Lithium ion battery negative electrode active material, preparation method thereof, negative electrode and lithium ion battery comprising negative electrode

Abstract

The invention proposes a lithium ion battery negative electrode active material, a preparation method thereof, a negative electrode and a lithium ion battery comprising the negative electrode. The negative electrode active material is of a core-shell structure, wherein the core comprises lithium silicon alloy particles, and the shell is a carbon layer. In the negative electrode active material employing the core-shell structure of which the core is the lithium silicon alloy particles and the shell is the carbon layer, the volume expansion effect of silicon used as the negative electrode can be effectively reduced; and when the negative electrode is applied to the battery, relatively high capacity of the obtained battery can be maintained, and meanwhile, the battery also has good cycle property.

Description

technical field [0001] The invention relates to the technical field of lithium ion batteries, in particular to a lithium ion battery negative electrode active material, a preparation method thereof, a negative electrode and a lithium ion battery containing the negative electrode. Background technique [0002] In the prior art, as the negative electrode active material of lithium-ion batteries, the actual capacity of graphite is close to the theoretical value of 372 mAh / g, but it still cannot meet the high requirements of power battery specific capacity and energy density; while the theoretical capacity of silicon is as high as 4212 mAh / g, so it has received extensive attention in the field of lithium-ion batteries in recent years; the lithium intercalation mechanism of silicon is an alloying mechanism, and its theoretical capacity is calculated in the final lithium intercalation state (Li 22 Si 5 ) when the volume expansion is 400% of the original. Due to the volume expans...

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Problems solved by technology

[0002] In the prior art, as the negative electrode active material of lithium-ion batteries, the actual capacity of graphite is close to the theoretical value of 372 mAh / g, but it still cannot meet the high requirements of power battery specific capacity and energy density; while the theoretical capacity of silicon is as high as 4212 mAh / g, so it has received extensive attention in the field of lithium-ion batteries in recent years; the lithium intercalation mechanism of silicon is an alloying mechanism, and its theoretical capacity is calculated in the final lithium intercalation state (Li 22 Si 5 ) when the volume expansion is 400% of the original. Due to the volume expansion problem, when used as a negative electrode active material, it will seriously cause the powdering and fragmentation of the negative electrode material, and at the same time, the SEI film on the surface of the negative electrode will also be destroyed and regenerated. Eventually, the expansion of the pole piece will be further increased, resulting in a significant decline in the electrode capacity, and the battery cycle performance is extremely poor

[0003] In order to solve the problem of silicon system expansion and make the prepared battery have better cycle performance, the existing technical solution is mainly by adding a small amount (3~10%) of silicon powder, silicon monoxide powder or silicon alloy material to the carbon material. , although this method can increase the specific capacity of the negative electrode material to 400~450mAh / g, the first charge and discharge efficiency of the material will decrease, and if the capacity of the negative electrode material is designed to be greater than 600mAh / g, it is necessary to add 20% The above-mentioned silicon not only greatly reduces the first charge and discharge efficiency of the material, but the large amount of silicon material added has a serious volume expansion problem, which will lead to the destruction of the conductive network of the pole piece and the material falling off from the current collector, resulting in poor cycle performance of the battery, unable to Meet practical needs

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