A Hybrid Na//K⁺-Containing Electrolyte//O₂ Battery with High Rechargeability and Cycle Stability

Na-O₂ and K-O₂ batteries have attracted extensive attention in recent years. However, the parasitic reactions involving the discharge product of NaO₂ or K anode with electrolytes and the severe Na or K dendrites plague their rechargeability and cycle stability. Herein, we report a hybrid Na//K⁺-containing electrolyte//O₂ battery consisting of a Na anode, 1.0 M of potassium triflate in diglyme, and a porous carbon cathode. Upon discharging, KO₂ is preferentially produced via oxygen reduction in the cathode with Na⁺ stripped from the Na anode, and reversely, the KO₂ is electrochemically decomposed with Na⁺ plated back onto the anode. The new reaction pathway can circumvent the parasitic reactions involving instable NaO₂ and active K anode, and alternatively, the good stability and conductivity of KO₂ and stable Na stripping/plating in the presence of K⁺ enable the hybrid battery to exhibit an average discharge/charge voltage gap of 0.15 V, high Coulombic efficiency of >96%, and superior cycling stability of 120 cycles. This will pave a new pathway to promote metal-air batteries.