Self‐Medicating Molten‐Salt Synthesis of Bulk‐Stabilized High‐Energy Cathodes for Li‐Ion Batteries

High-energy lithium-ion batteries necessitate stable Ni-rich layered cathodes, yet critical challenges such as lattice distortion and surface structure collapse remain unresolved. While conventional high-valence doping greatly alleviates surface degradations, it is ineffective in stabilizing bulk lattice due to dopant segregation. Here, we propose a slightly Li-rich (SLR) lattice design by partially substituting transition-metal (TM) ions with Li⁺ ions in TM layers, reducing electrostatic repulsion against high-valence dopants. Integrated theory-experiment analyses reveal uniform bulk doping of Mo⁶⁺ in SLR cathodes, realized via a self-medicating and scalable molten-salt synthesis route. An optimized high-energy cathode (880 Wh kg^-1 _cathode) achieves 89% retention after 1000 cycles in Ah-scale pouch cells, sustains 10C ultrafast charging/discharging for 300 cycles (3.8 min to 80% state-of-charge), and operates stably in all-solid-state batteries. Multimodal characterizations link uniform Mo⁶⁺ doping to suppressed lattice strain and structural collapse. This work establishes a new paradigm for bulk lattice engineering of advanced battery cathodes.