Abstract
Lithium–sulfur batteries have great potential as next-generation energy-storage devices because of their high theoretical charge-storage capacity and the low cost of the sulfur cathode. To accelerate the development of lithium–sulfur technology, it is necessary to address the intrinsic material and extrinsic technological challenges brought about by the insulating active solid-state materials and the soluble active liquid-state materials. Herein, we report a systematic investigation of module-designed carbon-coated separators, where the carbon coating layer on the polypropylene membrane decreases the irreversible loss of dissolved polysulfides and increases the reaction kinetics of the high-loading sulfur cathode. Eight different conductive carbon coatings were considered to investigate how the materials’ characteristics contribute to the lithium–sulfur cell’s cathode performance. The cell with a nonporous-carbon-coated separator delivered an optimized peak capacity of 1112 mA∙h g−1 at a cycling rate of C/10 and retained a high reversible capacity of 710 mA∙h g−1 after 200 cycles under lean-electrolyte conditions. Moreover, we demonstrate the practical high specific capacity of the cathode and its commercial potential, achieving high sulfur loading and content of 4.0 mg cm−2 and 70 wt%, respectively, and attaining high areal and gravimetric capacities of 4.45 mA∙h cm−2 and 778 mA∙h g−1, respectively.
Highlights
Conventional lithium-ion batteries apply composite insertion electrodes to generate high and stable charge-storage capacities; this approach dominates the commercial market of energy-storage devices
We considered a series of conductive carbon black materials as the coating materials, characterized by their unique nanoporosity and increased specific surface area
We examined the effect of the nanopores and their resulting surface area on the polysulfide-trapping capability of the conductive carbon coatings
Summary
Conventional lithium-ion batteries apply composite insertion electrodes to generate high and stable charge-storage capacities; this approach dominates the commercial market of energy-storage devices. The intrinsically low electronic conductivity of the active solid-state materials (i.e., sulfur and its end-discharge product, lithium sulfide) produces a high cathode resistance, limiting the electrochemical utilization and retention of the active material during cell cycling [7,9,13,14]. Our experimental and analytical results demonstrate that the application of acetylene black as the coating material, with its limited porosity and small nanopore size, allows the high-loading sulfur cathode to attain high charge-storage and reversible capacities of 1112 mA·h g−1 and 710 mA·h g−1 after 200 cycles, respectively, under the lean-electrolyte condition. The nanoporosity of acetylene black addresses the issue of fast electrolyte consumption through the use of porous carbon coating materials in the lean-electrolyte cell
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