Investigation on effective thermal conductivities of porous electrodes for the commercial Li-ion battery

Abstract

The effective thermal conductivities (ETCs) of porous electrodes in electrolyte are of rather significance for determining the thermal conductivity of Li-ion battery which is an important factor in designing battery thermal management system and predicting battery thermal behaviour. In this study, the representative Li-ion battery consisting of a Li(NiCoMn)O2 positive electrode and a graphite negative electrode was chosen to explore the ETCs of porous electrodes. The effects of ETCs of porous electrodes on the Li-ion battery's thermal conductivity were firstly discussed, and the ETCs were analysed based on its internal configuration and basic assumptions. Most importantly, the ETCs bounds of porous electrodes were acquired using basic thermal conductivity models and the limits of ETCs were obtained based on Maxwell 2 model combined with volume fractions of electrolyte. The results show that the ETCs of porous electrodes in electrolyte are obviously lower than the thermal conductivities of active materials, namely Li(NiCoMn)O2 and graphite. In addition, the ETCs of porous electrodes are not constant but variable values caused by the variation of volume fractions of electrolyte in porous electrodes which indicates that the volume fractions of electrolyte should be considered for accurately estimate the thermal conductivity of commercial Li-ion battery.