Influence of lithium-cyclo-difluoromethane-1,1-bis(sulfonyl)imide as electrolyte additive on the reversibility of lithium metal batteries

Electrolyte solutions containing lithium-cyclo-difluoromethane-1,1-bis(sulfonyl) imide (LiDMSI) as an additive were specifically designed for measurements in lithium plating-stripping model experiments on copper electrodes. LiDMSI was implemented into two different electrolyte solutions. The first electrolyte setup consisted of a 1 M solution of LiTFSI in PC as an electrolyte which is known to show a comparably limited performance for reversible Li deposition. The second setup was comprised 1 M LiAsF6 in 1,3-dioxolane as the base electrolyte which depicts a well-tested performance for lithium deposition-dissolution. The addition of LiDMSI yielded significantly improved results in regard to Coulombic efficiencies and cycling stability in both electrolyte compositions. Furthermore, it negated the formation of high surface area, e.g., dendritic lithium, which depicts the main source for the limited safety of rechargeable lithium metal batteries. In the case of the PC-based electrolyte system, the LiDMSI-containing electrolyte illustrates a slightly lowered over-potential on the copper substrate, while for the dioxolane-based setup the over-potentials were almost completely equal. In order to compare the morphologies of the lithium deposits, SEM images were utilized.