Mechanistic Multi-Stage Constant Current and Constant Stress Charging Strategies for Silicon Electrodes in Lithium-Ion Batteries

Silicon (Si) electrodes with different geometries are considered as one of the main lithium-ion (Li-ion) battery material candidates to achieve high gravimetric energy density. However, the widespread use of Si is hindered by high mechanical instability due to large volume expansion caused by both elastic and plastic deformation. The performance can be further improved by controlling the lithiation/delithiation process through charging strategies. Therefore, in this paper, mechanistic charging strategies are proposed to prevent the Cauchy stress from exceeding a threshold value to prevent lifetime degradation while reducing the charging time. A computationally efficient closed-form formula is extracted to describe the Cauchy stress in the Si films, especially for plastic deformation. Two charging strategies are derived that can effectively limit the mechanical stress: (1) constant stress (CS) and (2) multi-stage constant current with controlled stress (MSCCS) charging strategies. Numerical results are presented for a 2.5 mAh battery. The results indicate a linear decreasing current profile with increasing SOC for the CS charging strategy.