Phosphorus Vacancies as Effective Polysulfide Promoter for High‐Energy‐Density Lithium–Sulfur Batteries

Abstract

However, the development of Li-S batteries is still facing many challenges, mainly including the insulating properties of S/Li 2 S 2 /Li 2 S, the huge volume changes during cycles as well as the dissolution and shuttle of lithium polysulfides (LiPSs) in the electrolyte. Additionally, the complex multi-electron and multi-phase reactions of sulfur species cause sluggish redox kinetics, which severely limits the battery performance. [2] Furthermore, for the purpose of taking full advantages of high-energy-density of Li-S batteries in practical applications, high sulfur loadings and low amount of electrolyte are necessary. It further increases the electrochemical polarization and aggravates the loss of LiPSs, leading to the inferior cycling stability and low specific capacity. [3] Nowadays, many researches concentrate on the design and optimization of sulfur host to solve the above problems. [4] Carbon materials and metal compounds are generally combined as the sulfur host to construct channels for transferring electrons and ions, adsorb LiPSs and catalyze the conversions of LiPSs. [5] Among the metal compounds, transition metal phosphides (TMPs) have drawn increasing interests because of their excellent electronic conductivity, easily adjustable electronic structure and high catalytic activity. [6] Some studies have shown that TMPs can chemically immobilize LiPSs through M-S and PLi bonds to restrain the shuttle effect and expedite redox kinetics in electrochemical conversions of LiPSs. Chen et al. found that CoP nanoparticles can effectively capture LiPSs and reduce the overpotential of Li 2 S nucleation. [7] Wang et al. demonstrated that MoP nanoparticles can inhibit the formation of "dead sulfur" under lean electrolyte conditions. [8] Qian et al. revealed the best catalytic behavior of CoP among several cobalt-based metal compounds (Co 3 O 4 , CoS 2 , Co 4 N, and CoP). [9] Although some progress has been made in the application of TMPs in Li-S batteries, it is still a challenge to further restrain the shuttle effect and improve the electrochemical kinetics through regulating its electronic structures.Since defect engineering has been shown to effectively tailor the electronic structure of metal compounds, the possibility of tuning the adsorption and electrochemical conversions of LiPSs on the surface of sulfur hosts through anion vacancy Lithium-sulfur batteries have aroused great interest in the context of rechargeable batteries, while the shuttle effect and sluggish conversion kinetics severely handicap their development. Defect engineering, which can adjust the electronic structures of electrocatalyst, and thus affect the surface adsorption and catalytic process, has been recognized as a good strategy to solve the above problems. However, research on phosphorus vacancies has been rarely reported, and how phosphorus vacancies affect battery performance remains unclear. Herein, CoP with phosphorus vacancies (CoP-Vp) is fabricated to study the enhancement mechanism of phosphorus vacancies in Li-S chemistry...

Ionic‐Liquid‐Assisted Synthesis of FeSe–MnSe Heterointerfaces with Abundant Se Vacancies Embedded in N,B Co‐Doped Hollow Carbon Microspheres for Accelerating the Sulfur Reduction Reaction

“…The high-sulfur-loading electrochemical performances of the developed cells were comparable to those reported in recent studies (Figure 7c and Table S5, Supporting Information). [2,[49][50][51][52][53][54] In addition, pouch cells were also fabricated according to the schematic diagram shown in Figure 7d, delivering an opencircuit voltage of 2.65 V (Figure 7e). Impressively, the Li-S pouch cell assembled using the FeSe-MnSe/NBC/S cathode operating under a higher sulfur loading of 3 mg cm −2 and lean E/S of 8 mL g −1 exhibited an excellent electrochemical performance, delivering an initial specific capacity of 1193 mAh g −1 (3.6 mAh cm −2 ) and favorable cycle stability even after 50 cycles at 0.1 C, which was comparable, and in some cases superior to those of the reported pouch cells (Table S6, Supporting Information).…”

Understanding the Catalytic Kinetics of Polysulfide Redox Reactions on Transition Metal Compounds in Li–S Batteries

“…However, it is not clear how phosphorus vacancies (PVs) affect the performance of Li−S batteries. Hence, Sun's group 141 used CoP with PVs (CoP-Vp) as a model to explore the impact of PVs. The electronic configuration of CoP-Vp enhanced the chemical affinity with polysulfides and accelerated the redox kinetics of polysulfide conversion.…”

“…(c) The binding energies of CoP-Vp-Li 2 S x and CoP-Li 2 S x . Reprinted with permission from ref . Copyright 2022 Wiley-VCH.…”

Oxygen Vacancies in Bismuth Tantalum Oxide to Anchor Polysulfide and Accelerate the Sulfur Evolution Reaction in Lithium–Sulfur Batteries

“…Their specific electronic states offer them enhanced LiPSs with adsorptive and catalytic features. However, a detailed explanation of the mechanism by which anion vacancies enhance the Li-S battery performance is still required [ 18 , 19 ].…”