Nitrile co-additives for stabilization of practical low-temperature lithium cobalt oxide batteries

With the extended applications of advanced lithium-ion batteries, pursuing excellent low-temperature discharge and high-temperature storage performances has become an urgent demand for traditional LiCoO₂ (LCO) batteries under high voltage. This study proposes an efficient approach to simultaneously realize the above-mentioned performances via incorporating multiple nitrile additives (i.e., succinonitrile (SN), adiponitrile (ADN), and 1,3,6-hexanetricarbonitrile (HTCN)) into a low-temperature electrolyte composed of carbonate (EC/PC/EMC) and carboxylate (EP/PP) solvents. By tailoring the composition of these nitrile additives, an organic- and inorganic-rich solid electrolyte interface has been engineered that can enhance the high-voltage and wide-temperature tolerance of LCO batteries. It is demonstrated that cyano groups in SN, ADN, and HTCN with high binding energy can effectively enhance the thermal stability of batteries (capacity decay < 6% after 4 h at 80 °C), while their low freezing point promotes excellent low temperature performances (capacity retention > 60% at −40 °C under 0.2C). The preferential degradation of multiple nitrile additives on LCO surface is found beneficial for suppressing the electrolyte decomposition, irreversible phase transition, and cobalt dissolution of LCO. This work unveils the importance of engineering on multiple nitrile additives, providing an innovative approach for the rational design of low-temperature electrolytes for LCO batteries.