Publication
The hydrogen evolution reaction is the most prominent parasitic reaction for aqueous battery chemistries. Although water-in-salt electrolytes show greatly enhanced electrochemical stability, increasing the voltage of aqueous batteries further by lowering the potential of the negative electrode remains a major challenges due to reductive water splitting. Here, we systematically investigate twelve niobium-based anode materials that show much lower activity towards hydrogen evolution reaction than classic titanium-based anode materials such as lithium titanate (Li4Ti5O12) 4 Ti 5 O 12 ) or titanium dioxide and are therefore a much better choice for aqueous batteries. . We confirm Zn2Nb34O87 2 Nb 34 O 87 to be the most suitable anode material for aqueous batteries among these niobates and present full-cell cycling data with LiMn2O4 2 O 4 and LiNi 0.8 Mn 0.1 Co 0.1 O 2 cathodes in a water-in-salt/ionic liquid hybrid electrolyte. Furthermore, we compare the catalytic activities of Zn2Nb34O87 2 Nb 34 O 87 and Cu2Nb34O87, 2 Nb 34 O 87 , with the latter being incompatible with aqueous batteries, and discuss the origin of the large difference in activity toward hydrogen evolution reaction.