Gradient Mo Doping via Fick's Law for Stabilizing Lattice Oxygen in Lithium-Rich Manganese-Based Cathodes

Abstract

Lithium-rich manganese-based (LR) cathodes can deliver high capacity through oxygen redox, but irreversible oxygen release often causes structural degradation, voltage decay, and poor cycling stability. Herein, we propose a Fick's law–guided gradient molybdenum (Mo) doping strategy to simultaneously stabilize bulk lattice oxygen and protect surface interfaces. Gradient-distributed Mo forms strong Mo–O bonds that suppress oxygen loss, while high-valent Mo induces an in situ Li₂MoO₄ coating and a partial spinel structure, mitigating electrolyte erosion and facilitating Li⁺ diffusion. The optimized LR@S-Mo cathode delivers a reversible capacity of 195.1 mAh·g⁻¹ with 88.6% retention after 300 cycles at 1C. Theoretical calculations support that Mo doping reduces the Li⁺ diffusion barrier and enhances oxygen stability. This work provides a unified surface-to-bulk modification route for high-energy-density LR cathodes. In this work, a surface-enriched, depth-dependent Mo distribution is constructed based on a diffusion-guided design, accompanied by an in situ Li₂MoO₄/spinel surface layer, which correlates with improved electrochemical stability of lithium-rich Mn-based cathodes.