Effect of electrolyte/sulfur ratio in the cathode on the electrochemical performance of Li-S batteries

Emerce, Nur Ber
In this study, the effect of electrolyte to sulfur (E/S) ratio in the cathode, which is an important cell design parameter, on the electrochemical and cell- and system-level performance of a Lithium-Sulfur (Li-S) battery is investigated through modeling efforts. First, a 1-D electrochemical model is developed for an isothermal, constant-current discharge of a Li-S cell to predict the voltage at 60% discharge depth. In the model, cathode exchange current density is defined as a linear function of the electrolyte amount. Increasing the E/S ratio improves the electrochemical performance at different current densities. Next, cell- and system-level performance models based on the developed electrochemical model are proposed. In these models, the cathode specific capacity is either defined as a linear function of the E/S ratio or taken constant. The model, in which the cathode specific capacity depends on the E/S ratio, predicts that increasing E/S ratio increases the cell- and system-level specific energy and energy density until 10 mL gsulfur-1. However, when the cathode specific capacity is kept constant at 1200 mAh gs-1 in the model, the specific energy and energy density at the cell and system level decrease significantly with increasing electrolyte amount. In the cell- and system-level performance analysis, the effect of other critical cell parameters such as the cathode thickness, carbon to sulfur ratio, S loading and excess Li amount are also considered. As a result, Li-S batteries with high cell- and system-level performance can be designed with the optimum E/S ratio and specified cell design parameters.


Effect of Electrolyte-to-Sulfur Ratio in the Cell on the Li-S Battery Performance
Emerce, Nur Ber; Eroglu, Damla (The Electrochemical Society, 2019-05-02)
The effect of electrolyte-to-sulfur (E/S) ratio on the electrochemical and cell- and systems-level performance of a Li-S battery is investigated through modeling efforts. A 1-D electrochemical model is proposed predicting the cell voltage at 60% discharge depth. In the model, increasing electrolyte amount improves the cell voltage by linearly increasing the cathode exchange current density, which is the single kinetic model parameter. Moreover, cathode specific capacity is either defined as a linear functio...
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Citation Formats
N. B. Emerce, “Effect of electrolyte/sulfur ratio in the cathode on the electrochemical performance of Li-S batteries,” M.S. - Master of Science, Middle East Technical University, 2019.