in an exemplary embodiment of the present invention, there is provided an electrolyte for a lithium battery, including an organic solvent, a lithium salt, an ionic liquid and a low resistance additive, the ionic liquid being 1-methyl-3-ethoxymethylimidazole bistrifluoromethylsulfonyl imide salt and/or 1-methyl-3-butylimidazole bistrifluoromethylsulfonyl imide salt, and the low resistance additive being vinylene carbonate and/or methylene methanedisulfonate.
The two ionic liquids in the electrolyte have high solubility to lithium salt, good thermal stability and wide electrochemical window, and have higher conductivity when added into the electrolyte, thereby obviously improving the high-low temperature discharge performance and the cycle performance of the lithium battery. The low-impedance additive can also well improve the SEI film structure of the lithium ion battery and further reduce the low-temperature resistance of the SEI film, so that the charge and discharge performance and the cycle performance of the lithium ion battery in the high-temperature and low-temperature environment are further improved under the synergistic effect of the low-impedance additive and the ionic liquid.
In particular, compared with 1-ethyl-3-methylimidazole bistrifluoromethane sulfimide salt or 1-octyl-2, 3-dimethylimidazole trifluoromethanesulfonate which is commonly used in the prior art, the ionic liquid disclosed by the invention is easier to synthesize, better in thermal stability and wider in electrochemical window, and can better improve the high and low temperature performance of a battery by combining with a low-impedance additive. In conclusion, the ionic liquid 1-methyl-3-ethoxymethylimidazole bistrifluoromethylsulfonyl imide salt and/or 1-methyl-3-butylimidazole bistrifluoromethylsulfonyl imide salt is added into the lithium battery electrolyte, so that the stability and the conductivity of the electrolyte can be improved, the electrochemical window is obviously widened, the low-impedance additive vinylene carbonate and/or methylene methanedisulfonate is added, the internal resistance of the battery can be further reduced, and the cycle performance of the lithium battery in a wide temperature range of high temperature, normal temperature and low temperature can be improved under the synergistic effect of the ionic liquid.
Because the ionic liquid and the low-impedance additive have better wide-temperature-range service performance, the conductivity and the ion diffusion rate of the lithium battery electrolyte can be further improved by adding a small amount of the ionic liquid and the low-impedance additive into the electrolyte, in a preferred embodiment, the mass of the ionic liquid accounts for 3-10% of the total mass of the electrolyte, the mass of the low-impedance additive accounts for 1-2% of the total mass of the electrolyte, the ionic liquid and the low-impedance additive in the content range can better improve the stability and the conductivity of the electrolyte, the SEI high and low temperature resistance is further reduced, and the internal resistance of the lithium battery can be further reduced, so that the lithium battery has better cycle performance at high and low temperatures.
In a preferred embodiment, the low impedance additive is vinylene carbonate and methylene methanedisulfonate; preferably, the mass ratio of vinylene carbonate to methylene methanedisulfonate is (0.5-2): 1, and when the content of the low-impedance additive is within the range, an SEI film formed in the lithium battery is lower in impedance, so that positive and negative electrode interfaces can be better protected, the migration impedance of lithium ions is lower, the insertion and extraction speed is higher, and the cycle performance at high and low temperatures is better.
The specific type of the solvent is not particularly limited in the present invention, and can be selected according to actual requirements. In a preferred embodiment, the mass of the organic solvent accounts for 89-96% of the total mass of the electrolyte; preferably, the organic solvent is a cyclic ester and/or a chain ester, so that the electrolyte has higher conductivity in high and low temperature environments, the solubility to lithium salt is better, and the wettability of the electrolyte is further improved.
Specifically, in a preferred embodiment, the cyclic ester is selected from one or more of ethylene carbonate, propylene carbonate and γ -butyrolactone; the chain ester is selected from one or more of dimethyl carbonate, butylene carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate and propyl propionate.
The addition amount of the lithium salt is 1-3 mol per liter of the electrolyte, and in a preferred embodiment, the lithium salt is selected from one or more of lithium hexafluorophosphate, lithium difluorophosphate, lithium difluorobis (oxalato) phosphate, lithium tetrafluorooxalato phosphate, lithium oxalato phosphate, lithium bis (oxalato) borate, lithium difluorooxalato borate, lithium tetrafluoroborate and lithium bis (fluorosulfonyl) imide. The lithium salts have relatively high thermal stability and are not easy to decompose, and meanwhile, anions and cations are easy to dissociate, so that the lithium battery has better cycle performance.
In still another exemplary embodiment of the present invention, there is also provided a secondary battery including a cathode, an anode, a separator, and an electrolytic solution, the electrolytic solution being the electrolytic solution of the present invention. By using the electrolyte, the SEI film structure of the lithium ion battery is well improved, the stability and the conductivity of the electrolyte are greatly improved, and the internal resistance of the lithium battery is also reduced, so that the lithium battery has better cycle performance in wide temperature ranges of high temperature, normal temperature and low temperature.
To further improve the cycling performance and rate capability of the lithium ion battery, in a preferred embodiment, the positive electrode comprises a positive active material selected from the group consisting of LiCoO 2 、LiMn 2 O 4 、LiMnO 2 、Li 2 MnO 4 、LiFePO 4 、Li 1+ a Mn 1-x M x O 2 、LiCo 1-x M x O 2 、LiFe 1-x M x PO 4 、LiMn 2-y M y O 4 、Li 2 Mn 1-x O 4 Wherein M is selected from one or more of Ni, Co, Mn, Al, Cr, Mg, Zr, Mo, V, Ti, B, F and Y, and a is more than or equal to 0 and less than 02, x is less than 1, y is less than 2, and the high-temperature storage performance and the cycling stability performance of the lithium ion battery are not influenced by the positive active material.
For the purpose of further reducing the impedance of the material at high and low temperatures, in a preferred embodiment, the negative electrode comprises a negative active material selected from one or more of natural graphite, artificial graphite, soft carbon, hard carbon, lithium titanate, silicon carbon alloy; wherein the soft carbon is one or more of petroleum coke, needle coke, carbon fiber and carbon microspheres, and the hard carbon is one or more of resin carbon, organic polymer pyrolytic carbon and carbon black. The negative active material can simultaneously improve the liquid absorption performance, improve the high and low temperature discharge voltage platform of the lithium battery and better improve the high and low temperature cycle performance of the lithium battery.
The diaphragm can be made of materials conventional in the field, and in a preferred embodiment, the diaphragm is a PE film and/or a PP-PE-PP film; preferably, the separator is a PE film and/or a PP-PE-PP film with a ceramic or PVDF coated surface, which is more suitable for the electrolyte of the present invention.
The present application is described in further detail below with reference to specific examples, which should not be construed as limiting the scope of the invention as claimed.
It should be noted that the percentages in the following examples are mass percentages.
Example 1
(1) Preparing a positive plate: preparing positive electrode active material nickel cobalt lithium manganate (LiNi) 0.6 Co 0.1 Mn 0.3 O 2 ) Dissolving a conductive agent Super-P, a carbon nano tube CNT and an adhesive PVDF in a solvent N-methyl pyrrolidone according to a mass ratio of 96:1:1:2, uniformly mixing to prepare positive electrode slurry, uniformly coating the positive electrode slurry on a current collector aluminum foil, drying, rolling, cutting edges, cutting pieces, drying at 85 ℃ under a vacuum condition, welding tabs, and preparing the positive electrode piece of the lithium ion secondary battery.
(2) Preparing a negative plate: dispersing the negative active material artificial graphite, the conductive agent Super-P, the thickening agent CMC and the adhesive SBR into deionized water according to the mass ratio of 97:2:1, uniformly mixing to prepare negative slurry, uniformly coating the negative slurry on a current collector copper foil, drying, rolling, cutting edges, cutting pieces, drying at 85 ℃ under a vacuum condition, and welding tabs to prepare the negative piece of the lithium ion secondary battery.
(3) Preparing an electrolyte: 1mol/L LiPF6 is used as lithium salt, a mixture of Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC) in a mass ratio of 1:1:1 is used as a non-aqueous organic solvent, the solvent ratio is 96%, the 1-methyl-3-butylimidazole bistrifluoromethanesulfonylimide salt is 3%, and the low-impedance additives of vinylene carbonate and methylene methanedisulfonate are 0.5 wt% respectively.
(4) Preparation of lithium ion secondary battery: and (2) manufacturing the positive plate, the negative plate and the isolating film PE film of the lithium ion secondary battery prepared by the process into a soft package battery core through a lamination process, removing water, injecting electrolyte, standing for 24h, charging to 3.8V at 45 ℃ by using a constant current of 0.1C, aging at high temperature of 45 ℃ for 72h, charging to 4.2V by using a constant current of 0.33C, then charging at constant voltage until the current is reduced to 0.05C, then discharging to 2.8V by using a constant current of 0.33C, and repeating the charging and discharging for 2 times to finish the preparation of the lithium ion secondary battery.
Example 2
A lithium ion secondary battery of example 2 was prepared in the same manner as in example 1, except that: the electrolyte contains 94% of organic solvent, 5% of 1-methyl-3-butylimidazole bistrifluoromethylsulfonyl imide salt and 0.5 wt.% of each of vinylene carbonate and methylene methanedisulfonate as low-impedance additives.
Example 3
A lithium ion secondary battery of example 3 was prepared in the same manner as in example 1, except that: the electrolyte contains 89% of organic solvent, 10% of 1-methyl-3-butylimidazole bistrifluoromethylsulfonyl imide salt and 0.5 wt.% of each of vinylene carbonate and methylene methanedisulfonate as low-impedance additives.
Example 4
A lithium ion secondary battery of example 4 was prepared in the same manner as in example 1, except that: the electrolyte had an organic solvent ratio of 95.5%, 1-methyl-3-butylimidazole bistrifluoromethylsulfonyl imide salt of 3%, a low impedance additive of 0.5 wt.% vinylene carbonate, and methylene methanedisulfonate of 1.0 wt.%.
Example 5
A lithium ion secondary battery of example 5 was prepared in the same manner as in example 1, except that: the electrolyte had an organic solvent ratio of 95.5%, 1-methyl-3-butylimidazole bistrifluoromethylsulfonyl imide salt of 3%, a low impedance additive of vinylene carbonate of 1.0 wt.%, and methylene methanedisulfonate of 0.5 wt.%.
Example 6
A lithium ion secondary battery of example 6 was prepared in the same manner as in example 1, except that: the electrolyte contains 95% of organic solvent, 3% of 1-methyl-3-butylimidazole bistrifluoromethylsulfonyl imide salt and 1.0 wt.% of each of vinylene carbonate and methylene methanedisulfonate as low-impedance additives.
Example 7
A lithium ion secondary battery of example 7 was prepared in the same manner as in example 1, except that: the ionic liquid is 1-methyl-3-ethoxymethyl imidazole bis (trifluoromethanesulfonimide) salt.
Comparative example 1
The lithium ion secondary battery of comparative example 1 was manufactured in the same manner as in example 1, except that: no ionic liquid was added to the electrolyte, and the low impedance additives vinylene carbonate and methylene methanedisulfonate were each 0.5 wt.%.
Comparative example 2
A lithium ion secondary battery of comparative example 2 was prepared in the same manner as in example 1, except that: the electrolyte is not added with low-impedance additives, the proportion of the carbonate solvent is 97 percent, and the proportion of the 1-methyl-3-butylimidazole bistrifluoromethanesulfonylimide salt is 3 percent.
Comparative example 3
A lithium ion secondary battery of comparative example 2 was prepared in the same manner as in example 1, except that: no ionic liquid and low impedance additive were added to the electrolyte.
Comparative example 4
A lithium ion secondary battery of comparative example 2 was prepared in the same manner as in example 1, except that: the ionic liquid is 1-ethyl-3-methylimidazole bistrifluoromethanesulfonylimide salt.
The lithium ion secondary batteries of examples 1 to 7 and comparative examples 1 to 4 were subjected to cycle performance tests, and the results are shown in table 1.
The cycle test method comprises the following steps:
1) high-temperature circulation: respectively carrying out 1C/1C cycle test on the prepared lithium ion secondary battery at 45 ℃, and analyzing the influence of the addition of ionic liquid with different contents and additives on the cycle performance of the battery.
The capacity retention (%) after 500 cycles of the lithium ion secondary battery was equal to (discharge capacity at 500 th cycle ÷ discharge capacity at 1 st cycle) × 100%.
2) And (3) normal-temperature circulation: respectively carrying out 1C/1C cycle test on the prepared lithium ion secondary battery at 25 ℃, and analyzing the influence of the addition of ionic liquid with different contents and additives on the cycle performance of the battery.
3) And (3) low-temperature circulation: and respectively carrying out 0.05C/0.33C cycle test on the prepared lithium ion secondary battery at the temperature of-20 ℃, and analyzing the influence of the addition of ionic liquid with different contents and additives on the cycle performance of the battery.
TABLE 1
Figure BDA0003724924450000061
Figure BDA0003724924450000071
As can be seen from the above, in examples 1 to 6, the high-temperature, normal-temperature, and low-temperature cycle performance of the battery can be significantly improved by adding ionic liquids and low-resistance additives in different proportions to the electrolyte, in combination, as compared to the comparative examples. And the electrolyte only added with the ionic liquid or the low-impedance additive has poorer cycle performance than the battery simultaneously added with the ionic liquid and the low-impedance additive. The ionic liquid is added into the lithium battery electrolyte, so that the stability and the conductivity of the electrolyte can be improved, the electrochemical window is obviously widened, the high-low temperature discharge performance and the cycle performance of the lithium battery are obviously improved, meanwhile, the low-impedance additive is added to further reduce the internal resistance of the battery, and the cycle performance of the lithium battery in a wide temperature range of high temperature, normal temperature and low temperature can be improved under the synergistic effect of the ionic liquid and the ionic liquid.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. The electrolyte of the lithium battery is characterized by comprising an organic solvent, a lithium salt, an ionic liquid and a low-impedance additive, wherein the ionic liquid is 1-methyl-3-ethoxymethylimidazole bistrifluoromethylsulfonyl imide salt and/or 1-methyl-3-butylimidazole bistrifluoromethylsulfonyl imide salt, and the low-impedance additive is vinylene carbonate and/or methylene methanedisulfonate.
2. The electrolyte according to claim 1, wherein the mass of the ionic liquid accounts for 3-10% of the total mass of the electrolyte, and the mass of the low impedance additive accounts for 1-2% of the total mass of the electrolyte.
3. The electrolyte of claim 1 or 2, wherein the low impedance additive is the vinylene carbonate and the methylene methanedisulfonate; preferably, the mass ratio of the vinylene carbonate to the methylene methanedisulfonate is (0.5-2): 1.
4. The electrolyte according to any one of claims 1 to 3, wherein the mass of the organic solvent accounts for 89-96% of the total mass of the electrolyte; preferably, the organic solvent is a cyclic ester and/or a chain ester.
5. The electrolyte of claim 4, wherein the cyclic ester is selected from one or more of ethylene carbonate, propylene carbonate, and γ -butyrolactone; the chain ester is selected from one or more of dimethyl carbonate, butylene carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate and propyl propionate.
6. The electrolyte of any one of claims 1 to 5, wherein the lithium salt is selected from one or more of lithium hexafluorophosphate, lithium difluorophosphate, lithium difluorobis (oxalato) phosphate, lithium tetrafluorooxalato phosphate, lithium oxalato phosphate, lithium bis (oxalato) borate, lithium difluorooxalato borate, lithium tetrafluoroborate and lithium bis (fluorosulfonylimide).
7. A secondary battery comprising a positive electrode, a negative electrode, a separator and an electrolytic solution, characterized in that the electrolytic solution is the electrolytic solution according to any one of claims 1 to 6.
8. The secondary battery of claim 7, wherein the positive electrode comprises a positive active material selected from LiCoO 2 、LiMn 2 O 4 、LiMnO 2 、Li 2 MnO 4 、LiFePO 4 、Li 1+a Mn 1-x M x O 2 、LiCo 1-x M x O 2 、LiFe 1-x M x PO 4 、LiMn 2-y M y O 4 、Li 2 Mn 1-x O 4 Wherein M is selected from one or more of Ni, Co, Mn, Al, Cr, Mg, Zr, Mo, V, Ti, B, F and Y, a is more than or equal to 0 and less than 0.2, x is less than 1, and Y is less than 2.
9. The secondary battery according to claim 7 or 8, wherein the negative electrode comprises a negative active material selected from one or more of natural graphite, artificial graphite, soft carbon, hard carbon, lithium titanate, silicon carbon alloy; wherein the soft carbon is one or more of petroleum coke, needle coke, carbon fiber and carbon microspheres, and the hard carbon is one or more of resin carbon, organic polymer pyrolytic carbon and carbon black.
10. The secondary battery according to any one of claims 7 to 9, wherein the separator is a PE film and/or a PP-PE-PP film; preferably, the separator is a PE film and/or a PP-PE-PP film with the surface coated with ceramic or PVDF.
CN202210764322.8A 2022-06-30 2022-06-30 Lithium battery electrolyte and secondary battery Pending CN114976251A (en)

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