V3Se4 embedded within N/P co-doped carbon fibers for sodium/potassium ion batteries

The development of electrode materials with high reversible capacity, superior rate capability, and long lifespan for sodium-ion and potassium-ion batteries (SIBs/PIBs) is gaining great attention. Herein, V3Se4 nanoparticles embedded in nitrogen/phosphorus co-doped carbon nanofibers (V3Se4/NPCNFs) were initially synthesized with the assistance of biomass algae (Chlorella pyrenoidosa) and employed as anodes in SIBs and PIBs for the first time. The experimental findings and DFT calculation results reveal that heteroatom N/P co-doping could increase the content of pyridinic N with more open edge sites and boost the Na+/K+ storage performance by optimizing the distribution of electron density and enhancing ion reaction kinetics. As a result, the V3Se4/NPCNFs electrode exhibits an admirable capacity (527 mAh g−1/0.1 A g−1/60 cycles) and ultralong cycle performance (340 mAh g−1/5 A g−1/8000 cycles and 240 mAh g−1/10 A g−1/13000 cycles) for SIBs as well as an excellent electrochemical performance for PIBs (450 mAh g−1/100 cycles at 50 mA g−1 and 207 mAh g−1/800 cycles at 2 A g−1). The SIB full cell obtained by pairing with a Na3V2(PO4)3 cathode also reveals outstanding cycling performance. Thus, this work helps explain how biomass algae is a sustainable and economical source of heteroatoms and reactor in constructing energy storage materials.