Preparation method for silicon negative electrode material for lithium ion battery and silicon negative electrode material

Abstract

The invention relates to a preparation method for a silicon negative electrode material for a lithium ion battery and the silicon negative electrode material. The preparation method comprises the following steps of step 1, surface hydroxylation: putting silicon monoxide into a mixed solution of ammonium hydroxide, hydrogen peroxide and water, and then heating, boiling and stirring for 10-60min, next, carrying out water washing, filtering and vacuum drying at a temperature of 80-120 DEG C for 2-12h; step 2, stirring: putting the dried product obtained in the step 1 into an absolute ethyl alcohol solution containing a titanium source, and stirring for 2-10h, then adding water and stirring for 15-75min, next, adding graphite, and then adding an absolute ethyl alcohol solution containing a lithium source, finally adding glacial acetic acid and stirring, and stopping stirring when black sol is changed into gel; step 3, aging and drying: aging the gel generated in the step 2 for 12h or more than 12h, then carrying out vacuum drying on the gel at a temperature of 70-90 DEG C for 8-16h; and step 4, calcining: smashing the gel which is aged and dried in the step 3, and calcining the processed gel under protection of an inert gas atmosphere; and finally, cooling to the room temperature to obtain the silicon negative electrode material.

Description

technical field [0001] The invention belongs to the technical field of lithium ion battery materials, and in particular relates to a preparation method of a silicon negative electrode material for lithium ion batteries and the silicon negative electrode material. Background technique [0002] At present, the lithium-ion batteries used in production mainly use graphite-based negative electrode materials, but the theoretical lithium intercalation capacity of graphite is 372mAh / g, but it has actually reached 370mAh / g. Therefore, there is almost no room for improvement in the capacity of graphite-based negative electrode materials. [0003] Silicon-based materials have attracted attention due to their high theoretical capacity, but they undergo severe volume expansion and contraction during the process of intercalation and delithiation, with a volume expansion rate of >300%, resulting in a significant drop in electrode cycle stability. For suppressing its volume expansion and...

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Problems solved by technology

However, due to the good stability of graphite, it is difficult to form a good contact interface with silicon, so that the silicon is still exposed outside and directly in contact with the electrolyte.

In the subsequent cycle process, due to the serious volume expansion, the SEI film formed on the silicon surface is easily destroyed during the expansion and contraction process, resulting in the continuous exposure of new surfaces on the silicon surface and contact with the electrolyte, which will be released in the next charge and discharge process. A new SEI film is formed in the middle, which eventually leads to a much lower Coulombic efficiency in the subsequent charge and discharge process than the material of amorphous carbon-coated silicon. In addition, when the SEI film is thick enough, the electronic conductivity of the material decreases, which eventually makes it difficult to embed in silicon particles. Lithium, the specific capacity gradually decays

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