Improved Performance and Fabrication of Interlayer for Advanced Lithium-Sulfur Batteries

Abstract

In the search for next-generation energy-storage materials, the lithium-sulfur battery has drawn much attention due to its immensely high theoretical specific capacity of 1675 mAh g-1 and energy density of 2600 Wh kg-1. Its added benefit of being a low-cost, copiously available, and environmentally benign material has also prioritized the Li-S battery as an auspicious candidate. Despite such auspiciousness, the lithium-sulfur battery has inherent disadvantages that hinder its commercialization: (i) elemental sulfur and Li2S suffer from poor electrical conductivity which makes the use of high-sulfur content electrodes challenging and (ii) polysulfide migration to and reverse reaction at the negative electrode during the charge/discharge process, known as shuttle effect, result in a loss of active material and degeneration of capacity and Coulombic efficiency. A plethora of efforts has been made to resolve these issues. A traditional approach taken by researchers is the use of sulfur mixed with, confined by, and impregnated in all kinds of carbons to augment conductivity. However, polysulfide migration still occurs and cycle life is inadequate for practical applications. Previous papers 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.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.