Preparation method of silicon/porous carbon nano-composite particle

Abstract

The invention discloses a preparation method of a silicon / porous carbon nano-composite particle, comprising the following steps: dispersing silica beads, hexachlorocyclotriphosphazene and 4,4'-dihydroxydiphenylsulfone into an organic solvent under an ultrasound condition, then adding triethylamine, an acid binding agent, into the solvent for ultrasonic reaction at a temperature of 20-40 DEG C for 6-10h, and after the reaction, obtaining a core-shell structured silicon / polyphosphazene nano-composite particle through the processes of centrifugal separation, washing and vacuum drying; transferring the obtained silicon / polyphosphazene nano-composite particle into a quartz tube type carbonizing plant, under the protection of inert atmosphere, heating up the plant at a rate of 1-5 DEG C / min and insulating the plant at a temperature of 600 DEG C for 2h, then continuing heating up the plant at a rate of 1-5 DEG C / min to a preset temperature of 700-1000 DEG C and insulating the plant for 5h, then naturally cooling the plant to room temperature, thus obtaining the silicon / porous carbon nano-composite particle. The silicon / porous carbon nano-composite particle has the core-shell structure with the silica beads as the core and the porous carbon as the shell. The specific capacity of lithium-ion batteries using the silicon / porous carbon nano-composite particle as the anode material is higher than 950mAh / g, the initial efficiency thereof reaches 73% and the capacity decrease after 40 cycles is as low as 7.5-38%, therefore, the lithium-ion batteries show higher specific capacity, higher initial efficiency and good cycle stability.

Description

Technical field: [0001] The invention relates to a preparation method of nanocomposite microspheres, in particular to a preparation method of silicon / porous carbon nanocomposite microspheres, which are used for negative electrode materials of lithium ion batteries. Background technique: [0002] With the development of industry and the improvement of human material life and spiritual civilization, the demand for energy is also increasing day by day. The energy consumption in the world in the past 25 years is equivalent to the consumption in the past 100 years, and most of these energy sources are natural minerals on the earth. Primary energy produces a large amount of environmental pollution while consuming it. For this reason, green energy represented by lithium-ion batteries has attracted widespread attention from the world, and the preparation of lithium-ion battery anode materials with high specific capacity and good cycle performance is a key to the development of high-...

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Problems solved by technology

Patents CN 1767234A, CN 101244814A, CN 1913200A, CN 101162775A, CN 101153358A, CN 101339987A, etc. have also reported the preparation of silicon-carbon composite materials, but the microstructure of the products obtained by these preparation methods is not perfect. Simple dispersion, even if the coating of silicon with carbon material is achieved, the coating effect is poor, and the silicon content is low, resulting in low lithium storage capacity of silicon-carbon composite materials and insufficient cycle stability

Recently, Chemistry of Materials reported a new strategy for the preparation of silicon / porous carbon composites in 2009, volume 21, pages 6-8, which uses the hydrosilylation reaction of HSi and o-allylphenol to realize the Then the modified silicon balls are mixed with resorcinol and formaldehyde and gelled, and the product is carbonized at high temperature to form a silicon / porous carbon composite system. The structure of porous carbon can well inhibit the silicon material from intercalating. Due to the expansion effect in the delithiation process, this material shows a high lithium storage capacity (640-1029mAh / g) as a negative electrode material for lithium-ion batteries, but the cycle stability needs to be improved

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