fig1

Figure 1. (A) Crystal structure of NVPF with the Amam space group;(B) Corresponding crystal structural evolution of NVPF during Na+ extraction. Reproduced with permission[57]. Copyright 2015, American Chemical Society; (C) The key benefits and intrinsic challenges of NVPF cathodes in SIBs. NVPF: Na3V2(PO4)2F3; SIB: sodium-ion battery.