Copper‐Stabilized Sulfur‐Microporous Carbon Cathodes for Li–S Batteries

Abstract

4156www.MaterialsViews.com wileyonlinelibrary.com interact with two Li atoms per S atom, the S cathode can provide reversible high capacity of 1675 mAh g -1 at average potentials of 2.0 V, [1][2][3] which is 10× higher energy density than that of classical commercial LiCoO 2 cathode. Since the capacity of current LiCoO 2 -graphite Li-ion battery is controlled by LiCoO 2 cathode, replacement of expensive LiCoO 2 with cheap S will largely enhance the battery energy density. However, the S cathodes are still suffering from poor cycle life, high selfdischarge, low Coulumbic effi ciency and low overall capacity because of: i) low S utilization and low S loading arising from insulating nature of S; [4][5][6] ii) internal "shuttle reaction" induced by dissolution of lithium polysulfi de intermediates (Li 2 S x , 4 ≤ x ≤ 8) in liquid organic electrolytes and highly reactive of lithium polysulfi de anions to carbonate solvent in carbonated electrolyte, [ 7,8 ] and iii) large volume change of S during lithiation/delithiation. [ 9,10 ] Current strategies to overcome these challenges focus on: 1) using carbon materials (microporous carbon, [11][12][13][14][15][16] carbon nanotubes, [17][18][19] graphene, [20][21][22] and carbon spheres. [23][24][25][26] and other conductive materials [27][28][29] to physically restrain polysulfi des, facilitate electron transport and provide free-space to accommodate the volume change of S/polysulfi des, [ 4,10 ] 2) adopting mesoporous silica as polysulfi de intermediates absorber through weak bond to suppress the dissolution of polysulfi des, [ 30 ] 3) preparing composites with small-chain S 2 to avert the formation of soluble high-order polysulfi des, [ 16,17 ] and 4) employing different organic electrolytes to manipulate the solubility of S/polysulfi des. [31][32][33] Although S encapsulated by porous carbon can signifi cantly improve the S utilization and reduce the "shuttle reaction", the full electrochemical reversibility is hardly achieved, which leads to a gradual capacity deterioration upon cycling. [34][35][36] This is because the current technology for carbon encapsulation of S just reduces but not totally eliminates the "shuttle reaction". To avoid forming soluble high-order polysulfi de (Li 2 S x , 4 ≤ x ≤ 8) during charge/discharge, we prepared a microporous carbon-S composite by breaking cyclic molecules S 8 into a diatomic molecule S 2 and infusing the S 2 into porous carbon at high temperature, which largely increases the cycling stability and Coulumbic effi ciency of S cathode. [ 16,17 ] However, the S loading is limited to around 30% in the microporous carbon-S composite due to the insulating nature of S 2 , Li 2 S 2 , and Li 2 S, Copper-Stabilized Sulfur-Microporous Carbon Cathodes for Li-S BatteriesShiyou Zheng , Feng Yi , Zhipeng Li , Yujie Zhu , Yunhua Xu , Chao Luo , Junhe Yang , * and Chunsheng Wang * A copper-stabilized sulfur-microporous carbon ( MC-Cu-S) composite is synthesized by uniformly dispersing 10% highly electronically conductive Cu nanoparticles into m...

Application of a Sulfur Cathode in Nucleophilic Electrolytes for Magnesium/Sulfur Batteries

“…The second step is similar to those reported in C-Cu-S composites synthesized by a chemical reaction between Cu and S, which are attributed to strong chemical bonding between S and Cu. 19,20 The delay in extracting S from the electrode confirms the occurrence of chemical bonds between sulfur and Cu current collector through copper sulfides. Additionally, the temperature ranges of weight loss for the sulfur electrode on Cu are evidently different from those of the mixtures of Cu and S powders with 2:1 and 1:1 molar ratios, which suggests that Cu 2 S and CuS are already formed at 50…”

“…The same CV behavior with a large overpotential in the first reduction process is also reported in a Li/S cell with a high S loading, which results from the large strain/stress due to large volume change. 20 The relatively stable cathodic and anodic current peaks in the following scans demonstrate the cycling stability of the S cathode in the nucleophilic electrolyte.…”

“…In the composite of MC-Cu-S, the microporous structure of the MC physical confines the S, while the Cu nanoparticles anchored in the MC further chemically interact with S/polysulfides through Cu-polysulfides CuS x , thereby resulting in a more effective reduction in the active material loss on prolonged cycling. 20 It is demonstrated that CuS and Cu 2 S exhibit some reversible electrochemical activity in Mg(AlCl 2 BuEt) 2 /THF nucleophilic electrolyte via the displacement of transition metal with pronounced capacity fading with respect to initial cycling. 35 In this study, all possible contributions of CuS and Cu 2 S to the performance of the sulfur electrode are considered, and commercial CuS and Cu 2 S as the cathodes with Cu current collector are prepared by following a fabrication procedure identical to that S electrode with Cu current collector.…”

Sulfur-Nickel Foam as Cathode Materials for Lithium-Sulfur Batteries

“…The diffusion of the dissolved polysulfides between the Li anode and cathode leads to shuttle between the two electrodes, 3,4 which may cause the loss of active materials, low coulombic efficiencies and poor cyclability of Li-S batteries. 5 Recent studies have shown that a metal can stabilize sulfur through chemical bonding 6 and its metallic porous nanostructure can suppress the shuttle effect 7 to attain the excellent coulumbic efficiency and cyclability. Based on the reactivity with sulfur, 8 three-dimensional architecture and good electronic conductivity of nickel foam, 9-11 here we present a sulfur-nickel foam cathode material for Li-S batteries.…”

“…Recent studies have shown that a metal can stabilize sulfur through chemical bonding 6 and its metallic porous nanostructure can suppress the shuttle effect 7 to attain the excellent coulumbic efficiency and cyclability. Based on the reactivity with sulfur, 8 three-dimensional architecture and good electronic conductivity of nickel foam, 9-11 here we present a sulfur-nickel foam cathode material for Li-S batteries.…”