High performance of HNaV6O16·4H2O nanobelts for aqueous zinc-ion batteries with in-situ phase transformation by Zn(CF3SO3)2 electrolyte

Zn(CF3SO3)2 as an electrolyte has been widely used to improve the electrochemical performance for ZIBs due to that the bulky CF3SO3− can reduce the solvation effect of Zn2+ and promote the ionic diffusion. Herein, we found that Zn(CF3SO3)2 electrolyte can induce different electrochemical mechanisms from ZnSO4 electrolyte. Compared to the ZnSO4 electrolyte, the HNaV6O16·4H2O electrode with Zn(CF3SO3)2 electrolyte exhibits a high capacity of 444 mAh·g−1 at 500 mA·g−1 with a capacity retention of 92.3% after 80 cycles. Even, at a high rate of 5 A·g−1, the HNaV6O16·4H2O electrode delivers an initial discharge capacity of 328 mAh·g−1 with a capacity retention of 93.7% after 1000 cycles. Differing from the mechanism with ZnSO4 electrolyte, the excellent cycle stability of HNaV6O16·4H2O electrode can be attributed to the in-situ phase transformation to ZnxV2O5·nH2O based on the co-intercalation of Zn2+/H+.