Superior coulombic efficiency of lithium anodes for rechargeable batteries utilizing high-concentration ether electrolytes

• Published in: Electrochimica acta 2019-10, Vol.319, p.625-633
• Main Authors: Xie, Jian-De, Liu, Weng-Jing, Li, Chi, Patra, Jagabandhu, Gandomi, Yasser Ashraf, Dong, Quan-Feng, Chang, Jeng-Kuei
• Format: Article
• Language: English
• Subjects: Anodes; Batteries; Copper; Coulombic efficiency; Dendritic structure; Electrochemical analysis; Electrolytes; Ether electrolyte; Flammability; High concentration electrolyte; Li dendritic structure; Li metal battery; Lithium; Lithium-ion batteries; Metal foils; Molecular chains; Molecular structure; Rechargeable batteries
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2019.07.020

This study adopts high-concentration ether electrolytes to improve high-rate capability, cycling stability, and Coulombic efficiency (CE) for lithium ion batteries with lithium anode. A series of ether-based electrolytes including lithium bis(fluorosulfonyl)imide (LiFSI)-glyme/ethylene carbonate (EC), LiFSI-glyme/EC, LiFSI-diglyme/EC, LiFSI-triglyme/EC, LiFSI-tetraglyme (G4)/EC, and LiFSI-1,3-dioxolane (DOL)/EC, along with commonly used LiPF6-DEC/EC were prepared to delineate the influences of concentration, chain length, molecular structure (linear or ring ether), and EC additive on the electrochemical performance of Li anodes. An optimum composition for ether-based electrolyte was determined resulting in significant improvement in anti-flammability as well as CE at both low and high rates. At ultra-high current density operation (e.g. 6 mA cm−2), the CE was 95.5 and 97.1% with 3 M LiFSI-G4/EC and 3 M LiFSI-DOL/EC, respectively. Using 1 M LiPF6 carbonate-based electrolyte tend to grow a needle-like dendritic structure when depositing lithium metal on Cu foils, whereas high-concentration ether electrolyte promotes a knot-like and rounded Li metal microstructure. High concentration EC-based electrolytes, are capable of facilitating Li+ almost in tandem with solvent molecules, thereby reducing the number of free molecules, reducing the chance of side reaction with Li metal, and subsequently inhibiting the formation of dendritic Li structures. [Display omitted] •Ether electrolytes are used to improve Coulombic efficiency for Li-ion batteries.•This study reveals two key factors: chain length and molecular structure in ether.•An optimal composition for ether electrolyte is beneficial anti-flammability.•The Coulombic efficiency reaches 95.5% at high current using 3 M LiFSI-G4/EC.•High-concentration ether electrolyte promotes a knot-like Li metal microstructure.