Enhancing Polysulfide Confinement and Electrochemical Kinetics by Amorphous Cobalt Phosphide for Highly Efficient Lithium–Sulfur Batteries

Abstract

The application of lithium−sulfur (Li−S) batteries is severely hampered by the shuttle effect and sluggish redox kinetics. Herein, amorphous cobalt phosphide grown on a reduced graphene oxide-multiwalled carbon nanotube (rGO-CNT-CoP(A)) is designed as the sulfur host to conquer the above bottlenecks. The differences between amorphous cobalt phosphide (CoP) and crystalline CoP on the surface adsorption as well as conversion of lithium polysulfides (LiPSs) are investigated by systematical experiments and densityfunctional theory (DFT) calculations. Specifically, the amorphous CoP not only strengthens the chemical adsorption to LiPSs but also greatly accelerates liquidphase conversions of LiPSs as well as the nucleation and growth of Li 2 S. DFT calculation reveals that the amorphous CoP possesses higher binding energies and lower diffusion energy barriers for LiPSs. In addition, the amorphous CoP features reduced energy gap and the increased electronic concentrations of adsorbed LiPSs near Fermi level. These characteristics contribute to the enhanced chemisorption ability and the accelerated redox kinetics. Simultaneously, the prepared S/rGO-CNT-CoP(A) electrode delivers an impressive initial capacity of 872 mAh g −1 at 2 C and 617 mAh g −1 can be obtained after 200 cycles, exhibiting excellent cycling stability. Especially, it achieves outstanding electrochemical performance even under high sulfur loading (5.3 mg cm −2 ) and lean electrolyte (E/S = 7 μL E mg −1 S ) conditions. This work exploits the application potential for amorphous materials and contributes to the development of highly efficient Li−S batteries.

Multisize CoS2 Particles Intercalated/Coated‐Montmorillonite as Efficient Sulfur Host for High‐Performance Lithium‐Sulfur Batteries

“…In addition, a new semicircle, representing the impedance caused by Li 2 S/Li 2 S 2 insulating layer (denoted as R g ), is appeared in each plot of the three cathodes after 200 cycles. The S/CoS 2 @MMT‐10 cathode exhibits much lower R g after cycling than that of the S/MMT cathode, which can be attributed to that the CoS 2 has enhanced the oxidation process of Li 2 S/Li 2 S 2 to S 8 [45] …”

“…The S/CoS 2 @MMT-10 cathode exhibits much lower R g after cycling than that of the S/MMT cathode, which can be attributed to that the CoS 2 has enhanced the oxidation process of Li 2 S/Li 2 S 2 to S 8 . [45] In order to further study the Li ion diffusion capacity in the composite cathodes, CV measurements were conducted at various scan rates (from 0.1 to 1.2 mV s À 1 ) on the S/CoS 2 @MMT-10, S/MMT, and S/CoS 2 cathodes. As shown in Figure 4d-f, the peak currents of the redox peaks increase with a higher scan rate for all three of the cathodes.…”

Synergetic Anion Vacancies and Dense Heterointerfaces into Bimetal Chalcogenide Nanosheet Arrays for Boosting Electrocatalysis Sulfur Conversion

“…[ 2,3 ] However, the sulfur conversion involves a multi‐electron redox process with sluggish reaction kinetics, which leads to Li−S batteries with low discharge capacity and poor cycle life. [ 4,5 ] The slow sulfur conversion reactions severely limit the electrochemical performances of Li−S batteries especially under high sulfur loading and lean electrolyte operation. [ 6,7 ]…”

Designing principles of advanced sulfur cathodes toward practical lithium‐sulfur batteries

“…34 By modulating the sulfur concentration and droplets number, the sulfur loading content could be readily adjusted. CS 2 35 and toluene 36 are the most common solvents to dissolve sulfur. However, because of their toxicity, ethanol was also used in certain situations.…”

“…To enhance the sulfur adsorption ability and catalytic capacity of host materials, surface modification, such as encompassing modulating the surface lattice distortion, electronic states, and chemical groups, were successfully realized by straining engineering, 201,202 amorphization, 35,70,203 and surface chemistry, 184,204,205 respectively. For example, Chen and coworkers fabricated tensile-strained Mxene/CNT porous microspheres by facile spray-drying process.…”