Zeolitic imidazolate framework derived ZnCo₂O₄ hollow tubular nanofibers for long-life supercapacitors

Uniform one-dimensional metal oxide hollow tubular nanofibers (HTNs) have been controllably prepared using a calcination strategy using electrospun polymer nanofibers as soft templates and zeolitic imidazolate framework nanoparticles as precursors. Utilizing the general synthesis method, the ZnO HTNs, Co₃O₄ HTNs and ZnCo₂O₄ HTNs have been successfully prepared. The optimal ZnCo₂O₄ HTNs, as a representative substance applied in supercapacitors as the positive electrode, delivers a high specific capacity of 181 C g^-1 at a current density of 0.5 A g^-1, an excellent rate performance of 75.14% and a superior capacity retention of 97.42% after 10 000 cycles. Furthermore, an asymmetric supercapacitor assembled from ZnCo₂O₄ HTNs and active carbon also shows a stable and ultrahigh cycling stability with 95.38% of its original capacity after 20 000 cycle tests.