High power NaV(PO) symmetric full cell for sodium-ion batteries

Sodium-ion batteries (SIBs) are a viable substitute for lithium-ion batteries due to the low cost and wide availability of sodium. However, practical applications require the development of fast charging sodium-ion-based full-cells with high power densities. Na 3 V 2 (PO 4 ) 3 (NVP) is a bipolar material with excellent characteristics as both a cathode and an anode material in SIBs. Designing symmetric cells with NVP results in a single voltage plateau with significant specific capacity which is ideal for a full cell. Here we demonstrate for the first time a tremendous improvement in the performance of NVP symmetric full cells by introducing an ether-based electrolyte which favors fast reaction kinetics. In a symmetric full cell configuration, 75.5% of the initial capacity was retained even after 4000 cycles at 2 A g −1 , revealing ultra-long cyclability. Excellent rate performances were obtained at current densities as high as 1000C, based on the cathode mass, revealing ultrafast Na + transfer. The power density obtained for this NVP symmetric cell (48 250 W kg −1 ) is the best among those of all the sodium-ion-based full cells reported to date. The study details the electrochemical characterization of NVP anodes and symmetric NVP cells in a DME electrolyte for the first time.