Efficient lithium-oxygen batteries with low charge overpotential via solid-state design and thermal catalyst activation

Excessive charging overpotential leading to low energy efficiency and detrimental side reactions is pronounced in lithium-oxygen batteries which employs lightweight cathode materials combined with lithium metal anodes to achieve high energy density. Most researchers use noble metal catalysts to address this issue, but their synthesis is complex and costly. In this study, we achieve ultra-low charge overpotential by employing an innovative design of solid-state structures and thermally activating cost-effective catalysts in all-solid-state cathodes. (i) The electrolyte layer is integrated with the cathode, eliminating interfacial resistance and reducing its thickness to ∼ 20 μm. (ii) A gel layer with high ionic conductivity (1.08 × 10⁻³ S cm⁻¹) is proposed to protect the anode and enhance lithium-ion diffusion. (iii) Oxygen in cathodes bypasses the solubility limitations of liquid electrolytes, maximizing oxygen transport efficiency. (iv) The integrated design and nano-deposition technique increase the cathode's active area ∼ 300-fold. (v) A uniform 10 nm carbon layer on the cathode surface enhances rapid substance transport and establishes a robust solid–solid contact interface, while also exhibiting distinct temperature activation characteristics. Ultimately, the charging voltage plateau of this battery is reduced from 4.35 V to 3.13 V at 150 mA g_carbon⁻¹. And, the battery achieves a capacity of 22550 mAh g_carbon⁻¹ and an energy efficiency of 87.86 %, surpassing the ∼ 60 % efficiency of existing lithium-oxygen batteries. Theoretical calculations suggest that electrochemical performance is limited by lithium-ion transport and the active sites, rather than the typical oxygen or electron transport. This design strategy offers critical insights for the advancement of all-solid-state lithium-oxygen batteries.