Oxidation States Regulation of Cobalt Active Sites through Crystal Surface Engineering for Enhanced Polysulfide Conversion in Lithium–Sulfur Batteries

Abstract

In this work, unique Co 3 O 4 /N-doped reduced graphene oxide (Co 3 O 4 /N-rGO) composites as favorable sulfur immobilizers and promoters for lithium-sulfur (Li-S) batteries are developed. The prepared Co 3 O 4 nanopolyhedrons (Co 3 O 4 -NP) and Co 3 O 4 nanocubes mainly expose (112) and (001) surfaces, respectively, with different atomic configurations of Co 2+ /Co 3+ sites. Experiments and theoretical calculations confirm that the octahedral coordination Co 3+ (Co 3+ Oh ) sites with different oxidation states from tetrahedral coordination Co 2+ sites optimize the adsorption and catalytic conversion of lithium polysulfides. Specially, the Co 3 O 4 -NP crystals loaded on N-rGO expose (112) planes with ample Co 3+Oh active sites, exhibiting stronger adsorbability and superior catalytic activity for polysulfides, thus inhibiting the shuttle effect. Therefore, the S@Co 3 O 4 -NP/N-rGO cathodes deliver excellent electrochemical properties, for example, stable cyclability at 1 C with a low capacity decay rate of 0.058% over 500 cycles, superb rate capability up to 3 C, and high areal capacity of 4.1 mAh cm −2 . This catalyst's design incorporating crystal surface engineering and oxidation state regulation strategies also provides new approaches for addressing the complicated issues of Li-S batteries.

Transition Metal Compounds Family for Li–S Batteries: The DFT‐Guide for Suppressing Polysulfides Shuttle

“…Among them, TMOs (Fe 2 O 3 , [22] Co 3 O 4 , [23] ZnO, [24] and MoO 2 [25] ) are widely used in LSBs due to their strong chemisorption for polysulfides. Compared with TMOs, TMSs (VS 2 , [26] CoS 2 , [27] NiS 2 , [28] ZnS, [29] and MoS 2 [30] ) enjoy sulfophilic sites, lower lithiation potential, and better electrical conductivity, which are extensively used as sulfur-based materials.…”

The Metal–Organic Frameworks Derived Co3O4/TiO2 Heterojunction as a High‐Efficiency Sulfur Carrier for Lithium–Sulfur Batteries

“…Figure 15 compares the different electrode performances of this study with previous reports, and it can be seen that the S@Co 3 O 4 /TiO 2 cathode has excellent electrochemical performance with high capacity retention at 1C, indicating that the shuttle effect and other problems are effectively mitigated and the S cathode performance is improved. [25,[59][60][61][62][63][64]…”

Status and Prospects of High-Entropy Materials for Lithium–Sulfur Batteries

“…In view of LiPSs are negatively charged polar substances, as a Lewis base, they can provide Lewis acids with excess electron pairs to form coordination bonds. Metal atoms with abundant polar sites can be strongly bonded to LiPSs through Lewis acid-base interactions, polar-polar interactions, and sulfur-chain catenation, thus anchoring and trapping them to the host surface and reducing the loss of active substances [19,20]. However, single compound catalysts cannot balance the adsorption and desorption of LiPSs, resulting in poor catalytic activity [21].…”