Preparation of g-C3N4/CNTs composite by dissolution-precipitation method as sulfur host for high-performance lithium-sulfur batteries

Three-Dimensional Nitrogen-Doped Carbon Nanoskeleton Cladded with a Graphitic C3N5 Nanolayer as a Sulfur Host for Lithium–Sulfur Batteries

“…Three peaks at around 286.6, 285.6, and 284.6 eV can be fitted by the Gauss equation in the highresolution C 1s XPS spectra of these samples (Figure 3a), which are related to C−N/C�O/C−O, C−C sp 3 , and C−C sp 2 . 31,51,61 Another dominant peak at around 289.2 eV was observed for pristine g-C 3 N 5 , which originated from C sp 2 in N�C−N 2 type aromatic carbons as the characteristic component in the carbon nitride-like framework. 59 Dramatically, a decrease of the N�C−N 2 peak is observed for the CS/ U−C 3 N 5 −K sample, which is mainly due to the limited content of g-C 3 N 5 in the CS/U−C 3 N 5 −K sample.…”

“…All of them exhibited one obliquely longish charging voltage plateau at 2.2–2.3 V and two discharging voltage plateaus at approximately 2.3–2.4 and 2.1 V, respectively. The charging voltage plateaus at 2.2–2.3 V were assigned to the oxidation process of solid Li 2 S 2 /Li 2 S to solid S 8 via soluble LiPS intermediates. , In contrast, the discharging plateau at a higher voltage (2.3–2.4 V) was closely related to the inverse reduction of solid S 8 first to the long-chain soluble LiPS (e.g., Li 2 S 8 , Li 2 S 6 , and Li 2 S 4 ) intermediates, while the discharging plateau at a lower voltage (2.1 V) was related to the further reduction of LiPS intermediates to the solid Li 2 S 2 /Li 2 S deposited in the hosts. It has been demonstrated that the second discharging platform is the specific capacity-determining process with a contribution of three-quarters of the total theoretical specific capacity. ,, It is believed that a higher capacity ratio of the second stage to the first stage ( Q H / Q L ) value indicates better sulfur redox performance.…”

“…KOH etching is also a valid method to introduce intrinsic carbon defects into carbon nanomaterials . However, as an organically polymeric semiconductor in the family of graphitic carbon nitrides, g-C 3 N 4 possesses plenty of nitrogen sites and has been theoretically and experimentally confirmed to accelerate the sulfur redox reaction. , The intrinsic semiconductivity urges g-C 3 N 4 to combine with other high-conductive materials to obtain better electrochemical properties. , As another typical graphitic carbon nitride, g-C 3 N 5 has recently received increasing attention for photocatalytic and/or electrocatalytic applications. − For example, Li et al deposited g-C 3 N 5 onto hollow carbon nanospheres and realized enhanced oxygen electroreduction activity . To the best of our knowledge, few research reports have been devoted to investigating the sulfur redox performance of g-C 3 N 5 .…”

“…48,49 The intrinsic semiconductivity urges g-C 3 N 4 to combine with other highconductive materials to obtain better electrochemical properties. 50,51 As another typical graphitic carbon nitride, g-C 3 N 5 has recently received increasing attention for photocatalytic and/or electrocatalytic applications. 52−55 For example, Li et al deposited g-C 3 N 5 onto hollow carbon nanospheres and realized enhanced oxygen electroreduction activity.…”

Intrinsic Carbon Defects in Nitrogen and Sulfur Doped Porous Carbon Nanotubes Accelerate Oxygen Reduction and Sulfur Reduction for Electrochemical Energy Conversion and Storage

“…Carbon-based materials have been widely investigated as both ORR and SRR catalysts and gained more focus owing to their good conductivity, flexible structural tailorability, and curtailed cost. , However, pristine bulky carbon materials show poor catalytic activity due to a low specific surface area and weak adsorption affinity to oxygen and sulfur. The electrochemical performance of carbon-based materials can be greatly boosted by morphology and type of active site engineering, such as construction of nanoscale architectures and incorporation of defects. − Carbon-based materials with various nanostructures of high specific surface area and large pore volume, including nanosheets, , nanoscrolls, nanofibers, , nanotubes, − nanorods, hollow nanospheres, − nanocubes, nanocages, etc., have been constructed to expose more active sites, accommodate more reactants and products, and facilitate mass transfer. On the other hand, highly efficient catalytic active sites within carbon-based materials are equally important to electrochemical performance.…”