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 the 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 one dimensional tunnel-structure titanosilicate sitinakite compound with an ideal formula of Na_1.68H_0.32Ti₂O₃SiO₄·1.76H₂O employed as a new type anode material in 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 pre-dehydration as an effective avenue to further improve the capacity of Na_1.68H_0.32Ti₂O₃SiO₄·1.76H₂O anode (reversible capacity of 131 mAh g^-1 at a current density of 20 mA g^-1 after pre-dehydration process). In addition, cation Nb doped Na_1.68H_0.32Ti₂O₃SiO₄·1.76H₂O compounds have been synthesized and systematically investigated the electrochemical performances in SIBs.

Reference

[1] Liu, Y.; Xia, Y., Na_1.68H_0.32Ti₂O₃SiO₄·1.76H₂O as a Low-Potential Anode Material for Sodium-Ion Battery. ACS Applied Energy Materials 2018, doi:10.1021/acsaem.8b01412.