Electrocatalysis of Lithium Polysulfides: Current Collectors as Electrodes in Li/S Battery Configuration

Abstract

Lithium Sulfur (Li/S) chemistries are amongst the most promising next-generation battery technologies due to their high theoretical energy density. However, the detrimental effects of their intermediate byproducts, polysulfides (PS), have to be resolved to realize these theoretical performance limits. Confined approaches on using porous carbons to entrap PS have yielded limited success. In this study, we deviate from the prevalent approach by introducing catalysis concept in Li/S battery configuration. Engineered current collectors were found to be catalytically active towards PS, thereby eliminating the need for carbon matrix and their processing obligatory binders, additives and solvents. We reveal substantial enhancement in electrochemical performance and corroborate our findings using a detailed experimental parametric study involving variation of several kinetic parameters such as surface area, temperature, current rate and concentration of PS. The resultant novel battery configuration delivered a discharge capacity of 700 mAh g−1 with the two dimensional (2D) planar Ni current collectors and an enhancement in the capacity up to 900 mAh g−1 has been realized using the engineered three dimensional (3D) current collectors. The battery capacity has been tested for stability over 100 cycles of charge-discharge.

Nickel fibers/sulfur composites cathode with enhanced electrochemical performance for rechargeable lithium-sulfur batteries

“…In addition, due to the nickel decoration, lower oxidation onset potential are also observed, indicating the catalytic effect of the nickel on the oxidation of Li 2 S/Li 2 S 2 . This is similar to previous reports, in which some metals, such as Pt, Au, were also found to have a catalytic effect on the Li-S redox reaction [15].…”

“…6 (b). These results imply that the nickel have a catalytic effect on sulfur reduction [15,23]. In addition, due to the nickel decoration, lower oxidation onset potential are also observed, indicating the catalytic effect of the nickel on the oxidation of Li 2 S/Li 2 S 2 .…”

“…In recent researches, Babu et al [15] reported that electrocatalysts (such as Ni) have better reaction kinetics towards polysulfides conversion process. So, in order to investigate the electrocatalysis of nickel fiber, cyclic voltammograms of the nickel fibers/sulfur composites at a various scanning rates of 0.6 mV s À1 and 2 mV s À1 are shown in Fig.…”

“…In addition, some research groups also studied the modification of current collector using porous nickel foam to increase the electronic conductivity of sulfur electrode [12][13][14]. Recent studies have shown that the metal (Pt, Au, Ni) as electrocatalyst of lithium polysulfides and its metallic porous nanostructure can suppress the shuttle effect to attain the excellent coulumbic efficiency and cyclability [15]. However, the pore size of nickel foams investigated varies from hundreds of microns to several millimeters, which is difficult to restrain the polysulfides from diffusing in chargedischarge process.…”

Electrochemistry of Molten Sulfides: Copper Extraction from BaS-Cu2S

“…19 The oxidation-reduction processes of sulfur have therefore been investigated in different electrolytes, including sulfide melts, and on different electrodes. [18][19][20][21][22] Voltammetry indicates that the oxidation of sulfide ions (S 2− ) to elemental sulfur is presumably a single step reaction, while sulfur reduction consists in multiple steps 22 leading to the formation of polysulfides of the alkaline metals. 22 The solubility and stability of those species have been reported as the critical challenge for battery applications.…”