Improving Sodium Storage Performance of Hard Carbon Anodes in Cyclic Ether Electrolytes by an Anion Receptor Additive

The intrinsic ring-opening polymerization of five-membered cyclic ether induced by Lewis acid hinder its practical application as electrolyte solvents in sodium-ion batteries. In this work, we find that introducing tris (2,2,2-trifluoroethyl) borate (TTFEB), an anion acceptor additive, into cyclic ether-based electrolyte solution effectively inhibits its polymerization by tethering the PF6 (-) anion. In addition, a stable inorganics-rich SEI layer is formed in TTFEB-containing electrolyte solution, which ensures fast Na+ transport kinetics upon extensive cycles. As a result, the cycle stability and rate capability of HC anodes in 1,3-dioxolane-based electrolyte solutions are evidently improved by TTFEB additive. Our study paves the way for the application of cyclic ethers in sodium-ion batteries.