Modeling the effect of key cathode design parameters on the electrochemical performance of a lithium-sulfur battery


Erisen N., Emerce N. B. , Erensoy S. C. , Eroglu D.

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, vol.42, no.8, pp.2631-2642, 2018 (Peer-Reviewed Journal) identifier identifier

  • Publication Type: Article / Article
  • Volume: 42 Issue: 8
  • Publication Date: 2018
  • Doi Number: 10.1002/er.4045
  • Journal Name: INTERNATIONAL JOURNAL OF ENERGY RESEARCH
  • Journal Indexes: Science Citation Index Expanded, Scopus
  • Page Numbers: pp.2631-2642
  • Keywords: carbon-to-sulfur ratio in the cathode, cathode design, electrochemical modeling, electrolyte-to-sulfur ratio in the cathode, lithium-sulfur battery, HIGH-ENERGY DENSITY, LI-S BATTERY, IMPEDANCE SPECTROSCOPY, MATHEMATICAL-MODEL, ELECTROLYTE/SULFUR RATIO, POLYSULFIDE SHUTTLE, AIR BATTERIES, CELLS, DISCHARGE, CAPACITY

Abstract

A 1D model is developed for the Li-S cell to predict the effect of critical cathode design parameterscarbon-to-sulfur (C/S) and electrolyte-to-sulfur (E/S) ratios in the cathodeon the electrochemical performance. Cell voltage at 60% depth of discharge corresponding to the lower voltage plateau is used as a metric for calculating the cell performance. The cathode kinetics in the lower voltage plateau is defined with a single electrochemical reaction; thus, the model has a single apparent kinetic model parameter, the cathode exchange current density (i(0,pe)). The model predicts that cell voltage increases considerably with increasing carbon content until a C/S ratio of 1 is attained, whereas the enhancement in the cell voltage at higher ratios is less obvious. The model can capture the effect of the C/S ratio on the cathode kinetics by expressing the electrochemically active area in the cathode in carbon volume fraction; the C/S ratio in the cathode does not affect i(0,pe) in the model. On the other hand, the electrolyte amount has a significant impact on the kinetic model parameter such that increasing electrolyte amount improves the cell voltage as a result of increasing i(0,pe). Therefore, in the model, i(0,pe) needs to be defined as a function of the electrolyte volume fraction, which is known to have a crucial effect on reaction kinetics.