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 .