Porous silicon negative electrode material covered by composite carbon and preparing method thereof

Abstract

The invention discloses a porous silicon negative electrode material covered by a composite carbon layer and a preparing method thereof. On the basis of porous silicon after dealloying, the first covering of loose carbon and overall covering of exterior high-density carbon are achieved by covering a compounded carbon layer in which graphene and the high-density carbon are combined or low-density carbon and the high-density carbon are combined, interior low-density carbon can improve interior electrical conductivity of a whole micron structure, and the exterior high-density carbon can well prevent an electrolyte from penetrating through the carbon layer and entering the interior of micron particles, accordingly well solve the problem that a silicon material reacts with a battery liquid, ensure a high coulombic efficiency, and accordingly well ensure cycle performance of a battery. According to the porous silicon negative electrode material covered by the composite carbon layer and the preparing method thereof, a core innovation point is double carbon layer covering, and the silicon / carbon / carbon composite negative electrode material is prepared by combining the low-density carbon and the high-density carbon.

Description

technical field [0001] The invention relates to the preparation of battery electrode materials, in particular to a composite carbon-coated porous silicon negative electrode material and a preparation method thereof. Background technique [0002] In recent years, electronic equipment is developing toward intelligence, multi-function and portability, and the requirements for battery technology are getting higher and higher. First, light electronic devices require light batteries to keep the overall mass of the device at a low level. Secondly, the capacity of the battery should be high enough to meet the long-term operation of electronic equipment. Therefore, the high specific energy lithium-ion battery industry came into being. Lithium-ion batteries have become ideal supporting power sources for portable electronics, mobile products, and electric vehicles due to their high voltage, high specific energy, long cycle life, and environmental friendliness. [0003] Lithium-ion b...

AI Technical Summary

Problems solved by technology

[0005] But silicon also has an Achilles' heel: ① As a semiconductor material, silicon is far less conductive than graphite

②The silicon material is dense, and compared with the relatively fluffy graphite, the penetration ability of lithium ions is poor

Although this invention improves the rate performance of the material through the compounding of silicon and graphene, the problem of direct contact between silicon and electrolyte still exists. performance degradation

[0008] In the previous patent "a graphene-coated porous silicon material and its preparation method", the applicant of this patent used the in-situ reduction of aluminum to realize the coating effect of graphene on porous silicon particles, but in the subsequent dealloying During the chemical reaction, the reaction between aluminum and acid will generate a large amount of hydrogen gas, and the removal of hydrogen gas will partly cause the loosening of the graphene coating layer on the silicon surface. During the subsequent battery cycle, part of the electrolyte will still enter the material. The interior of the silicon, affecting the cycle of silicon

[0009] To sum up, in the prior art, problems such as the poor electrical conductivity of the porous silicon negative electrode material itself, the sharp reduction in battery capacity caused by the dramatic volume change in the electrochemical deintercalation during charging and discharging, and the reaction with the electrolyte affecting the Coulombic efficiency of the battery have not yet been solved. lack of effective solutions

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