Prognostic analysis of thermal interface material effects on anisotropic heat transfer characteristics and state of health of a 21700 cylindrical lithium-ion battery module

In this study, a semi-empirical computational heat transfer model has been developed to simulate anisotropic thermal characteristics in nickel-rich rechargeable 21700 lithium-ion battery modules with thermal interface materials. A set of conservation equations were developed and numerically solved using a finite-volume-based computational fluid dynamics technique. Experimental measurements of direct current internal resistance, temperature-dependent open circuit potential, and electrochemical impedance were conducted to obtain thermal and electrical data prior to the development of battery heat generation and performance aging models. Detailed reversible and irreversible heat generation rates in battery modeling could be fully addressed and evaluated from the experimental data for post-extensive numerical analysis. After validating the developed battery models against measured experimental data, further numerical analyses were performed to evaluate the effect of thermal interface materials on the battery module temperatures and the state of health. Numerical results showed that the cooling performance of the battery module was improved by reducing interfacial thermal contact resistances after the thermal interfacing application. Moreover, it was found that the parallel thermal conductivity of the interfacing materials to bottom cooling channels is primarily related to the uniform temperature distribution of the battery module, whereas the vertical thermal conductivity is rather associated with maximum temperature. These features are clearly apparent with increased coolant flow rate and thermal interfacing thickness. Lastly, the state of health of the battery module can be enhanced with improved temperature uniformity and decreased maximum temperature of the module when the thermal interfacing materials are employed.