With the Hot Disk technique it is possible to perform anisotropic measurements on modern Li-ion batteries with a regular stack structure. The stack structure can be either cylindrical stack, or a plane stack structure.

 

Batteries of the above types, Figure left, with dimension 65 mm height, and 26 mm diameter, are possible to measure with the Hot Disk anisotropy module. Please note that the number of layers, for the measurement, should be at least approx. 10 layers (from the centre line to the outer rim). Also, the layers should have equal thickness, in order to obtain stable anisotropic results for both through-plane, as well as in-plane directions. (The Hot Disk anisotropic method assumes a homogeneous anisotropic structure.)

For Li-Ion batteries developed in 1998, typically the stack structure provided results approx. 60-65 W/mK in-plane, and through-plane of approx. 0.4-0.8 W/mK. More recently, the Li-Ion batteries we have tested at customers’ sites have displayed much higher thermal conductivity in both in-plane, as well as through plane, directions. We have during demonstration tests at customer facilities, found up to 140 W/mK in-plane, and up to 1.4 W/mK through-plane. For the through-plane, or across the stack structures, the mechanical pressure, as well as surface roughness, and/or other chemical solutions, will strongly influence the thermal contact resistance between the layers, which will in turn directly influence the effective thermal conductivity in the through-plane direction. The Hot Disk system with anisotropic module is an excellent tool for R&D of modern batteries and fuel cell systems.