LiNi0.5Mn0.5-x-yCoxMgyO2 Cathode Material for High-Rate Lithium Batteries

The patent applies local quality by creating a core-shell structure where the inner core region and outer shell region have different compositions. The core maintains high Ni content for capacity while the shell has modified composition for stability and rate performance. This is achieved through controlled co-precipitation and calcination processes that create radial composition gradients, allowing different regions to serve different functional purposes.

The patent uses composite materials by combining multiple elements (Ni, Mn, Co, Mg) in a layered oxide structure with formula LiNi0.5-Mn0.5-MCoxMgyO2. The composite nature allows synergistic effects where each element contributes specific properties: Ni provides capacity, Mn provides stability, Co enhances rate performance, and Mg further stabilizes the structure. The layered composite structure enables both high capacity and good rate capability.

The patent extracts the harmful thermal instability associated with LiCoO2 by reducing cobalt content and replacing it with safer elements like Mn, Co (in controlled amounts), and Mg. The invention removes the excessive cobalt that causes thermal issues while retaining enough to maintain electrochemical performance. This extraction of the harmful element allows the material to achieve long lifespan without the thermal instability problems of conventional LiCoO2.

The patent replaces expensive and problematic cobalt with cheaper and safer alternatives (Mn, Mg, and controlled Co amounts). While pure Mn-based materials may have stability issues, the controlled substitution strategy creates a material that achieves both cost reduction and improved thermal stability while maintaining acceptable lifespan through the synergistic composite structure.