Superior electrochemical performance of TiO2 sodium-ion battery anodes in diglyme-based electrolyte solution

• Published in: Journal of power sources 2019-08, Vol.432, p.82-91
• Main Authors: Rubio, Saúl, Maça, Rudi Ruben, Aragón, María J., Cabello, Marta, Castillo-Rodríguez, Miguel, Lavela, Pedro, Tirado, José L., Etacheri, Vinodkumar, Ortiz, Gregorio F.
• Format: Article
• Language: English
• Subjects: Diglyme-based electrolyte; High energy density; Na-ion batteries; Pseudocapacitance; Titania
• ISSN: 0378-7753; 1873-2755
• 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, ∼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. [Display omitted] •Novel application of diglyme-based electrolyte for TiO2 and C@TiO2 nanosheets.•Enhanced electrochemical performance in diglyme as compared to carbonate-based ones.•Na-ion full cells are built with C@TiO2, diglyme and Na3V2(PO4)3.•Full cells show high energy density (440 W h kg−1) and electrochemical stability.