Building highly stable and industrial NaVPOF/C as bipolar electrodes for high-rate symmetric rechargeable sodium-ion full batteries

We report the synthesis of carbon coated NaVPO 4 F (NaVPO 4 F/C) via industrial high-temperature calcination and its application as bipolar electrodes to build symmetric sodium ion full batteries (SIFBs). The reaction mechanism and electrochemical performance of NaVPO 4 F/C electrodes as both the anode and cathode have been deeply studied, respectively. This indicates that NaVPO 4 F/C electrodes, with negligible structural change and stable valence adjustment, are very applicable for the symmetric system. The electrodes deliver a high reversible capacity of 136 and 134 mA h g 1 with a high ion diffusion coefficient of 3.1 10 11 cm 2 s 1 and 2.56 10 11 cm 2 s 1 as the anode and cathode, respectively. Moreover, the symmetric SIFBs with NaVPO 4 F/C electrodes as both the anode and cathode at the same time exhibit a considerable reversible capacity, good rate performance and long cycle life (capacity retention is 90% after 400 cycles) as designed. This work displays the potential commercial application of the symmetric SIFBs with NaVPO 4 F/C bipolar electrodes. We report the synthesis of carbon coated NaVPO 4 F (NaVPO 4 F/C) via industrial high-temperature calcination and its application as bipolar electrodes to build symmetric sodium ion full batteries (SIFBs).