Lithium secondary battery electrolyte, preparation method of lithium secondary battery electrolyte as well as lithium secondary battery

Abstract

The invention discloses lithium secondary battery electrolyte, a preparation method of the lithium secondary battery electrolyte as well as a lithium secondary battery. The lithium secondary battery electrolyte comprises a non-aqueous organic solvent, electrolyte lithium salt and an additive; the non-aqueous organic solvent comprises carbonic ester and carboxylic ester; the electrolyte also comprises fluoroalkyl boric acid ester with the structural formula of (R1O)B(OR2)(OR3), wherein R1, R2 and R3 are alkyl group or alkyl group containing flourine with the number of carbon atoms being 1 to 10. Fluoroalkyl boric acid ester has favorable oxidation resistance, surface active performance and film forming performance; proper amount of fluoroalkyl boric acid ester is added into the electrolyte, and the liquid injection processing property, the circulation performance and the high-voltage-resistant performance of the lithium secondary battery are improved.

Description

Technical field [0001] The present invention involves the field of lithium secondary battery. More specific, the invention involves a lithium secondary battery electrolyte containing fluorine -alkamate. Background technique [0002] Lithium -ion batteries have the advantages of high working voltage, large energy density, long circular life, low self -discharge rate, no memory effect, and small environmental pollution. They have been widely used in the electronic consumer goods market.Ideal power source. [0003] At present, liquid lithium secondary battery electrolytes generally use ring -shaped carbonate (such as carbonate, carbonate, carbonate) and chain -shaped carbonate (such as carbonate, carbonate, ethyl carbonate) mixed solvents.Among them, the viscosity of ring -shaped carbonate is high and the surface tension is relatively large, so during the process of liquid injection, the electrolyte is not very good, especially at the low temperature or the compact density of the el...

AI Technical Summary

Problems solved by technology

[0003] At present, cyclic carbonates (such as ethylene carbonate, propylene carbonate) and chain carbonates (such as dimethyl carbonate) are commonly used in liquid lithium secondary battery electrolytes ester, diethyl carbonate, ethyl methyl carbonate) mixed solvent, in which the viscosity of cyclic carbonate is relatively high, and the surface tension is relatively high, so the wettability of the electrolyte is not very good during the liquid injection process of the lithium secondary battery , especially when the temperature is low or the compaction density of the electrode sheet is relatively high, the wettability of the electrolyte to the electrode material and the separator becomes poor, which will lead to a relatively large contact resistance between the electrode material and the electrolyte, and will affect the positive The utilization rate of the negative electrode material is not conducive to the play of battery capacity, and is not conducive to the formation of passivation film on the electrode surface, thus damaging the cycle life of the battery

In addition, the carbon-hydrogen chemical bond is easy to break on the surface of the positive electrode at a high potential to cause an oxidation reaction. For example, when the cut-off voltage of lithium cobaltate is raised above 4.4V, the electrochemical reaction on the surface of the electrode is intensified, resulting in cycle life and safety of the battery. question

[0004] Due to the urgent need for battery life of electronic products and power batteries, the current technical level is mainly to further release the capacity of lithium secondary batteries by increasing the voltage of the battery, or Improve the compaction density of the electrode sheet, thereby increasing the energy density of the battery, and these two solutions will lead to the above-mentioned electrolyte oxidation and wettability problems

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