Necklace-like carbon nanofibers encapsulating V3S4 microspheres for ultrafast and stable potassium-ion storage

Potassium-ion batteries (PIBs) are promising candidates for scalable energy storage devices due to their low cost, high operating voltage and fast ionic conductivity in electrolyte. However, the research progress of PIBs still faces great challenges due to the lack of suitable hosts for reversible depotassiation/potassiation of large size K+, thus leading to low reversible capacity and poor cycling stability and rate capability. Herein, we have rationally designed a new necklace-like V3S4/carbon composite composed of V3S4 microspheres encapsulated in N-doped carbon nanofibers (V3S4@NCNFs) as an advanced anode for PIBs. Benefiting from the remarkable ion/electronic conductivity, fast electron transport, structural integrity upon cycling, and significant pseudocapacitance contributions, the V3S4@NCNF electrodes exhibit a high reversible capacity of 445 mA h g(-1) after 300 cycles at 0.2 A g(-1), a prolonged cycling stability of 245 mA h g(-1) capacity retention over 1000 cycles at 2 A g(-1), and an excellent rate performance of 249/202 mA h g(-1) at 5/10 A g(-1), which are superior to those of most reported anode materials for PIBs.