Temperature-Responsive Formation Cycling Enabling LiF-Rich Cathode-Electrolyte Interphase.

ABSTRACT

Formation of LiF-rich cathode-electrolyte interphase is highly desirable for wide-temperature battery, but its application is hindered by the unwanted side reactions associated with conventional method of introducing fluorinated additives. Here, we developed an additive-free strategy to produce LiF-rich cathode electrolyte interphase (CEI) by low-temperature formation cycling. Using LiNi0.33Mn0.33Co0.33O2 as a model cathode, the atomic ratio of LiF in the CEI formed at -5 °C is about 17.7%, enhanced by ~550% compared to CEI formed at 25 °C (2.7%). The underlying mechanism is uncovered by both experiments and theoretic simulation, indicating that the decomposition of LiPF6 to LiF is transformed into spontaneous and exothermic on positively charged cathode surface and lowering the temperature shift chemical equilibrium towards the formation of LiF-rich CEI. Superior to conventional fluorinated additives, this approach is free from unwanted side reactions, imparting batteries with both high-temperature (60 oC) cyclability and low-temperature rate performance (capacity enhanced by 100% at 3 C at -20 oC). This low-temperature formation cycling to construct LiF-rich CEI is extended to various cathode systems, such as LiNi0.8Mn0.1Co0.1O2, LiCoO2, LiMn2O4, demonstrating the versatility and potential impact of our strategy in advancing the performance and stability of wide-temperature batteries and beyond.