Lithium-ion battery anode material

Abstract

The invention provides a negative electrode material for a lithium ion battery. The negative electrode material has a silicon nitride structure mainly composed of β-phase silicon nitride, and the silicon nitride contains more than 50 wt% of the β-phase silicon nitride. The β-phase silicon nitride has a layered hexagonal crystal structure. Because of its layered characteristics, it facilitates the insertion and extraction of lithium ions, reduces the lithium dendrite (Lithium Dendrites) structure due to the inability to insert lithium ions smoothly, and Due to the stable structure and size during charging and discharging, it can greatly reduce the decline in capacitance caused by material breakage and disintegration, so as to improve the cycle life. The β-phase silicon nitride disclosed in the present invention has a chemical formula of β-Si3Nx, where 1≦x≦4, and due to the low nitrogen atomic weight percentage, the β-phase silicon nitride (β-Si3Nx) has unstable dangling bonds , unsaturated bonds and other unpaired bonds can improve the activity and capacitance of negative electrode materials.

Description

technical field [0001] The invention provides a lithium ion battery negative electrode material, in particular to a β-phase silicon nitride lithium ion battery negative electrode material including unsaturated bonds. Background technique [0002] Lithium-ion batteries have been widely used in electronic products, but with the development of science and technology, they can no longer meet the needs of high-capacity batteries. Silicon-based negative electrode materials have high capacitance characteristics, up to 4200mAh / g, which is the negative electrode material with the highest capacity today. , but there are shortcomings of the negative electrode material being broken and pulverized after intercalation and intercalation of lithium ions. In order to solve the above problems, many studies have modified and modified silicon-based materials in terms of composition and structure. Among them, the modification of the composition is that silicon and one or more non-silicon atoms a...

AI Technical Summary

Problems solved by technology

In the above patents, silicon nitride is mainly used as an auxiliary and buffering material for negative electrodes, and cannot increase the capacity of lithium-ion batteries, and its effect on improving the cycle life of lithium-ion batteries is limited.

[0004] From the change in the appearance of silicon nitride, the molding technology can be used to make silicon nitride in a columnar or hollow nanotube structure, and the surrounding space is reserved, which can make the volume expansion of lithium ion intercalation and intercalation easy, and achieve stability. cycle life[8-10], but it still has structural strength defects. Under the lithium ion intercalation and intercalation reactions, the volume expansion and contraction will concentrate on the contact surface of the negative electrode material and the current collector due to stress, and the negative electrode material At the top position, there are problems such as cracking and pulverization, which will reduce the capacitance and cycle life of the negative electrode material.

[0005] Although it is mentioned in the existing literature that the crystal phase structure of silicon nitride is used as the negative electrode material [11-12], there is no specific mention of the crystal structure and composition of the silicon nitride, and its proportion range, α-phase silicon nitride It is a trigonal crystal structure, and the steric barrier of its crystal lattice is larger than that of the layered structure of β-phase silicon nitride, which affects the intercalation and intercalation of lithium ions, and is not conducive to the capacitance and cycle life of negative electrode materials.

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