Investigation of the Nanocrystal CoS₂ Embedded in 3D Honeycomb-like Graphitic Carbon with a Synergistic Effect for High-Performance Lithium Sulfur Batteries

Abstract

Lithium sulfur (Li–S) batteries can offer great opportunities for the next-generation energy storage systems with tremendous energy density. However, challenges still exist in practical Li–S batteries including low sulfur utilization, and poor cycling stability and rate capability. Herein, we propose a novel hybrid catalyst structure by in situ implanting nanocrystal CoS2 in three-dimensional honeycomb-like hierarchical porous graphitic carbon (HPGC) for high-performance Li–S batteries. A unique synergistic absorption-catalysis-functional effect is demonstrated by comprehensive experimental and theoretical analysis: strong physical and chemical co-absorption effects are originated from the large quantity of microporous HPGC and the polar surface of metallic CoS2; the introduced nanocrystal CoS2 with a large specific area can impose an exceptional catalytic effect on the liquid–liquid, solid–liquid, and solid–solid phase redox reactions in Li–S batteries; the reaction dynamics are further guaranteed by the multifunctional properties of the HPGC backbone, including the capabilities in polysulfide sustention, reaction product transportation, electrolyte compensation, and efficiency in assisting diverse electrochemical reaction dynamics. In this way, our results not only develop a novel CoS2@HPGC structure, but also provide fundamental understanding on the catalytic dynamics during each reaction process. Moreover, we further propose the necessity and philosophy of the rational design of catalysts’ special structure, which can fulfill the functional dynamics requirements of Li–S batteries, and can be promoted to other Li–S-related cathode design and composite catalytic structure design.

Improved Redox Reaction of Lithium Polysulfides on the Interfacial Boundary of Polar CoC2O4 as a Polysulfide Catenator for a High‐Capacity Lithium‐Sulfur Battery

“…On such surfaces, the soluble LiPS are chemically converted to polythionate, and lower molecular weight LiPS species via the disproportionation reaction, except for the production of inactive sulfate species (SO 3 2− and SO 4 2− ), occurring over 170 eV. The reaction mechanism conforms with other recently published reports, wherein an electrocatalytic redox activity was strongly emphasized for the LiPS redox reaction [48–54] …”

Sandwiched Cathodes Assembled from CoS2‐Modified Carbon Clothes for High‐Performance Lithium‐Sulfur Batteries

“…These shifts are considered to be resulted from the interaction between CoS 2 nanoparticles and negatively charged polysulfides. [ 61 ] The polythionate (168.8 eV), thiosulfate (167.1 eV), Li 2 S 4 (163.8 eV), and Li 2 S 2 (161.8 eV) are also detected from the S 2p spectrum as shown in Figure S8b , Supporting Information. These peaks can be ascribed to the catalytic reactions of long‐chain polysulfides with CoS 2 to form intermediate thiosulfate and short‐chain polysulfides.…”

Surface/Interface Structure and Chemistry of Lithium–Sulfur Batteries: From Density Functional Theory Calculations’ Perspective

“…The hollow structures can effectively physically nanoconfine LPSs, and the carbon shell with embedded metal can also ensure good conductivity and chemical confinement for LPSs. After carbonization at high temperature in an inert atmosphere, ZIF‐67 can be converted to Co@C. [ 14,144 ] After that, through various conversion reactions, cobalt sulfides, [ 142,145,147,149,150 ] phosphides, [ 148,151,152 ] oxides, [ 143,153 ] selenides, [ 46 ] and nitrides [ 51,146 ] can be easily obtained. He et al [ 144 ] designed a 3D porous multifunctional graphite carbon matrix (C–Co–N) as the host material for Li 2 S cathode.…”