Sulfur in Hyper-cross-linked Porous Polymer as Cathode in Lithium–Sulfur Batteries with Enhanced Electrochemical Properties

Abstract

Sulfur was impregnated into hyper-cross-linked porous polymer (HCP) with a high specific area and unique porous structure. Compared to its inorganic or carbon counterparts, the HCP has a relatively high specific surface area of 1980 m g with a total pore volume of 2.61 cm g, resulting in sulfur content in HCP/S of as high as 80 wt %. As a benefit of the unique HCP structure, the HCP/S composite exhibits a high initial discharge specific capacity (1333 mA h g at 0.2 C), high-rate property, and good cycling stability (658 mA h g after 120 cycles at 0.5 C and 604 mA h g after 80 cycles at 1 C). Furthermore, the capacity of cells loses less than 1% after the first 20 charge/discharge cycles, while the HCP/S cathode can be cycled with an excellent Coulombic efficiency of above 94% after 120 cycles. Compared with pristine sulfur, the superior electrochemical performance of HCP/S composite is related to the cross-linked porous framework. Such structure could provide short ionic/electronic conduction pathways and suppress the polysulfide shuttle during the discharge process.

Progress Report on Phase Separation in Polymer Solutions

“…Furthermore, thanks to alterable ultrahigh surface areas, PPM have been adopted for catalyst supports to increase the efficiency of chemical reactions [14,15] and for electrodes of lithium-ion battery to enhance the electrochemical performance. [16][17][18] PPM have also been exploited for energy storage devices, [19] fuel cells, [20] low-dielectric-constant materials, [21] photonic bandgap materials, [22,23] scaffolds for tissue engineering, [4] proton exchange membranes, [24,25] masks for nanopatterning or lithography, [26] antireflection coating, [27] and many other applications. In these high-value applications, the functionality, the reliability, and the durability of PPM crucially depend on the microstructural patterns resulting from different formation processes associated with diverse underlying mechanisms.…”

Using the Cahn–Hilliard Theory in Metastable Binary Solutions

“…Phase separation is a useful technique for fabricating functional binary materials. This method is used in a variety of applications such as in polymer-dispersed liquid crystal films for electro-optical devices [1,2], porous polymeric membranes for separation processes [3,4], the paper, paint and pharmaceutical industries [5,6], biophysics [7,8], nanocomposite materials [9], fabricating electrodes for lithium ion batteries [10], energy storage devices [11], fuel cells [12], scaffolds for tissue engineering [13], and molecular biology to produce protein crystals [14,15]. A binary solution may have favorable lower energy when the solution is phase separated rather than being in the uniform state.…”

Novel Non‐Carbon Sulfur Hosts Based on Strong Chemisorption for Lithium–Sulfur Batteries

“…In addition, as some polymers are electrochemically active, they can also act as a capacity contributor to provide extra capacity for the sulfur/polymer composite electrode . To date, various conductive polymers including polypyrrole (PPy), polyaniline (PANI), poly(3,4‐ethylenedioxythiophene) (PEDOT), polyacrylonitrile, and polythiophene have been extensively studied to combine with sulfur for Li–S batteries. Representative reports of sulfur/polymer composite materials and the corresponding electrochemical performance are outlined in Table 1 .…”

“…With a suitable ratio between sulfur and polythiophene, the sulfur/polythiophene composite exhibited improved sulfur utilization, cycle life, and rate capability in the Li–S battery compared to that of the pure sulfur electrode. Recently, Zeng et al reported the sulfur impregnated into hyper‐cross‐linked porous polymer (HCP) as composite sulfur electrode . As shown in Figure a, sulfur was impregnated into the novel porous organic polymer via thermal treatment.…”

“…a) Schematic illustration of the synthesis route for the HCP/S composites. b) Coulombic efficiency and cycling performance of the HCP/S (80 wt%) composite electrode at a constant rate of 0.5 C. Reproduced with permission . Copyright 2017, American Chemical Society.…”