Design of multifunctional graphene oxide-modified nanofiber film with heterostructure (ZnS-CoS@GO@CNFs) for long-term stable potassium ion storage

When transition metal sulfides are used as high-theoretical-capacity anodes for potassium ion batteries (PIBs), their low conductivity and large volume expansion resulted in inferior rate performance and cyclic stability. In this study, multifunctional graphene oxide (GO) was employed to control the diameter and distribution of nanoparticles within composite fibers, which improved their conductivity and tensile deformation. In addition, a three-dimensional conductive carbon network composed of heterostructures and GO (ZnS-CoS@GO@CNFs) accelerated the kinetics and stabilized potassium ion storage. As the anode material of PIBs, the composite provided an excellent rate performance of 210 mA h g−1 at 3 A g−1, and after 2800 cycles under a large current of 2 A g−1, the capacity retention rate was 97.7% (171 mA h g−1). Furthermore, when the nanofiber film was used as a self-supporting anode, it maintained a stable capacity output (302 mA h g−1 after 100 cycles at 0.1 A g−1). A foldable pouch cell was assembled using a potassium ion hybrid super-capacitor, and it was found to operate safely and normally under multiangle repeated bending and final recovery; further, it provided a high energy density (134 W h kg−1) and power density (5815 W kg−1). The excellent electrochemical properties determined here further reveal the application prospects of multifunctional GO composite fiber film.