How does temperature affect the degradation rate of lithium-ion batteries?

Temperature significantly affects the degradation rate of lithium-ion batteries; generally, higher temperatures accelerate degradation, while lower temperatures (within a reasonable range) can slow it down. Increased temperatures promote several degradation mechanisms within the battery. One major mechanism is the formation of the Solid Electrolyte Interphase (SEI) layer on the anode. The SEI layer is formed by the decomposition of the electrolyte on the surface of the anode, and while a stable SEI layer is necessary for battery function, excessive SEI growth increases resistance and consumes lithium ions, leading to capacity fade, which is the gradual loss of the battery's ability to store charge. Higher temperatures also accelerate electrolyte decomposition, reducing the amount of electrolyte available for ion transport and increasing internal resistance. Elevated temperatures enhance the rate of lithium plating, a process where metallic lithium deposits on the anode surface instead of intercalating into the graphite structure. Lithium plating reduces the amount of cyclable lithium and can also lead to safety issues. Furthermore, high temperatures can exacerbate corrosion of the current collectors and other internal components, contributing to increased resistance and decreased performance. The Arrhenius equation describes the relationship between temperature and reaction rates, indicating that reaction rates increase exponentially with temperature. This means that even a small increase in temperature can lead to a substantial increase in the degradation rate of the battery. Conversely, operating lithium-ion batteries at lower temperatures (but above freezing to avoid electrolyte freezing) can help to slow down these degradation mechanisms and extend the battery's lifespan. However, extremely low temperatures can also reduce battery performance, particularly the discharge rate. Therefore, maintaining the battery within its optimal temperature range through effective thermal management is crucial for maximizing its lifespan and performance.