Lithium-ion batteries provide higher energy and power densities when compared with nickel cadmium, nickel metal hydride, and lead acid batteries. However, abusive usage of such batteries, that is, high discharge/charge rate or operation under extreme ambient temperature leads to excessive heat generation. As the temperature rises to approximately , exothermic side reactions are promoted that generate additional heat. This dramatically increases internal temperature and the release of gases builds up pressure, ultimately leading to a disastrous event known as thermal runaway. Eliminating this threat requires a deeper understanding of the electrochemical heat generation and the prevalent anisotropic thermal transport within the battery that leads to accumulation of heat within the core. Accurate characterization of thermal

conductivity will enable a better understanding of transport as well as aid numerical electrochemical-thermal modeling, which will improve thermal management strategies. Currently, thermal conductivity data is lacking for certain cathode materials like (LMO) and (NCA) at the electrode-level and the cell-level. In this paper, infrared (IR) microscopy is used to characterize and visualize cross-plane thermal conduction in electrode (LMO cathode and graphite anode) and separator materials. In this work, IR microscopy is also used to investigate in situ spatial distribution of temperature across cathode-separator-anode, with the ultimate goal of characterizing spatio-temporal variation of heat generation. For the purpose, we have built an air-tight set-up that houses the electrodes, separator and the electrolyte with visualization through an infrared-transparent calcium fluoride (CaF₂ )  window. Temperature and charging/discharging voltages and currents are recorded simultaneously during charging and discharging for further analysis.