High Rate Capability and Enhanced Cyclability of Na V (PO ) F Cathode by In Situ Coating of Carbon Nanofibers for Sodium-Ion Battery Applications.

A facile chemical vapor deposition method is developed for the preparation of carbon nanofiber (CNF) composite Na V (PO ) F @C as cathodes for sodium-ion batteries. In all materials under investigation, the optimized composite content, denoted as NVPF@C@CNF-5, shows excellent sodium storage performance (86.3 % capacity retention over 5000 cycles at 20 C rate) and high rate capability (84.3 mA h g at 50 C). The superior sodium storage performance benefits from the enhanced electrical conductivity of the working electrode after formation of a composite with CNF. Furthermore, the full cell using NVPF@C@CNF-5 and hard carbon as the cathode and anode, respectively, demonstrates an impressive electrochemical performance, realizing an ultrahigh rate charge/discharge at a current rate of 30 C and long-term stability over 1000 cycles. This approach is facile and effective, and could be extended to other materials for energy-storage applications.