A Hybrid Na//K(+)-Containing Electrolyte//O(2) Battery with High Rechargeability and Cycle Stability

Na-O(2) and K-O(2) batteries have attracted extensive attention in recent years. However, the parasitic reactions involving the discharge product of NaO(2) 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(2) battery consisting of a Na anode, 1.0 M of potassium triflate in diglyme, and a porous carbon cathode. Upon discharging, KO(2) is preferentially produced via oxygen reduction in the cathode with Na(+) stripped from the Na anode, and reversely, the KO(2) is electrochemically decomposed with Na(+) plated back onto the anode. The new reaction pathway can circumvent the parasitic reactions involving instable NaO(2) and active K anode, and alternatively, the good stability and conductivity of KO(2) 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.