Solid Carbon Spheres with Interconnected Open Pore Channels Enabling High-Efficient Polysulfide Conversion for High-Rate Lithium–Sulfur Batteries

Abstract

Hollow carbon spheres or core–sheath porous carbon spheres have been widely used in the S cathode of lithium–sulfur batteries. However, the sphere shells or the pore walls may block the free transport of active species to a certain extent and may have a negative influence on the effective accommodation of elemental sulfur. Herein, solid but porous carbon spheres (PNCS) with large porosity and high specific surface area are developed, which enable high sulfur loading and ample cathode/electrolyte contact area, and the interconnected open pore channels significantly shorten the ion/electron transport pathways. Together with high-conducting nitrogen-doped graphene (NG), facilitated polysulfide conversion kinetics is realized in the as-assembled Li–S batteries, which deliver a high initial discharge capacity of 1445 mAh g–1 at 0.2 C, excellent rate capability of 872 mAh g–1 at 4 C, and low capacity decay of 0.047% per cycle for 500 cycles at 1 C. Even under high sulfur loading of 5.5 mg cm–2 and low electrolyte/sulfur (E/S) ratio of 5 μL mg–1, the Li–S batteries still display high specific capacities of 896 mAh g–1 and 4.96 mAh cm–2. The real application of PNCS/NG is also demonstrated by the corresponding Li–S pouch cells showing high discharging capacity and stable open circuit voltage. This work exhibits the promising application of the solid carbon spheres as the S host for effectively addressing the polysulfide shuttle and propelling the development of high-performance Li–S batteries.

Proton‐Induced Defect‐Rich Vanadium Oxides as Reversible Polysulfide Conversion Sites for High‐Performance Lithium Sulfur Batteries

“…Moreover, the high resolution XPS spectrum of C 1s could be divided into four characteristic peaks located at 284.0, 284.5, 285.8, and 288.1 eV, assigning to CÀ C, CÀ O, C=O and OÀ C=O bonds, respectively (Figure 2b). [47] Notably, there are typical Raman peaks located at 1340 cm À 1 (D band) and 1580 cm À 1 (G band) of GO, rGO, and G@HNVO, corresponding to the disordered carbon and sp 2 hybrid graphitic carbon structure, (Figure 2c). In addition, the intensity of I D /I G ratio of GO, G@HNVO and rGO increases from 0.99, 1.04 to 1.15, further demonstrating the reduction of graphene oxide during the hydrothermal process and the residual defect in G@HNVO.…”

(Fe0.5Ni0.5)0.96S with Bimetallic Cation Vacancy Defect as an Efficient Catalyst for Regulating the Reaction Kinetics of Li2S

“…Additionally, we conducted cycling performance studies of the NFS-rGO/S electrode at low electrolyte/sulfur ratios. As depicted in Figure S3, the substance is denoted as NFS-rGO/ S-X (X = 23,30,38), where X represents the low electrolyte/ sulfur ratio. After 50 cycles, the capacities of NFS-rGO/S-X (X = 23, 30, 38) are 749.2, 732.3, and 697.5 mAh g −1 , respectively.…”

“…The above experimental results validate that NFS-rGO can remarkably promote the nucleation transition of Li 2 S, reduce the nucleation barrier of Li 2 S, and effectively inhibit the shuttle of LiPSs. 37,38 The effect of bimetallic cation vacancies on electrochemical kinetics was studied using EIS. In Figure 7a, the semicircle of NFS-rGO/S in the midhigh frequency region is smallest, meaning that the charge transfer resistance in it is lowest.…”

“…Meanwhile, NFS-rGO presents a lower nucleation reaction time (only 4639 s), which is much lower than that of NS-rGO (7640 s) and FS-rGO (7940 s). The above experimental results validate that NFS-rGO can remarkably promote the nucleation transition of Li 2 S, reduce the nucleation barrier of Li 2 S, and effectively inhibit the shuttle of LiPSs. , …”

Graphene oxide wrapped hollow mesoporous carbon spheres as a dynamically bipolar host for lithium–sulfur batteries

“…5 To solve the above problems, various conducting support materials, particularly with hollow micro/nanostructures, 6 have been adopted to load sulfur species with reduced polarization and increased utilization of sulfur cathodes. Particularly, various carbon substrates, such as ordered mesoporous carbon, 7 (porous) carbon (nano)spheres, [8][9][10][11][12][13] carbon nanotubes, [14][15][16] graphene, 17 etc., with controllable pore structures and morphologies, have been studied as sulfur hosts due to their high electrical conductivity, light weight and low cost.…”