Owing to the slight volume expansion after potassiation, hard carbon is regarded as a promising anode material for potassium-ion batteries (PIBs). Heteroatom doping (such as sulfur or nitrogen) is a common method to modify hard carbon for high K-storage capacity and long cycling performance. High sulfur-doped hard carbon with a sulfur content of 25.8 wt % is prepared by calcining glucose in molten salt (K2SO4@LiCl/KCl). It exhibits high specific capacities of 361.4 mA h g–1 during the 1st cycle and 317.7 mA h g–1 during the 100th cycle at 0.05 A g–1. The high capacity arises from the K–S reaction behavior, which is demonstrated by the cyclic voltammetry test and galvanostatic intermittent titration technique. This work is an effective application of the molten salt method for PIBs, furnishing an understanding to K-storage behaviors of hard carbon- with high sulfur content.
Known to all, the transport of Li + is associated with the movement ability of the polymer chains, thus the cooperation the fillers in the electrolyte to enhance the movability is a common method to improve the ionic conductivity. Inorganic electrolytes, [4] metal organic frameworks materials, and [5] passive oxides [6] were applied to construct composite electrolytes, which can effectively promote the transport of Li + in the composite electrolytes for the reason of i) increased amorphous polymer phase which is beneficial to the ion transport, ii) fast ion path of polymer electrolyte/filler interface. However, the ionic conductivity is deeply affected by the morphology, concentration, and the distribution of the filler in the composite electrolytes. Fillers without nanostructure size are hard to improve the ionic conductivity effectively. Vertically aligned 2D vermiculite was applied to create aligned, [7] continuous interfacial paths to guide the Li + migration. Furthermore, proper concentration of fillers is available for increasing the fast percolation paths, which is reflected on the ionic conductivity. Goodenough and co-workers proved that high concentrations of Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 fillers in the composite electrolyte were a barrier to the Li + conductivity. [8] Since the polymer electrolyte membrane is fabricated through solvent casting, the inorganic fillers with poor dispersity are easy to agglomerate to form disconnected pathway. The proper selecting of the appropriate filler with special morphology, good compatibility in the composite electrolyte is a critical step to construct high ionic conductivity electrolyte accompanying excellent electrochemical performance.Carbon dots (CDs), defined as the spherical carbon nanoparticles with diameters less than 10 nm, had been demonstrated to have great potential in various fields, such as bio-imaging, [9] solar cells, [10] and sensors [11] . At the same time, the characteristics of CDs make it a great possibility in the field of solid electrolytes to overcome the issues revealed by other fillers in composite electrolytes: the uniform small size can avoid blocking ion channels; the organic functional groups on the surface of CDs might provide a good dispersity in the electrolyte. In our previous work, kilogram-scale synthesis and functionalization of CDs were investigated in depth, [12] and they can afford a very sufficient space to explore the mechanism acting on the polymer chain segment and present more possibility to the industrial production.Solid composite electrolyte-based Li battery is viewed as one of the most competitive system for the next generation batteries; however, it is still restricted by sluggish ion diffusion. Fast ion transport is a characteristic of the polyethylene oxide (PEO) amorphous phase, and the mobility of Li + is restrained by the coordination interaction within PEO and Li + . Herein, the design of applying functionalized carbon dots (CDs) with abundant surface features as fillers is proposed. High ionic conductivity is ...
Highlights The chemical process of local oxidation–partial reduction–deep coupling for stibnite reduction of carbon dots (CDs) is revealed by in-situ high-temperature X-ray diffraction. Sb2S3@xCDs anode delivers high initial coulombic efficiency in lithium ion batteries (85.2%) and sodium ion batteries (82.9%), respectively. C–S bond influenced by oxygen-rich carbon matrix can restrain the conversion of sulfur to sulfite, well confirmed by X-ray photoelectron spectroscopy characterization of solid electrolyte interphase layers helped with density functional theory calculations. CDs-induced Sb–O–C bond is proved to effectively regulate the interfacial electronic structure. Abstract The application of Sb2S3 with marvelous theoretical capacity for alkali metal-ion batteries is seriously limited by its poor electrical conductivity and low initial coulombic efficiency (ICE). In this work, natural stibnite modified by carbon dots (Sb2S3@xCDs) is elaborately designed with high ICE. Greatly, chemical processes of local oxidation–partial reduction–deep coupling for stibnite reduction of CDs are clearly demonstrated, confirmed with in situ high-temperature X-ray diffraction. More impressively, the ICE for lithium-ion batteries (LIBs) is enhanced to 85%, through the effect of oxygen-rich carbon matrix on C–S bonds which inhibit the conversion of sulfur to sulfite, well supported by X-ray photoelectron spectroscopy characterization of solid electrolyte interphase layers helped with density functional theory calculations. Not than less, it is found that Sb–O–C bonds existed in the interface effectively promote the electronic conductivity and expedite ion transmission by reducing the bandgap and restraining the slip of the dislocation. As a result, the optimal sample delivers a tremendous reversible capacity of 660 mAh g−1 in LIBs at a high current rate of 5 A g−1. This work provides a new methodology for enhancing the electrochemical energy storage performance of metal sulfides, especially for improving the ICE.
Carbon dots (CDs) as new nanomaterials have attracted much attention in recent years due to their unique characteristics. Notably, structure and interface modification (carbon core, edge, defects, and functional groups) of CDs have been considered as valid methods to regulate their properties, which contain electron transfer effect, electrochemical activity, fluorescence luminescent, and so on. Additionally, CDs with ultrasmall size, excellent dispersibility, high specific surface area, and abundant functional groups can guarantee positive and extraordinary effects in electrical energy storage and conversion. Therefore, CDs are used to couple with other materials by constructing a special interface structure to enhance their properties. Here, diverse structural and interfacial modifications of CDs with various heteroatoms and synergy effects are systematically analyzed. And not only several main syntheses of CDs‐based composites (CDs/X) are summarized but also the merit and demerit of CDs/X in electrical energy storage are discussed. Finally, the applications of CDs/X in energy storage devices (supercapacitors, batteries) and electrocatalysts for practical applications are discussed. This review mainly provides a comprehensive summary and future prospect for synthesis, modification, and electrochemical applications of CDs.
Figure 8. a) Band structure of a) SbQD@C and c) Sb (R-3m); the total density of states and partial density of states for b) SbQD@C and d) Sb (R-3m).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.