Electrochemical Performance and Thermal Stability Studies of Two Lithium Sulfonyl Methide Salts in Lithium-Ion Battery Electrolytes

Electrolyte solutions, containing the lithium sulfonyl methide salts lithium-tris(trifluoromethanesulfonyl)methide (LiTFSM) and lithium-[bis(trifluoromethylsulfonyl)-pentafluoroethylsulfonyl]methide (LiPFSM) dissolved in organic carbonate solvents, were electrochemically investigated in Li/graphite, Li/LiNi 1/3 Co 1/3 Mn 1/3 O 2 (NCM) half-cells and compared to the LiPF 6 based electrolyte with regard to their ionic conductivity, electrochemical stability, thermal stability at 60°C and the anodic dissolution behavior vs. Al. While the investigated salts show almost the same performance in Li/graphite half-cells compared to the LiPF 6 containing electrolyte, the methide salts show very promising results in Li/NCM half-cells, which depict superior capacity retention as well as higher Coulombic efficiencies compared to the LiPF 6 containing electrolyte. Taking the limited anodic stability as well as the occurring anodic dissolution into account, both salts but especially LiTFSM indicate the applicability in lithium ion battery electrolytes for cells with a cutoff potential up to 4.3 V vs. Li/Li + .