A Highly Reversible Aqueous Ammonium-Ion Battery based on -MoO₃/Ti₃C₂T_z Anodes and (NH₄)_xMnO₂/CNTs Cathodes

Aqueous ammonium-ion batteries (AAIBs) are appealing due to their relatively low cost and good rate performance. In general, AAIBs are environmentally friendlier than their non-aqueous counterparts. However, it is still a challenge to achieve highly reversible AAIBs with decent voltages and energy/power densities. Herein, we report on a full-cell configuration using alpha-MoO3/Ti3C2Tz films as anodes, and (NH4)(x)MnO2/CNTs films as cathodes in a 1 M ammonium acetate (NH4Ac) electrolyte. At 2 V, the operating cell voltage, OCV, is one of the highest reported for AAIBs. A maximum energy density of similar to 32 Wh kg(-1) (similar to 54 Wh L-1) at 0.2 A g(-1) and a maximum power density of similar to 10 kW kg(-1) (similar to 17 kW L-1) at 10 A g(-1) are attained. When the full cells are cycled 2,000 times at 1 A g(-1) they retain similar to 73 % of their initial capacity. When cycling at 10 A g(-1), similar to 96 % of capacity is retained after 43,500 cycles. After 10 h, self-discharge reduces the OCV to similar to 72 % of its original value. This work provides a roadmap for developing high performance AAIBs with high voltages and high energy/power densities. Before this is possible it is imperative that the self-discharge rate be substantially reduced.