Heat transfer enhancement in a lithium-ion cell through improved material-level thermal transport

Abstract

h i g h l i g h t sIdentifies rate-limiting material-level thermal conduction process in a Li-ion cell. Shows that interfacial thermal conduction between cathode and separator contributes 88% of total thermal resistance. Experimental data agrees with theoretical model on thermal contact resistance. Chemical bridging of this interface results in 4X reduction in thermal contact resistance. Results may contribute towards thermal safety of Li-ion cells. a b s t r a c tWhile Li-ion cells offer excellent electrochemical performance for several applications including electric vehicles, they also exhibit poor thermal transport characteristics, resulting in reduced performance, overheating and thermal runaway. Inadequate heat removal from Li-ion cells originates from poor thermal conductivity within the cell. This paper identifies the rate-limiting material-level process that dominates overall thermal conduction in a Li-ion cell. Results indicate that thermal characteristics of a Liion cell are largely dominated by heat transfer across the cathode-separator interface rather than heat transfer through the materials themselves. This interfacial thermal resistance contributes around 88% of total thermal resistance in the cell. Measured value of interfacial resistance is close to that obtained from theoretical models that account for weak adhesion and large acoustic mismatch between cathode and separator. Further, to address this problem, an amine-based chemical bridging of the interface is carried out. This is shown to result in in four-times lower interfacial thermal resistance without deterioration in electrochemical performance, thereby increasing effective thermal conductivity by three-fold. This improvement is expected to reduce peak temperature rise during operation by 60%. By identifying and addressing the material-level root cause of poor thermal transport in Li-ion cells, this work may contributes towards improved thermal performance of Li-ion cells.

Measurement of Multiscale Thermal Transport Phenomena in Li-Ion Cells: A Review

“…Thermal property measurements are primarily done either at material level or at the cell level in Li-ion cells. At material level, the thermal property measurements of electrodes [45][46][47][48][49], electrolyte [50], separator [51,52], electrode stack [46,53], and contact thermal resistance [54,55] have been reported. Such material-level measurements are key in understanding the heat transfer inside a Li-ion cell and in determining the rate-limiting heat transfer processes.…”

Non-invasive measurement of internal temperature of a cylindrical Li-ion cell during high-rate discharge

“…For reference, the C-rate of a charge/discharge process is defined as the reciprocal of the number of hours needed to complete charge or discharge the cell [1,7]. However, due to poor thermal conductance of the cell [9] resulting from material and interfacial thermal resistances in the cell [10], this causes significant temperature rise [11,12], particularly in the core of the cell, where heat accumulation tends to occur due to the lack of a direct access for heat removal [13]. While high core temperature may improve cell performance due to reduced internal resistance, it is also known that high cell temperature increases the rate of capacity fade [14,15].…”

Prediction of thermal runaway and thermal management requirements in cylindrical Li‐ion cells in realistic scenarios

“…When the cell is not being cooled effectively by external convection, a larger increase in thermal conductivity may be required to influence the thermal runaway behavior of the cell. Some work has been carried out on improving cell thermal conductivity by improving material and interfacial thermal transport . Figure A helps evaluate the actual impact of such improvements on the thermal runaway performance of the cell.…”

“…Some work has been carried out on improving cell thermal conductivity by improving material and interfacial thermal transport. 38,39 Figure 5A helps evaluate the actual impact of such improvements on the thermal runaway performance of the cell.…”