Hierarchical multi-layer surface engineering via dual-function polydopamine for Li0.5La0.5TiO3 coating and surface rearrangement to spinel phase in Li, Mn-rich cathodes

Li, Mn-rich cathodes (LMR) have attracted considerable interest as next-generation cathode materials for rechargeable batteries owing to their high operating voltage, large specific capacity, and outstanding energy density. However, challenges such as parasitic reactions with electrolytes and irreversible phase transitions have limited their commercial potential. This study proposes a dual-modification strategy to simultaneously address these issues by introducing a Li_0.5La_0.5TiO₃ (LLTO) coating layer alongside a surface-region Li₄Mn₅O₁₂ spinel heterostructure. Polydopamine (PDA), incorporated during synthesis, serves a dual purpose acting as a dispersing agent for the LLTO precursor and as a reductant that facilitates carbothermal reactions during annealing, thereby facilitating the formation of a new surface phase on the LMR. The resulting LLTO-coated spinel heterostructured LMR shows considerably improved rate capability and cycling stability compared to the pristine LMR. Additionally, the modified cathodes maintain superior performance under harsh conditions, including cycling after high-temperature (HT) storage and during HT cycling tests. This study presents a rational design strategy that leverages the multifunctional role of PDA to simultaneously stabilize both the interface and surface structure of LMR cathodes, providing a promising pathway toward their practical application.