Sandwich-Type Nitrogen and Sulfur Codoped Graphene-Backboned Porous Carbon Coated Separator for High Performance Lithium-Sulfur Batteries

Abstract

Lithium-sulfur (Li-S) batteries have been identified as the greatest potential next- generation energy-storage systems because of the large theoretical energy density of 2600 Wh kg−1. However, its practical application on a massive scale is impeded by severe capacity loss resulted from the notorious polysulfides shuttle. Here, we first present a novel technique to synthesize sandwich-type nitrogen and sulfur codoped graphene-backboned porous carbon (NSGPC) to modify the commercial polypropylene separator in Li-S batteries. The as-synthesized NSGPC exhibits a unique micro/mesoporous carbon framework, large specific surface area (2439.0 m2 g−1), high pore volume (1.78 cm3 g−1), good conductivity, and in situ nitrogen (1.86 at %) and sulfur (5.26 at %) co-doping. Benefiting from the particular physical properties and chemical components of NSGPC, the resultant NSGPC-coated separator not only can facilitate rapid Li+ ions and electrons transfer, but also can restrict the dissolution of polysulfides to alleviate the shuttle effect by combining the physical absorption and strong chemical adsorption. As a result, Li-S batteries with NSGPC-coated separator exhibit high initial reversible capacity (1208.6 mAh g−1 at 0.2 C), excellent rate capability (596.6 mAh g−1 at 5 C), and superior cycling stability (over 500 cycles at 2 C with 0.074% capacity decay each cycle). Propelling our easy-designed pure sulfur cathode to a extremely increased mass loading of 3.4 mg cm−2 (70 wt. % sulfur), the Li-S batteries with this functional composite separator exhibit a superior high initial capacity of 1171.7 mAh g−1, which is quite beneficial to commercialized applications.

Biomass-derived carbon/γ-MnO2 nanorods/S composites prepared by facile procedures with improved performance for Li/S batteries

“…Experimental evidence on this hypothesis was obtained from two complementary measures (i) study of the absorption properties of carbon and oxide towards polysulfides and (ii) the analysis of the S distribution in the composites after cell cycling. The adsorption properties of the AC and MnO 2 towards polysulfides, prepared according to previously reported literature [65], is shown in Fig. S5.…”

Wheat Straw-Derived N-, O-, and S-Tri-doped Porous Carbon with Ultrahigh Specific Surface Area for Lithium-Sulfur Batteries

“…The ultrahigh surface area of NOSPC favors the sulfur distribution in the carbon framework, the molten sulfur thus can easily permeate into the NOSPC by capillary force, the specific surface area and pore volume of the obtained NOSPC/S composites then decreased seriously (17.4 m 2 ·g −1 and 0.026 cm 3 ·g −1 , respectively). Meanwhile, from Table 1 and the inset of Figure 4 d, we can see that almost all micropores vanished and mesopores only partially reserved for NOSPC/S, which not only can endure the volume expansion during the charge/discharge process, and thus improve the cycling durability, but also can promote the full impregnation of electrolyte and the rapid transfer of lithium ions [ 2 , 16 , 45 ].…”

“…Lithium-sulfur (Li-S) batteries have attracted a lot of fashionable attention in various technology applications, ranging from portable electronic apparatuses to electric automobiles, because of their very high theoretical specific capacity (1675 mAh·g −1 ), large nominal energy density (2600 Wh·kg −1 ), low material cost, natural abundance, and environmental benignity [ 1 , 2 ]. Whereas the full commercialization of Li-S batteries is still hindered by several chronic issues involving inferior electroconductivity of elemental sulfur and its solid-state discharge products (i.e., Li 2 S 2 and Li 2 S), over 80% volumetric expansion during discharge/charge processes, and dissolution of lithium polysulfides (Li 2 S x , 4 ≤ x ≤ 8), along with the notorious “shuttle effect” [ 3 , 4 ].…”

Mechanistic understanding of the role separators playing in advanced lithium‐sulfur batteries

“…Doping heteroatoms into carbons can create a nonuniform electron distribution on the carbon surface, therefore generate chemical adsorption sites for polysulfides and enhance the carbon‐polysulfide interactions . For example, nitrogen doping can improve the trapping effect of carbon‐based materials: pyridinic‐N and pyrrolic‐N enhance the polysulfides adsorption capacity while graphitic‐N improves the electronic conductivity of the trapping layer .…”