A composite acidic electrolyte for ultra-long-life hydrogen-ion storage

Aqueous hydrogen ion batteries (HIBs) are emerging as a potential alternative to lithium ion batteries due to their advantages in cost effectivity and intrinsic safety. However, their low cycling performances due to instability of electrode materials in acidic electrolytes significantly retard the practical applications of HIBs. Herein, we propose a simple composite acidic electrolyte composed of H2SO4 and H3PO4 to improve the cycling stability of the normal anode. Intriguingly, the hydrogen bonds within the as-prepared electrolyte are strongly enhanced compared with in the electrolytes of either component alone, which efficiently reduces dissolution of the anode material and promotes intercalation of hydrogen ions. Benefiting from this effect, the prototype MoO3 anode showed an excellent long-term cycling stability in the electrolyte with 85% capacity retention at 5 A g−1 even after 2000 cycles. The assembled full-cell also presented outstanding electrochemical performances including high rate capability of 33 mAh g−1 at 100 A g−1 and improved stability to a wide temperature change from 0 to 60 °C. This work sheds light on the design of advanced electrolytes for HIBs and may provide basis for potentially promoting aqueous batteries towards practical use.