Lithium cobaltate positive electrode material and preparation method thereof, and lithium ion secondary battery

Abstract

The present invention provides a high-voltage lithium cobaltate positive electrode material, which is a compound structure of a doped lithium cobaltate substrate and a surface coating layer, wherein the general formula of the doped lithium cobaltate substrate is Li1+zCo1-x-yMaxMbyO2, x is more than or equal to 0 and is less than or equal to 0.01, y is more than or equal to 0 and is less than or equal to 0.01, z is more than or equal to -0.05 and is less than or equal to 0.08, Ma is a doped element with unchanged valence, and is at least one selected from Al, Ga, Hf, Mg, Sn, Zn and Zr, Mb is adoped valence-changing element, and is at least one selected from Ni, Mn, V, Mo, Nb, Cu, Fe, In, W and Cr, and the surface coating layer is a high-voltage (more than 4.5 V) positive electrode material. According to the present invention, the element with unchanged valence is doped through substitution, such that the layered structure distortion caused by lithium removing can be minimized; the valence-changing element is subjected to gap doping, such that the Co<3+> oxidation is blended and delayed during the charging; and the surface coating layer has the stable structure at the voltage of more than 4.5 V, can separate the electrolytic solution from the lithium cobaltate substrate, can reduce the side reaction between the electrolytic solution and the lithium cobaltate substrate, can suppress the dissolution of the transition metal, and further can provide electrochemical energy.

Description

technical field [0001] The invention relates to the field of materials, in particular to a lithium cobaltate cathode material, a method for preparing the lithium cobaltate cathode material and a lithium ion secondary battery. Background technique [0002] At present, lithium-ion batteries have been widely used in various electronic devices (such as mobile phones and tablet computers). With the continuous improvement of people's requirements for the performance of electronic devices, higher requirements are placed on the energy density of lithium-ion batteries. The volumetric energy density of the battery = discharge capacity × discharge voltage platform × compaction density. Increasing the charge cut-off voltage of the positive electrode material can increase the discharge capacity and discharge voltage platform, thereby increasing its energy density. However, when a Li-ion battery is charged to 4.2V, LiCoO 2 Lithium ions in Li are extracted to form Li 1-x CoO 2 (0≤x≤0.5...

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Problems solved by technology

[0004] However, it should be pointed out that although the above-mentioned positive electrode material doped with elements can stabilize the layered structure of lithium cobalt oxide in a high-voltage environment, it has a limited effect on stabilizing the structure because the positive electrode material cannot be well Buffer or release the stress caused by the change of lattice constant during charging and discharging;

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