Reduced Order Electrochemical-Thermal Modeling of Cylindrical Cells Containing Graphite-Silicon Anodes Considering Thermal Gradients and Hysteresis

Abstract

Electrochemical thermal modeling of cylindrical cells presents unique challenges compared to other cell formats due to the effect of internal temperature gradients, which typically requires time-consuming simulations due to the number of mesh elements solved numerically. Adding to the difficulty, the emergence of silicon anodes induces voltage hysteresis that affects the cell behavior. In this paper, a reduced-order electrochemical-thermal model is developed for a 21700 cell, which is highlighted by three microcells considering the effects of internal temperature gradients, and an anodic stress model capturing the hysteresis effects caused by the silicon content. The electrochemical, thermal, and mechanical behaviors are investigated. During operations, a temperature gradient arises in the radial direction, resulting in a decrease in local resistance and an increase in reaction rate at the high-temperature core location. The presence of silicon causes a voltage hysteresis that is dominant in the low SOC range, which affects not only the irreversible but also the entropic heat generation. The proposed method achieves an 85% calculation time reduction compared with the existing literature method and a 95% reduction compared with the full order method, while maintaining the accuracy of the terminal voltage and heat generation rate predictions that are validated by experiments.