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

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 LiNi_0.33Mn_0.33Co_0.33O₂ 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 °C) cyclability and low-temperature rate performance (capacity enhanced by 100 % at 3 C at −20 °C). This low-temperature formation cycling to construct LiF-rich CEI is extended to various cathode systems, such as LiNi_0.8Mn_0.1Co_0.1O₂, LiCoO₂, LiMn₂O₄, demonstrating the versatility and potential impact of our strategy in advancing the performance and stability of wide-temperature batteries and beyond.