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.