Influence of cell dimensions and housing material on the energy density and fast-charging performance of tabless cylindrical lithium-ion cells

Abstract

The utilization of large-format cylindrical lithium-ion cells with innovative tab design has been confirmed by a number of automotive manufacturers for future vehicle generations. The cell dimensions and housing materials are however widely discussed and will vary depending on the application and vehicle class. In this study, geometrical models are developed that describe the properties of the cells structural components with regard to certain defining loadcases. The volume efficiency and energy density as a function of cell dimensions and housing material choices are explored. A thermo-electrical-electrochemical modeling framework is used to generate a deep understanding of the investigated variables on the key characteristics of fast-charging processes. A 3-stage coolant flow controlling procedure is proposed that ensures the best possible performance for all dimensions and material choices and enables a consistent basis for meaningful comparisons. Results show that cells with aluminum housings provide slightly less volumetric energy density of 3% - 4% compared to nickel plated steel housings while providing 9% - 11% more gravimetric energy density. The fast-charging performance of a 4695 cell with bottom cooling can be optimized by 15% from 13 min 45 s to 11 min 45 s when introducing an aluminum housing due to less heat generation and less thermal resistance in axial direction. The electrical and thermal resistances imposed by the connection between the tabless jelly roll and the cell ends are identified as having significant influence on the cells performance as a function of dimensions.