What Limits the Rate Capability of Li-S Batteries during Discharge: Charge Transfer or Mass Transfer?. Issue 1 (14th June 2017)

• Record Type: Journal Article
• Authors: Zhang, T.; Marinescu, M.; Walus, S.; Kovacik, P.; Offer, G. J.
• Is Part Of: Journal of the Electrochemical Society. Volume 165:Issue 1(2018)
• Page Start: A6001
• Page End: A6004
• Publication Date: 2017-06-14
• Subjects: lithium-sulfur -- mass transfer -- mathematical model -- precipitation; Electrochemistry -- Periodicals; 541.3705
• DOI: 10.1149/2.0011801jes
• Languages: English
• ISSNs: 0013-4651

Abstract

Abstract : Li-S batteries exhibit poor rate capability under lean electrolyte conditions required for achieving high practical energy densities. In this contribution, we argue that the rate capability of commercially-viable Li-S batteries is mainly limited by mass transfer rather than charge transfer during discharge. We first present experimental evidence showing that the charge-transfer resistance of Li-S batteries and hence the cathode surface covered by Li2 S are proportional to the state-of-charge (SoC) and not to the current, directly contradicting previous theories. We further demonstrate that the observed Li-S behaviors for different discharge rates are qualitatively captured by a zero-dimensional Li-S model with transport-limited reaction currents. This is the first Li-S model to also reproduce the characteristic overshoot in voltage at the beginning of charge, suggesting its cause is the increase in charge transfer resistance brought by Li2 S precipitation.