Authors: Rubio, S; Maca, RR; Aragon, MJ; Cabello, M; Castillo-Rodriguez, M; Lavela, P; Tirado, JL; Etacheri, V; Ortiz, GF

J. Power Sources. vol: 432. page: 0378-7753.
Date: AUG 31. 2019.
Doi: 10.1016/j.jpowsour.2019.05.070.

Sodium-ion batteries are considered a promising alternative to lithium-ion batteries due to its low cost and potential applications for large-scale energy storage. In this work, we focus on improving the Na-ion storage electrochemical performance of TiO2 anodes by using diglyme-based electrolyte solutions. Significantly better performances are observed for the first time in diglyme-based electrolyte solution, as compared to conventional carbonate electrolyte solutions with and without additives such as fluoroethylene carbonate (FEC) and vinylene (VC). The best TiO2 electrode demonstrated a high specific capacity of 248 mA h g(-1) at 25 mA g(-1) current density, similar to 100% coulombic efficiency, superior pseudocapacitive Na-ion storage, and good capacity retention on extended galvanostatic charge-discharge cycles. A full-cell assembled with TiO2 anode, Na3V2(PO4)(3) cathode and NaPF6-diglyme electrolyte solution demonstrated an energy density as high as 440 W h kg(-1). Superior electrochemical performance of TiO2 anodes in diglyme-based electrolyte is credited to the enhanced passivation and Na-ion conducting properties of polyether-based solid electrolyte interfaces (SEI) compared to polycarbonate-based counterparts. Carbon coating also resulted in the reduced decomposition of both diglyme and carbonate based electrolyte solutions. These results potentially encourage the use of ether-based electrolyte solutions for further improving the electrochemical performance and commercialization of rechargeable Na-ion batteries..