Polypyrrole-Assisted Nitrogen Doping Strategy to Boost Vanadium Dioxide Performance for Wearable Nonpolarity Supercapacitor and Aqueous Zinc-Ion Battery

摘要

Fiber-shaped energy-storage devices with high energy and power density arecrucial for powering wearable electronics. However, the improvement of theirenergy and power density is limited by the low mass loading of active materialsand slow diffusion of ions, which further hinders the application as flexibleenergy-storage devices. Herein, a facile and cost-effective strategy is proposedto fabricate polypyrrole (Ppy)-assisted nitrogen-doped vanadium dioxide/nitrogen-doped carbon (N–VO2@NC) heterostructures by the pyrolyzationof vanadium oxide (VO_x)/Ppy supported on carbon nanotube fiber (CNTF).The carbonization of Ppy nanowire not only forms nitrogen-doped carbon 3Dconductive scaffold for enhancing ion transport pathways and mass loading ofN–VO_2 but also provides source of nitrogen in situ doping into Vox to produceN–VO_2 for improving electronic conductivity and energy-storage capacity. Consequently,the well-designed N–VO_2@NC@CNTF electrode delivers impressiveelectrochemical performance and extraordinary mechanical flexibility bothapplied in all-solid-state fiber-shaped nonpolarity supercapacitors and aqueouszinc-ion batteries. Furthermore, the results of theoretical calculations discoveredthat the band gap of Ppy-assisted N–VO_2 can be significantly reducedfrom 0.55 to 0.23 eV and thus its conductivity is greatly enhanced. This worksheds light on the construction of high-performance free-standing electrodesfor next-generation wearable aqueous energy-storage devices.