Lithium-Sulfur batteries have long been a technology of interest. Despite their prolonged development cycle,[1] there are several challenges to overcome before these cells can be deployed at scale. [2,3] Extensive reviews have been published [4] on the choice of cell components including binders, separators, electrolytes and other cell components for lithium-sulfur batteries. These articles also address several practically important concerns such as the temperature range of operation, and thermal runaway mechanisms in lithium sulfur batteries. In general, the amount of heat generation from the sulfur-based cathodes is higher than the typical intercalation electrodes due to the poor electrical and thermal conductivity of the system. Combined with the critical metrics outlined in [2] for practical deployment of these cells, there is a critical need to identify heat generation routes and to develop a fundamental understanding that links the different mechanisms of heat generation in these cells, to cell-level performance (both under nominal operation and under abuse scenario). Towards this, several mathematical models have been proposed. [5-8] We recently published a detailed model incorporating approximations to simulate capacity loss. [9]

Motivated by the questions raised by the experimental observations and modeling results, we recently measured the amount of heat generated in pouch format lithium sulfur cells as a function of the depth of discharge using double-pulse current perturbations (Fig. 1). The use of a forward (discharge) and a reverse (charge) pulse helped us distinguish ohmic versus reaction heats as a function of the cell voltage. Combined with the detailed reaction models presented in [9] we attempt to quantify the amount of heat generated from the intermediate reactions at different cell voltages.

These results are then used to develop a thermal budget for lithium sulfur batteries as a function of various parameters such as the E/S ratio and the sulfur loading on the cathode. Operating at slightly elevated temperatures will likely improve transport in the cathode and enable better solubility of the intermediates; but might impact cycling performance. We present a series of case-studies summarizing the implications of these results for transportation applications, in this presentation.

References

[1] A. Manthiram, Y. Fu, S-H. Chung, C. Zu, Y-S. Su, Chem. Rev. 2014, 114, 23, 11751–11787.

[2] A. Bhargav, J. Je, A. Gupta, A. Manthiram, 2020, Joule, 4(2), 285-291.

[3] H. Pan, Z. Cheng, P. He, H. Zhou, Energy Fuels, 2020, 34(10), 11942-11961.

[4] Z. Zhou, G. Li, J. Zhang, Y. Zhao, Advanced Functional Materials, 2021, 31(50), 2107136.

[5] K. Kumaresan, Y. Mikhaylik and R.E. White, J. Electrochem. Soc., 2008, 155(8), A576-A582.

[6] M. Marinescu, T. Zhang, G.J. Offer, Phys. Chem. Chem. Phys., 2016,18, 584-593.

[7] Caitlin D. Parke, A. Subramaniam, S. Kolluri, M. Pathak. V.R. Subramanian, 2020, Electrochem. Soc., Meet. Abstr. MA2020-01 167.

[8] N. Kamyab, Mathematical Modeling of Lithium-Sulfur Batteries, 2020, PhD Dissertation, University of South Carolina.

[9] K. Niloofar, P.T. Coman, S.K.M. Reddy, S. Santhanagopalan and R.E. White, J. Electrochem. Soc., 2020, 167, 130532.