Surface‐Dependent Electrocatalytic Activity of CoSe₂ for Lithium Sulfur Battery

Abstract

Electrocatalysts play key roles in improving the performance of lithium sulfur (Li‐S) batteries. Here, the electrocatalytic activity of different CoSe2 surfaces for the polysulfide redox reactions in Li‐S batteries, by means of first‐principle calculations is considered. The authors demonstrate that there are obvious differences in surface energy (0.7–2.34 J m−2), adsorption energy for lithium polysulfides (LiPSs) (1.2–3.5 eV), Gibbs free energy of sulfur reduction reaction (SRR) (0.37–1.16 eV), and Li2S decomposition barrier (0.15–0.94 eV) among different CoSe2 surfaces, and thus lead to the different electrocatalytic activity for different CoSe2 surface. The stoichiometric CoSe2 surface with high surface energy, such as the (001) surface, tends to have stronger adsorption energy and larger SRR Gibbs free energy for LiPSs. The surface electron states are mainly dominated by p–d hybridization orbitals and the p‐band center is vital for the surface electrocatalytic properties. Such surface‐dependent mechanism may shed light on the design of sulfur host materials for high‐performance Li‐S batteries.

Density Functional Theory Studies on Tuning p-Band Electronic Structures of TiS2-Based Single-Atom Catalysts for Polysulfide Conversion in Lithium–Sulfur Batteries

“…Our analysis reveals that the initial step involving the conversion of S 8 to Li 2 S 8 is exothermic on AMs, consistent with prior studies. , The Li 2 S 2 –Li 2 S is the rate-determining step in most Li–S battery studies, such as graphene, oxychloride . This applies to the Be-TiS 2 , but the rate-determining step is Li 2 S 4 –Li 2 S 2 in other M-TiS 2 and the pristine TiS 2 , which is consistent with calculations in other TMDs, such as NbS 2 and CoSe 2 . Furthermore, Zhao et al found that the difference between E ZPE and T Δ S was less than 0.05 and 0.1 eV, and the same E ZPE and T Δ S were used to shorten the calculations.…”

“…12 This applies to the Be-TiS 2 , but the ratedetermining step is Li 2 S 4 −Li 2 S 2 in other M-TiS 2 and the pristine TiS 2 , which is consistent with calculations in other TMDs, such as NbS 2 55 and CoSe 2 . 56 Furthermore, Zhao et al 56 found that the difference between E ZPE and TΔS was less than 0.05 and 0.1 eV, and the same E ZPE and TΔS were used to shorten the calculations. It shows that the ΔE has an important effect on the Gibbs free energy.…”

Spontaneous Built‐In Electric Field in C3N4‐CoSe2 Modified Multifunctional Separator with Accelerating Sulfur Evolution Kinetics and Li Deposition for Lithium‐Sulfur Batteries

“…[25][26][27][28] Furthermore, CoSe 2 can also reduce the nucleation barrier of Li 2 S and promote the uniform deposition of Li 2 S due to its excellent catalytic activity. [29][30][31][32] In particular, the CoSe 2 derived from ZIF-67 can provide abundant catalytic active sites for the conversion of LiPSs and contribute to the realization of high-sulfur loaded LSBs. [26,29,33] Unfortunately, such CoSe 2 electrocatalysts are anchored to a 3D porous carbon framework and composed of many discontinuous nanoparticles, which are easy to agglomerate or even break up during continuous charge and discharge process.…”