Embedding Cobalt Atom Clusters in CNT‐Wired MoS₂ Tube‐in‐Tube Nanostructures with Enhanced Sulfur Immobilization and Catalyzation for Li–S Batteries

Abstract

cathodes, fast capacity degradation, and low Coulombic efficiency. The low electrical/ionic conductivities of sulfur, shuttle effect of long-chain lithium polysulfides (Li 2 S n , 4 ≦ n ≦ 8) and large volume expansion of sulfur cathode (80%) upon lithiation during charge/discharge hinder the practical application of Li-S batteries. [6][7][8] Various strategies have been implemented to overcome these problems including a) designing novel cathodes to increase the electrode conductivity and inhibiting lithium polysulfides (LiPSs) shuttle, b) investigating new electrolyte, separator, and binder to minimize polysulfide migration, and c) protecting Li anode to avoid LiPSs passivation. [9][10][11][12] Despite much time and effort that has been devoted, the life and energy density of Li−S batteries is far from satisfactory to meet the needs of daily life so far.The insulating nature of sulfur itself and polysulfides shuttle effects become the initiator problems of Li−S batteries, therefore finding suitable cathode materials is a crucial step for the commercialization of Li-S batteries. [3,5] Initially, carbon-based materials have been extensively studied, such as micro/mesoporous carbons, hollow porous carbon spheres, carbon nanotubes/fibers, etc, but most nonpolar carbonaceous materials cannot effectively inhibit the shuttling of LiPSs. [13][14][15] The polar compounds such as metal oxides, [16,17] sulfides, [18,19] carbides, [20,21] nitrides, [22,23] metal−organic frameworks, [24] etc., as sulfur hosts have been used for LiPSs adsorption by forming chemical bonds with LiPSs. However, the low catalytic ability of oxides, [16,17] the weak affinity of carbides, [20,21] the aggregation of nitrides, [22,23] and the low conductivity of metal−organic frameworks, [24] are issues that still restrict their further application. Transition metal sulfides (TMSs) have a strong absorption with polysulfides by chemical bonding. [18,19] In particular, molybdenum disulfide (MoS 2 ) as the host cathode material is a promising candidate because of its intrinsic chemical activity and low cost. [25,26] Arava and co-workers demonstrated the preferential adsorption and conversion of LiPSs by electrocatalytic MoS 2 atomic layers. [27] Chen and co-workers also reported 3D graphene/1T MoS 2 heterostructures as highly efficient Lithium-sulfur batteries are one of the most promising next-generation energy storage systems. The efficient interconversion between sulfur/lithium polysulfides and lithium sulfide is a performance-determining factor for lithium-sulfur batteries. Herein, a novel strategy to synthesize a unique tubein-tube CNT-wired sulfur-deficient MoS 2 nanostructure embedding cobalt atom clusters as an efficient polysulfide regulator is successfully conducted in Li−S batteries. It is confirmed that encapsulating MWCNTs into hollow porous sulfur-deficient MoS 2 nanotubes embedded with metal cobalt clusters not only can accelerate electron transport and confine the dissolution of lithium polysulfide by physical/chemical adsorption, but als...

Enhanced Polysulfide Conversion with Highly Conductive and Electrocatalytic Iodine‐Doped Bismuth Selenide Nanosheets in Lithium–Sulfur Batteries

“…[ 25–30 ] Among the tested metal compounds, sulfides such as MoS 2 , VS 2 , CoS 2 , Ni 3 S 2 , and Sb 2 S 3 , have demonstrated particularly strong sulfiphilic ability toward LiPS trapping and low lithiation voltages. [ 31–36 ] However, cathodes based on metal sulfides are generally characterized by moderate electrical conductivities, limited sulfur utilization, insufficient cycling stability, and low rate capabilities. [ 37–41 ]…”

Crystal Facet Engineering of MXene‐Derived TiN Nanoflakes as Efficient Bidirectional Electrocatalyst for Advanced Lithium‐Sulfur Batteries

“…While the battery assembled with S/TiN NPs@rGO electrode exhibited capacities of 1123, 914, 768, 646, 570, and 483 mAh g −1 , respectively. In addition, the rate performance of S/TiN NFs@rGO electrode was also compared with some reported cathodes based on TiN or some other catalytic materials [ 23,24,39–41 ] (Figure 6g), which demonstrated the excellent properties of S/TiN NFs@rGO electrode. Figure 6h displays the initial discharge capacity of 895 mAh g −1 at 2 C and a capacity retention of 659 mAh g −1 after 200 cycles at 2 C for S/TiN NFs@rGO electrode.…”

Electrocatalysis in Room Temperature Sodium‐Sulfur Batteries: Tunable Pathway of Sulfur Speciation

“…Recently, researchers have found that atomic clusters and nanoparticles exhibited excellent catalytic performance in facilitating the conversion of polysulfides. [121,122] Currently, transition metals are the main choice for such catalysts, which have been shown to significantly improve the electrochemical performance of RT NaS batteries. Thus, Qiao et al developed the transition-metal (Fe, Cu, and Ni) clusters loaded onto hollow carbon nanospheres (HC) as host for sulfur (S@M-HC, where M stands for metal) to improve the performance of RT NaS batteries.…”

“…Recently, researchers have found that atomic clusters and nanoparticles exhibited excellent catalytic performance in facilitating the conversion of polysulfides. [ 121,122 ]…”