Overcoming the Unfavorable Kinetics of Na3V2(PO4)(2)F-3//SnPx Full-Cell Sodium-Ion Batteries for High Specific Energy and Energy Efficiency

Abstract

In this work, a full-cell sodium-ion battery (SIB) with a high specific energy approaching 300 Wh kg(-1) is realized using a sodium vanadium fluorophosphate (Na3V2(PO4)(2)F-3, NVPF) cathode and a tin phosphide (SnPx) anode, despite both electrode materials having greatly unbalanced specific capacities. The use of a cathode employing an areal loading more than eight times larger than that of the anode can be achieved by designing a nanostructured nanosized NVPF (n-NVPF) cathode with well-defined particle size, porosity, and conductivity. Furthermore, the high rate capability and high potential window of the full-cell can be obtained by tuning the Sn/P ratio (4/3, 1/1, and 1/2) and the nanostructure of an SnPx/carbon composite anode. As a result, the full-cell SIBs employing the nanostructured n-NVPF cathode and the SnPx/carbon composite anode (Sn/P = 1/1) exhibit outstanding specific energy (approximate to 280 Wh kg((cathode+anode))(-1)) and energy efficiency (approximate to 78%); furthermore, the results are comparable to those of state-of-the-art lithium-ion batteries.