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

Abstract

Abstract Aqueous ammonium‐ion (NH4+) 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 NH4+‐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 NH4+ and V–O layers to some extent and enlarge interlayer space, which improves the efficiency of reversible NH4+ (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 NH4+ storage for the first time. Theoretical calculations reveal that the lowered electron transport barrier and enhanced electronic conductivity improve NH4+ 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 NH4+ storage of VOH by interlayer engineering. The strategy can be used to design other materials for aqueous energy storage systems.

Keywords

• ammonium‐ion hybrid supercapacitor
• interlayer engineering
• K+/PANI co‐intercalation