Dual-Gradient Engineering of Elemental Concentration and Crystalline Architecture Enables High-Performance Ni-Rich Layered Oxide Cathodes

Ni-rich layered oxides stand as pivotal cathode candidates for high-energy lithium-ion batteries, yet their elevated nickel content (Ni ≥ 0.9) exacerbates structural instability through interfacial degradation and lattice stress accumulation during cycling, leading to accelerated capacity decay. Here, we propose a dual-gradient architecture for Ni-rich cathodes that synergistically integrates germanium concentration gradients with controlled phase evolution. By engineering radial Ge doping gradients within spherical particles, we achieve coherent phase progression from disordered rock-salt through spinel to layered configurations. This structural design not only markedly enhances Li⁺ diffusion kinetics but also efficaciously suppresses interfacial parasitic reactions by modulating the oxidation state of Ni. Moreover, the coherent transition from disordered to ordered structures minimizes the crystallographic mismatch, stabilizes the internal layered framework, and alleviates anisotropic stress accumulation, ultimately achieving extraordinary cycling stability. Under high-rate conditions (4.3 V, 10 C), the material exhibits a discharge capacity of 171.4 mAh g^-1, with a capacity retention of 97.0% after 200 cycles at 1 C. This dual-gradient strategy offers a promising approach to developing advanced cathode materials that meet the demanding requirements of high-rate and long-life lithium-ion batteries.