Lithium-Excess Cathode Core-Shell Gradient for High-Rate Capability

The patent applies local quality by creating a core-shell structure where the inner core region maintains a layered structure for high capacity while the outer shell region transforms to a spinel structure for improved kinetics. This spatial differentiation allows different regions of the particle to serve different functions: the core provides lithium storage capacity while the shell facilitates rapid lithium diffusion, thereby resolving the contradiction between particle size reduction and packing density maintenance.

The invention implements local quality by spatially differentiating the crystal structure within the particle: the inner core retains the layered structure optimized for capacity, while the outer shell transforms to spinel structure optimized for rate capability. This allows the particle to simultaneously achieve high energy density (from the core) and high power density (from the shell), resolving the contradiction between productivity and energy usage.

The patent applies preliminary action by pre-forming a gradient transition layer during the heat treatment process, where the crystal structure gradually changes from layered in the core to spinel in the shell. This gradual transition, rather than an abrupt boundary, is prepared in advance to facilitate continuous lithium diffusion pathways, thereby maintaining both structural compatibility and high lithium diffusion rates.

The invention applies parameter changes by transforming the surface crystal structure from layered to spinel through controlled heat treatment with a reducing agent, rather than using acid treatment. This thermal-chemical transformation modifies surface properties to improve initial charge-discharge efficiency while maintaining structural integrity and stability, thereby avoiding the surface damage that would deteriorate cycle performance.