Piezoelectric Engineering Interrupting Autocatalytic Interfacial Degradation to Enable High-Voltage Cathodes.

Lithium-rich manganese-based oxide (LRMO) cathode materials hold great promise for high-energy-density lithium-ion batteries but suffer from severe interfacial degradation under high-voltage operation, owing to the intertwined chain reactions involving lithium salt hydrolysis, solvent dehydrogenation/oxidation, and lattice oxygen release. Herein, we propose a piezoelectric interfacial regulation strategy by coating a LiGaO2 piezoelectric layer onto the LRMO surface. The periodic lattice strain during delithiation induces a built-in piezoelectric field that generates negative charges on the outer surface, which electrostatically suppress electron extraction from electrolyte solvents, thereby cutting off the autocatalytic cycle of LiPF6 hydrolysis and HF generation. The optimized LRG-05 (0.5 mol % LiGaO2) cathode achieves 85.0% capacity retention after 500 cycles at 1.0 C (vs 76.5% for LRMO) and reduced voltage decay (1.17 vs 1.33 mV per cycle), along with enhanced rate capability. In situ differential electrochemical mass spectrometry shows substantially suppressed O2 and CO2 evolution, while X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry depth profiling reveal a uniform, LiF-enriched cathode-electrolyte interphase (CEI) on LRG-05, in contrast to the cracked, organic-rich CEI on pristine LRMO. This work demonstrates piezoelectric surface engineering as a robust strategy to interrupt the interfacial side-reaction cascades and stabilize high-voltage cathodes.