Electrocatalytic Interlayer with Fast Lithium–Polysulfides Diffusion for Lithium–Sulfur Batteries to Enhance Electrochemical Kinetics under Lean Electrolyte Conditions

Abstract

Lithium–sulfur batteries are promising energy‐storage devices because of their high theoretical energy densities. For practical Li–S batteries, reducing the amount of electrolyte used is essential for achieving the high energy densities. However, reducing the electrolyte amount leads to severe performance degradation, mainly because of sluggish deposition of discharge products (Li2S) and the accompanying passivation issue that arise from the insulating nature of Li2S. In this study, a lightweight, robust interlayer, with a 3D open structure and a low surface area is designed and fabricated. The structure facilitates electrolyte infiltration without trapping too much electrolyte. Moreover, the electrocatalytic Co nanoparticles embedded in the skeleton surface within the interlayer effectively promote Li ion diffusion, polysulfides conversion, and Li2S deposition, and therefore enhance the electrochemical kinetics under lean electrolyte conditions. The mechanisms involved in the interlayer effects are investigated by microstructural characterizations, electrochemical performance tests, density functional theory calculations, and in situ X‐ray diffraction characterization. These results show the feasibility of using an interlayer strategy to improve the electrochemical performances of Li–S batteries under lean electrolyte conditions to potentially increase the practical energy densities of Li–S batteries.

Rational Design of Multifunctional Integrated Host Configuration with Lithiophilicity‐Sulfiphilicity toward High‐Performance Li–S Full Batteries

“…It should be noted that the other valence state species were also deconvoluted, which mainly originated from the partially oxidized Co nanoparticles when exposed to ambient environment during XPS tests. [42,43] In addition, the XPS spectrum of the N 1s region (Figure 2f) exhibits three peaks corresponding to pyridinic (398.3 eV), pyrrolic (400.3 eV), and graphitic N (401.5 eV), respectively, which indicate the presence of N doping in the Col-Fs-derived carbon framework. The N-heteroatom doping is believed to boost the surface polarization and wetness of carbon host materials to favor the adsorption toward Li atoms and LiPSs as well as the accessibility of the electrolyte.…”

Enhanced Electrochemical Kinetics with Highly Dispersed Conductive and Electrocatalytic Mediators for Lithium–Sulfur Batteries

“…After 200 cycles, a capacity of 894 mAh g −1 can be achieved, corresponding to an ultralow capacity decay of 0.055‰ per cycle. Taking into accounts the critical parameters, including the sulfur loading, E/S, and current rate, such performance of the high sulfur loading Li–S cell under lean electrolyte conditions is competitive with other recent reported works, [ 12,17–21 ] especially at high current rates (Figure 6d; Table S3, Supporting Information).…”

“…In the case of a high sulfur loading of 3 mg cm −2 , the Li–S cell with a GN interlayer exhibits a low initial discharge capacity of 534.2 mAh g −1 , although it is higher than that of the cell without an interlayer (Figure S8, Supporting Information). It is due to severe surface passivation in the high sulfur loading cathode, [ 12 ] leading to a low sulfur utilization, which reveals that the introduced GN interlayer is insufficient to alleviate the problem. The cell with a MoO 2 /CHS separator shows a higher initial capacity of 730 mAh g −1 , however the capacity decays to 627.2 mAh g −1 after 100 cycles, which is close to that of the cell with a GN interlayer.…”

Material design and structure optimization for rechargeable lithium-sulfur batteries

“…[173][174][175][176] Given that the effects of adsorbents, heterogeneous mediators, and electrocatalysts in enhancing the performance of sulfur cathodes have been successfully demonstrated, these materials were also considered to be incorporated into interlayers for achieving high-performance Li-S batteries. [177][178][179][180] For instance, a 2D g-C 3 N 4 /graphene sheet (g-C 3 N 4 /GS) was developed as an effective composite interlayer in Li-S batteries (Figure 6A). 181 The 2D g-C 3 N 4 and graphene nanosheets stack with each other to generate a laminated structure, which can greatly enhance the interception of polysulfides.…”