A kind of porous graphite and porous silicon composite negative electrode material and its preparation method and application

Abstract

The invention discloses a method for preparing a composite negative electrode material of porous graphite and porous silicon, which comprises: (1) washing biomass with high silicon content with deionized water and soaking it in alkaline solution; (2) washing the biomass with high silicon content The biomass was suction filtered, washed with deionized water, dried to obtain dry biomass materials, crushed, and sieved to obtain micron-sized biomass materials; (3) micron-sized biomass materials were carried out under the protection of inert gas The temperature is raised stepwise to make the porous carbon highly graphitized and the simple porous silicon highly crystallized; (4) the graphitized product is taken out after being cooled to normal temperature under the protection of an inert gas; (5) the porous graphite is combined with the porous silicon The material is uniformly mixed in a weak acid solution, and the remaining metal ions are washed away, then washed to neutrality with deionized water, and dried to obtain a composite negative electrode material of porous graphite and porous silicon; the silicon dioxide is fully exposed by stepwise heating, The carbothermal reduction reaction is more thorough to increase the specific surface area and the proportion of silicon element content.

Description

technical field [0001] The invention relates to the technical field of battery negative electrode materials, in particular to a composite negative electrode material of porous graphite and porous silicon, a preparation method and application thereof. Background technique [0002] At present, lithium-ion batteries are one of the most attractive energy storage devices today due to their high energy density, long life, and environmental friendliness, and they are playing an increasingly important role in modern society. They have captured the market for portable electronics such as cell phones, laptops and digital cameras. They are also identified as a power source option for electric vehicles and stationary energy storage. However, the current state-of-the-art lithium-ion batteries cannot meet the growing demands of electric vehicles and large-scale energy batteries. Silicon is considered the most promising candidate to replace graphite. It is the second most abundant eleme...

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Problems solved by technology

[0005] The existing preparation method of silicon-oxygen-carbon composite negative electrode materials for lithium batteries is divided into two parts, one part is to reduce silicon dioxide into silicon-oxygen compounds through simple and easy-to-operate reduction means, and the other part is to generate dense carbon by mechanically mixing with carbon materials. The coated SiOx@G composite anode material, the prepared SiOx@G composite anode material has a discharge capacity of 681mA h / g after 200 cycles, which reflects excellent cycle performance. Some metal elements exposed at high temperature are removed, and there are potential safety hazards during battery testing. Moreover, the specific surface area and silicon content of the prepared composite negative electrode material are relatively low, and the theoretical specific capacity is low. It can be used as a lithium battery negative electrode Material performance is poor

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