Yolk‐Shell NiCo 2 P X as a Bidirectional Catalyst for Liquid‐Solid Processes in Advanced Lithium‐Sulfur Batteries

Manipulating Orbital Hybridization of CoSe2 by S Doping for the Highly Active Catalytic Effect of Lithium-Sulfur Batteries

In recent years, various transition metal compounds have been extensively studied to deal with the problems of slow reaction kinetics and the shuttle effect of lithium-sulfur (Li-S) batteries. Nevertheless, their catalytic performance still needs to be further improved by enhancing intrinsic catalytic activity and enriching active sites. Doping is an effective means to boost the catalytic performance through adjusting the electron structure of the catalysts. Herein, the electron structure of CoSe2 is adjusted by doping P, S with different p electron numbers and electronegativity. After S doping (S-CoSe2), the content of Co2+ increases, and charge is redistributed. Furthermore, more electrons are transferred between Li2S4/Li2S and S-CoSe2, and optimal Co-S bonds are formed between them with optimized d-p orbital hybridization, making the bonds of Li2S4/Li2S the longest and easy to break and decompose. Consequently, the Li-S batteries with the S-CoSe2-modified separator achieve improved rate performance and cycling performance, benefiting from the better bidirectional catalytic activity. This work will provide reference for the selection of the anion doping element to enhance the catalytic effect of transition metal compounds.

A review of metal phosphides with catalytic effects in Li-S batteries: boosting the redox kinetics

Lithium-sulfur batteries (Li-S batteries) are being widely studied as promising energy-storage solutions for the next generation owing to their excellent properties including high energy density, eco-friendliness, and low cost. Nevertheless, drawbacks, especially the severe "shuttle effect" and slow transformation of polysulfides, hinder the road to commercialization of Li-S batteries. The functional utilization of metal compounds in Li-S batteries has been verified, such as enhancing the conductivity, adsorption of lithium polysulfides (LPSs) and improving the kinetics of electrode processes. Benefiting from the outstanding catalytic capability and relatively good conductivity, metal phosphides have gradually received intense attention over the past few years. Consequently, significant progress has been achieved in the optimization of phosphides for Li-S batteries in recent years. This review introduces the application of metal phosphides in Li-S batteries from the aspects of their own characteristics, material structure design, and material interface control. The aim of this review is to enhance the understanding of the operational mechanism of metal phosphides and provide guidance for the development of Li-S batteries.

g-C3N4/MoO3 composite with optimized crystal face: A synergistic adsorption-catalysis for boosting cathode performance of lithium-sulfur batteries

The commercial application of lithium-sulfur batteries (LSBs) has been seriously hindered by the shuttle effect of lithium polysulfides (LiPSs) and their slow redox kinetics. In this work, g-C₃N₄/MoO₃ composed of graphite carbon nitride (g-C₃N₄) nanoflake and MoO₃ nanosheet is designed and applied to modify the separator. The polar MoO₃ can form chemical bond with LiPSs, effectively slowing down the dissolution of LiPSs. And based on the principle of "Goldilocks", LiPSs will be oxidized by MoO₃ to thiosulfate, which will promote the rapid conversion from long-chain LiPSs to Li₂S. Moreover, g-C₃N₄ can promote the electron transportation, and its high specific surface area can facilitate the deposition and decomposition of Li₂S. What's more, the g-C₃N₄ promotes the preferential orientation on the MoO₃(021) and MoO₃(040) crystal planes, which optimizes the adsorption capacity of g-C₃N₄/MoO₃ for LiPSs. As a result, the LSBs with g-C₃N₄/MoO₃ modified separator with a synergistic adsorption-catalysis, can achieve an initial capacity of 542 mAh g^-1 at 4C with capacity decay rate of 0.0053% per cycle for 700 cycles. This work achieves the synergy of adsorption and catalysis of LiPSs through the combination of two materials, providing a material design strategy for advanced LSBs.

Research progress of yolk-shell structured nanoparticles and their application in catalysis

Yolk-shell nanoparticles (YSNs) have attracted a broad interest in the field of catalysis due to their unique structure and properties. The hollow structure of YSNs brings high porosity and specific surface areas which is conducive to the catalytic reactions. The flexible tailorability and functionality of both the cores and shells allow a rational design of the catalyst and may have synergistic effect which will improve the catalytic performance. Herein, an overview of the research progress with respect to the synthesis and catalytic applications of YSNs is provided. The major strategies for the synthesis of YSNs are presented, including hard template method, soft template method, ship-in-a-bottle method, galvanic replacement method, Kirkendall diffusion method as well as the Ostwald ripening method. Moreover, we discuss in detail the recent progress of YSNs in catalytic applications including chemical catalysis, photocatalysis and electrocatalysis. Finally, the future research and development of YSNs are prospected.