Lithium batteries (LB) with metallic Lithium (Li) anode have higher volumetric and gravimetric energy densities compared to graphite anodes. Several commercial primary LBs utilize metallic Li due to its light weight, high voltage, wide operating temperature range, high theoretical capacity, and satisfactory conductivity. Since their initial employment in defense applications in the 1970s, their size has become smaller, and they are used in countless of different areas such as cameras, watches, calculators, security devices etc.

Electrochemical Impedance Spectroscopy (EIS) has become one of the most popular analysis methods for LBs, which is a non-destructive, in situ and comprehensive practice. It can provide valuable information about Li charge and mass transfer at active electrode areas, electrolytes, and interphases. Furthermore, it helps to model those parameters by building equivalent circuits.

In this study, we have worked with two chemistries of LBs. The first is Li/SOCl₂ (AA size) batteries, which are made of metallic Li anode and carbon cathode, SOCl₂ as solvent with LiAlCl₄ solute, with a non-woven glass separator. The second is Li/MnO₂ (coin size) batteries that are made of MnO₂ as cathode, PC and DME solvent with Li salt, and polypropylene separator.

Li batteries are heavily dependent on the temperature, even though they have larger operating range than many other battery types. This dependency can be investigated by measuring EIS at a broad temperature range from -15ᵒC to 65ᵒC. Equivalent circuit models can be fit to the obtained spectrum, and their temperature dependent behavior can be seen. The power of EIS comes from investigating different time scales which end up yielding information about different processes. High frequency region (100 kHz to 100 Hz) represents the interfacial processes, which is the movement of Li⁺ ions through solid electrolyte interface. Then, middle frequency region (100 Hz to 100 mHz) shows anodic charge transfer processes, which is Li oxidation. Finally, the low frequency region (100 mHz to 1 mHz) is adsorption of Li⁺ on porous carbon cathode surface.

We will show that some parameters or fits are less dependent on varying temperature than others. For instance, solution resistance (R_S) shows a less steep fit than solid electrolyte interface resistance (R_SEI) for both batteries. On the other hand, charge transfer resistance shows an exponential dependency. These obtained resistance values can be linked to an activation energy (E_A). This dependence suggests an activated transport mechanism with a measurable activation energy. In addition, some deviations from linearity were observed. Those non-Arrhenius regions differ from battery to battery, where different processes occur. However, metallic Li anode is common in both cells, resulting similar anodic process results. Also, the dominating process shows the highest impedance, that can change significantly with respect to temperature.

In this study, we demonstrate capability of temperature dependent EIS, in terms of evaluating the electrochemical processes different of Li batteries. Further, we have identified the activated and non-activated processes. Thereafter, thermodynamic and kinetic properties of individual processes are calculated.