Core-shell structure Si/C material, preparation method and application

Abstract

The invention belongs to the field of lithium ion batteries and particularly relates to a preparation method of a core-shell structure Si / C material. The method comprises the following steps of (1) preparing Fe(NO3)3 solution; (2) uniformly stirring Si powder in the solution to form turbid liquid; (3) dropping liquid nitrogen into the turbid liquid to form icy Si / Fe(NO3)3; (4) carrying out vacuum freeze drying to obtain an Si / Fe(NO3)3 sample; (5) carrying out high-temperature carbon coating on the Si / Fe(NO3)3 sample to obtain Si / C powder including Fe3O4; and (6) carrying out acid pickling and drying to obtain the core-shell structure Si / C material. The invention also discloses the core-shell structure Si / C material and application thereof. The core-shell structure Si / C material prepared by the method of the invention has excellent electrochemical performance, no high-concentration acetylene and professional CVD device and higher operability and safety.

Description

technical field [0001] The invention belongs to the field of lithium-ion batteries, and more specifically relates to a core-shell structure Si / C material and its preparation method and application. The core-shell structure Si / C material is especially suitable for lithium-ion batteries Negative material. Background technique [0002] As early as the emergence of Si-based negative electrode materials, Si / C composite materials were considered the most potential Si-based materials. Carbon materials have good electrical conductivity and cycle stability. Carbon in Si / C materials can improve the performance of Si-based materials. The role of conductivity, stabilizing the SEI film and buffering the volume effect. [0003] The earliest preparation of Si / C composite materials is mainly the composite of simple Si and carbon source. Kumta and Kim et al. used polystyrene (PS) as C source, Si powder as Si source, and prepared Si / C composite by high-energy ball milling in an inert atmosph...

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Problems solved by technology

[0004] According to the above research, the core-shell structure Si / C composite has excellent electrochemical performance. However, when preparing the core-shell structure Si / C composite, the decomposition of the polymer to form a carbon layer requires a special polymer coating method. Compared with the general use of acetylene gas to wrap carbon, the use of acetylene to wrap carbon to prepare Si / C composites with a core-shell structure has the following problems: (1) A high concentration of acetylene gas is required during the preparation process, so the preparation method is very complicated and unsafe , (2) low concentration C 2 h 2 It is difficult for gas to deposit directly on the Si surface, therefore, C 2 h 2 When the gas is low, the performance of the prepared material is difficult to meet the needs of use (3) The preparation method has a long synthesis process and requires a professional CVD device, which increases the cost and difficulty of preparation

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