Cathode Active Material for Lithium Secondary Batteries and Lithium Secondary Battery Comprising the Same

Highly Stable High-Nickel Cathode Active Material Based on Mn4+ Superstructure with Lithium Substitution in the Transition Metal Layer

This technology forms a highly stable superstructure by substituting a portion of the transition metal layer in a layered rhombohedral (R-3m) structure with lithium, maintaining the oxidation state of Mn at +4 and Ni and Co at +3.

Conventional high-capacity nickel-based cathode active materials suffer from thermal instability due to crystal structure degradation during charge and discharge cycles. This structural deterioration inherently limits the battery's cycle life.

This technology induces an Mn4+ superstructure through lithium substitution within the transition metal layer and maintains the Mn4+, Ni3+, and Co3+ oxidation states via heat treatment between 670–750℃. This superstructure, identifiable by XRD peaks at 2θ 20°–25° and TEM diffraction patterns, serves as a quality control metric. Applicable to EV batteries using >85% Ni NCM cathodes and energy storage systems exposed to high temperatures, it enhances thermal stability through internal crystal ordering without requiring additional coatings.

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Key Features:

• A superstructure with a layered rhombohedral R-3m structure where Li is substituted in the transition metal layer, resulting in an Mn oxidation state of +4
• A layered crystal structure exhibiting peaks in the XRD 2θ 20° to 25° range and Mn4+ diffraction patterns in TEM
• A cathode active material for lithium secondary batteries with a composition of Lia[NixCoyMnz]O2, where Ni and Co oxidation states are maintained at +3 and nickel content is x≥0.85
• A process involving mixing a metal composite hydroxide obtained via co-precipitation with a lithium salt, followed by heat treatment at 670 to 750℃

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