A Highly Reversible Aqueous Ammonium-Ion Battery based on α-MoO3/Ti3C2Tz Anodes and (NH4)xMnO2/CNTs Cathodes

Abstract

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 α-MoO3/Ti3C2Tz films as anodes, and (NH4)xMnO2/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 ∼32 Wh kg−1 (∼54 Wh L−1) at 0.2 A g−1 and a maximum power density of ∼10 kW kg−1 (∼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 ∼73 % of their initial capacity. When cycling at 10 A g−1, ∼96 % of capacity is retained after 43,500 cycles. After 10 h, self-discharge reduces the OCV 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.