Significance of electrolyte additive molecule structure in stabilizing interphase in LiNi0.8Co0.1Mn0.1O2/artificial graphite pouch cells at high temperature

Electrolyte additives are pivotal for stable cycling of rechargeable lithium ion batteries (LIBs), which dictate the creation of the protective interphases on electrodes. Many additives have been proposed but less knowledge is available on the relationship between their molecular structure and interphase stability. This research compares three electrolyte additives with systematic changes in their cyclic ethylene sulfate structures, i.e. 1,3,2-dioxathiolane-2,2-dioxide (DTD), 4-methyl-1,3,2-dioxathiolane-2,2-dioxide (MDTD) and 4-propyl-[1,3,2] dioxathiolane-2,2-dioxide (PDTD) to investigate their effects on the performance of LiNi0.8Co0.1Mn0.1O2/artificial graphite lithium ion pouch cells at high temperature. Comprehensive character-izations reveal that all these additives exhibit similar oxidative and reductive activity, but they lead to diverse long-term cycling performance at 55 degrees C. The sulfate species derived from the propyl functionalized PDTD form the most effective cathode and anode interphases in preventing electrolyte decomposition and improving cycling capabilities, with capacity retention of 85 % after 900 cycles at 55 degrees C. Meanwhile, a super stable (3000 cycles), high-capacity (1668 mAh) pouch cell is constructed at 25 degrees C. This work paves a road to design electrolyte additive more efficiently for high-energy-density LIBs at elevated temperature.