Enhanced Cycling Performance for Lithium–Sulfur Batteries by a Laminated 2D g‐C₃N₄/Graphene Cathode Interlayer

Abstract

Decay in electrochemical performance resulting from the “shuttle effect” of dissolved lithium polysulfides is one of the biggest obstacles for the realization of practical applications of lithium–sulfur (Li–S) batteries. To meet this challenge, a 2D g‐C3N4/graphene sheet composite (g‐C3N4/GS) was fabricated as an interlayer for a sulfur/carbon (S/KB) cathode. It forms a laminated structure of channels to trap polysulfides by physical and chemical interactions. The thin g‐C3N4/GS interlayer significantly suppresses diffusion of the dissolved polysulfide species (Li2Sx; 2<x≤8) from the cathode to the anode, as proven by using an H‐type glass cell divided by a g‐C3N4/GS‐coated separator. The S/KB cathode with the g‐C3N4/GS interlayer (S/KB@C3N4/GS) delivers a discharge capacity of 1191.7 mAh g−1 at 0.1 C after 100 cycles, an increase of more than 90 % compared with an S/KB cathode alone (625.8 mAh g−1). The S/KB@C3N4/GS cathode shows good cycling life, delivering a discharge capacity as high as 612.4 mAh g−1 for 1 C after 1000 cycles. According to XPS results, the anchoring of the g‐C3N4/GS interlayer to Li2Sx can be attributed to a coefficient chemical binding effect of g‐C3N4 and graphene on long‐chain polysulfides. Generally, the improvement in electrochemical performance originates from a coefficient of the enhanced Li+ diffusion coefficient, increased charge transfer, and the weakening of the shuttle effect of the dissolved Li2Sx as a result of the g‐C3N4/GS interlayer.

MoS2 nanorods with inner caves through synchronous encapsulation of sulfur for high performance Li–S cathodes

“…It is notable that slight peak changes occurred in the second cycle, where the reduction peak II moved to a high potential by 20 mV, while the oxidation peak III shifted by 30 mV to a low potential. The peak shifts could be attributed to the rearrangement http://engine.scichina.com/doi/10.1016/j.jechem.2019.09.032 of pristine orthorhombic sulfur species and interface activation during the initial charging-discharging [34] . There were nearly no position shifts of peak I and IV, which suggest favorable physical confinement of the MoS 2 nanostructure to long-chain Li 2 S x and S 8 .…”

Reduced graphene oxide/TiO2(B) nanocomposite-modified separator as an efficient inhibitor of polysulfide shuttling in Li–S batteries

“…Thus, there is a faster electrochemical reaction dynamic in the batteries due to the presence of the polar TiO 2 (B), which also explains the results of the higher rate capability for the RGO/ TiO 2 (B) sample. 64…”

Sustainable Synthesis of N‐Doped Hollow Porous Carbon Spheres via a Spray‐Drying Method for Lithium‐Sulfur Storage with Ultralong Cycle Life

“…Developments in transportation and grid applications have increased the demand for high energy density, low‐cost energy storage systems. Among various energy‐storage devices, lithium‐sulfur (Li−S) batteries have become one of the most attractive potential batteries for the next‐generation energy storage device, due to their high theoretical capacity (1675 mA h g −1 ) and energy density (2600 Wh kg −1 ), as well as the lightweight, low cost, natural richness and environmental friendliness of S [1–3] . Despite these advantages, there are still some shortcomings hindering the commercial development of Li−S batteries, including the poor conductivity of S and its discharge byproducts (Li 2 S 2 /Li 2 S), volume expansion by 80 % during the charge‐discharge process, and the dissolution and shuttling effects of soluble polysulfides intermediates [4–6] …”

“…The surface chemical modification of polar heteroatom doping (such as N, B, P, etc.) can change the hybrid orbital form of carbon and effectively improve the chemical adsorption capacity of carbon materials for polysulfides [3,22–24] . Owing to the electronegativity of the nitrogen (N) element (3.04) being higher than that of carbon (2.55) with comparable atomic size, the N element is considered to be a promising candidate for heteroatom doping, which affects the electrostatic potential distribution around the carbon atoms, changes the surface chemistry of the carbon material, and increases the electrical conductivity and active sites of the carbon cathode [25,26] .…”