High performance lithium ionic cell cathode material and method for producing the same

Abstract

The present invention belongs to a high-performance lithium-ion battery cathode material and a method for preparing the same; solvent, resin and asphalt are added to a container and graphite grains are then added by stirring; the solvent is steamed out through heating up and decompression to form the graphite coated with resin and asphalt which is then put to an inert atmosphere charring furnace for heat treatment; the graphite is cooled to the cycle process less than 100 DEG C after 1 hour to 10 hours; material is taken out, smashed and sieved to grains with grain diameter less than 5 um; after the accumulated volume fraction of grains is less than 10 percent, the high-performance lithium-ion battery cathode material is achieved. As the graphite grains are covered with mixed high molecular polymer made of resin and asphalt, not only the advantages of the resin and asphalt are used, but also the resin has the characteristics of solving asphalt and having condensation polymerization with asphalt, thereby the uniformity, operability and electrical property of covering the graphite grains are improved. By adjusting the proportion of asphalt to resin and controlling the specific surface area of covering graphite grains, the invention has different cycle stability and multiplying power property.

Description

technical field [0001] The invention belongs to the technical field of lithium-ion battery materials, and in particular relates to a high-performance lithium-ion battery negative electrode material and a preparation method thereof. Background technique [0002] Lithium-ion batteries have developed rapidly since they were launched in the early 1990s. At present, the application scope has expanded from mobile communication power supplies, notebook computers, cameras, etc. to electric tools, electric vehicles, etc. The development trend of environmental friendliness is obvious, which all benefit from the improvement and innovation of electrode materials. Graphite materials as negative electrode materials have the characteristics of low lithium intercalation / deintercalation potential, suitable reversible capacity, abundant resources, and low price. They are ideal negative electrode materials for lithium-ion batteries, especially power lithium-ion batteries. [0003] Graphite ma...

AI Technical Summary

Problems solved by technology

If these materials are not processed, they have low tap density and large specific surface area. When they are made into negative electrode slurry with adhesives, conductive agents and solvents, their fluidity is poor, and their adhesion to copper foil current collectors is also poor.

In addition, when the battery is formed, there is a large difference in reactivity between the edge and bottom of the graphite crystallite and the electrolyte, and the surface cannot form a uniform, dense and thin passivation film. Therefore, these materials cannot be used directly, and need to be pulverized, purified, manufactured It has good comprehensive electrical properties only after particle, stabilization and surface modification

Pulverization, grading and processing graphite particles into spherical shapes have indeed significantly improved the tap density and rate characteristics of graphite, but the charge-discharge efficiency and cycle stability are poor

[0004] Known people carry out the method for surface treatment of graphite at present: as U.S. Patent US Patent, No.6,096,454 and US Patent, No.3,011,920 adopt lithium salt or alkali passivation graphite surface, make graphite surface generate one deck passivation film, this The method is simple to operate and easy to realize large-scale industrial production. The key to realize this method is to increase the wettability or hydrophilicity of the graphite surface. Difficult to achieve the desired effect; US Patent No.5344726 and US Patent No.6432583B 1 Chemical vapor deposition is used to thermally decompose toluene, propylene, etc. in a fluidized bed formed by carrier gas such as nitrogen or argon, and deposit a layer of carbon material with high crystallinity on the surface of graphite. This method has relatively high requirements for equipment. High, and the technology is difficult to master; U.S. Patent No.5,401,598 discloses that a layer of organic polymer is coated on the graphite surface, and then pyrolyzed at a high temperature under an inert atmosphere, so that the generated hard carbon is coated on the graphite surface, thereby improving the graphite surface. cycle stability, this method has certain difficulties in actual operation, because the organic polymer is difficult to evenly coat the graphite surface, and it has little effect on reducing the irreversible capacity loss of the first charge and discharge; US Patent No.5908715, Chinese patents CN 1224251A and CN1304187A, etc. use resinous polymer pyrolytic carbon to coat graphite materials, which can also significantly improve the electrical properties of graphite. It is easy to penetrate into the interior of graphite particles through the micropores in graphite, which is beneficial to improve the tap density and electronic conductivity of graphite particles. It can also be cured by heating, introducing catalysts or ultraviolet radiation. The resin will not melt during pyrolysis deformation, and will not produce obvious expansion, but there are also some problems, mainly: the affinity between resin materials and graphite is poor, the carbon materials obtained by their pyrolysis and graphite are not firmly bonded, and the carbon materials obtained by resin pyrolysis The carbon material has a low yield and is brittle. During the pyrolysis process of the resin, there are many volatiles, and the specific surface area is relatively high. The adhesiveness of the resin is strong, which is easy to cause the coated particles to stick together. Destruction of cladding

The above problems have affected the cycle efficiency, cycle stability and compressibility of graphite electrodes of resin-coated graphite materials; US Patent No.5906900, US Patent No.6156432, US Patent No.6596437B 2 and US Patent No. 6869546B 1 etc., Chinese patents CN96198348.5 and CN03140199.6 etc. adopt pitch, petroleum tar, coal tar or their mixtures to coat graphite, and pitch pyrolytic carbon has a smaller specific surface area than resin pyrolytic carbon coated graphite, and graphite The affinity is better and the structure is firmer, but the asphalt coating layer is deformed due to melting during the heating process. If the amount is too large, it will easily cause the coated graphite particles to bond to each other. Easy to expand during the process, affecting the electrical properties of coated graphite