Coordination and Hydrogen Bond Chemistry in Tungsten Oxide@Polyaniline Composite toward High-Capacity Aqueous...

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.