Large format lithium ion pouch cell full thermal characterisation for improved electric vehicle thermal management

Abstract

A note on versions:The version presented here may differ from the published version or, version of record, if you wish to cite this item you are advised to consult the publisher's version. Please see the 'permanent WRAP url' above for details on accessing the published version and note that access may require a subscription.  Gradients across the cell thickness can be larger than across the cell surface. Similar heat distribution between charge and discharge scenarios. Self heating increases available capacity at low temperatures *Highlights (for review) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 AbstractIt is crucial to maintain temperature homogeneity in lithium ion batteries in order to prevent adverse voltage distributions and differential ageing within the cell. As such, the thermal behaviour of a large-format 20 Ah lithium iron phosphate pouch cell is investigated over a wide range of ambient temperatures and C rates during both charging and discharging. Whilst previous studies have only considered one surface, this article presents experimental results, which characterise both surfaces of the cell exposed to similar thermal media and boundary conditions, allowing for thermal gradients in-plane and perpendicular to the stack to be quantified. Temperature gradients, caused by self-heating, are found to increase with increasing C rate and decreasing temperature to such an extent that 13.4 ± 0.7% capacity can be extracted using a 10C discharge compared to a 0.5C discharge, both at -10°C ambient temperature. The former condition causes a 18.8 ± 1.1˚C in plane gradient and a 19.7 ± 0.8˚C thermal gradient perpendicular to the stack, which results in large current density distributions and local state of charge differences within the cell. The implications of these thermal and electrical inhomogeneities on ageing and battery pack design for the automotive industry are discussed.

Experimental Analysis of a Novel Cooling Material for Large Format Automotive Lithium-Ion Cells

“…Cooling at the tabs may be caused due to the brass busbar blocks providing a large thermal mass, where any accumulated heat is further conducted through the busbar and along the protruding brass screw to be dissipated to the ambient via the active air circulation within the climate chamber. This is consistent with the observations of Grandjean et al [22], who applied a similar mechanism of achieving an electrical connection to the tabs of large format pouch cells and witnessed a cooling effect on the tabs during aggressive electrical loading conditions (5 C in their case). A similar behavior is observed for the copper fin which is shown in Figure 11b.…”

“…Large format pouch-type lithium-ion batteries are a common choice as the battery form factor within automotive energy storage systems [22] and have received growing attention towards their thermal management method. Forced air cooling [23] across the cell body benefits from its simplistic (low cost) and light-weight design, given that weighty metallic cold plates and secondary liquid-to-air heat exchangers are not required [24].…”

Unballanced Performance of Parallel Connected Large Format Lithium Ion Batteries for Electric Vehicle Application

“…This can be more crucial in case of large format batteries with high current flows which generate a higher amount of heat and have a larger surface area. Generally it is difficult to manage the heat from large format batteries very efficiently [18][19][20][21]. This part presents the impact of nonidentical initial temperatures on the performance of the parallel cells within the (1S 5P) ESS during the constant 3C discharge event.…”

Duty-cycle characterisation of large-format automotive lithium ion pouch cells for high performance vehicle applications

“…4. This observation may be a feature of individual cells, as reported within [34] or, alternatively, attributed to uneven pressure distribution across the cell surface arising from an uneven surface of the polystyrene and FOAMGLAS® slabs, the swelling of cells during cycling, or a shift in position of the thermocouples. The cold-spot of the cell is always measured on the edge of the cell, located closest to the cooling plate in Pos.…”