High-temperature-resistant and high-voltage-resistant lithium ion battery electrolyte, and preparation method and application thereof

Abstract

The invention belongs to the field of lithium ion batteries, and particularly relates to a high-temperature-resistant and high-voltage-resistant lithium ion battery electrolyte, and a preparation method and application thereof. The electrolyte comprises an electrolyte salt and an organic solvent, the electrolyte salt is a mixed lithium salt, the HOMO energy level of the mixed lithium salt is higher than that of the organic solvent, and the mixed lithium salt can be decomposed on the surface of a positive electrode in the charging process to form an inorganic unit boundary film. According to the electrolyte disclosed by the invention, a high-voltage-resistant interfacial film containing F, B and P can be formed on a positive electrode by using the mixed lithium salt, and irreversible transformation of a high-nickel ternary positive electrode active material from a layered state to an inert rock salt phase under a high voltage can be inhibited, so that the cycling stability of the lithium ion battery at a normal temperature under a high cut-off voltage of 4.7 V is improved, the capacity retention ratio is still 92% after 180 cycles under the high cut-off voltage of 4.7 V, and the cycle stability of the lithium ion battery under the high temperature of 45 DEG C and the high cut-off voltage of 4.5 V can be improved.

Description

technical field [0001] The invention belongs to the field of lithium-ion batteries, and in particular relates to a high-temperature-resistant, high-voltage lithium-ion battery electrolyte and a preparation method and application thereof. Background technique [0002] Among many cathode materials, the ternary material LiNi x mn y co z o 2 (NMC) has an excellent theoretical specific capacity (270mAh / g), and the high-nickel ternary cathode NMC811 (x≈0.8) has an outstanding reversible capacity, excellent rate performance and satisfactory conductivity (about 2.8×10 -5 S / cm) and lithium ion mobility (about 10 -8 -10 -9 cm 2 / s), thus becoming one of the preferred cathode materials for current commercial electric vehicles. However, the increase of nickel content, the increase of charge cut-off voltage, and the increase of temperature all make the high-nickel ternary cathode-electrolyte interface more susceptible to electrochemical oxidation, the release of oxygen inside the ...

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Problems solved by technology

[0006] Aiming at the deficiencies of the prior art, the present invention provides an electrolyte solution in which a lithium salt is mixed as an electrolyte salt. The mixed lithium salt can be preferentially decomposed in a small amount to form a positive electrode-electrolyte interface film, which can solve the severe decomposition of the electrolyte solution at a high cut-off voltage of 4.7V. It can also solve the problem of high cut-off voltage of 4.5V and more serious side reactions at the positive electrolyte interface at 45°C high temperature, thereby improving the cycle performance of lithium-ion batteries under high voltage / high temperature conditions

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