Composite positive electrode material, preparation method thereof and lithium ion battery

Abstract

The invention provides a composite positive electrode material, a preparation method thereof and a lithium ion battery. The composite positive electrode material comprises a core layer formed by lithium iron phosphate doped with metal phosphide, and a first shell layer, a second shell layer and a third shell layer which sequentially coat the surface of the core layer, the metal phosphide comprises at least one of ferrous phosphide, iron phosphide, iron phosphide I and iron phosphide II; and the second shell layer is a modified lithium manganate material layer. According to the invention, lithium iron phosphate is mixed with metal phosphide, so that the low-temperature cycle performance and the rate capability of the composite positive electrode material can be improved; and the coated second shell layer is a modified lithium manganate material layer, so that the stability of the lithium manganate positive electrode material structure can be improved, the rapid attenuation of the specific capacity in the long-cycle process is avoided, and meanwhile, the lithium manganate has good low-temperature cycle performance.

Description

technical field [0001] The invention belongs to the technical field of electrode materials, and in particular relates to a composite positive electrode material, a preparation method thereof, and a lithium ion battery. Background technique [0002] At present, lithium-ion batteries are widely used in the fields of new energy vehicles, electric energy storage, and mobile communication power supplies. Among many types of lithium-ion batteries, the safety performance of lithium-ion batteries assembled from ternary materials needs to be improved urgently. Lithium iron phosphate has the advantage of low cost, so improving the electrochemical performance of lithium iron phosphate is conducive to the further development of high-performance lithium-ion batteries. [0003] In recent years, lithium-ion batteries have been used more and more in power storage, so the performance requirements of batteries are also getting higher and higher. Especially in the northern and northwestern re...

AI Technical Summary

Problems solved by technology

However, lithium cobalt oxide and rare earth metal resources are scarce and costly, and can only be used in a few special occasions such as the military mentioned above, and cannot be used on a large scale, but a single lithium manganese oxide material cannot well meet high-temperature cycle performance; There is lithium iron phosphate mixed with nickel-cobalt lithium manganese oxide, and CN104377353A discloses mixing carbon-coated nickel-cobalt lithium manganese oxide with carbon-coated lithium iron phosphate in different proportions, although the obtained mixed material has excellent high-voltage performance Lithium iron phosphate is a single material, but the mixed material is still mainly nickel-cobalt lithium manganese oxide. The cost and cycle performance of the mixed material have no obvious advantages, and simple blending cannot effectively guarantee the long-term stability of the material performance.

Images