Aqueous proton battery stably operates in mild electrolyte and low-temperature conditions

The electrode based on the conversion reaction of Mn2+/MnO2 is regarded as a promising cathode for aqueous proton batteries (APBs) due to its high redox potential and cost-effectiveness, but it needs a strongly acidic medium to trigger this redox reaction. Herein, a mild perchlorate-based electrolyte without strong acid addition (3.5 M Mn(ClO4)(2)) is proposed to improve the deposition/dissolution efficiency of Mn2+/MnO2. Comprehensive analyses confirm that the ClO4- anion not only ensures the fast and stable deposition of Mn2+ by regulating the solvation energy of Mn2+ but also accelerates the dissolution of MnO2 by improving the degree of freedom of water molecules. Hence, the novel aqueous proton battery with a carbon felt (CF) cathode, polyaniline anode and 3.5 M Mn(ClO4)(2) electrolyte exhibits a lifetime of 500 cycles with an 81.6% capacity retention rate and excellent rate capability of up to 100C (18 A g(-1)). Surprisingly, this system operates well even at low-temperature conditions because of the anti-freezing electrolyte with a -122 degrees C freezing point. High discharge capacities of 112 mA h g(-1) and 52.9 mA h g(-1) are obtained at -50 degrees C and -70 degrees C, respectively.

Automated summary

This study proposes a mild perchlorate-based electrolyte without strong acid addition to improve the efficiency of the Mn2+/MnO2 redox reaction. The results show that this novel aqueous proton battery exhibits excellent rate capability and cycle life, even under low-temperature conditions.