Facile and scalable fabrication of highly loaded sulfur cathodes and lithium–sulfur pouch cells via air-controlled electrospray

Abstract

Lithium – Sulfur batteries provide prominent benefits such as being environmentally friendly and cost-effective, and offering a high capacity and energy density. Although this battery chemistry carries many advantages, it is offset by the major challenges of producing cathodes with high loading of sulfur and applying them to large pouch cells for commercialization and ultimately realizing their value as the next generation energy storage system. Developing large and highly loaded sulfur cathodes are elusive because it introduces other problems such as causing the cathode to become less conductive and inducing the effect of polysulfide dissolution and shuttling to amplify. Herein, we present a facile approach to potentially solve the problem. We fabricated sulfur cathodes by air-controlled electrospraying/gas-assisted electrospinning. To elaborate, gas-assisted electrospinning was implemented to form mesoporous carbon nanofiber web substrates and sulfur particles were subsequently air-controlled electrosprayed onto these fibrous materials. The same substrates were also applied as an interlayer between the cathode and separator to enhance the cycling performance. This strategy enables 3.5 mg cm−2 loading of sulfur which exhibits an exceptionally high capacity of 1554 mA h g−1 during the initial cycle and 1223 mA h g−1 after 100 cycles at C/4. It also shows great rate capability, maintaining the capacity about 900 mA h g−1 at 2C. The cell with even higher sulfur loading of 6.2 mg cm−2, exhibited a high capacity of 1526 mA h g−1 during the initial cycle, and 1005 mA h g−1 and thus an areal capacity of 6.2 mAh cm−2 after 100 cycles at C/4. In addition, we fabricated a large-sized thin film pouch cell (5.08 × 7.62 cm) with 5.5 mg cm−2 of sulfur loading which delivered a capacity of 1532 mA h g−1 during the initial cycle and 845 mA h g−1 after 100 cycles at C/4. These results, demonstrate that the approach based on air-controlled electrospray of sulfur solution on a mesoporous carbon nanofiber substrate is quite promising for developing highly loading sulfur cathodes and feasible for generating large-sized pouch cells with high capacity.