Structural regulation of vanadium oxide by poly(3,4-ethylenedioxithiophene) intercalation for ammonium-ion supercapacitors

Recently, ammonium-ion (NH₄⁺) storage is in a booming stage in aqueous energy storage systems due to its multitudinous merits. To seek suitable electrode materials with excellent NH₄⁺-storage is still in the exploratory stage and full of challenge. Herein, an inorganic-polymer hybrid, poly(3,4-ethylenedioxithiophene) (PEDOT) intercalated hydrated vanadium oxide (VOH), named as VOH/PEDOT, is developed to tune the structure of VOH for boosting NH₄⁺ storage. By the intercalation of PEDOT, the interlayer space of VOH is increased from 11.5 Å to 14.2 Å, which notably facilitates the rapid transport of electrons and charges between layers and improves the electrochemical properties for NH₄⁺ storage. The achieved performances are much better than progressive NH₄⁺ hosting materials. In addition, the concentration of polyvinyl alcohol/ammonium chloride (PVA/NH₄Cl) electrolyte exerts a great impact on the NH₄⁺ storage in VOH/PEDOT. The VOH/PEDOT electrode delivers specific capacitance of 327 F g⁻¹ in 1 M PVA/NH₄Cl electrolyte at −0.2–1 V. Furthermore, the quasi-solid-state VOH/PEDOT//active carbon hybrid supercapacitor (QSS VOH/PEDOT//AC HSC) device is assembled for NH₄⁺ storage, and it exhibits the capacitance of 328 mF cm⁻² at 1 mA cm⁻². The energy density of QSS VOH/PEDOT//AC NH₄⁺-HSC can reach 2.9 Wh m⁻² (2.6 mWh cm⁻³, 10.4 Wh kg⁻¹) at 1 W m⁻² (0.9 mWh cm⁻³, 35.7 W kg⁻¹). This work not only proves that the PEDOT intercalation can boost the NH₄⁺ storage capacity of vanadium oxides, but also provides a novel direction for the development of NH₄⁺ storage materials.