NASICON-type V-doped Ca0.5Ti2 (PO4)3/C nanofibers for fast and stable potassium storage

[Display omitted] •Ca0.5Ti1.9V0.1(PO4)3 nanoparticles embed in carbon nanofibers to form the composite by electrospinning.•Moderate V doping enhances electrochemical conductivity greatly.•The Ca0.5Ti1.9V0.1(PO4)3/C nanofibers exhibit outstanding rate performance.•The fact that pseudocapacitance effect boosts the rate performance is verified. Potassium ion batteries (PIBs) are considered as the next-generation energy storage devices owing to the relatively low cost and the plentiful reserves. In addition, the redox potential of K+/K is comparable to that of Li+/Li. When it comes to the negative electrode, NASICON type materials draw much attention owing to their robust structure and high ionic mobility. Herein, vanadium doped Ca0.5Ti2 (PO4)3/C nanofibers are prepared by means of electrospinning and post-annealing, and vanadium is doped into the matrix in order to boost the ionic/electronic conductivities. When assembled as PIBs half cells, it delivers a high capacity of 131 mAh g−1 at 5 A g−1, which performs best in analogues. Furthermore, it provides a stable capacity of 112 mAh g−1 after 1000 cycles at 1 A g−1. This finding indicates that V-doped Ca0.5Ti2 (PO4)3/C nanofibers have the potential to be an attractive anode choice for PIBs.