Hierarchical Porous N‐Doped Carbon Nanosheets Obtained by Organic–Inorganic Bipolymeric Engineering for Improved Lithium–Sulfur Batteries

Abstract

A new route for obtaining N‐doped carbon nanosheets through an in situ solid‐state thermal organic–inorganic polymerization and carbonization method, with glucose and melamine as precursors, due to different temperature intervals for glucose or melamine polymerization, is reported. At a current rate of 0.2 C, as a cathode for a lithium–sulfur cell, the N‐doped carbon nanosheet/sulfur hybrid delivers a high capacity of 1313 and 722 mA h g−1 in the 1st and 200th cycles, respectively; these values are over 40 % higher than that of cells with glucose‐derived carbon nanosheets.

Recent advances in interlayer and separator engineering for lithium-sulfur batteries

“…S 2À ). The charging process undergoes an opposite reaction [8][9][10][11]. Li-S battery has several advantages comparing with other rechargeable batteries.…”

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

“…As shown in Figure 2a, two broad diffraction peaks of HPCS and N‐HPCS appear at 23.4° and 43.5°, which were ascribed to the plane reflection of (002) and (100) of graphite carbon, respectively [33–35] . Compared to the peak of the carbon spheres without N‐doping, the peak of the N‐doped carbon spheres (N‐HPCS‐1, N‐HPCS and N‐HPCS‐2) have relatively broader peaks (Figure S3a), demonstrating that the N‐doped carbon spheres have more disordered carbon structures because the introduction of N atoms inhibits the continuous sp 2 ‐C plane conformation of the carbon material [27,36] . The sharp and strong diffraction peaks observed in the N‐HPCS/S at around 25° exhibited an orthogonal structure of S [33,37] .…”

“…In addition, pyrrolic‐N is p‐type doping, which can cause a large number of vacancy defects [45,46] . Each pyrrolic‐N atom can provide a lone pair of electrons in the aromatic ring of the carbon spheres, providing a binding site for the highly positively charged Li + in the lithium polysulfide (Li 2 S x ), thereby forming the Li 2 S x ‐N bond, and preventing the dissolution and shuttling effect of Li 2 S x more efficiently [4,47] . It is worth noting that after the introduction of S species, the proportion of the three N species changed significantly, illustrating the interaction between S and pyrrolic‐N (Figure S7).…”

“…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] …”

“…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] . In particular, due to the interaction between the electrophilic Li + and the electronegative N atoms, the introduction of N atoms into the carbon skeleton can form a chemical bond Li 2 S x −N between the polysulfide (or lithium sulfide) and the N atoms, which is stronger than that of the physical adsorption of non‐polar porous carbon [4,27,28] . Thus, the dissolution of polysulfide and lithium sulfide is effectively suppressed, and the utilization of S is improved, further strengthening the cycle performance of the Li−S batteries.…”