Lithium ion power battery composite cathode material and its preparation method

Abstract

The invention relates to a battery cathode material, mainly relates to a lithium ion power battery composite cathode material and its preparation method, and belongs to the lithium battery making field. The lithium ion power battery composite cathode material is characterized in that the lithium ion power battery composite cathode material comprises a core-shell structure composed of a natural graphite matrix and a hard carbon layer coated on the surface of the natural graphite matrix, and a secondary modification layer for modifying the core-shell structure through adopting a modifying agent; the above coating is hard carbon formed through pyrolysis of a thermosetting resin; the thermosetting resin is at least one selected from a phenolic resin, an epoxy resin and a furan resin; and the modifying agent is at least one selected from coal tar pitch and petroleum asphalt. The lithium ion power battery composite cathode material having good electrochemical performances comprising capacity, first efficiency, cycle, rate and the like is prepared through adopting the primary coating and secondary modifying method.

Description

technical field [0001] The invention relates to a battery negative electrode material, mainly relates to a lithium ion power battery composite negative electrode material and a preparation method thereof, and belongs to the field of lithium battery production. Background technique [0002] Lithium-ion batteries have the advantages of high working voltage, large specific energy, and good safety performance, and are widely used in mobile communications, notebook computers and other fields. Especially with the wide application of electric vehicles in the future, higher requirements are put forward for lithium-ion batteries. . Natural graphite materials as negative electrode materials have the advantages of abundant reserves, high specific capacity, low voltage platform, and very strong cost performance, but there are serious defects in direct use, such as low initial discharge efficiency, poor cycle performance, and electrolysis. The shortcomings of high liquid selectivity lim...

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Problems solved by technology

The key to this method is to form a complete coating on the outside of the graphite, otherwise it will not be able to prevent the contact between the electrolyte and the graphite. Generally, a layer of resin carbon is coated on the surface of the natural microcrystalline graphite particles to form a core-shell structure. The inside is natural microcrystalline graphite, and the outside is a 1-2 μm phenolic resin pyrolytic carbon layer. Coating treatment can reduce the first irreversible capacity of natural microcrystalline graphite, but only coating the resin hard carbon precursor will make it incompatible with graphite materials. In addition, due to the low degree of graphitization of the hard carbon precursor, it will affect the first charge and discharge performance of the material and its specific surface area is large, which is not conducive to the manufacturing process of the battery. Therefore, the graphite material coated with hard carbon needs to be processed. Processing to make its cycle and rate performance more superior

The Chinese patent with the publication number CN101162775A (2008-04-16) adopts the method of mixing resin and pitch to coat the graphite material. This method also has some deficiencies in practical application, resulting in a low carbonization rate of the resin, which affects the final first-time efficiency of the material.

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