Lithium ion battery non-aqueous electrolyte, lithium ion battery negative electrode and lithium ion battery comprising negative electrode

Abstract

The invention proposes a silicon negative electrode lithium ion battery non-aqueous electrolyte, a lithium ion battery negative electrode and a lithium ion battery comprising the negative electrode. The non-aqueous electrolyte comprises a lithium salt, a non-aqueous solvent and a film formation additive, wherein the film formation additive is silane having a structure shown in a formula (1), the formula (1) is shown in specification, M is chained alkyl-Cn<1>H<2n1+1>, and R1, R2 and R3 are same and are one of -C1, -F, chained alkoxy-C<n2>H<2n2+1>O and amino-H<2>N(CH<2>)<n3>; or the M is chained amino-H<2>N(CH<2>)<n1'>, the R1, the R2 and the R3 are same and are one of -C1, -F and chained alkoxy-C<n2>H<2n2+1>O, 1<=n1<=20, 3<=n1'<=20, 1<=n2<=4, and 2<=n3<=15. By adding the silane film formation additive with the structure into the electrolyte, the problem of film breakage due to a volume expansion effect of the silicon negative electrode in an existing lithium ion battery is solved.

Description

technical field [0001] The invention belongs to the field of lithium ion batteries, and in particular relates to a nonaqueous electrolyte solution of a silicon negative electrode lithium ion battery, a lithium ion battery negative electrode and a lithium ion battery containing the negative electrode. Background technique [0002] In the prior art, silicon-based materials (silicon, silicon alloys, and silicon-carbon composites) have ultra-high theoretical specific capacity and suitable operating voltage at room temperature. Therefore, silicon negative electrodes are likely to be used in next-generation lithium-ion batteries. On the other hand, compared with graphite electrodes, silicon electrodes have larger volume changes during charging and discharging, and the silicon surface has a stronger reactivity with the electrolyte. After cycling, the reduction reaction of the electrolyte still occurs on the surface of the silicon electrode. Therefore, these reactions will aggravate...

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Problems solved by technology

[0002] In the prior art, silicon-based materials (silicon, silicon alloys, and silicon-carbon composites) have ultra-high theoretical specific capacity and suitable operating voltage at room temperature. Therefore, silicon negative electrodes are likely to be used in next-generation lithium-ion batteries. On the other hand, compared with graphite electrodes, silicon electrodes have larger volume changes during charging and discharging, and the silicon surface has a stronger reactivity with the electrolyte. After cycling, the reduction reaction of the electrolyte still occurs on the surface of the silicon electrode. Therefore, these reactions will aggravate the loss of the specific capacity of the electrode when there is no SEI passivation film on the electrode surface or the SEI passivation film is not completely covered.

[0003] According to further research, if silicon is used as the negative electrode active material, the anion of silicon and lithium salt in the electrolyte (such as PF 6 − ) is more reactive than the organic solvents in the lithium battery electrolyte (such as ethylene carbonate (EC), diethyl carbonate (DEC), etc.); silicon and lithium salts in the electrolyte anions (such as PF 6 − ) will generate stable phosphorus-fluorine compounds, and the silicon electrodes covered by these phosphorus-fluorine compounds can no longer react with lithium, resulting in a decrease in the specific capacity of the battery; therefore, in order to prevent the silicon electrode and electrolyte between Direct reaction, the modification of the SEI layer between the electrode / organic electrolyte interface is particularly necessary

[0004] At present, most researchers still use vinylene carbonate (VC) or other film-forming additives in the electrolyte as the film-forming additives for silicon negative electrodes, and the film-forming principles of such film-forming additives are roughly the same. A reduction reaction occurs under the potential and a protective film is formed on the negative electrode; this type of method has a big problem, because the silicon negative electrode will undergo obvious volume expansion during the intercalation and extraction of lithium ions, which makes the surface of the negative electrode The formed protective film ruptures due to the volume expansion of silicon. During the next charging and discharging process of the lithium battery, the ruptured part of the protective film will have a side reaction with the electrolyte and consume the electrolyte, thus forming a vicious circle.

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