Preparation method for double-layer carbon coated metal sulfide composite electrode material with core-shell structure

Abstract

The invention discloses a preparation method for a double-layer carbon coated metal sulfide composite electrode material with a core-shell structure. An amorphous carbon material is arranged on an outer layer of the composite electrode material and a nitrogen-doped carbon coated metal sulfide is arranged on an inner layer. The preparation method disclosed by the invention is simple and feasible. The double-layer carbon coated metal sulfide composite electrode material with the core-shell structure is acquired according to the following steps: adopting a room temperature aggregation method foracquiring a polypyrrole coated Co9S8 precursor, and then taking a shielding gas as a carrier gas for uniformly filling ethyl alcohol into a tube furnace, and performing thermal treatment. When the composite material prepared according to the method is used as a cathode material of a lithium ion secondary battery, the outer layer carbon is capable of effectively inhibiting the direct contact between active material metal sulfide and electrolyte, so that the initial coulombic efficiency and cycle performance of the composite material are promoted. Meanwhile, the nitrogen-doped carbon material isintroduced, so that the conductivity of the material is further promoted, the huge volume expansion of the metal sulfide in charging and discharging processes is relieved and the structural stabilityand rate capability of the composite material are greatly improved.

Description

technical field [0001] The invention relates to the technical field of lithium ion batteries. Specifically relates to a preparation method of a double-layer carbon-coated metal sulfide composite electrode material with a core-shell structure. Background technique [0002] Due to its high energy density and safety, lithium-ion secondary batteries are attracting more and more attention along with the popularization of electric (hybrid) vehicles. Although graphitic carbon materials are widely used as anode materials for commercial lithium-ion batteries due to their good cycle performance, their low theoretical specific capacity cannot meet the increasing demand for energy, especially power energy, in today's society. Metal sulfides have a high theoretical capacity (such as Co 9 S 8 544mAh / g, CoS589mAh / g, CoS 2 871mAh / g and Ni 2 S609mAh / g), low price, and low pollution have attracted extensive research by researchers, and are considered to be one of the more promising anode...

AI Technical Summary

Problems solved by technology

One is to nanosize the metal sulfide material, and reduce the internal stress generated during the charge and discharge process by shortening the transmission path of lithium ions and electrons, thereby improving the cycle stability and rate performance of the material. However, in fact, the nanoparticles directly interact with the electrolytic The contact with the liquid will catalyze the decomposition of the electrolyte, resulting in an increase in the irreversible capacity and low Coulombic efficiency. In addition, due to the large specific surface area and high specific surface energy of the nanoparticles, it is easy to cause the particles to agglomerate into large inactive clusters, which will affect the performance of the material. capacity and performance; the second is to combine the metal sulfide with an inactive matrix such as carbon material, and use the hardness and strength of carbon to suppress the volume change and mechanical stress of the active component during charge and discharge. At the same time, the carbon material itself is good Conductive properties, improve the overall performance of the material

At present, the synthesis of metal sulfide / carbon composite materials usually adopts the method of physical mixing or chemical compounding. Although the above-mentioned method improves the electrochemical performance of the composite material to a certain extent, due to the limitation of the method, it is inevitable that the surface of the carbon material There will be some metal sulfide nanoparticles that are not fully coated, and the direct contact of these active particles with the electrolyte will cause side reactions to occur, and at the same time, they will fall off the surface of the carbon-based material due to the repeated expansion / contraction of its volume during the cycle. resulting in reduced performance

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