All-solid-state lithium-oxygen batteries with high areal capacity and fast rate capability enabled by amorphous lithium peroxide

Abstract

All-solid-state lithium-oxygen batteries (ASSLOBs) offer a promising route to overcome the safety and reversibility challenges that are encountered in liquid-electrolyte-based Li-O2 systems. However, their reaction mechanisms and dynamic behavior remain insufficiently understood. Here, we report a high-areal-capacity, high-rate ASSLOB that integrates a gas-diffusion carbon cathode, composite polymer electrolyte (CPE), and lithium anode, enabling direct visualization of discharge product formation and decomposition under all-solid-state conditions. The cell achieves an areal capacity of 6.33 mAh·cm-2, rapid discharge capability up to 5C (related to the current density of 1.0 mA·cm-2), and long-term cycling with 100% Coulombic efficiency and >67% round-trip energy efficiency over 169 cycles. We further reveal that amorphous Li2O₂ nucleates on both carbon black and existing Li₂O₂ surfaces, progressively infiltrates interparticle pores, and ultimately fills the entire microporous cathode. This film-like, amorphous Li₂O₂ morphology, together with the high ionic conductivity of CPE, is critical for achieving high areal capacity and fast kinetics. These mechanistic insights into Li₂O₂ growth and decomposition provide design principles for next-generation high-energy, high-power ASSLOBs tailored for demanding electrification applications.