Efficient thermal management of the large-format pouch lithium-ion cell via the boiling-cooling system operated with intermittent flow.

• A boiling-cooling system is proposed for large-format pouch lithium-ion cells. • The system has good performance for single-discharge processes in static mode. • The flow mode enables the system a stable performance during cyclic operations. • The temperature gradient is abnormally enlarged by the fast flow of the coolant. • The intermittent flow mode delivers an impressive cooling performance. To manage the undesirable temperature spike and significant temperature gradient developed on the large-format lithium-ion cell, we propose and experimentally demonstrate a boiling-cooling thermal management system using NOVEC 7000 as coolant for a large-format 20-Ah LiFePO 4 lithium-ion cell. It shows that the boiling-cooling system delivers excellent capabilities in reducing maximum temperature and improving temperature uniformity under the static mode even for the 4C discharge process. To enable the boiling-cooling system a stable cooling performance during cyclic operations, the flow mode is explored. The maximum temperature is successfully controlled over cycles but a large temperature difference between regions near cell bottom and tabs is observed, especially at high flow rates. To resolve issues of the static and flow modes, the intermittent flow mode is finally conceived for the boiling-cooling system, with which the temperature spike and maximum temperature difference are controlled to be less than 36 °C and 2 °C at 2C operation. Such an impressive cooling performance, combined with the substantially low pumping work, suggests that efficient thermal management of large-format lithium-ion cells can be achieved by the boiling cooling system operated with an intermittent flow mode, which takes full advantage of the large latent heat absorbed and the high heat transfer coefficient during the boiling process. [ABSTRACT FROM AUTHOR]