Cathode porosity is a missing key parameter to optimize lithium-sulfur battery energy density

Abstract

While high sulfur loading has been pursued as a key parameter to build realistic high-energy lithium-sulfur batteries, less attention has been paid to the cathode porosity, which is much higher in sulfur/carbon composite cathodes than in traditional lithium-ion battery electrodes. For high-energy lithium-sulfur batteries, a dense electrode with low porosity is desired to minimize electrolyte intake, parasitic weight, and cost. Here we report the profound impact on the discharge polarization, reversible capacity, and cell cycling life of lithium-sulfur batteries by decreasing cathode porosities from 70 to 40%. According to the developed mechanism-based analytical model, we demonstrate that sulfur utilization is limited by the solubility of lithium-polysulfides and further conversion from lithium-polysulfides to Li2S is limited by the electronically accessible surface area of the carbon matrix. Finally, we predict an optimized cathode porosity to maximize the cell level volumetric energy density without sacrificing the sulfur utilization.

Mass Production of Calendering-Compatible Sulfur-Rich Secondary Particles via Hail-Inspired Nanostorm Technology for Advanced Metal-Sulfur Batteries

“…Generally, larger size of SP possesses smaller speci c surface area that needs a less amount of electrolyte for wetting, thus boosting the gravimetric energy (Eg) of Li-S batteries. 36 However, both sulfur AP@HTM and sulfur SP@HSN particles show similar pore distribution in the range of 5 nm-100 nm ( Figure S3b), which is probably related to the stacking pores inside the sulfur SP@HSN. These stacking pores will provide ion-transportation channels inside the secondary particles.…”

“…From the AM microenvironment point of view, the calendering processing not only smoothies the electrode surface, but also shrinks the volume fraction of microenvironment (mainly the ITN part), improving the energy density by decreasing the electrolyte/AM ratio. 29,36,38 At the same time, calendering is also a critical process regulating the physical structures and structural stability of the AM microenvironment and its assembling structures, that is, the entire ETN and ITN on the electrode level. In this case, the mechanical property of AM is critical for the structural evolution of microenvironment.…”

Practical energy densities, cost, and technical challenges for magnesium‐sulfur batteries

“…We assume that porosity in cathode is 60 vol% to accommodate the volume change of cathode given that cathode porosity should be optimized at 50 to 60 vol% in liquid Li/S cells to achieve a highest energy density. 106 There exists a critical electrolyte volume (ie, critical ratio of E/S has been saved in an Excel S2 [SI]) where liquid electrolyte fills all the pores of cathode and separator exactly. The cathode is coated on a carbon-coated Al foil with a thickness of 18 μm.…”

Recyclable cobalt-molybdenum bimetallic carbide modified separator boosts the polysulfide adsorption-catalysis of lithium sulfur battery

“…Notably, given the fact that the absorption ability of polysulfides mainly depends on the pore structures of carbon substrates [28]. Hierarchical pore distribution, especially the mixed micropore/low-range mesopore [29,30], is well accepted as the favorable carbon substrate. Whilst porous carbon-modified separator could enable fast ion transfer and good polysulfide shuttling control via the physical restriction ( Fig.…”