A Hybrid Na//K-Containing Electrolyte//O Battery with High Rechargeability and Cycle Stability.

Na-O and K-O batteries have attracted extensive attention in recent years. However, the parasitic reactions involving the discharge product of NaO 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//O battery consisting of a Na anode, 1.0 M of potassium triflate in diglyme, and a porous carbon cathode. Upon discharging, KO is preferentially produced via oxygen reduction in the cathode with Na stripped from the Na anode, and reversely, the KO is electrochemically decomposed with Na plated back onto the anode. The new reaction pathway can circumvent the parasitic reactions involving instable NaO and active K anode, and alternatively, the good stability and conductivity of KO 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.