A kind of electrolyte solution suitable for silicon carbon negative electrode lithium ion battery and silicon carbon negative electrode lithium ion battery

Abstract

The invention relates to the technical field of lithium ion batteries, in particular to an electrolyte suitable for a silicon-carbon negative electrode lithium ion battery and the silicon-carbon negative electrode lithium ion battery. The electrolyte suitable for the lithium ion battery is prepared from a non-aqueous organic solvent, lithium salt and additives. The additives comprise fluoroethylene carbonate, tris(trimethylsilyl) borate and a sulphate compound with the formula (1) or the formula (2). Compared with the prior art, under the synergistic effect of the three additives in combined use, the capability of changing and controlling SEI composition and stability is achieved, the overall impedance of a formed SEI film is small, and the components and the structure of the SEI film are stable, so that the reversible capacity of the silicon-carbon negative electrode lithium ion battery is greatly increased, the actual discharge capability of the silicon-carbon negative electrode lithium ion battery is greatly improved, then the battery has good cycle performance and good high-and-low temperature performance, and it is guaranteed that the battery can be used within a wide ambient temperature range.

Description

technical field [0001] The invention relates to the technical field of lithium-ion batteries, in particular to an electrolyte suitable for a silicon-carbon negative electrode lithium-ion battery and a silicon-carbon negative electrode lithium-ion battery. Background technique [0002] Lithium-ion batteries are widely used in 3C digital products, electric vehicles, military aerospace and other fields due to their high working voltage, high energy density, long cycle life, and environmental friendliness. With the improvement of people's living standards, higher requirements are placed on the energy density and working environment of lithium-ion batteries. [0003] The energy density of negative electrode materials is an important factor restricting the energy density of lithium-ion batteries. At present, the gram capacity of commercial graphite negative electrodes is close to the theoretical value of 372mAh / g. The theoretical gram capacity of elemental silicon anode can reach...

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Problems solved by technology

For example, fluoroethylene carbonate (FEC) can form a uniform, stable and thin SEI film on the surface of the negative electrode, vinylene carbonate (VC) also has a good film-forming effect, but the SEI film formed by VC is relatively thick , resulting in higher battery impedance and more irreversible capacity loss of the battery

[0006] Due to the particularity of silicon-carbon anode materials, the electrolyte system often requires more film-forming additives than graphite anode systems, and usually requires the use of a large amount of FEC additives. Since FEC is easily decomposed by heat in a high-temperature environment, it cannot meet the high-temperature use of batteries. Require

In the prior art, although the combined use of FEC and VC can improve the cycle life and high-temperature performance of the battery, experiments have found that when the combination of FEC and VC is used, the irreversible capacity loss of the battery is large, and the impedance of the battery is relatively low when discharged in a low-temperature environment. High, its discharge platform is very low, and the thermal stability of VC itself is not very good, it cannot meet the long-term use in high temperature environment

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