A method to determine the specific heat capacity of lithium-ion battery cells using thermal insulation

Abstract

Thermal simulations of lithium-ion batteries that contribute to improvements in the safety and lifetime of battery systems require precise thermal parameters, such as the specific heat capacity. In contrast to the vast number of lithium-ion batteries, the number of specific heat capacity results is very low. This work presents a new method for accurately and easily determining the specific heat capacity of battery cells of any form factor. Using an extruded polystyrene thermal resistor, temperature logging equipment, and two temperature chambers at different temperatures, the presented approach determines the specific heat capacity of cylindrical 18650 and 21700 cells, in addition to two pouch cells, through simple temperature changes. While the cylindrical cells have very similar specific heat capacities, both pouch cells have significantly higher specific heat capacities most likely due to their different material compositions. Linear approximations of the results agree well with a temperature sensitivity of all battery models between 1.6 and 2.0 JkgK per ∘C over the range of 0 ∘C to 40 ∘C. Compared to a reference material with a known specific heat capacity, validation measurements reveal an error between 1% and 3%.