Ionic liquid as electrostatic shielding additive for dendrite-free lithium metal battery

Abstract

Lithium (Li) metal anodes have attracted much attention as their high specific capacity and low electrochemical potential significantly boost the energy density of secondary batteries. Nonetheless, the uncontrolled growth of Li dendrites causing a poor cycle capability restricts the commercialization of Li metal batteries. Herein, an ionic liquid with a long aliphatic chain (N-methyl-N-decyl pyrrolidinium (Pyr1(10)+) bis(trifluoromethanesulphonyl)imide (TFSI−)) is introduced as a non-consuming electrostatic shielding additive into the ether-based electrolyte. The admirable compatibility of Pyr1(10)+ cation with Li metal is verified via electrochemical analysis, and the adsorption of Pyr1(10)+ on the Li-metal/electrolyte interface is confirmed by Surface-enhanced Raman spectroscopy technique. Through redistributing the Li ions on the surface of Li metal, the growth of Li dendrites is suppressed, so as to improve the cycling performance of Li metal anodes in symmetric cells, asymmetric cells and Li||LiFePO4 full cells with low N/P ratio (3:1). This study provides new insights into revealing the electrostatic shielding mechanism of regulating Li metal deposition and prolonging the long-term cycling.