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Page 14 of 27 Wang et al. Soft Sci 2024;4:32 https://dx.doi.org/10.20517/ss.2024.15

symmetrically positioned. Through numerical simulations and physical experiments, the three different
TEC layouts were compared to determine the optimal configuration. The effects of input current to the TEC
and coolant mass flow rate on battery cooling were also studied. Additionally, the capability of TEC to
function interchangeably as both a heating and cooling element allows for battery preheating in cold
conditions by reversing the current flow. Experimental outcomes revealed that, when subjected to a 2C
discharge rate and an ambient temperature of 313 K, the DA-BTMS equipped with sole liquid cooling
efficiently regulated temperature within the targeted range, optimizing performance at a coolant mass flow
-1
rate of 0.59 g·s . Even at a discharge rate of 3C, the DA-BTMS could reliably maintain system operation
with TEC-assisted cooling. In environments with excessively high temperatures of 323 K, the system
demonstrated a remarkable reduction in peak temperature, plummeting from 323 to 315.32 K at a 2C
discharge rate and with an optimal TEC input current of 1.6 A. This reduction is attributed to the potent
refrigeration effect of the TECs. This system not only enhances the spatial efficiency of the battery pack but
also keeps the maximum temperature of the battery modules within acceptable limits, resiliently adapting to
both harsh hot and cold environmental conditions, effectively saving energy compared to traditional pure
TEC cooling methods.

BTMS based on TEC and PCM cooling
The PCM-based BTMS (PCM-BTMS) is a passive thermal management system that utilizes PCM to store
and release latent heat, maintaining the battery pack at optimal temperatures without consuming energy,
having moving parts, and with low maintenance costs. In high-temperature environments, PCM undergoes
a phase transition and stores the heat generated during battery discharge in the form of latent heat, thus
offering significant advantages in maintaining uniform battery surface temperatures [58,73-76] . Hallaj and
Selman were the first to apply PCM to electric vehicles, demonstrating that integrating PCM resulted in
better battery temperature uniformity compared to batteries without PCM integration . However, phase
[77]
change processes are prone to issues such as volume changes, container corrosion, and liquid leakage. The
cooling effect generated by solid-state TECs can prevent PCM from becoming oversaturated.

[38]
Song et al. developed a BTMS by integrating TEC and PCM devices [Figure 8A] . The battery pack, rated
at 48 V and 80 Ah, consisted of 60 cells arranged in a configuration of 4 cells in parallel and 15 cells in series.
PCM was strategically positioned underneath and around the battery module, filling the aluminum casing
to stabilize the temperature field of the battery. This design not only enhanced heat transfer efficiency
between PCM by utilizing the aluminum casing but also provided structural support for the battery module.
TECs (40 mm × 40 mm × 2.5 mm) were attached to the surface of the aluminum casing, with aluminum fin
heat sinks connected on the other side to enhance heat transfer further. Additionally, ten monitoring points
were identified on the distribution map, all located at the center of the corresponding surfaces for precise
monitoring of temperature changes in the battery pack. Results indicated that the TEC and PCM-based
BTMS maintained the optimal temperature range for outdoor backup battery packs for 4.4 days after
cooling once in a 323 K environment and for 3.52 days after heating once in a 263 K environment.
Furthermore, compared to other configurations, distributing the semiconductor thermoelectric devices on
both sides of the minimum size direction wings improved temperature uniformity and insulation time. The
results showed that the standby battery pack, equipped with TEC and PCMs, maintained stable cooling and
heat preservation across various temperatures, effectively prolonging battery life.

Liao et al. designed a BTMS integrating TEC and PCM to meet the cooling, heating, and thermal insulation
requirements of lithium-ion batteries . The geometric model [Figure 8B], includes 16 individual battery
[51]
cells, a cylindrical PCM casing, a honeycomb-like thermal conduction framework, a heat conduction plate,
two TECs (40 mm × 40 mm × 2.5 mm, maximum working current 3 A), and heat sinks. The heat sinks
enhance heat transfer between the TECs and the external environment, while the honeycomb-like thermal