Regulating the Li+ -Solvation Structure of Ester Electrolyte for High-Energy-Density Lithium Metal Batteries.

Abstract

The development of high-energy-density Li metal batteries are hindered by electrolyte consumption and uneven lithium deposition due to the unstable lithium-electrolyte interface (SEI). In this work, tetraglyme is introduced into ester electrolyte to regulate the Li+ -solvation structures for stable SEI while remaining appropriate voltage window for high-voltage cathodes. In the modified solvation structures, an enhanced lowest unoccupied molecular orbital energy level occurs, resulting in relieved electrolyte degradation. In addition, the modified solvation structures can facilitate adequate LiNO3 dissolution in the ester electrolyte (denoted as E-LiNO3 ), contributing to constant supplement of constructing highly conductive LiNx Oy -containing SEI for dendrite-free Li deposition under high capacity condition. As a result, the Li||Cu cell-based on this electrolyte exhibits high Li plating/stripping Coulombic efficiency of 98.2% over 350 cycles. Furthermore, when paired with high-voltage LiNi0.5 Co0.2 Mn0.3 O2 cathodes, the E-LiNO3 enables a stable cycling with a high-energy-density of 296Wh kg-1 based on the full cell under realistic testing conditions (lean electrolyte of 3 gAh-1 , limited Li excess of 2.45-fold, and high areal capacity of 4 mAh cm-2 ).