Coordination and Hydrogen Bond Chemistry in Tungsten Oxide@Polyaniline Composite toward High‐Capacity Aqueous Ammonium Storage

Aqueous ammonium ion batteries (AAIBs) have garnered significant attention due to their unique energy storage mechanism. However, their progress is hindered by the relatively low capacities of NH₄ ⁺ host materials. Herein, the study proposes an electrodeposited tungsten oxide@polyaniline (WO_x@PANI) composite electrode as a NH₄ ⁺ host, which achieves an ultrahigh capacity of 280.3 mAh g^-1 at 1 A g^-1, surpassing the vast majority of previously reported NH₄ ⁺ host materials. The synergistic interaction of coordination chemistry and hydrogen bond chemistry between the WO_x and PANI enhances the charge storage capacity. Experimental results indicate that the strong interfacial coordination bonding (N: →W⁶⁺) effectively modulates the chemical environment of W atoms, enhances the protonation level of PANI, and thus consequently the conductivity and stability of the composites. Spectroscopy analysis further reveals a unique NH₄ ⁺/H⁺ co-insertion mechanism, in which the interfacial hydrogen bond network (N-H···O) accelerates proton involvement in the energy storage process and activates the Grotthuss hopping conduction of H⁺ between the hydrated tungsten oxide layers. This work opens a new avenue to achieving high-capacity NH₄ ⁺ storage through interfacial chemistry interactions, overcoming the capacity limitations of NH₄ ⁺ host materials for aqueous energy storage.