A lithium ion (Li-ion) battery module includes a container with one or more partitions that define compartments within the container. Each of the compartments is configured to receive and hold a prismatic Li-ion electrochemical cell element, and a cover is configured to be disposed over the container to close the compartments. The container includes a polymer blend including a base polymer and one or more additives blended into the base polymer. The base polymer is electrically nonconductive and the one or more additives are configured to increase a thermal conductivity of the container to promote transfer of heat generated from the electrochemical cell elements through the container.