An Investigation into the Insertion of a Solid Mandrel into a Commercial Cylindrical Li-Ion Cell for Improved Thermal Performance

Cylindrical Li-ion cells have found utilisation in numerous industries, but they are susceptible to thermal issues, and so they require suitable thermal management. One of the conceptual methods for addressing this issue is the introduction of a metallic mandrel inserted axially through the cell’s central cavity, which has previously been shown to have a thermal benefit through simulation, thermal emulation, and experimentally through bespoke functional test cells. This work has demonstrated the potential ability to modify a commercial LGM50 21700 cell to accept a 2 mm solid metal mandrel whilst maintaining functionality, and then to quantify the thermal behaviour under representative real-world operating conditions. The modification to external geometry is believed to have reduced the effective cooling area, and therefore leads to a temperature increase of 1–5.2 °C on the mandrel cell. The pristine reference cell then underwent the same external geometry modification, which showed no consistent thermal benefit compared to the mandrel cell, which was then validated through simulation. The simulated model evaluated the additional thermal resistances introduced by the modification process and highlighted the potential benefits of using a bespoke cell housing with an integrated mandrel over mandrel insertion. This was more significant under higher current loads, with a 7.2 °C maximum temperature reduction for the bespoke cell housing during a 3 C discharge.