Conjugated polyaniline as “conveyor” in tungstate boosting cation storage for high-performance aqueous batteries

Aqueous ion storage systems have motivated great interest by virtue of low reduction, high eco-sustainability and safety. Among various cathode candidates, transition metal compounds are featured with easy dissolution in aqueous solutions and inferior conductivity, which severely hinder their application. Herein, advantages are taken of the “conveyor effect” of conjugated polyaniline to prepare an oxygen defective tungstate-linked polyaniline (O_d-WOP) material with chrysanthemum-like microstructure. By virtue of the high electronic conductivity derived from conductive conjugated polyaniline skeleton, unbalanced charge distribution triggered by the defective structure, and reversibly rapid ion (de)intercalation benefited from the open framework with porous chrysanthemum-like microstructure, it delivers outstanding rate capability with a maximum specific capacity of 162.2 mAh g-1 and great cycle stability for storing NH₄⁺. Additionally, it also adopts a high reversible capacity of 140.4 mAh g-1 and outstanding cycling performance to store Ca²⁺. Consequently, the assembled O_d-WOP//PTCDI flexible aqueous ammonium ion batteries and calcium ion batteries exhibit superior capacities, energy densities and flexibilities. O_d-WOP achieves the NH₄⁺ and Ca²⁺ storage capability by interacting with them through hydrogen and ionic bonds, respectively. The deep insight from this work sheds light upon a novel strategy to excavate greater potential of transition metal compounds for aqueous ion batteries.