A fast formation protocol considering mechanical pressure improving capacity during lithium-ion battery long-term cycling

The formation process plays a vital role in lithium-ion battery manufacturing, which influences the follow-up performance of batteries. To develop high-quality and fast formation protocols, current studies have extensively investigated the effects of factors such as current, voltage, and temperature on the formation process. However, the influence of initial mechanical pressure on battery formation has been rarely studied, although it is an important parameter during battery operation due to the electrochemical-mechanical coupling in batteries. A formation device with a pressure sensor was developed in this study to precisely control the initial pressure. 15 groups of experiments were designed using initial pressure as the variable and three types of voltage-current formation cycles. Multiscale characterization methods were employed to analyze the mechanism and effects of different initial pressures and voltage-current formation cycles on the battery formation process. An optimized fast formation protocol considering initial pressure is developed, which improves battery capacity by 5 %, reduces 1/3 formation time, and maintains a higher capacity during the long-term cycling compared to the baseline formation protocol. The proposed formation protocol provides valuable guidance for optimizing the production of lithium-ion batteries, promoting the low-cost and large-scale deployment of energy storage power stations and electric vehicles.