Nano-silicon-carbon compound and preparation method and application thereof

Abstract

The invention belongs to the comprehensive technical field of biological waste resources, and in particular a nano-silicon-carbon compound and a preparation method and application thereof. The preparation method comprises the following steps: performing acid-cooking on silicon-containing biomass to remove inorganic ion impurities, cleaning and drying the silicon-containing biomass, and then grinding the biomass into powder; carbonizing the biomass in an inert atmosphere to obtain a compound product of silicon dioxide and carbon; and uniformly mixing the carbonized product, metal powder and anhydrous chloride metal salt, placing the mixture in a tubular furnace, and obtaining a nano-silicon-carbon compound material with silicon nano-particles uniformly distributed in the carbon by reaction in the inert atmosphere. The method disclosed by the invention is simple and easy to implement, the raw material is rich in source, the most important is that the added anhydrous chloride enables the reaction to be generated in an extremely low temperature; the preparation process of the super-thin nano-silicon has the features of being low in energy consumption, simple in process, small in pollution, high in product purity, and uniform in particle; and the obtained silicon nano-particle is uniform in particle size and distribution, and can be applied to the field of a negative electrode material of a lithium ion battery.

Description

technical field [0001] The invention belongs to the technical field of comprehensive biological waste resources, and in particular relates to a nanometer silicon-carbon composite and its preparation method and application. Background technique [0002] As a green energy storage device, lithium-ion batteries have the advantages of high operating voltage, high energy density, and low self-discharge rate, and are widely used in various portable electronic devices. The theoretical lithium storage capacity of silicon (Si) is as high as 4200mAh / g, which is more than 10 times the theoretical capacity of graphite, the mainstream commercial material, and the voltage platform of Si is slightly higher than that of graphite, so it is not easy to cause the phenomenon of lithium precipitation on the surface during charging, and the safety performance It is superior to graphite-based C anode materials, so silicon is expected to replace commercial graphite as the anode material for next-gen...

AI Technical Summary

Problems solved by technology

However, there are some very obvious deficiencies in silicon anode materials: First, lithium ions (Li + ) into the Si negative electrode can form an alloy phase volume expansion of up to 420%, making the internal stress of the material as high as 1-2GPa, resulting in the pulverization of the Si active material, separation of the electrode material and the current collector, resulting in a rapid decline in electrode cycle performance; secondly, Si has a low intrinsic conductivity of 6.7x10 -4 S / cm, which limits its rate performance under high current charge and discharge conditions

[0003] The preparation of silicon-carbon composite electrode materials in the current literature and patents is achieved by a multi-step method. First, silicon or carbon is synthesized, and then another component is loaded by physical and chemical methods. The commonly used method is pyrolysis. , ball milling method, vapor deposition method and polymerization-pyrolysis method, etc. The silicon-carbon composite materials obtained by these methods have poor uniformity, high cost, serious pollution, and large-scale production cannot be realized.

[0004] In addition, there are many reports in the literature that silicon oxide can be reduced to silicon at relatively low temperatures (above 650°C) by using magnesia, thermite and other reactions. However, these methods have problems such as insufficient silicon reaction and easy agglomeration of the formed silicon, which require follow-up The impurity removal step, therefore not only increases the production cost, but also makes the performance of the prepared product unsatisfactory

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