Improving battery safety and longevity through uncertainty modeling of lithium-ion batteries and preventing the local over-charge/over-discharge 2020-01-0450
The battery electrodes are porous and have complicated microstructures due to irregular sizes and shapes of pores. Electrode design parameters like porosity, thickness, particle size, and conductivity can vary from one local area to another in one cell. Even under the normal operating range, some local areas may experience over-charge/over-discharge, extensive degradation, and rapid heat generation. These local events are not easy to observe or measure at the beginning and can eventually lead to catastrophic failure of the whole cell if no actions are taken. Therefore, the uncertainty of these parameters has a significant effect on the longevity and safety of batteries. Most of the electrochemical battery models assume design parameters have constant values in a cell which is not able to capture the uncertainty described above. To prevent any catastrophic failure, the applied current should be cut off before any over-charge/over-discharge and rapid heat generation caused by these random local areas. In this work, a new method is developed to simulate random local events and design new control strategies to increase longevity and safety. An electrochemical-based battery degradation model is integrated with the Monte Carlo simulation to capture the unknown random design parameters in a cell. Random samples are taken to represent the complex microstructure. The battery model can simulate major side reactions, Lithium plating, state of health, and heat generation. This work opens the possibility to predict the uncertainties of batteries without detailed 3D modeling and can also be used for battery design optimization, battery management systems, and state estimations due to its flexibility and reasonable computational cost. The simulation results show that under the normal cutoff voltage range, local areas experience over-charge/over-discharge and high heat generation, which can damage the overall safety and longevity of batteries.