Heterostructured hollow fibers stitched together from nickel sulfides capped S, N-codoped carbon nanotubes as a trifunctional electrode for flexible hybrid Zn batteries

The explorations of highly performance cathodes are the key concerns of hybrid Zn batteries (HZBs) that combine the Zn-ion (ZIBs) and Zn-air (ZABs) batteries. Herein, a freestanding hollow fiber stitched by the heterostructures of S, N-codoped carbon nanotubes (SNCNT) confined nickel sulfides (Ni3S2) nanoparticles are designed as a trifunctional electrode for HZB. The nickel sulfide nanoparticles are encapsulated by in-situ grown S, N-codoped carbon nanotubes, which stitch together to assemble the hollow fibers. Their highly porous and conductive frame gives fast electron/ion pathways and abundant active sites. The interaction between Ni3S2 and SNCNT favors the OER catalytic properties and the S, N-codopant in SNCNT endows ORR activities in the heterostructured unit. Both experimental and theoretical results demonstrate the Ni3S2@SNCNT hollow fiber is a trifunctional and flexible electrode with high OER/ORR electrocatalytic activities and superior electrochemical properties. The hybrid Zn battery based on Ni3S2@SNCNT hollow fiber cathode manifests two-set charge/discharge characteristics, high energy/power densities and good long-term durability. Additionally, the flexible HZB devices based on the Ni3S2@SNCNT flexible cathode achieve the high performance, unique “self-breathing” abilities and high adaptation in multfarious working conditions. More impressively, they exhibit good uninterrupted working ability even in the sudden transitions on working conditions. Therefore, this work not only provides a highly reliable, trifunctional and flexible electrode, but also promotes the development of the high-performance power sources for the electronics in multifarious conditions.