Ionic liquid crystal with fast ion-conductive tunnels for potential application in solvent-free Li-ion batteries. (20th January 2019)

• Record Type: Journal Article
• Authors: Yuan, Fen; Chi, Shuai; Dong, Shunping; Zou, Xin; Lv, Shuyi; Bao, Lixia; Wang, Jiliang
• Is Part Of: Electrochimica acta. Volume 294(2019)
• Page Start: 249
• Page End: 259
• Publication Date: 2019-01-20
• Subjects: Ionic liquid crystal -- Fast ion-conductive -- Solvent-free -- Energy storage -- Secondary Li-ion battery; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2018.10.079
• Languages: English
• ISSNs: 0013-4686

Abstract

Abstract: Insulated polymer host and lithium salt need to be separately dissolved into organic solvents prior to assembly of lithium batteries, implying a large usage of organic solvents and the consequent disadvantages of poor thermal stability, flammability, and explosibility of the end products. Herein, a new generation of thermotropic ionic liquid crystalline lithium salt (LiBIB) with potential bilayer fast ion-conductive tunnels, having functionalities of both lithium salt and polymer host or electrolyte, is successfully synthesized. Molecular structure, thermal stability, ionic conductivity, electrochemical stability, and ion-conductive mechanism of the LiBIB are extensively assessed. The obtained LiBIB shows typical behaviors of both ionic liquid and liquid crystal. Melt point at 43 °C, much lower than that of traditional lithium salts like LiClO4 and LiPF6, and clear point of the LiBIB at 83 °C are both detected. Solid LiBIB salt shows better ionic conductivity (3 × 10 −3 S cm −1 ) and electrochemical stability at room temperature in comparison with those of traditional lithium salts. Time-resolved and perturbation-correlation moving window 2D-COR FTIR results indicate that the high ionic conductivity of the LiBIB is mainly originated from the formation of fast ion-conductive tunnels, implying a promising application in solvent-free Li-ion batteries. Graphical abstract: Highlights: Thermotropic ionic liquid crystalline lithium salt (LiBIB) with fast ion-conductive tunnels is successfully synthesized. LiBIB shows excellent electrochemical stability and self-ionic conductivity of 3 × 10 −3 S cm −1 at room temperature. The high ionic conductivity of LiBIB is originated from the formation of fast ion-conductive tunnels. The quasi-period of Li-ion migration in solid LiBIB is lower than 70 ns.