Dual‐Functional V₂C MXene Assembly in Facilitating Sulfur Evolution Kinetics and Li‐Ion Sieving toward Practical Lithium–Sulfur Batteries

Abstract

Lithium–sulfur (Li–S) batteries are considered as one of the most promising candidates to achieve an energy density of 500 Wh kg⁻1. However, the challenges of shuttle effect, sluggish sulfur conversion kinetics, and lithium‐dendrite growth severely obstruct their practical implementation. Herein, multiscale V2C MXene (VC) with a spherical confinement structure is designed as a high‐efficiency bifunctional promotor for the evolution of sulfur and lithium species in Li–S batteries. Combining synchrotron X‐ray 3D nano‐computed tomography (X‐ray 3D nano‐CT), small‐angle neutron scattering (SANS), and first‐principle calculations, it is revealed that the activity of VC can be maximized by tuning the scale, and the as‐attained functions are conducted as follows: (i) the VC acts as the efficient lithium polysulfide (LiPS) scavenger due to the large number of active sites; (ii) the VC exhibits significantly improved electrocatalytic function for the Li2S nucleation and decomposition reaction kinetics owing to the scale effect; and (iii) the VC can regulate the dynamic behavior of Li‐ions and thus stabilize the lithium plating/stripping effectively on account of the unique ion‐sieving effect.

Engineering Configuration Compatibility and Electronic Structure in Axially Assembled Metal–Organic Framework Nanowires for High-Performance Lithium Sulfur Batteries

“…Different from the electrochemical reaction such as the hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR), , the SRR involves complex sulfur species comprising Li and S, which requires at least two active sites to match with both Li and S and interact with LiPSs with different lengths. , Thus, configuration compatibility between the active centers and LiPSs needs to be tailored as well because a mismatched configuration may lead to the strained affinity between active centers and LiPSs, resulting in weakened adsorption. However, traditional catalysts, such as metal compound catalysts (metal oxides/sulfides, nitrides, carbides, single-atom catalysts et al) and organic molecule catalysts, , normally have only one active center, and the close distance (1.0–2.0 Å) between polar adsorption sites in the corresponding active center (M–O/N/S) is normally mismatched with the configuration of LiPSs with different lengths (around 3.9 Å, Li 2 S 6 for instance), leading to insufficient chemical interaction (Figure a). Moreover, electronic structures of catalytic centers are difficult to rationally engineer at the atomic level in traditional catalysts, which is however significant for regulating the degree of orbital hybridization and catalytic efficiency.…”

Hollow Structure Co1–xS/3D-Ti3C2Tx MXene Composite for Separator Modification of Lithium–Sulfur Batteries

“…Compared to the 3D-Ti 3 C 2 T x modified separator with a hollow structure, the Co 1– x S/3D-Ti 3 C 2 T x composite material with a multilayered hierarchical structure improved the reaction rate of LiPSs conversion. This can be attributed to the larger specific surface area of Co 1– x S/3D-Ti 3 C 2 T x , which provides more reaction contact sites for the adsorption and catalysis of LiPSs . In addition, the multiple interconnected conductive network structure composed of graphene and hollow Ti 3 C 2 T x microspheres facilitates rapid electron transfer and enables the catalytic activity of Co 1– x S.…”

MoO2/t-C3N4 Heterogeneous Materials with Bidirectional Catalysis for the Rapid Conversion of S Species in Li–S Batteries

“…Lithium–sulfur batteries (LSBs) have gained a substantial amount of attention in the field of energy storage research because of their high energy density and economic advantages. − However, there are many challenges in the study of LSBs, such as the extremely poor conductivity of S, significant volume changes and poor redox kinetics of S species during charge and discharge process, and the shuttle effect of lithium polysulfides (LiPSs), and the most critical issue is the shuttle effect of LiPSs. This is because the final reduction product of the S species is solid Li 2 S 2 /Li 2 S, a substance with very low electrical conductivity and poor electrochemical activity. , When LiPSs are shuttled to the anode region, they deposit a portion of Li 2 S 2 /Li 2 S on the surface of the lithium anode, thus rendering the covered portion of the lithium metal unusable. This results in a sharp drop in battery capacity.…”

“…This is because the final reduction product of the S species is solid Li 2 S 2 /Li 2 S, a substance with very low electrical conductivity and poor electrochemical activity. 6,7 When LiPSs are shuttled to the anode region, they deposit a portion of Li 2 S 2 /Li 2 S on the surface of the lithium anode, thus rendering the covered portion of the lithium metal unusable. This results in a sharp drop in battery capacity.…”