Electrochemical Properties and Discharge Mechanism of Na/TiS₂Cells with Liquid Electrolyte at Room Temperature

The electrochemical properties of Na/TiS 2 cells fabricated from Na anodes and TiS 2 cathodes and 1M sodium trifluoromethanesulfonate in tetraethyleneglycol dimethylether liquid electrolyte have been investigated. The discharge curve has two plateau regions of 2.1 V and 1.6 V. The loss of discharge capacity appeared mainly in the upper plateau (UP) region (2.0–2.6 V) and the discharge capacity in the low plateau (LP) region (0.8–2.0 V) does not decrease and is consistent during 40 cycles. The discharge process between Na and TiS 2 has a complex reaction mechanism, the intercalation at the upper plateau region and the conversion at the low plateau region. Because, a distorted TiS 2 phase appeared in the upper plateau, a new phase of Na x TiS 2 was observed in the lower plateau, and the Na x TiS 2 phase was disappeared after full discharge from the XRD and TEM results. The decrease of discharge capacity during cycling is occurred from the formation of Na x TiS 2 phase in the cathode after full charging and is accumulated over cycling