Mechanical-electrochemical modeling of silicon-graphite composite anode for lithium-ion batteries

Silicon-graphite (Si–C) composite anode is considered as the promising next-generation commercial anode due to its mild volume change and relatively high capacity compared with Si and graphite anode. However, local huge volume expansion of Si–C composite anode during charge leads to a large expansion force of the cell, resulting in safety problems and performance degradation. Herein, we present a coupled mechanical-electrochemical model to investigate the electrochemistry and swelling behavior of lithium-ion batteries with Si–C composite anode. The influence of designed parameters on the electrochemical performance and volume change of the cell have been studied. The results reveal that the casing constraints significantly affect the change of cell structure parameters, but have a slight impact on electrochemical behavior. In addition, the design of the N/P ratio and press density can directly affect the power density and energy density of the cell. With the consideration of the designed threshold value of volume change (6% and 10%) for the batteries, the limited designed capacities for the Si–C composite anode are calculated to be 650 mAh g−1 and 1150 mAh g−1 respectively. Thus, the present simulation model is a useful tool for the future design of high energy density and safety batteries.