Ag-coated 3D groove as a study platform in evaluating the throwing power of electrolytes for Li metal batteries

Abstract

Selecting electrolytes is critical before assembling a cell to achieve good performance in a Li metal battery. An Ag-coated groove with hill and valley features is prepared by magnetron sputtering on a 3D structure array pattern laying on a commercial Cu foil to act as a platform to evaluate liquid electrolytes in Li//Cu half-cell configuration. The 3D Ag-coated groove with hill and valley feature provides the capability to determine the uniformity in terms of throwing power (TP) of various electrolytes, which is correlated with their electrochemical performance. The increase in TP value after applying fluoroethylene carbonate (FEC) (−3.59%) and tris(trimethylsilyl) phosphite (TMSP) (−49.60%) as an additive is in contrast to the TP value of the pristine electrolyte w/o additive (−66.84%), which is in line with the higher average coulombic efficiency achieved (95.39% for FEC and 94.87% for TMSP) compared to LiPF6 alone (91.89%). Moreover, the FEC-contained electrolyte achieves the lowest value of resistance (18.76 Ω and 10.92 Ω) and average surface roughness Ra (24.8 and 22.4 nm) on hill and valley, respectively, among the investigated electrolytes. Applying the design of an Ag-coated groove gives significant insight into how a platform can be built to comply with the effort in screening the good options for liquid electrolytes in Li metal battery application.