Current‐Driven Li ₂ O Formation in Catalyst‐Free Solid‐State Li‐O ₂ Batteries Enabling Simultaneous High Energy and High Power

ABSTRACT Li‐O 2 batteries offer a compelling pathway toward next‐generation energy storage owing to their ultrahigh theoretical energy density; however, practical realization has been severely constrained by parasitic reactions, poor reversibility, and the predominance of one‐ or two‐electron oxygen reduction pathways. Here, we report a catalyst‐free solid‐state Li‐O 2 battery (SSLOB) that achieves a four‐electron reaction with Li 2 O formation through a current‐driven, phase‐conversion lithiation mechanism, enabling simultaneous high‐energy and high‐power operation. Comprehensive structural and chemical analyses, including x‐ray diffraction, UV–vis spectroscopy, acid titration, and high‐resolution transmission electron microscopy, confirm Li 2 O formation. Systematic investigations reveal that discharge current density is the dominant kinetic parameter governing Li 2 O formation, whereas operating temperature and depth of discharge exert minimal influence on the Li 2 O/Li 2 O 2 phase ratio. At high current densities, enhanced Li + flux and interfacial electrochemical driving forces promote two‐electron lithiation of Li 2 O 2 to Li 2 O to complete the entire four‐electron transfer pathway. The present SSLOB delivers an areal capacity of 8.25 mAh·cm −2 at 3.0 mA·cm −2 , corresponding to a cell‐level specific energy of ∼1032 Wh·kg −1 with a continuous power of ∼374 W·kg −1 . This work represents the first demonstration of catalyst‐free four‐electron Li 2 O formation and establishes a scalable solid‐state platform for achieving cell‐level energy densities exceeding 1000 Wh·kg −1 .