Cascade reactors for long-life solid-state sodium–air batteries

Sodium (Na)-air batteries show significant potential as alternatives to lithium-air batteries due to their high theoretical energy density and the abundant availability of sodium reserves. Nevertheless, the formation of complex products, specifically NaO2, Na2O2, Na2CO3·xH2O, during the multi-step reactions inevitably raises reconciled potential incompatibility that causes low efficiency and large overpotential. Here, we introduce a cascade electrocatalysis strategy that involves switchable metal and oxygen redox chemistry through electrochemical potential tuning. Leveraging the lithium ion spatial pinning effect, sodium ions trigger in the Na[Li1/3Ru2/3]O2 electrode system to toggle the geometric state at a low electrochemical potential and oscillate among different catalytic states to achieve sequential conversion of complicated multi-step intermediates. The Na[Li1/3Ru2/3]O2 catalyst effectively compartmentalizes the threshold potential that circumvents deactivating or competing pathways while coupling different catalytic cycles. As a result, the sodium-air battery employing this catalyst exhibits long-term reversibility over 1000 cycles with a decent catalysis efficiency exceeding 99%. Our results demonstrate that the cascade electrocatalysis strategy contributes to the design of integrated sodium-air batteries with long-term cycling stability.