Nitrogen-Doped Porous Carbon Networks with Active Fe–N_x Sites to Enhance Catalytic Conversion of Polysulfides in Lithium–Sulfur Batteries

Abstract

The practical development of lithium–sulfur (Li–S) batteries is largely obstructed by their poor cycling stability due to the shuttling effect of soluble polysulfides. To address this issue, we herein report an interconnected porous N-doped carbon network (NPCN) incorporating Fe3C nanoparticles and Fe–N x moieties, which is used for separator modification. The NPCN can facilitate lithium ion and electron transport and localize polysulfides within the separator’s cathode side due to strong chemisorption; the Fe3C/Fe–N x species also provides chemical adsorption to trap polysulfides and Fe3C catalyzes the redox conversion of polysulfides. More importantly, the catalysis effect of Fe3C is promoted by the presence of Fe–N x coordination sites as indicated by the enhanced redox current in cyclic voltammetry. Due to the above synergistic effects, the battery with the Fe3C/Fe–N x @NPCN modified separator exhibits high capacity and good cycling performance: at a current density of 0.1C, it yields a high capacity of 1517 mAh g–1 with 1.2 mg cm–2 sulfur loading and only experiences a capacity decay rate of 0.034% per cycle after 500 cycles at 1C; it also delivers a good capacity of 683 mAh g–1 at 0.1C with a high sulfur loading of 5.0 mg cm–2; after 200 cycles, the battery capacity can still reach 596 mAh g–1, corresponding to 87% capacity retention. Our work provides a new and effective strategy to achieve the catalytic conversion of polysulfide and is beneficial for the development of rechargeable Li–S batteries.

Unraveling the Catalytic Activity of Fe–Based Compounds toward Li2Sx in Li–S Chemical System from d–p Bands

“…[ 49,50 ] As the typical earth‐abundant, low‐cost, and environmentally friendly materials, iron‐based compounds have already been widely researched in Li–S batteries. [ 51–54 ]…”

“…[49,50] As the typical earthabundant, low-cost, and environmentally friendly materials, iron-based compounds have already been widely researched in Li-S batteries. [51][52][53][54] For a long time, the researchers mainly ascribed the enhanced performance of Li-S batteries to strong absorbability of sulfur host materials to LPS (Li 2 S x , x = 1, 2, 4, 6, 8). However, according to the previous researches, [7,20] the binding energy of polar metal-based compounds toward LPS may not the decisive factor; relatively speaking, the catalyst effect of host materials toward LPS plays a leading role in improving the performance of Li-S batteries.…”

Anchoring Polysulfides and Accelerating Redox Reaction Enabled by Fe‐Based Compounds in Lithium–Sulfur Batteries

“…Fe 3 C with the low catalytic activity can't satisfy the fast conversion of LiPSs while Fe‐based oxides with poor electronic conductivity are undesirable for fast electron transport. [ 6c,9 ] Thus, designing and fabricating multifunctional Fe‐based compounds with strong chemisorption and catalysis as sulfur host and interlayer by regulating their composition and microstructure is a promising strategy to develop high‐performance Li–S batteries.…”

Pod‐Like Fe7S8@N−C Nanowires for High Performance Sodium Ion Batteries

“…Three peaks located at 284.8, 285.8, 288.7 eV in the high‐resolution C 1s spectrum shown in Figure 2(e), can be ascribed to C=C, C=N− and C=O bonds, respectively [2] . Figure 2(f) shows the high‐resolution spectrum of Fe 2p, the peak at 706.8 eV is assigned to Fe 0 , two peaks centered at 711.1 and 724.7 eV are indexed to ferrous state (Fe 2+ ), [31,32] and two peaks at 713.9 and 728.2 eV are related to ferric state (Fe 3+ ). In addition, there are two satellite peaks of Fe 3+ and Fe 2+ at 719.24 and 733.1 eV, respectively [33] .…”