Non-aqueous electrolyte and lithium ion battery containing same

Abstract

The invention discloses a non-aqueous electrolyte and a lithium ion battery containing the non-aqueous electrolyte. The non-aqueous electrolyte comprises a sulfonamide additive. Furthermore, the non-aqueous electrolyte also comprises an ester additive. In the electrolyte provided by the invention, the sulfonamide additive can be oxidized into a CEI film with good high-temperature stability on the surface of a positive electrode so as to inhibit the catalytic oxidation decomposition of a high-nickel positive electrode material on the electrolyte. Besides, the sulfonamide additive and the ester additive are matched with each other, so that the acidity of the electrolyte is inhibited from being increased, the ester additive can be reduced into an SEI film with good mechanical property on the surface of the negative electrode, and the normal-temperature circulation, high-temperature circulation and high-temperature storage performance of the battery are remarkably improved through the mutual synergistic effect of the sulfonamide additive and the ester additive.

Description

technical field [0001] The invention belongs to the technical field of batteries, and in particular relates to a nonaqueous electrolytic solution, a preparation method thereof and a lithium ion battery containing the nonaqueous electrolytic solution. Background technique [0002] Using high-nickel materials as the positive electrode of lithium-ion batteries and using silicon-carbon composite materials as the negative electrode can significantly increase the specific energy of the battery. However, in a lithium-ion battery system using high-nickel materials as the positive electrode and silicon-carbon composite materials as the negative electrode, due to the increase in the Ni content in the high-nickel material, and during the charging process, with the increase of the charging voltage, the high-nickel material positive electrode Surface Ni 3+ and Ni 4+ content increased due to the Ni 4+ It has strong oxidizing properties, which will not only react with the electrolyte, d...

AI Technical Summary

Problems solved by technology

However, in a lithium-ion battery system using high-nickel materials as the positive electrode and silicon-carbon composite materials as the negative electrode, due to the increase in the Ni content in the high-nickel material, and during the charging process, with the increase of the charging voltage, the high-nickel material positive electrode Surface Ni 3+ and Ni 4+ content increased due to the Ni 4+ It has strong oxidizing properties, which will not only react with the electrolyte, destroy the function of the electrolyte, but also cause the positive electrode material to decompose and decompose O at low temperature. 2 , generate a lot of heat, and then under high temperature conditions, the electrolyte will decompose and generate a lot of gas, which will bring safety hazards to the battery

Moreover, the surface of the high-nickel ternary positive electrode material is highly alkaline, and at the same time, during the charging and discharging process, especially under high temperature conditions, metal ions (such as Co, Mn, Ni) in the positive electrode material are prone to dissolve into the electrolyte, while The dissolved metal ions have strong catalytic activity and can cause side reactions with the electrolyte, resulting in a decrease in the high-temperature storage performance and cycle performance of the battery.

Although the silicon-carbon composite negative electrode material has a high specific capacity, due to the huge volume effect of silicon in the process of lithium intercalation and deintercalation, the SEI film on the surface of the negative electrode is continuously destroyed and regenerated, and at the same time, the silicon particles are broken or powdered due to huge stress. It will cause the active material on the silicon negative electrode to fall off, thereby deteriorating the electrical contact between the active material and the current collector, which will lead to an increase in the internal resistance of the battery and poor battery performance.

However, lithium hexafluorophosphate has poor thermal stability and is prone to the following decomposition reactions: LiPF 6 →LiF+PF 5 , resulting in PF 5 The chemical properties are lively, and can react with the proton impurities in the electrolyte, which will cause the acidity and chroma of the electrolyte to rise rapidly, thereby deteriorating the quality of the electrolyte, reducing the cycle performance and high temperature performance of the battery

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