Boosting Polysulfide Conversion in Lithium–Sulfur Batteries by Cobalt-Doped Vanadium Nitride Microflowers

Abstract

The shuttle effect of polysulfide (Li 2 S n , 2 < n ≤ 8) and the sluggish reaction kinetics seriously hinder the development of lithium−sulfur (Li−S) batteries. Regulating the electronic structure of substrate materials could be an effective strategy to further modulate surface polysulfide adsorption and interface electron transfer for advanced Li−S batteries. Herein, a cobalt-doped vanadium nitride (Co-VN) microflower hierarchical structure with a 5% Co/V ratio was synthesized as a substrate material. Theoretical calculation indicated that the polysulfide adsorption energy of Co-VN (−5.04 eV) was enhanced compared to that of VN (−4.14 eV). Electrochemical experiments verified that the polarization and internal resistance of VN were lowed after Co doping. Electrochemical tests showed that the cyclic stability of the Co-VN/sulfur (Co-VN/S) composite cathode was greatly improved compared to the undoped one, achieving an impressive initial capacity of 706 mAh g −1 at 2.0 C and that the fading rate of discharge capacity over 500 cycles was only 0.034% per cycle. A discharge capacity of 873 mAh g −1 under remarkable sulfur loading (4.42 mg cm −2 ) was also achieved with a capacity decay rate of 0.028% per cycle over 100 cycles.

Dissolving Vanadium into Titanium Nitride Lattice Framework for Rational Polysulfide Regulation in Li–S Batteries

“…The strong peaks at 36.6 o and 42.6 o refer to the (111) and (200) plane, respectively, in TiN lattice. [ 26,27 ] Noticeably, these peaks witness a continuous positive shift along with the increase of V content (from TVN‐5 to TVN‐4 and TVN‐3), suggesting a reduction in interplanar spacing. However, it should be noted that these peaks are relatively closer to TiN rather than VN, signifying that the TVNs are still dominated by TiN‐based lattice framework but with structural distortion to a varying extent.…”

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

“…[ 23,24 ] To overcome current cathode limitations, metal‐based compounds and metal‐organic frameworks have been added to strengthen the chemical interaction with LiPS and reduce the shuttle effect. [ 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.…”

Recent Progress in High‐Performance Lithium Sulfur Batteries: The Emerging Strategies for Advanced Separators/Electrolytes Based on Nanomaterials and Corresponding Interfaces

“…Compared with non-polar carbons, nanostructured polar inorganic compounds such as metal oxides, [95,96] sulfides, [97][98][99][100][101] carbides, [102,103] and nitrides [104][105][106] et al (Figure 5a-e) have gradually ascended as coating materials toward sulfur cathodes. Among them, metal sulfides attract particular interest due to strong sulfiphilicity together with multiple thermodynamically stable crystal structures and abundant reactive sites.…”

“…Compared with non‐polar carbons, nanostructured polar inorganic compounds such as metal oxides, [95,96] sulfides, [97–101] carbides, [102,103] and nitrides [104–106] et al. (Figure 5a–e) have gradually ascended as coating materials toward sulfur cathodes.…”