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

Abstract

Provided is a lithium cobalt oxide positive-electrode material, said material being a composite structure having a doped lithium-cobalt-oxide substrate and surface coating; the general formula of said doped lithium-cobalt-oxide substrate is Li 1+zCo 1-x-yMa xMb yO 2, wherein 0≤x≤0.01, 0≤y≤0.01 and -0.05≤z≤0.08; said Ma is a doped invariable-valence element, at least one of Al, Ga, Hf, Mg, Sn, Zn, and Zr; said Mb is a doped variable-valence element, at least one of Ni, Mn, V, Mo, Nb, Cu, Fe, In, W, and Cr; the surface coating layer is a high-voltage (>4.5 V) positive-electrode material. By means of substitution doping of the variable-valence element, distortion resulting from delithiation of the layered structure is reduced by the maximum extent; the variable-valence element is doped by means of gaps, and during the process of charging, the oxidation of Co 3+is reconciled and delayed. The surface coating layer of the high-voltage positive-electrode material has a stable structure at voltages of 4.5 V or higher, and is capable of isolating an electrolyte solution and a lithium-cobalt-oxide substrate, thus reducing side reactions between the two and inhibiting the dissolution of transition metals; it also provides 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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