Rechargeable batteries are one of the prime approaches for electrical energy storage. The current lithium-ion battery technology based on transition-metal oxide cathodes and graphite anode have limited energy storage capacity, so there is immense interest to develop alternate high-capacity cathode and anode materials. Lithium-sulfur (Li-S) batteries are appealing in this regard as they offer a high energy density of 2500 Wh kg^-1 when coupled with lithium-metal anode due to the large charge-storage capacity of sulfur.^[1] Moreover, sulfur is much more abundant, inexpensive, and non-toxic compared to the transition-metal oxide cathodes.

There are several challenges with the Li-S batteries, such as low electrical conductivity of sulfur and the discharge product Li₂S and the migration of dissolved polysulfides from the cathode to the anode, resulting in low efficiency and inadequate cycle life.^[2] Well-designed carbon-sulfur composites have been extensively explored to overcome these issues.^[3] In these strategies, sulfur was entrapped in carbon structures using porous carbon, carbon nanotubes (CNT), and hollow carbon spheres. Carbon backbone serves as the electron conducting path for sulfur and reduce polysulfide migration by trapping the polysulfides during cycling. However, polysulfide migration still occurs and cycle life is inadequate for practical applications. Manthiram group and other groups introduced the use of carbon-paper interlayers in between the sulfur cathode and the polymer separator or carbon-coated membrane and demonstrated high sulfur utilization with better cycle life due to the suppression of polysulfide diffusion to the anode and the serving of the carbon-paper interlayer as a pseudo-upper current collector.^[4]

We present here the fabrication of an interlayer consisting of MWCNT and the electrolyte in a single fabrication process. Such MWCNT-electrolyte-paper interlayers are much more effective compared to the bare MWCNT-paper interlayer due to the fast ionic and electronic transport and a better interface between the sulfur cathode and the interlayer as well as between the separator and the interlayer.

References

[1]. B. Scrosati, J. Hassoun, Y.-K. Sun, Energy Environ. Sci. 2011, 4, 3287.

[2]. Y.-X. Yin, S. Xin, Y.-G. Guo, L.-J. Wan, Angew. Chem. Int. Ed. 2013, 52, 13186-13200

[3]. A. Rosenman, E. Markevich, G. Salitra, D. Aurbach, A. Garsuch, F.F. Chesneau, Pan, Adv. Energy Mater. 2014,1500212.

[4]. Y.-S. Su, A. Manthiram, Chem Comm. 2012, 48, 8817-8819.