Ternary electrolyte additive mixture for 5V lithium-ion battery cells

Cobalt-free LiNi_0.5Mn_1.5O₄ (LNMO) is a promising alternative to the commonly used cobalt-containing positive electrode active materials in lithium-ion batteries (LIBs), owing to its high redox potential, relatively low cost, and low environmental impact. The high cell voltage, however, comes along with several challenges that need to be overcome before the material can be successfully used in commercial cells. Herein, these challenges are addressed by introducing three additives into the liquid organic carbonate-based electrolyte, namely tris(trimethylsilyl)-phosphite (TTSPi), lithium bis(oxalato) borate (LiBOB), and ethyl-(2,2,2-trifluoroethyl) carbonate (TFEC). The optimized electrolyte composition enables superior performance of Li‖LNMO and graphite‖LNMO cells because of the stabilized interphases at both the negative and the positive electrode and, thus, suppressed electrolyte decomposition. This is demonstrated by the substantially reduced gassing upon cycling and shelf-storage. These results are anticipated to contribute to the successful commercialization of LNMO in more sustainable LIBs.