High-performance monoclinic WO3 nanospheres with the novel NH4+diffusion behaviors for aqueous ammonium-ion batteries

Aqueous ammonium-ion batteries (AAIBs) have attracted tremendous attentions due to their plentiful resources, inherent security and environmental friendliness. From the first-principles calculations and ex-situ measure-ments, monoclinic WO3 revealed the three-dimensional equilibrium diffusion behaviors during the electro-chemical processes, and the novel evolution processes of reversible building/breaking between geometric hydrogen bonds and traditional linear hydrogen bonds. Specifically, monoclinic WO3 delivered a high specific capacity of 150.6 mAh g-1 at the current density of 0.1 A g-1, and exhibited excellent rate capability of 48 mAh g-1 at the current density of 5.0 A g-1 and outstanding cycling stability of 86.6 % capacity retention after 500 cycles. Furthermore, the ammonium-ion full batteries based on the monoclinic WO3 anode and gamma-MnO2 cathode ach-ieved a perfect energy density of 64.9 Wh kg-1 and an extreme ultra-long lifespan with 95.4 % capacity retention after 5000 cycles at the current density of 3.0 A g-1. Thus, the novel insights on NH4+ diffusion behaviors and the evolution mechanisms of hydrogen bonds could promote the development of the practical applications for monoclinic WO3 in aqueous ammonium-ion batteries.

Automated summary

Monoclinic WO3 demonstrated three-dimensional equilibrium diffusion behaviors and reversible evolution processes between geometric hydrogen bonds and traditional linear hydrogen bonds during electrochemical processes. It exhibited high specific capacity, excellent rate capability, and outstanding cycling stability, which could promote its practical application development in aqueous ammonium-ion batteries.