Single Nickel Atoms on Nitrogen‐Doped Graphene Enabling Enhanced Kinetics of Lithium–Sulfur Batteries

Abstract

Lithium–sulfur (Li–S) batteries have arousing interest because of their high theoretical energy density. However, they often suffer from sluggish conversion of lithium polysulfides (LiPS) during the charge/discharge process. Single nickel (Ni) atoms on nitrogen‐doped graphene (Ni@NG) with Ni–N4 structure are prepared and introduced to modify the separators of Li–S batteries. The oxidized Ni sites of the Ni–N4 structure act as polysulfide traps, efficiently accommodating polysulfide ion electrons by forming strong Sx 2−⋅⋅⋅NiN bonding. Additionally, charge transfer between the LiPS and oxidized Ni sites endows the LiPS on Ni@NG with low free energy and decomposition energy barrier in an electrochemical process, accelerating the kinetic conversion of LiPS during the charge/discharge process. Furthermore, the large binding energy of LiPS on Ni@NG also shows its ability to immobilize the LiPS and further suppresses the undesirable shuttle effect. Therefore, a Li–S battery based on a Ni@NG modified separator exhibits excellent rate performance and stable cycling life with only 0.06% capacity decay per cycle. It affords fresh insights for developing single‐atom catalysts to accelerate the kinetic conversion of LiPS for highly stable Li–S batteries.

Amidation‐Dominated Re‐Assembly Strategy for Single‐Atom Design/Nano‐Engineering: Constructing Ni/S/C Nanotubes with Fast and Stable K‐Storage

“…The Gibbs free energy is calculated and comparably displayed in Figure B. As reported, the reaction speed is determined by the difference of the nearby Gibbs free energy (Δ E ) values of the potassium sulphate, and the lower Δ E indicates the faster reaction rates . It is obvious that the Δ E of NiSA/NG is lower than that of NG in the spontaneous exothermic conversion from S 3 to K 2 S 3 , suggesting the faster kinetic conversion of potassium sulphate on NiSA/NG in electrochemical process.…”

“…Recently, the single‐atom designs are introduced in the alkali ion battery field, to remedy the sluggish kinetics of the electrode materials. The extraordinary electron structure of single atom structure with the separated energy level and dense exposed metal centers would efficiently catalyze the kinetic conversion of electrode materials in lithium‐ion batteries (LIBs) . For example, Ji et al.…”

“…Niu et al. prepared single nickel (Ni) atoms on nitrogen‐doped graphene composite with a Ni−N 4 structure, which is demonstrated to accelerate the kinetic conversion of lithium polysulfides during the charge/discharge process …”

Single‐Atom Catalytic Materials for Advanced Battery Systems

“…As another example, Zhang et al have presented an in situ pyrolysis strategy to prepare Ni@NG to be coated on the separator, in which single Ni atoms with high density were confined into the N‐doped graphene matrix by sacrificing g‐C 3 N 4 templates. [ 140 ] The oxidized Ni atoms in isolated Ni–N 4 sites were capable of trapping polysulfide anions, because polysulfides can synchronously transfer electrons to the unfilled d orbitals of the oxidized Ni sites and form NiS bonds according to the Lewis acid‐base theory. Simultaneously, the charge transfer between positively charged Li ions and the N atoms with lone pairs would result in a higher binding energy, contributing to a superior electrochemical performance (Figure 14f–h).…”

Integration of Binary Active Sites: Co3V2O8 as Polysulfide Traps and Catalysts for Lithium‐Sulfur Battery with Superior Cycling Stability

“…[ 25–30 ] Therefore, a series of active materials (such as metal oxides/sulfides) with chemically polar sites were also fabricated to anchor the LiPS via the formation of the chemical bonding. [ 31–37 ] In addition to the effective immobilization of the LiPS, the rapid conversion of the intermediates on the surface of active materials with catalytic activity is also conducive to enhance the performance of Li‐S batteries. [ 38–46 ] However, the synergetic effect of chemical interaction and catalytic activity are not attracting much attention.…”