Synergistic effect of K+and PANI in vanadium oxide hydration by interlayer engineering boosts the ammonium ion storage

Abstract Aqueous ammonium‐ion (NH 4 + ) hybrid supercapacitor (AA‐HSC), as a new type of energy storage device with great potential, is in the initial stage of rapid development. Based on its special energy storage mechanism, exploiting novel NH 4 + ‐hosting materials is still a great challenge. Herein, vanadium oxide hydration (VOH) tuned by interlayer engineering of K + /PANI co‐intercalation, named KVO/PANI, is designed for AA‐HSC. Intercalated PANI can shield interaction between NH 4 + and V–O layers to some extent and enlarge interlayer space, which improves the efficiency of reversible NH 4 + (de)insertion. However, K + enhances redox activity and electronic conductivity. The synergistic effect of co‐intercalation optimizes intercalation pseudocapacitive behavior during the (de)ammonization process, which is reported in NH 4 + storage for the first time. Theoretical calculations reveal that the lowered electron transport barrier and enhanced electronic conductivity improve NH 4 + kinetics and exhibit high capacitance for charge storage. The KVO/PANI can deliver the specific capacitance of 340 F g −1 at 0.5 A g −1 and retain 177 F g −1 at 10 A g −1 . Pairing with activated carbon, the AA‐HSC can achieve a decent energy density of 31.8 Wh kg −1 . This work gives inorganic/organic co‐intercalation that can enhance the NH 4 + storage of VOH by interlayer engineering. The strategy can be used to design other materials for aqueous energy storage systems.