Uncovering the key to safer energy storage devices that avoid thermal runaway

Excerpt from phys.org

Modern energy storage devices, such as supercapacitors and batteries, have highly temperature-dependent performance. If a device gets too hot, it become susceptible to “thermal runaway.” Thermal runaway—or uncontrolled overheating—can ultimately result in explosions or fires. Adopting a well-informed thermal management strategy is necessary for the stable and safe operation of devices. To do this, it is important to understand how certain thermal properties, like heat capacity (Cp), dynamically change during charging and discharging.

Recently, researchers from the Gwangju Institute of Science and Technology investigated the thermal properties of electric double-layer capacitors (EDLCs)—a type of supercapacitor having high power and long life—for a technical foundation in thermal measurement and revealed significant information. “Using the 3ω hot-wire method, we were able to measure the change in  of EDLCs in real-time in a microscopic electrode-electrolyte volume, which is an active site for the adsorption and desorption of ions,” explains Prof. Jae Hun Seol, who led the study. The study was made available online on 5 February 2022 and will be published in the International Journal of Heat and Mass Transfer on 1 June 2022.

The research team conducted experiments both in situ (under static conditions) and operando (during charging). They found that the temperatures of the positive and negative electrodes changed by 0.92% and 0.42% during charging, which corresponded to 9.14% and 3.91% reductions in their respective Cp. “According to thermodynamic theory, the ionic configuration entropy (a measure of randomness) of a system decreases during adsorption, i.e., charging. This also affects the free energy of the system. Together, this leads to a decrease in Cp,” explains Prof. Seol.