Piezoelectric Interphase Engineering Enables Reversible Oxygen Redox in Lithium‐Rich Layered Oxides

ABSTRACT In the last decade, the lithium‐rich layered oxides (LLOs) as cathode materials of lithium‐ion batteries (LIBs) have attracted considerable research interest owing to the high specific capacity (> 300 mAh g −1 ), elevated operating voltage, and cost‐effectiveness. However, these oxide materials suffer from severe interfacial degradation, capacity fading, and voltage decay, primarily attributed to the poor reversibility of anionic redox reactions. To address these limitations, we proposed a dual‐functional modification paradigm combining the surface piezoelectric interphase layer of lithium gallium oxide (LiGaO 2 ) with gradient Ga 3+ bulk doping to synergistically suppress lattice oxygen evolution in LLOs. Combined with simulation calculations, multiscale characterization, and electrochemical performance evaluation, this study unambiguously elucidates the underlying mechanism by which the engineered interface suppresses lattice oxygen release. This piezoelectric interphase spontaneously generated a persistent built‐in electric field through stress‐induced piezoelectric polarization during cycling, thereby dynamically restraining oxygen release at high operating voltages. Moreover, Ga‐doping into the subsurface lattice modulated the local electronic configuration and thus enhanced the reversibility of anionic redox reactions, avoiding the limitation of single‐strategy approaches that merely address symptoms rather than root causes. Benefitting from these advantages, the piezoelectric interphase modified cathode demonstrated significantly an improved cycling stability with 81.5% capacity retention after 300 cycles at 200 mA g −1 , coupled with a substantially mitigated average voltage decay rate of 1.03 mV per cycle (vs. 1.43 mV per cycle for the pristine sample). This work presents the first demonstration of piezoelectric interphase engineering for oxygen redox regulation, providing a new pathway for developing high‐energy‐density LLOs with a much extended cycling span.