Dual defect engineering tailored Li+ diffusion kinetics for sustainable Mn-based composite-structure cathode materials

Abstract

Manganese-rich layered oxides are promising cathode materials for next-generation lithium-ion batteries, yet their practical deployment is hindered by sluggish Li⁺ diffusion, voltage fading, and Mn dissolution triggered by lattice instability. To date, a generalizable design principle that simultaneously accelerates Li⁺ transport and suppresses electrochemical fading remains elusive. Here a dual-defect engineering strategy that concurrently generates twin-boundary interfaces and oxygen vacancies in phosphate-composite Mn-LLO crystal lattices is introduced. The twin boundary defect enlarges Li⁺ transport channels within the Li slabs, while oxygen vacancies efficiently lower Li⁺ migration barriers, guaranteeing fast Li⁺ transport and competitive electrochemistry. The engineered Mn-based composite cathode delivers 18% rate enhancement at 1C and 90.7% capacity retention after 1000 cycles at 45 °C in 250 mAh pouch cells. Post-mortem analysis reveals uniform Mn/Ni redox and suppressed electrolyte decomposition in the phosphate-composite cathode system. This scalable approach is compatible with commercial Mn-based oxide cathodes and can be extended to other layered oxide systems, offering a defect-centric pathway toward high-stability batteries.