The influence of micro-structured anode current collectors in combination with highly concentrated electrolyte on the coulombic efficiency of in-situ deposited li-metal electrodes with different counter electrodes

Abstract

This paper compares and combines two common methods to improve the cycle performance of lithium metal (Li) electrodes. One technique is to establish a micro-structured current collector by chemical separation of a copper/zinc alloy. Furthermore, the use of a highly concentrated ether-based electrolyte is applied as a second approach for improving the cycling behavior. The influence of the two measures compared with a planar current collector and a 1 M concentrated carbonate-based electrolyte, as well as the combination of the methods, are investigated in test cells both with Li and lithium nickel cobalt manganese oxide (NCM) as counter electrodes. In all cases Li is in-situ plated onto the micro-structured current collectors respectively a planar copper foil without presence of any excess Li before first deposition. In experiments with Li counter electrodes, the effect of a structured current collector is not visible whereas the influence of the electrolyte can be observed. With NCM counter electrodes and carbonate-based electrolyte structured current collectors can improve Coulombic efficiency. The confirmation of this outcome in experiments with highly concentrated ether-based electrolyte is challenging due to high deviations. However, these results indicate, that improvements in Coulombic efficiency achieved by structuring the current collector’s surface and using ether-based electrolyte do not necessarily add up, if both methods are combined in one cell.