Study of the effects of preheating on discharge characteristics and capacity benefit of Li-ion batteries in the cold

The Li-ion battery's sharp performance decline in the cold restricts the use of electric vehicles. Preheating is a crucial strategy for addressing the issue. The available energy released by the battery should be more of a concern in the current preheating method studies. The capacity benefit upon preheating is investigated in the study while the battery is being discharged at low temperatures. The battery was preheated by a heating film at −25 °C and discharged with varying preheating durations. The effects of preheating on discharge characteristics and capacity benefits were analyzed. The findings indicate that the inner temperature can better reflect the battery's preheating state. Preheating can solve the problem that the battery cannot discharge in the cold by improving the terminal voltage. The capacity benefit of the battery does not change monotonically with the preheating time. For 2.0C discharge cases, the maximum capacity benefit of the battery is obtained with 3 min preheating, which is higher by 6.8 % and 15.1 % than that with 1 and 5 min preheating, respectively. There is no need for the battery to be preheated, or only a short preheating time is needed, if the battery can discharge with a small current.