摘要: With the recent rapid development of electric vehicles, the use and decommissioning of Li-ion batteries have increased, causing environmental pollution and the waste of valuable materials in spent batteries. Commercial Li-ion batteries are mostly composed of transition metal oxide or phosphate-based cathodes, graphite-based anodes, organic electrolytes containing harmful lithium salts, polymer separators, and plastic or metal shells. After the battery is retired, many precious metals and graphite have a high recycling value. We review the current status of research on recovering these components with an emphasis on the leaching and separation of cathode and anode materials, and electrolytes in these batteries. The problems encountered in the different methods are outlined in terms of recycling cost and secondary pollution. Future research trends are outlined for the commercial full recovery of spent Li-ion batteries.
摘要: Carbon materials have attracted considerable attention as anodes for potassium ion batteries owing to their low-cost, nontoxicity, and controllable structures. The potassium storage behavior of carbon materials is highly associated with their active sites. In recent years, significant advances have been made in designing the active sites of carbon materials to meet the requirements of different potassium-based storage devices. Here, potassium storage mechanisms (intercalation and adsorption) for guiding the rational design of carbon materials are discussed. Based on these mechanisms, the review provides fundamental insight into the relationship between the structures and potassium storage performance of different carbon materials, including graphite, soft carbon, hard carbon, porous carbon, heteroatom-doped carbon, hybridized carbon and composited carbon. The structural design principles of carbon anode materials for potassium-ion full cell and potassium-ion capacitors are summarized based on the initial coulombic efficiency, capacity, potential plateau, rate performance, and cyclic stability. Finally, the problems and future research directions for the design of active sites in carbon materials for electrochemical potassium storage are considered.
摘要: Membrane technology for gas separation and purification has unique economic and environmental advantages over conventional purification processes. Carbon molecular sieve membranes (CMSMs) have a higher gas permeability, selectivity, chemical resistance, and better thermal stability than polymer membranes, and have therefore received more attention. CMSMs are commonly fabricated by the pyrolysis of polymer precursors such as polyimides, resins, cellulose and polyetherimide. The reported fabrication process and gas separation performance of CMSMs made from various precursors are summarized and discussed. Both the chemical and physical structures of the precursor membranes affect the carbon structures and gas separation performances of the resulting CMSMs. Overall, the gas separation performance of CMSMs has been significantly improved in the last 20 years, and their possible commercial use is not far away. An in-depth understanding of this progress on CMSMs should provide researchers from different fields an understanding of how to promote their fabrication and applications.
摘要: Aqueous zinc-ion hybrid capacitors (ZHCs) have an intrinsic safety and low cost, and are promising for use in large-scale energy storage devices. However, traditional porous carbon cathodes have inappropriate pore structures for zinc ion storage and diffusion. Moreover, zinc foil anodes suffer from the growth of Zn dendrites and side reactions, so that traditional ZHCs usually have a non-competitive energy density and unsatisfactory service life, seriously inhibiting their practical use. Two-dimensional transition metal carbide/nitride MXenes with a highly conductive matrix and abundant surface functional groups are good choices for constructing high-capacity cathodes and long-life Zn anodes for high-performance ZHCs. Recent progress in MXene-based nanomaterials as electrode materials of advanced ZHCs is summarized. The fundamentals of ZHCs are first introduced, such as working principles and key electrochemical parameters. The use of various MXene-based cathodes and anodes in high-performance aqueous ZHCs are then considered and, finally, the challenges and prospects for MXene-based nanomaterials for next-generation ZHCs are briefly discussed.
摘要: Lithium-sulfur batteries have attracted extensive attention because of their high theoretical specific energy storage capacity and energy density. However, the shuttling of polysulfides greatly hinders their practical use. Many studies show that engineering the interface between separators and cathodes is an effective strategy to solve this problem. Ways to inhibit the shuttling can be divided into physical blocking, chemical adsorption, and catalysis. Among the interfacial materials, carbon materials have attracted enormous attention due to their high electrical conductivity, large specific area, and high pore volume. However, their non-polarity makes it impossible for them to bind polysulfides tightly and heteroatoms/functional groups are incorporated in them or highly polar materials are composited with them in the design of the interfacial materials. In addition, the catalytic effect of the carbon in the polysulfide conversion is believed to be very important in effectively suppressing the shuttling. This review focuses on the detailed strategies and functions of interfacial engineering in addressing the problems and challenges in the use of lithium sulfur batteries. Finally, practical applications of lithium sulfur batteries are proposed, based on a combination of various measures including interfacial engineering.
摘要: Graphite serves as a key material for heat dissipation in electronic devices and nuclear engineering due to its remarkable thermal properties. The thermal expansion and conductivity of graphite have always been major scientific parameters in the field of carbon materials. Therefore, theoretical and experimental research in this area has received extensive attention. Research progress on the thermal expansion coefficient and thermal conductivity of graphite crystals is reviewed. Theoretical and experiment results on the thermal expansion coefficient of graphite are first introduced, followed by a discussion of the methods for measuring graphite thermal conductivity and the special phonon scattering mechanism in graphite. Finally, the uses of graphite in thermal management are summarized, and the development prospects in this field are discussed.
摘要: The rapid development of flexible electronics has produced an enormous demand for supercapacitors. Compared to batteries, supercapacitors have great advantages in terms of power density and cycling stability. They can also respond well on a time scale of seconds, but most have a poor frequency response, and behave more like pure resistors when used at high frequencies (e.g., above 100 Hz). It is therefore challenging to develop supercapacitors that work at a frequency of over 100 Hz. We report a high-frequency flexible symmetrical supercapacitor composed of a MnO2@carbon cloth hybrid electrode (CC@MnO2), which is synthesized by the defocused-laser ablation method. This CC@MnO2-based symmetric supercapacitor has an excellent specific areal capacitance of 1.53 mF cm−2 at a frequency of 120 Hz and has good cycling stability with over 92.10% capacitance retention after 100000 cycles at 100 V s−1. This remarkable electrochemical performance is attributed to the combined effect of the high conductivity of the 3D structure of the carbon cloth and the exceptional pseudo-capacitance of the laser-produced MnO2 nanosheets. The defocused laser ablation method can be used for large-scale production using roll-to-roll technology, which is promising for the wide use of the supercapacitor in high-frequency electronic devices.
摘要: An ideal supercapacitor electrode should contain three-dimensional (3D) interpenetrating electron and ion pathways with a short transport distance. Graphene-based carbon materials offer new and fascinating opportunities for high performance supercapacitor electrodes due to their excellent planar conductivity and large surface area. 3D graphene nanosheets coated with carbon nanolayers of controllable thickness from resorcinol-formaldehyde (RF) resin are constructed and activated by KOH to develop pores. Such a sandwich structure provides abundant transport channels for ions with short paths. The porous carbon nanolayers accelerate ion transport, while the graphene networks improve the conductivity, boosting electron transport. As expected, the prepared porous carbon has a high surface area of 690 m2 g−1 and a high specific capacitance of up to 324 F g−1 in a 6 mol L−1 KOH aqueous electrolyte at a current density of 0.2 A g−1. More than 99% of the capacitance is retained after 8000 charge–discharge cycles at a high current density of 5 A g−1, indicating good cycling stability. This research provides an effective strategy for the development of outstanding electrode materials for the enhanced transport of both electrons and ions.
摘要: The low volumetric capacity and sluggish diffusion of ions at high mass loadings of active materials per area limit any improvement of the energy and power densities of supercapacitors. A mixture of graphene oxide (GO) and urea in water was treated by an ultrasonic atomizer to form aerosol droplets, which were dried to obtain crumpled GO/urea particles. Crumpled graphene with a nitrogen content of 11.38% was obtained by the thermal shocking of these particles at 600 °C for 50 s. A volumetric capacitance of 384.0 F cm−3 was achieved when the crumpled graphene was used as supercapacitor electrodes. Even at a high current density (10 A g−1) and a high loading (74.3 mg/cm2 electrode), the specific capacitance retention still remained high. It is proposed that N-doping in the forms of pyrrole, imide, lactam and other types of pyridine-like nitrogen, and high surface area of the sample were key factors in improving the capacitance. The crumpled structure provided high mass transfer and high accessibility of ions to the active surface.
摘要: Photocatalytic H2 evolution is considered one of the most important processes for H2 production. Carbon materials are potential candidates for large-scale and cost-effective photocatalytic water splitting, yet their activity needs to be further improved. We report the synthesis of nitrogen-doped porous carbons using peat moss as a precursor and urea as a nitrogen source. The properties of carbons as photothermal-assisted visible-light photocatalysts were investigated. Due to the photothermal effect, the system temperature increased quickly to 55 °C in 15 min under visible light irradiation, which subsequently helps increase the photocatalytic activity by about 25%. It has been found that the crystallinity and nitrogen content of the carbon materials can be changed by changing the carbonization temperature, and these have an impact on their photocatalytic activity. A peat-derived carbon carbonized at 800 °C, with a N content of 4.88 at.% and an appropriate crystallinity has an outstanding photocatalytic activity with a high H2 evolution rate of 75.6 μmol H2 g−1 h−1 under visible-light irradiation.
摘要: A low-cost and simple method is reported for the synthesis of carbon nanodots (CDs) from waste wine cork using hydrothermal treatment. The structural and optical properties of the CDs were characterized by TEM, FTIR, Raman, UV-Vis absorption, and photoluminescence (PL) spectroscopy. Results indicate that the CDs have an average diameter of ~ 6.2 ± 2.7 nm and their excitation-dependent PL is related to the functional groups on their surface. The CDs have a quantum yield of 1.54%, estimated using quinine sulfate as a reference. They have been successfully applied in the bioimaging of mesenchymal stem cells (MSCs). After treatment with the CDs, the MSCs fluoresce green, yellow and red colors under the excitation wavelengths in the ranges 320-380 nm, 450-490 nm, and 515-560 nm, respectively, demonstrating their potential use in the field of fluorescence imaging.
摘要: Liquid-phase sintering combining an in-situ reaction method with a slurry method was used to prepare HfB2-MoSi2-SiC coatings of controllable composition and thickness. The effect of the MoSi2 content on the oxidation protection of HfB2-MoSi2-SiC composite coatings in a dynamic aerobic environment from room temperature to 1500 °C and a static constant temperature at 1500 °C in air was investigated. The relative oxygen permeability was used to characterize the oxidation resistance of the coatings. The results of dynamic oxidation test at room temperature~1500 °C show that the initial oxidation weight loss temperature of the samples is increased from 775 to 821 °C, and the maximum weight loss rate is decreased from 0.9×10−3 to 0.2×10−3 mg·cm−2·s−1 with increasing MoSi2 content, the lowest relative oxygen permeability is reduced to 12.2% with the weight loss of the sample being decreased from 1.8% to 0.21%. The mechanism of MoSi2 improving the oxidation protection of the coatings is revealed. With an increase of the MoSi2 content, the amount of SiO2 glass phase in the coating is increased, and the dispersion of Hf-oxide on the surface is improved so that a Hf-Si-O glass layer with high stability is formed and the weight loss of the sample is reduced from 0.46% to 0.08% after 200 h oxidation at 1500 °C in air.