O₂/O₂^– Crossover- and Dendrite-Free Hybrid Solid-State Na–O₂ Batteries

Superoxide-based Na–O2 batteries have attracted extensive research attention because of their high theoretical energy density and energy efficiency. However, the poor cycling performance caused by O2/O2– crossover and the uncontrollable Na dendrite growth severely hinder their practical applications. Addressing these issues comprehensively, we successfully developed a hybrid solid-state (HSS) Na–O2 battery based on solid-state electrolyte (SSE) and a protected Na anode. The dense structure of SSE effectively suppressed the O2/O2– crossover, thus mitigating the Na degradation and improving the cell reversibility. Solid electrolyte interphase formation on the Na anode in relation to the O2/O2– crossover was further revealed. Additionally, a three-dimensional protection layer on the Na anode facilitated uniform Na deposition within the conductive matrix. Consequently, the fabricated HSS Na–O2 battery demonstrated stable cycling for over 160 cycles at 0.2 mA cm–2 under the shallow cycling mode. Our results evidently emphasized the critical role of Na anode protection and the importance of O2/O2– blockage for safe and high-performance Na–O2 batteries.