PNNL

Abstract

The entropies (?S) in various cathode and anode materials, as well as complete lithium ion bat-teries, were investigated by Electrochemical Thermodynamic Measurement System (ETMS). A thermodynamic model based on the fundamental properties of individual electrodes is used to obtain the transient and equilibrium temperature distribution of lithium ion batteries. The results from theoretical simulations are compared with the results obtained in experimental measure-ments. It is found that detailed shape of the entropy curves strongly depends on the manufac-turer of the materials even for the same nominal compositions. LiCoO2 has a much larger en-tropy change than those of LiNixCoyMnzO2. This means that LiNixCoyMnzO2 is much more thermodynamically stable than LiCoO2. The temperatures around the positive terminal of a prismatic battery are consistently higher than those at the negative terminal. When all other simulation parameters are the same, the effects of using battery-averaged entropy in the simulation tends to overestimate the predicted temperatures than using individual entropies for anode and cathode.