Constructing Patch‐Ni‐Shelled Pt@Ni Nanoparticles within Confined Nanoreactors for Catalytic Oxidation of Insoluble Polysulfides in Li‐S Batteries

Abstract

the discharge capacity and cycle life. [2] Another weakness is the irreversible precipitation of Li 2 S 2 and Li 2 S on the cathode that leads to pore clogging and the loss of active materials, accompanied by severe polarization, large capacity degradation, and sluggish reaction kinetics. [3] Equally significant is that the dissolution of intermediate lithium polysulfides (LiPSs) induces inefficient self-discharge and the corrosion of the lithium metal anode. [4] In view of such a serious situation, tremendous efforts have been made to suppress polysulfide shuttling through physical confinement or chemical absorption mainly on the nanostructured carbon, [5] the rational structure design of carbonaceous materials with porous structures that efficiently provide the physical confinement of dissolved polysulfides, and a fast path for ion/electron transfer. [6] However, the nonpolar carbon cannot ensure strong adsorption of polar polysulfides. LiPSs detach from carbon hosts and diffuse into the electrolyte, resulting in capacity decay after several charge-discharge cycles. [7] In the meantime, it is also a large challenge for the oxidation of insoluble Li 2 S to sulfur during the charging process, which is important for achieving high reversible capacity and coulombic efficiency. However, the existence of overpotential in the charge process reveals that the oxidation of deposited short chain polysulfides needs a high activation energy, so it is crucial to reduce the activation energy of the reactions to promote the transformation of insulating short-chain LiPSs to long-chain LiPSs. [8] Hence, understanding and controlling the kinetics is the first step for remarkable improvement of battery performance. Reference to the fast reaction kinetics of the oxygen reduction reaction in fuel cells and the electrocatalysis concept of enhancing the redox reactions of polysulfides was developed by Arava et al., [9] who confirmed that Pt and Ni had an electrocatalysis effect on the reaction for LiPSs conversion. Subsequently, Pt nanoparticles loading on carbon spheres [10] and graphene sheets [11] also confirmed the efficacy of the Pt catalyst as well as the great adsorption strength for soluble LiPSs species. All the aforementioned reports involved inevitable catalyst outflow and heavy use of noble metal, which Reducing the deposit of discharge products and suppressing the polysulfide shuttle are critical to enhancing reaction kinetics in Li-S batteries. Herein, a Pt@Ni core-shell bimetallic catalyst with a patchlike or complete Ni shell based on a confined catalysis reaction in porous carbon spheres is reported. The Pt nanodots can effectively direct and catalyze in situ reduction of Ni 2+ ions to form core-shell catalysts with a seamless interface that facilitates the charge transfer between the two metals. Thus, the bimetallic catalysts offer a synergic effect on catalyzing reactions, which shows dual functions for catalytic oxidation of insoluble polysulfides to soluble polysulfides by effectively reducing the energy bar...

Polyaniline Encapsulated Amorphous V2O5 Nanowire‐Modified Multi‐Functional Separators for Lithium–Sulfur Batteries

“…The change of electronic state is also considered as a factor that improves the adsorption capability and catalytic properties for LiPSs. [ 71 ]…”

Single-atom catalysts for metal-sulfur batteries: Current progress and future perspectives

“…Recently, there have been unprecedented research activities on developing electrocatalysts to promote the electrochemical reaction of Li-S batteries [43,44]. These electrocatalysts mainly includes transition metals [45][46][47][48], transition metal compounds (oxides [49][50][51][52][53][54], sulfides [55][56][57][58], nitrides [59][60][61][62][63], phosphide [64] and carbide [65]), metal-free materials [66][67][68] and heterostructures [69][70][71][72], etc. These catalysts are usually at a nanometer scale, which not only exhibit strong chemisorption to LiPS, but possess a large number of catalytic sites.…”

Sb nanosheet modified separator for Li–S batteries with excellent electrochemical performance

“…Li-S batteries have been attracting increasingly interests due to their high theoretical specic capacity of 1675 mA h g À1 and high energy density of 2600 W h kg À1 , which is nearly 10 times higher than that of the traditional LIBs. [9][10][11][12][13] In addition, sulfur, which is environment-friendly and of low cost, is used as the active material in Li-S batteries. 14,15 However, the practical application of Li-S batteries are still restricted by some problems, such as the low conductivity of sulfur and the shuttle effect of lithium polysuldes (LiPSs).…”