Accessing the primary SEI on lithium metal – A method for low concentrated compound analysis

von Holtum, Bastian; Kubot, Maximilian; Peschel, Christoph; Rodehorst, Uta; Winter, Martin; Nowak, Sascha; Wiemers-Meyer, Simon

Abstract

Despite large research efforts in the fields of lithium ion and lithium metal batteries there are still unanswered questions. One of them is the formation of the SEI in lithium-metal-anode-based battery systems. Until now, a compound profile analysis of the SEI on lithium metal was challenging as the amounts of many compounds after simple contact of lithium metal and the electrolyte were too low for detection with analytical methods. This study presents a novel approach on unravelling the SEI compound profile via accumulation in the gas, liquid electrolyte and solid phase. The method uses the intrinsic behavior of lithium metal to spontaneously react with the liquid electrolyte. In combination with complementary, state-of-the-art analytical instrumentation and methods this approach provides qualitative and quantitative results on all three phases revealing the vast variety of compounds formed in carbonate-based electrolytes.