Rational Anion Selection of the Electrolyte Additive for Highly Reversible Lithium Plating/Stripping

摘要

Recruiting anions from electrolyte additives into the lithium ion solvationstructure is a promising strategy for the construction of long-lifespan Li-metalbatteries (LMBs). However, inadequate understanding of the anion-involvedLi~+ solvation hinders the finding of new anion additives. Herein, using NO_3~?as an example, the effects of the newly-introduced anion on the Li+ solvationstructure are investigated. It is demonstrated that the added NO_3~? reducesthe electrostatic potential of the Li~+ solvation cluster, especially for solvatedsolvents, which improves electrolyte stability against the Li anode. However,such a conclusion is not universal for all anion additives. It is also confirmedthat the anions with higher binding energy and smaller ion size are more aptto improve the Li stability and reversibility. Based on the above understanding,a new selection principle based on anion selection coefficient (the rate of theanion size to the binding energy toward Li~+, unit: A~3 eV~(?1)) is proposed, andwith which a new hexafluorosilicate anion is found to be beneficial to LMBs.