Ultrahigh‐Content CoP Cluster as a Dual‐Atom‐Site Electrocatalyst for Accelerating Polysulfides Conversion in Li–S Batteries

Abstract

Single‐atom catalysts (SACs) show high catalytic efficiency in accelerating conversion of lithium polysulfides (LiPS), and are thus promising for suppressing the shuttle effect observed in lithium−sulfur batteries (LSBs); however, single‐atom catalytic sites with low content of catalysts largely restrict their catalytic effect. Herein, a CoP cluster supported by a N‐doped carbon matrix (CoP cluster/NC) with atomic‐level dispersion and an ultrahigh content (25.5 wt.%) of Co atoms is fabricated via an in situ low‐temperature phosphorization strategy and employed as a dual‐atom‐site catalyst for catalyzing LiPS conversion. The CoP cluster/NC with abundant unsaturated CoP coordination provides dual‐atom sites of Co and P to dynamically adsorb/desorb sulfur species and Li+ ions, respectively, synergistically promoting the conversion of LiPS. The dual‐atom‐site catalytic mechanism is evidenced by substantial characterizations including X‐ray absorption fine structure measurements and density functional theory calculations. Consequently, the S@CoP cluster/NC cathode shows superior cycling and rate performance. Even at a high sulfur loading of 6.2 mg cm−2, a high areal capacity of 6.5 mAh cm−2 that surpasses most commercial lithium–ion batteries can be achieved. This study opens a new avenue in the development of advanced catalysts with new catalytic mechanisms for high‐performance LSBs.

Expediting Stepwise Sulfur Conversion via Spontaneous Built‐In Electric Field and Binary Sulfiphilic Effect of Conductive NbB2‐MXene Heterostructure in Lithium–Sulfur Batteries

“…Moreover, excessive adsorption performance was not conducive to the transfer of LiPSs and Li + diffusion, which retarded the redox kinetics. [ 24 ] While MXene showed weak adsorption and low catalytic activity for polysulfide conversion, thus leading to sluggish conversion and obvious shuttling effect of LiPSs. By contrast, NbB 2 ‐MXene heterostructure combined diverse superiority of two materials, especially, the BIEF exerted its efficient catalytic conversion of LiPSs, exhibiting fast bidirectional sulfur redox, which guaranteed the rapid conversion of LiPSs and effectively inhibited the LiPSs shuttling even at a high‐sulfur‐loaded cathode.…”

“…Such a difference is caused by the bulk of pure NbB 2 exposing fewer active sites compared to NbB 2 ‐MXene nanoflakes. [ 24 ]…”

“…Benefiting from the redistribution of electrons, the NbB 2 -MXene heterostructure shows a moderate adsorb-ability for LiPSs owing to Nb and B atoms obtained more electrons and weakened its strong adsorption properties, which is favorable to the transfer of polysulfides and accelerates Li + diffusion. [4,24] Meanwhile, both Nb and B atoms can chemically bond to polysulfide anions, and the charge redistribution and the boundary defects of the heterostructure also expose more active sites, thereby enriching chemical anchor sites and catalytic active sites, which is favorable to more electron transfer from NbB 2 surface directly to LiPSs anions without passing through Li + cations, thereby enhancing the redox kinetics of LiPSs conversion (Figure 1D). [17] Furthermore, the BIEF is also favorable to electrons transfer and lowers the Li 2 S nucleation and decomposition barrier, thereby improving the LiPSs conversion kinetics and alleviating the shuttling effect of LiPSs.…”

Advanced Nanostructured Materials for Electrocatalysis in Lithium–Sulfur Batteries

“…Based on the work of SACs, a dual-atom catalyst Co-P cluster/NC using P atoms as ligand atoms as well as catalytic progenitors ( Figure 18 a) was proposed, and the local structure and chemical environment of Co atoms were further analyzed by XANES and WT-EXAFS ( Figure 18 b), which demonstrated the Co-P cluster/NC configuration constructed by coordination of atomic Co with P, N [ 175 ]. This work demonstrates that P atoms with proper electronegativity as coordination atoms can synergize with Co atoms to effectively promote polysulfide conversion and Li 2 S nucleation ( Figure 18 c,d) and enhance the reaction kinetics.…”

“…( d ) Potentiostatic discharge profiles at 2.05 V on different electrodes with Li 2 S 8 catholyte for evaluating the nucleation kinetics of Li 2 S. Reprinted with permission from Ref. [ 175 ]. Copyright 2022 John Wiley and Sons.…”