Low-Temperature Charge/Discharge Mechanism in Li Ion Battery Anodes

Li ion rechargeable batteries are widely used in consumer applications, such as mobile devices and vehicles, but also in harsh environments such as space. To suppress degradation and ensure safety, they are preferably used under certain thermal conditions. Consequently, it is required to control the temperature of the battery within a certain range, for example, between 0°C and 45°C, by heating or cooling.
A Li ion rechargeable battery mainly consists of a cathode, anode, electrolyte, and a separator. At SEL we are conducting R&D on materials for these components to improve battery safety, capacity, and lifetime.
One of our achievements is a battery that can be charged and discharged at -40°C, thanks to an anode composite material consisting of graphite, which has favorable charge/discharge cycle characteristics with small degradation, and Si, which enables charging/discharging at -40 °C. Si is a well-known, high-capacity anode active material, but the fundamental principles behind its good low-temperature characteristics are not yet well understood. More research is therefore required.