High-temperature-resistant and high-voltage-resistant composite lithium cobalt oxide positive electrode material as well as preparation method and application thereof

Abstract

The invention relates to a high-temperature-resistant and high-voltage-resistant composite lithium cobalt oxide positive electrode material which is of a multi-layer structure and sequentially comprises a metal element doped particle inner core, an interface transition layer and an amorphous phosphate coating layer from inside to outside. The preparation method comprises the following steps: carrying out a co-precipitation reaction on a Co aqueous solution, an Ma aqueous solution and a carbonate solution to obtain Ma element doped cobalt carbonate; carrying out ball milling on the Ma element doped cobalt carbonate and an Ma compound, and calcining to obtain an Ma element doped cobaltosic oxide precursor; mixing the Ma element doped cobaltosic oxide precursor with a lithium source, and calcining to obtain an Ma element doped lithium cobalt oxide material; and carrying out ball milling on the Ma element doped lithium cobalt oxide material, phosphate and absolute ethyl alcohol, and calcining to obtain the high-temperature-resistant and high-voltage lithium cobalt oxide positive electrode material. The interface transition layer can enhance the connection between the coating layer and the inner core and improve the lattice stability of the interface.

Description

technical field [0001] The invention relates to the technical field of lithium-ion batteries, in particular to a high-temperature-resistant and high-voltage composite lithium cobalt oxide positive electrode material and a preparation method and application thereof. Background technique [0002] Lithium-ion batteries have attracted much attention since their commercialization due to their advantages such as high energy density, long life, and low self-discharge effect. In the field of power batteries, ternary materials and lithium iron phosphate materials are the preferred materials for cathode materials. In consumer electronic products, lithium cobalt oxide is still the main cathode material, because compared with other materials, lithium cobalt oxide has an absolute advantage in compaction density and working voltage, and there is still no effective alternative material. [0003] With the rapid development of electronic products, there are more stringent requirements for t...

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Problems solved by technology

[0004] There are many ways to increase the volume energy density. Among them, with the increase of charging voltage, the volume energy density increases greatly. Therefore, the development of high voltage is the current research focus, and charging to a higher voltage also brings many problems. With the increase of voltage As the temperature rises, the material gradually delithiates, a series of phase transitions occur, and the unit cell parameters change greatly, resulting in an unstable structure. After a long cycle, a large residual stress is generated inside the material, and microcracks are generated to cause particle breakage. At the same time Oxygen on the material surface may participate in irreversible charge compensation under high voltage, resulting in the release of oxygen

Under high voltage, the interface between the surface of the material and the electrolyte is more unstable, and adverse side reactions will occur, resulting in the consumption of the electrolyte and causing capacity fading

The above problems lead to severe capacity and voltage decline of lithium cobalt oxide under high pressure, and shortened battery life. Under high temperature conditions, the problem is even more serious. Therefore, stabilizing the bulk crystal structure of the material and building a stable interface are the key to solving the above problems

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