Yolk-shell type carbon-coated silicon composite negative electrode material and preparation method thereof

Abstract

The invention relates to a yolk-shell type carbon-coated silicon composite negative electrode material and a preparation method thereof.The preparation method comprises the steps that firstly, silicon alloy powder and a carbon material are mixed and dispersed under the action of a binder acrylonitrile-acrylic acid copolymer, and carbon material-coated silicon alloy composite powder is obtained; carrying out heat treatment on the composite powder in an inert atmosphere to carbonize the binder; the composite powder subjected to heat treatment is added into metal corrosion liquid to be stirred and dispersed, and metal in the composite powder is removed; and sequentially filtering, washing and drying the metal-removed composite powder, and finally carrying out heat treatment to completely carbonize organic matters in the compound, thereby obtaining the yolk-shell type carbon-coated silicon composite negative electrode material. The preparation method of the yolk-shell type carbon-coated silicon composite negative electrode material is low in cost and easy to implement, the prepared composite negative electrode material is of a yolk-shell type structure and is applied to a lithium ion battery, and the battery is high in capacity and good in cycle performance.

Description

technical field [0001] The invention belongs to the technical field of negative electrode materials for lithium ion batteries, and in particular relates to a yolk-shell carbon-coated silicon composite negative electrode material and a preparation method thereof. Background technique [0002] Due to the advantages of high working voltage, high energy density and long cycle life, lithium-ion batteries have become ideal power sources for portable electronic devices, electric vehicles and energy storage systems. It is important to develop new electrode materials with high specific energy, good safety and low cost. The core content of lithium-ion battery research field. At present, the main anode material of commercial lithium-ion batteries is graphite. Due to its low theoretical capacity (372 mAh / g) and poor high-rate charge-discharge performance, the further improvement of lithium-ion battery energy is limited. [0003] Silicon has a very high theoretical specific capacity (42...

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Problems solved by technology

However, silicon undergoes a huge volume change during the lithium intercalation and desorption cycle, which leads to the deterioration of the electrode structure, which in turn leads to a rapid decline in its capacity, which limits the practical application of silicon materials.

[0004] In order to buffer the volume change of silicon in battery applications, the common methods are: (1) Carbon coating (such as patents CN101710617A, CN105576209A, CN101244814A). Carbon materials are often It is used as a cladding material, but it needs to use nano-scale silicon powder to avoid the silicon particles from breaking themselves under expansion / shrinkage stress, and the cost of nano-silica powder is extremely high; (2) use low-cost silicon oxide materials and their Carbon coating (such as CN103474631A, CN103035917B, CN103219504A), silicon oxide is converted into elemental silicon with lithium storage capacity when the battery is formed, and the associated lithium silicate and lithium oxide become the buffer coated on the outside of silicon, However, the reduction of silicon oxide to silicon requires additional energy, which makes the first charge and discharge efficiency of this type of material low, and the lithium silicate and lithium oxide produced are electrical insulators, which affect the charge transport in the electrode.

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