Graphite/silicon@carbon core-shell structure composite spherical cathode material and preparation method thereof

Abstract

The invention discloses a graphite/silicon@carbon core-shell structure composite spherical cathode material and a preparation method thereof. By means of the material, the volume expansion effect of silicon in the lithium de-intercalation process can be inhibited, and a high-capacity lithium iron battery silicon/carbon composite cathode material is obtained. By means of the technical scheme, a spherical graphite/silicon framework precursor serves as the core of the composite cathode material, and an amorphous pyrolytic carbon or graphite-like carbon material wrapping layer serves as the shell; nanometer or micrometer silicon is embedded in flake graphite cracks to form a graphite framework, the volume expansion effect of silicon in the lithium de-intercalation process is inhibited through the mechanical characteristics of the graphite framework, then a spherical framework is formed by mixing and granulating 3-20 wt% of nanometer or micrometer silicon, 50-80 wt% of flake graphite and 10-40 wt% of amorphous pyrolytic carbon or graphite-like carbon, and an amorphous pyrolytic carbon or graphite-like carbon spherical composite conductive carbon net structure wrapping a graphite/silicon surface is formed.

Description

technical field [0001] The present invention relates to negative electrode materials in the application field of lithium-ion batteries. Specifically, the present invention relates to a graphite / silicon@carbon lithium-ion battery composite spherical negative electrode material with a core-shell structure and a preparation method thereof. Background technique [0002] Lithium-ion battery is a lithium-ion embedded battery developed on the basis of lithium secondary batteries. Lithium-ion batteries are a new generation of batteries after nickel-cadmium batteries, nickel-metal hydride batteries, and lead-acid batteries. It is widely used in various small portable products such as mobile phones and digital cameras. It also shows good application prospects in the fields of electric vehicles, satellites, aerospace and space military. It has become a new type of green high-energy product with great development potential in the world today. chemical power source. The core and key to...

AI Technical Summary

Problems solved by technology

As a negative electrode material for lithium-ion batteries, silicon has many advantages, but there are also many defects that cannot be overcome at present.

The main problems in the commercial application of silicon anode materials are: ① During the process of lithium deintercalation, the formation of lithium-silicon alloy phase has a serious volume effect, which leads to the collapse of the silicon material structure and the shedding of active materials, which seriously affects the silicon electrode material. The first coulombic efficiency and cycle stability; ②During the charging and discharging process, the silicon and the electrolyte cannot form a stable solid electrolyte film (SEI) on the electrode surface after the reaction, resulting in the continuous decay of the reversible capacity of the silicon material

Moreover, silicon and carbon will form SiC at 1000°C, resulting in capacity loss

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