Lithium-ion secondary battery and its composite positive electrode active material and preparation method

Abstract

The invention provides a lithium ion secondary battery, a composite positive electrode active material thereof and a preparation method. The composite positive electrode active material is prepared by compositing a lithium cobalt series oxide and lithium manganese phosphate (LMP). The composite positive electrode active material has a filling structure formed by filling and compositing primary particles of LMP in gaps and pits in the surfaces of secondary particles of the lithium cobalt series oxide, wherein the chemical general formula of the lithium cobalt series oxide is LiAxCo<1-x>O2; x is not less than 0 and is less than 1; A is at least one of Ni, Mn, Al, Mg, Ca, Cr, Zr, Mo, Ag and Nb; the chemical general formula of LMP is LiByMn<1-y>PO4; x is not less than 0 and is less than 1; B is at least one of Ni, Co, Fe, Al, Ca, Zn, Mg, Mo, Pb and Zr. The lithium ion secondary battery comprises the composite positive electrode active material. The lithium ion secondary battery has good capacity density, rate performance, cycle performance, storage performance and safety performance.

Description

technical field [0001] The invention relates to the field of batteries, in particular to a lithium-ion secondary battery, a composite positive electrode active material and a preparation method thereof. Background technique [0002] Lithium-ion secondary batteries are widely used in various fields due to their good electrochemical performance, such as mobile phones, computers, power tools, electric vehicles, etc. The safety performance of lithium-ion secondary batteries is the most important performance except electrochemical performance, which determines the safety and reliability of equipment using lithium-ion secondary batteries, and is closely related to the safety of life and property of consumers. [0003] The safety problems of lithium-ion secondary batteries are mainly various forms of thermal runaway problems, such as the fire and explosion of lithium-ion secondary batteries caused by the temperature rise of the internal short circuit point. [0004] Common transit...

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Problems solved by technology

[0006] However, the poor electrochemical performance of phosphate-based positive electrode active materials has severely limited the rate performance of lithium-ion secondary batteries using phosphate-based positive electrode active materials, thereby limiting their development as power batteries in related fields.

[0007] At present, the positive electrode active materials with high electrochemical performance used in power lithium-ion secondary batteries mainly include lithium nickel cobalt manganese oxide (NCM) ternary materials, lithium nickel cobalt aluminum oxide (NCA), etc., although they have high electrochemical performance. Performance, but poor safety performance, which limits the application of high-performance lithium-ion secondary batteries

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