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

Abstract

Summary A 1D model is developed for the Li‐S cell to predict the effect of critical cathode design parameters—carbon‐to‐sulfur (C/S) and electrolyte‐to‐sulfur (E/S) ratios in the cathode—on 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 (i0,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 i0,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 i0,pe. Therefore, in the model, i0,pe needs to be defined as a function of the electrolyte volume fraction, which is known to have a crucial effect on reaction kinetics.

Electrochemical performance and modeling of lithium-sulfur batteries with varying carbon to sulfur ratios

“…In this study, the impact of carbon to sulfur ratio on the electrochemical performance of a Li‐S cell has been investigated, and it was found that the capacity and cell polarization were very similar at low sulfur loadings. This trend, observed both experimentally and by model predictions, was consistent with the previous predictions . It is noted, however, that the range of sulfur loading that results in similar electrochemical performance will be dependent on other design parameters, in particular the electrolyte to sulfur ratio, cathode thickness, and relative binder amount.…”

Freestanding graphitic carbon nitride‐based carbon nanotubes hybrid membrane as electrode for lithium/polysulfides batteries

“…Lithium sulfur batteries, which perform an exceptional theoretical capacity (1675 mAh g −1 ) and specific energy density (2600 Wh kg −1 ), are a promising representative of the next‐generation high energy storage systems . However, there are still few technical challenges to the commercialization of lithium sulfur batteries, such as poor conductivity of kinetics of sulfur, shuttle effect of redox reaction intermediates, and volume expansion due to density differences between sulfur and Li 2 S. …”

“…1,2 Lithium sulfur batteries, which perform an exceptional theoretical capacity (1675 mAh g −1 ) and specific energy density (2600 Wh kg −1 ), are a promising representative of the next-generation high energy storage systems. 3 However, there are still few technical challenges to the commercialization of lithium sulfur batteries, such as poor conductivity of kinetics of sulfur, shuttle effect of redox reaction intermediates, and volume expansion due to density differences between sulfur and Li 2 S. 4,5 Recently, many efforts have been made by researchers to address the above problems. 6,7 The nanostructured carbon or doping them with heteroatoms (nitrogen, oxygen, phosphorus, and sulfur) as conductive framework were used as sulfur matrices, 8 such as porous carbon, 9 graphene, 10 conductive polymers, 11 and their hybrids.…”

Synergistic effect of sulfur on electrochemical performances of carbon‐coated vanadium pentoxide cathode materials with polyvinyl alcohol as carbon source for lithium‐ion batteries

“…Sulfur is deemed to be as the most promising cathode active material for a new generation of lithium‐ion battery (lithium‐sulfur battery), owing to their high theoretical specific capacity (1675 mAh g −1 ), low cost, and environmentally friendly . However, the insulation and volume of the sulfur and polysulfide “shuttle effect” limits its specific capacity and cycle life .…”

“…[15][16][17] Sulfur is deemed to be as the most promising cathode active material for a new generation of lithium-ion battery (lithium-sulfur battery), owing to their high theoretical specific capacity (1675 mAh g −1 ), low cost, and environmentally friendly. [18][19][20] However, the insulation and volume of the sulfur and polysulfide "shuttle effect" limits its specific capacity and cycle life. 21,22 In order to deal with these problems, many researchers believe that sulfur is required to be hosted on some matrix materials, such as carbon material, 23 metal compounds, 24,25 conductive polymer materials, 26,27 and so on.…”