Cobalt/MXene‐derived TiO₂ Heterostructure as a Functional Separator Coating to Trap Polysulfide and Accelerate Redox Kinetics for Reliable Lithium‐sulfur Battery

Abstract

Lithium‐sulfur (Li‐S) batteries are one of the most potential new energy storage systems due to their high theoretical capacity and high energy density. However, the application of Li‐S batteries is currently restricted due to the dissolution of polysulfides in the electrolyte, which leads to the shuttle effect of lithium polysulfides (LiPSs). Here, we present a Co@MXene‐derived TiO2 heterostructure decorated on carbon sheets derived from folic acid (Co@M‐TiO2/C) as a functional separator coating to trap polysulfide and accelerate redox kinetics in Li‐S batteries. The interconnected porous structure with good electrical conductivity of the heterostructure boasts rapid ion diffusion and efficient electron transfer within the battery. By attaching Co and MXene‐derived dual‐phased TiO2 to two‐dimensional carbon sheets, heterostructures are formed, ensuring complete exposure of the active sites. These heterostructures exhibit catalytic effects on LiPSs and excellent adsorption capabilities, effectively inhibiting the shuttle effect and accelerating the redox kinetics. Considering these advantages, the Li‐S battery with the optimized Co@M‐TiO2/C modified separator demonstrates a high specific capacity of 1481.7 mAh g‐1 at 0.2 C, superior rate performance of 855.5 mAh g‐1 at 2 C, and excellent cycling performance under a high sulfur load of 4.4 mg cm‐2.

Multifunction of MXene in Lithium–Sulfur Batteries: A Review

“…Moreover, the combination of some metal compounds with MXene is also the first choice for the catalytic conversion of polysulfides in LSBs, of which the most common contain Co- and Ni-based compounds. − In this regard, the combination of Co ions and negatively charged MXene nanosheets was achieved by electrostatic adsorption. Then, Co­(OH) 2 nanoparticles loaded on the surface of the MXene nanosheets were obtained by reflux.…”

Metal-doped Co9S8/MXene nanocomposites for high-performance electrochemical capacitor electrode materials

“…Currently, the strategies commonly adopted for the rational design of electrode materials include composition engineering, 22 defect engineering 23 and the construction of heterogeneous structures. 24–26 Aiming at the above problems, an effective solution is to grow Co 9 S 8 directly on a highly conductive substrate, which could increase the contact area with the electrolyte and accelerate the diffusion of ions. MXene is a two-dimensional transition metal carbide or nitride.…”