Preparation method for tin-carbon composite negative material

Abstract

The invention provides a preparation method for a tin-carbon composite negative material. An outer layer of the tin-carbon composite negative material is a composite cladding layer jointly formed by asphalt, resin and tin powder, and an inner layer is the tin-carbon composite negative material which is composed of graphite and has a core-shell structure. In the tin-carbon composite material prepared according to the method, high specific capacity characteristic of tin is maintained, meanwhile, a modification effect on the graphite is played, the overall cyclic stability of the material is improved, the energy density of the negative material of a lithium ion battery is improved, thus, the negative material has higher specific capacity than the carbon negative material commonly used in the lithium ion battery in the current market, and the increasing energy density requirement of various portable electric devices on the battery is met.

Description

technical field [0001] The invention relates to the field of lithium ion batteries, in particular to a method for preparing a tin-carbon composite negative electrode material used for the negative electrode of a lithium ion battery. The outer layer of the tin-carbon composite negative electrode material prepared by the method is jointly formed by pitch, resin and tin powder Composite cladding layer, the inner layer is a tin-carbon composite negative electrode material with a core-shell structure composed of graphite. Background technique [0002] Since Japan's Sony Corporation took the lead in developing and commercializing lithium-ion batteries in 1990, lithium-ion batteries have developed rapidly. Today lithium-ion batteries have been widely used in various fields of civil and military use. With the continuous advancement of science and technology, people have put forward more and higher requirements for the performance of batteries: the miniaturization and personalized d...

AI Technical Summary

Problems solved by technology

The main problem of the composite material prepared by this method is: due to the large specific surface area and the inability to completely prevent the micro-oxidation during the ball milling process, the first irreversible capacity is large;

[0006] (2) Polymer wrapping tin powder for carbonization: This method can disperse tin powder well in the carbon matrix and improve its cycle performance; but since the polymer is carbonized to form amorphous carbon, it cannot fully reflect The stability and conductivity of graphitic carbon materials, and may increase the first irreversible capacity of composite materials due to the amorphous structure, so the overall performance is not ideal;

The main advantage of using resin as the coating material is that the resin has good fluidity at low temperature. It can not only cover the surface, but also easily penetrate into the material particles through micropores, which is beneficial to improving the tap density and electronic conductivity of the material. It can also be cured by heating, introducing catalysts or ultraviolet radiation. During the pyrolysis process of the resin, it will not melt and deform, and will not produce obvious expansion, but there are still some problems, mainly: the yield of carbon materials obtained by resin pyrolysis Low, brittle, high volatile content during resin pyrolysis, high specific surface area, strong cohesive force of resin, easy to cause coating particles to stick together, easy to cause damage to the coating layer when pulverized after heat treatment

The above problems affect the cycle efficiency, cycle stability and compressibility of the resin coating material.

Pitch, petroleum tar, coal tar or their mixtures are used as coating materials. Compared with resin pyrolytic carbon, the specific surface area of ​​pitch pyrolytic carbon is smaller, and the affinity with materials is better, and the structure is stronger. During the heating process, it will be deformed due to melting. If the dosage is too much, it will easily cause the particles of the coating material to stick to each other. If the dosage is too small, it will easily cause uneven coating, and it will easily expand during the heating process, which will affect the electrical properties of the material.