Positive electrode active material and preparation method thereof, and lithium secondary battery

Abstract

The embodiment of the invention provides a positive electrode active material, which comprises a secondary particle formed by tightly stacking a plurality of primary particles, wherein closed pores are formed in the primary particles, the sizes of the closed pores are within the range of 1 to 300 nm, the primary particle comprises a compound LicNiaCobM1-a-bO2-dXd, M is selected from one or more ofMn, Al, Na, Mg, Ca, Zr, Sr, Ti, Cr, V, W, Si, Ga, Sn, lanthanide series elements and actinide series elements, X is selected from one or more of B, F, Cl and S, a is greater than or equal to 0 and less than or equal to 1, b is greater than or equal to 0 and less than or equal to 1, c is greater than or equal to 0.8 and less than or equal to 1.5, and d is greater than or equal to 0 and less than or equal to 0.5. According to the invention, the closed pores in the primary particles of the positive electrode active material can effectively release internal stress caused by volume change of the material in the lithium intercalation and deintercalation process, so that the cycling stability of the positive electrode active material is improved. The embodiment of the invention also provides a preparation method of the positive electrode active material, and a lithium secondary battery.

Description

technical field [0001] The embodiments of the present invention relate to the technical field of lithium secondary batteries, in particular to a positive electrode active material, a preparation method thereof, and a lithium secondary battery. Background technique [0002] With the development of mobile terminals, especially electric vehicles, the development of lithium-ion batteries with high energy density to meet consumers' demands for long battery life has become a current priority. Based on this, researchers use positive and negative active materials with high specific capacity and increase discharge voltage to achieve the purpose of increasing energy density. [0003] Among them, nickel-cobalt lithium manganate (NCM) ternary cathode material is currently a practical high-capacity cathode material, such as figure 1 Shown is a schematic structural diagram of a conventional nickel-cobalt-manganese-manganese oxide (NCM) ternary positive electrode material. From a macrosco...

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Problems solved by technology

[0004] In view of this, an embodiment of the present invention provides a positive electrode active material. By forming a closed-pore structure inside the primary particle, the closed-pore structure can effectively release the anisotropic volume change of the layered positive electrode active material during the charging and discharging process of the battery. The internal stress maintains the integrity of the primary particle structure, thereby ensuring that the secondary particles do not break, so as to solve the problems caused by the inhomogeneous lithium deintercalation state and the anisotropic volume change of the existing positive electrode active materials during the charging and discharging process. A large stress is generated inside the primary particle, which causes nano-cracks to form inside the primary particle, which in turn causes secondary particle breakage and leads to battery capacity attenuation.

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