In-plane nonuniform temperature effects on the performance of a large-format lithium-ion pouch cell

Simultaneous Operando Measurements of the Local Temperature, State of Charge, and Strain inside a Commercial Lithium-Ion Battery Pouch Cell

“…Instead, the outside temperature has usually been taken as a surrogate for the internal temperature. [6][7][8] If pouch cells are sufficiently thin, and if the thermal conductivity is high enough, then it is reasonable to assume that the temperature measured at an x-y location on the outside of a pouch cell, with a thermocouple or with a thermal infrared (IR) camera, is close to the temperature at that x-y location all the way through its thickness. 9 However, auto makers are motivated to make pouch cells thicker, reducing the number of expensive seals, electrical connections, and controls.…”

“…Nominal in-plane spatial resolution is 0.3 mm, permitting observation of spatial variations or heterogeneities 8,[23][24][25] of properties involved in performance and fade. This work follows our previous studies using neutron diffraction in which we made 2D time-dependent SOC maps demonstrating that failure in our pouch cell was strongly heterogeneous; 24,26,27 and the work of Paxton et al, 28 using X-rays, who also observed heterogeneities in cells.…”

Current Distribution Measurements in Parallel-Connected Lithium-Ion Cylindrical Cells under Non-Uniform Temperature Conditions

“…4 Additionally, nonuniform temperature causes non-uniform electrochemical impedance across the electrodes of individual cells and/or across cells in a module which will generate non-uniform current density and therefore non-uniform heating. [5][6][7] Several studies, particularly at high charge/discharge rates (i.e., above 1C), show single cell temperature differences greater than 20…”

“…4 Additionally, nonuniform temperature causes non-uniform electrochemical impedance across the electrodes of individual cells and/or across cells in a module which will generate non-uniform current density and therefore non-uniform heating. [5][6][7] Several studies, particularly at high charge/discharge rates (i.e., above 1C), show single cell temperature differences greater than 20• C. 3,4,8,9 As a result battery thermal management systems (BTMS) must be incorporated into large scale battery packs, particularly in automotive applications where high C-rates are common. Traditionally, the BTMS is designed in such a way that thermal non-uniformity is kept below 5…”

“…6 Finally, we previously studied the effects of non-uniform temperatures for a 10Ah NMC pouch cell similar to Troxler's study. 7 The non-uniform temperature effect was characterized using DC pulse testing and a two hour long US06 dynamic power schedule. For the DC pulse results we agreed with Troxler (performance improvement with increased gradient), but we observed continual buildup of average cell resistance (performance reduction) for the US06 charge depleting test.…”