Nonaqueous electrolyte for high-voltage lithium ion battery

Abstract

The invention discloses nonaqueous electrolyte for a high-voltage lithium ion battery. The nonaqueous electrolyte consists of a solvent, an inorganic lithium salt, a fluoro-ester additive, a sultone additive, an organic tri-nitrile additive, a bi(polyfluoroalkoxy sulfonyl) imine lithium salt and a lithium battery electrolyte additive, wherein the addition amount of the solvent is 100 weight parts; the addition amount of the fluoro-carbonate additive is 0.2-10 weight parts; the addition amount of the nitrile additive is 0.2-10 weight parts; the addition amount of the bi(polyfluoroalkoxy sulfonyl) imine lithium salt is 0.2-10 weight parts; the addition amount of the common lithium battery electrolyte additive is 0-10 weight parts; the solvent refers to cyclic carbonate and/or chain carbonate; and the molar concentration of the inorganic lithium salt in the solvent is 0.8-1.5mol/L. According to combined use of the sultone additive, the fluoro-ester carbonate additive, the bi(polyfluoroalkoxy sulfonyl) imine lithium salt and the organic tri-nitrile additive, the oxidation resistance of the SEI film during primary formation of the electrolyte can be improved, and the normal-temperature and high-temperature cycle performance of the high-voltage electrolyte is obviously improved.

Description

[Technical field] [0001] The invention relates to an electrolyte for lithium ion batteries, in particular to a non-aqueous electrolyte for high voltage lithium ion batteries. [Background technique] [0002] Lithium-ion battery cathode materials currently used, such as LiCo0 2 , LiMn 2 O 4 ,LiCoNiMnO 2 ,LiFePO 4 When the working voltage is lower than 4V, the gram capacity is 90-150mg / g. There are two main ways to improve the energy density of batteries. One is to increase the charge cut-off voltage of traditional cathode materials. For example, by increasing the charging voltage of lithium cobalt oxide to 4.35V or 4.4V, the capacity of the battery can be increased by about 15%. However, the method of increasing the charge cut-off voltage is limited, and further improvement will lead to excessive delithiation of lithium cobalt oxide, reducing the stability of the structure. The other is to use materials with higher capacity, such as silicon or some alloy materials, but a...

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Problems solved by technology

However, the method of increasing the charging cut-off voltage is limited. Further improvement will lead to excessive delithiation of lithium cobalt oxide, and the stability of the structure will be reduced.

The other is to use higher-capacity materials, such as silicon or some alloy materials, but at present, these materials have very poor compatibility with the electrolyte, and the cycle performance is difficult to guarantee

[0003] However, with the increase of operating voltage and charge cut-off voltage, the oxidation activity of the positive electrode material increases, and the reaction between the positive electrode active material and the electrolyte also accelerates, resulting in severe gas swelling of the battery under high voltage and a decrease in cycle performance, which seriously restricts the battery life. The performance of positive electrode materials

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