A kind of silicon composite negative electrode material, preparation method and lithium ion battery

Abstract

The invention relates to a silicon composited negative electrode material, a preparation method of the silicon composited negative electrode material and a lithium ion battery adopting the silicon composited negative electrode material. The silicon composited negative electrode material is of a core-shell structure, the inner core is composed of graphite and a carbon nano tube coated on the surface of the graphite and filled with nanometer silicon, and the shell is a conductive carbon material cladding layer. According to the silicon composited negative electrode material, the high-pressure filling technology is adopted to enable nanometer silicon particles to be filled into the carbon nano tube, and therefore, the dispersibility and the electrical conductivity of the silicon particles are improved; and besides, the surface modification and homogeneous phase wrapping technology is combined to prepare the core-shell silicon composited negative electrode material successfully. According to the preparation method of the silicon composited negative electrode material, silicon, carbon and graphite are composited, silicon expansion and pulverization are inhibited, the cycle performance and the initial efficiency of the material are greatly promoted, and the prepared silicon composited negative electrode material has high compaction density and good processability, is environment-friendly and has no pollution.

Description

technical field [0001] The invention belongs to the field of negative electrode materials of lithium ion batteries, and in particular relates to a silicon composite negative electrode material, a preparation method thereof, and a lithium ion battery using the negative electrode material. Background technique [0002] Lithium-ion batteries have been widely used in portable mobile electronic devices and electric vehicles due to their advantages such as large specific energy, high working voltage, long cycle life, no memory effect, small self-discharge, no pollution and environmental protection. At present, commercial lithium-ion batteries mainly use graphite-based negative electrode materials, but its theoretical specific capacity is only 372mAh / g, which cannot meet the demand for high energy density of lithium-ion batteries in the future. Domestic and foreign research reports, metal elements, metal oxides and metal alloy compounds that can form alloys with lithium, such as Si...

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Problems solved by technology

[0004] For example, CN 101521273A discloses an in-situ synthesis method for preparing tin-carbon / core-shell nanoparticles completely filled with carbon nanotube composite negative electrode materials. The invention utilizes organic gas to crack and grow carbon nanotubes outside the nanoparticles, and the Filled in the diameter of carbon nanotubes, the material obtained by this method has high capacity and good cycle performance, but the growth of carbon nanotubes in this method is difficult to control, the filling amount is relatively low, and the carbon nanotubes filled with active substances are simply used. The cost of tubes as lithium-ion anode materials is relatively high, which is not conducive to commercialization

[0005] CN 103199223A discloses a Cu-Cr-Si ternary negative electrode material and its preparation method. In this invention, copper powder, chromium powder and silicon powder are mixed and calcined to prepare alloy ingots, and then pulverized to obtain Cu- Cr-Si ternary alloy powder, the obtained material has a higher capacity, but the size of the continuous phase formed by silicon and chromium in the ternary material prepared by this method is still large, and the copper, chromium and silicon are not uniformly dispersed, resulting in Large material expansion, poor cycle performance

[0006] CN 103560249A discloses a multi-component composite negative electrode material and its preparation method. In this invention, silicon powder, carbon nanotubes, and expanded graphite are added to polyvinyl alcohol or polyethylene glycol water system, then dried and fired to obtain A multi-component composite material composed of nano-silicon powder, carbon nanotubes, expanded graphite and amorphous carbon, the composite material has good conductivity and high capacity, but it is difficult to fully disperse the nano-silicon powder during the preparation process, resulting in the The first charge and discharge efficiency of the material is low

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