Boosting ammonium-ion storage of V₂O₅·nH₂O by encapsulating engineering of polyaniline

The design and development of new host materials for ammonium-ion supercapacitors (NH₄⁺-SCs) has been one of the topics of ongoing concern in recent years. Vanadium oxide has always been one of the most eye-catching electrode materials in the field of aqueous NH₄⁺ energy storage. However, in the process of repeated charge/discharge, due to the direct contact with the aqueous electrolyte, vanadium oxide dissolution and structural collapse inevitably appear, and there is also the problem of low intrinsic conductivity, so it is urgent to address these issues. In this work, the conductive polymer polyaniline (PANI) is coated on the surface of V₂O₅·nH₂O (VOH) by a simple hydrothermal method to form V₂O₅·nH₂O@polyaniline (VOH@PANI) nanobelts with core-shell structure to improve the structural endurance and NH₄⁺ storage capacity. The experimental and theoretical calculation results show that the introduction of PANI shells on VOH nanobelts can enhance the structural stability, ion/charge transfer and transport dynamics, thereby improving the NH₄⁺ storage capacity and making it an ideal host material for NH₄⁺-SCs. VOH@PANI core-shell composite has a specific capacitance of 453 F·g^-1 at 0.5 A·g^-1, far exceeding VOH (271 F·g^-1) and PANI (295 F·g^-1). The VOH@PANI//active carbon (AC) hybrid supercapacitor (HSC) composed of VOH@PANI cathode and AC anode has good electrochemical performance and practical application value. The technique offers suggestions for strengthening electrical conductivity and preventing structural collapse of other fragile materials.