Redispersed Bi nanoparticles on graphene fiber fabric anode regulated by microwave irradiation for flexible sodium ion capacitors

Sp2 dominated carbon supported metal nanoparticles with well-controlled structures are promising for portable electrochemical energy storage device with “triple-high” (energy, power, and cycle) feature, yet remains elusive. We report here a flexible graphene fiber fabric (GFF) with well-dispersed Bi nanoparticles by a facile and efficient microwave (MW) irradiation method. By regulating the irradiation duration and π-π conjugated structure of GFF, the pristine micro-sized Bi particles can be uniformly redispersed on GFF with an average particle size of 20 nm in 5 s. The competitive mechanisms between the MW accumulated energy and surface energy of Bi nanoparticles as well as energy conversion efficiency are proposed to dominate this redispersion and particle size changing process. The entire Bi/GFF composite exhibits good conductivity, flexibility, and superior sodium ion storage specific capacity of 113 mAh g−1 at 30 A g−1, which are conceptionally demonstrated as an anode for flexible sodium ion capacitors (SICs). The quasi-solid-state SICs exhibit great mechanical-electrochemical stability, integration property, long-term stability, and high energy/power densities. This work offers a model material of sp2 dominated carbon supported metal nanoparticles with well-controlled structures by an efficient and facile route, demonstrating a potential for flexible, and “triple-high” energy storage device in the future.