Preparation method and application of high-stability silicon-based composite material constructed by in-situ fluorination

Abstract

The invention discloses a preparation method and application of a high-stability silicon-based composite material constructed through in-situ fluorination, the silicon-based composite material comprises an inner core silicon-based material and an outer fluorine-containing coating layer, and the thickness of the fluorine-containing coating layer is 1-10 nm; the fluorine-containing coating layer is lithium fluoride (Li2CO3-LiF) doped with lithium carbonate, and the fluorine-containing coating layer is obtained by carrying out an in-situ fluorination reaction on the surface of the silicon-based material through a fluorination reagent. The fluorine-containing coating layer is a stable coating layer constructed by performing in-situ fluorination on the surface of the silicon-based material through a fluorination reagent. Through an in-situ fluorination method, surface residual salt is directly converted into lithium fluoride, and a stable coating layer structure is constructed while the alkalinity of the material is reduced. The silicon-based composite material provided by the invention has high slurry stability when being used as a lithium ion battery negative electrode material, shows excellent interface stability in an electrochemical cycle process, and prolongs the cycle life of a battery.

Description

Technical field [0001] The present invention belongs to the technical field of the battery, and in particular, the preparation method and application of the in situ fluorinated construction of high stability silicon-based composites. Background technique [0002] With the continuous development and shortage of energy, the development of lithium-ion batteries has attracted attention. The lithium-ion battery is generally a positive electrode material using a lithium alloy metal oxide, graphite is a negative electrode material, and a nonaqueous electrolyte battery is used. However, due to the pursuit of high energy density, the graphite negative poor theory is less than the market demand, so the research on high-performance negative materials is also continuously promoted. At present, due to the wide recognition of silicon negative electrode materials (4200 mAh / g) with high theoretical comparison capacity, due to large volume changes of silicon cause particle break, loss of electr...

AI Technical Summary

Problems solved by technology

[0004] In the existing silicon-based negative electrode fluorination modification, most of them react with fluorinating reagents to form lithium fluoride by adding lithium salts, magnesium salts, and sodium salts, which will introduce a large amount of inert substances to the material itself, which is a negative effect on the material itself. This simple coating method has the problem of uneven coating, and the formed lithium fluoride layer has poor density, which has little effect on improving the stability of the negative electrode material.

The existing fluorination technology is to build a fluoride interface on the surface of the material by adding additional lithium salt and fluorine source. The coating layer of lithium fluoride obtained by this method is not uniform, and it increases the production cost, and cannot improve the defects of the material itself. Solve the problem of high residual alkali concentration on the surface and poor stability of negative electrode materials

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