Na1.68H0.32Ti2O3SiO4·1.76H2O as a Low-Potential Anode Material for Sodium-Ion Battery

Sodium-ion batteries (SIBs) have been considered as a promising candidate for large-scale energy storage applications, because of the low cost of sodium element and a broad choice of cathode materials which do not contain expensive raw materials. However, a lack of promising anode materials still hinders the development of SIBs technology. Herein, we for the first time report a new one-dimensional tunnel-structure anode material, Na1.68H0.32Ti2O3SiO4·1.76H2O, for SIBs. This material can deliver a reversible capacity of 110 mAh g–1 at a current density of 20 mA g–1 and with an average working voltage of 0.4 V vs Na+/Na. The structure changes of this material during discharge/charge processes were investigated by using in situ laboratory X-ray diffraction. The results indicated that sodium insertion proceeds via a topotactic intercalation pathway. We also identified predehydration as an effective avenue to further improve the capacity of Na1.68H0.32Ti2O3SiO4·1.76H2O anode (reversible capacity of 131 mAh g–1 at a current density of 20 mA g–1 after the predehydration process)