Flexible coal-derived carbon fibers via electrospinning for self-standing lithium-ion battery anodes

A series of flexible and self-standing coal-derived carbon fibers(CCFs)were fabricated through electro-spinning coupled with carbonization using bituminous coal and polyacrylonitrile(PAN)as the carbon precursors.These CCFs were utilized as free-standing lithium-ion battery(LIB)anodes.Optimizing car-bonization temperature reveals that the CCFs exhibit a one-dimensional solid linear structure with a uni-form distribution of graphite-like microcrystals.These fibers possess a dense structure and smooth surface,with averaging diameter from approximately 125.0 to 210.0 nm at carbonization temperatures ranging from 600 to 900℃.During electrospinning and carbonization,the aromatic rings enriched in bituminous coal crosslink with PAN chains,forming a robust three-dimensional(3D)framework.This 3D microstructure significantly enhances the flexibility and tensile strength of CCFs,while increasing the graphite-like sp^(2)microcrystalline carbon content,thus improving electrical conductivity.The CCFs carbonized at 700℃demonstrate an optimal balance of sp^(3)amorphous and sp^(2)graphite-like carbons.The average diameter of CCFs-700 is 177 nm and the specific surface area(SSA)is 7.2 m^(2)g^(-1).Additionally,the fibers contain oxygen-containing functional groups,as well as nitrogen-containing func-tional groups,including pyridinic nitrogen and pyrrolic nitrogen.Owing to its characteristics,the CCFs-700 showcases remarkable electrochemical performance,delivering a high reversible capacity of 631.4 mAh g^(-1).CCFs-700 also exhibit outstanding cycle stability,which retains approximately all of their first capacity(400.1 mAh g^(-1))after 120 cycles.This research offers an economical yet scalable approach for producing flexible and self-supporting anodes for LIBs that do not require current collectors,binders and conductive additives,thereby simplifying the electrode fabrication process.

Insight into the microstructural evolution of anthracite during carbonization-graphitization process from the perspective of materialization

Materialization of coal is one of effective and clean pathways for its utilization. The microstructures of coal-based carbon materials have an important influence on their functional applications. Herein, the microstructural evolution of anthracite in the temperature range of 1000–2800 ℃ was systematically investigated to provide a guidance for the microstructural regulation of coal-based carbon materials.The results indicate that the microstructure of anthracite undergoes an important change during carbonization-graphitization process. As the temperature increases, aromatic layers in anthracite gradually transform into disordered graphite microcrystals and further grow into ordered graphite microcrystals, and then ordered graphite microcrystals are laterally linked to form pseudo-graphite phase and eventually transformed into highly ordered graphite-like sheets. In particular, 2000–2200 ℃ is a critical temperature region for the qualitative change of ordered graphite crystallites to pseudo-graphite phase,in which the relevant structural parameters including stacking height, crystallite lateral size and graphitization degree show a rapid increase. Moreover, both aromaticity and graphitization degree have a linear positive correlation with carbonization-graphitization temperature in a specific temperature range.Besides, after initial carbonization, some defect structures in anthracite such as aliphatic carbon and oxygen-containing functional groups are released in the form of gaseous low-molecular volatiles along with an increased pore structure, and the intermediates derived from minerals could facilitate the conversion of sp^(3) amorphous carbon to sp^(2) graphitic carbon. This work provides a valuable reference for the rational design of microstructure of coal-based carbon materials.

Extraction of scandium from red mud by acid leaching with CaF2 and solvent extraction with P507

The extraction of Sc by acid leaching with CaF2 and solvent extraction with P507 from red mud was proposed.The influence of acid leaching and solvent extraction on recovery of Sc was investigated.The CaF2 can obviously improve the leaching efficiency of Sc and reduce the acid consumption.The leaching efficiency of Sc increases from 74%to 92%and the dosage of acid reduces under suitable conditions by adding 5%CaF2.The minerals in red mud can easily be decomposed and leached into the acid solution with CaF2 through analysis of XRD pattern.The particles of red mud become smaller and multihole.The Sc can be selectively extracted with 10%P507 at the pH value of 0.1 from the acid leaching solution.More than 98%of Sc and less than 10%of Al and Fe are extracted.The SC2O3 with purity of 99%is obtained after the process of reverse extraction with NaOH,H2SO4 dissolution,precipitation by oxalic acid and roasting at 750℃.

Electrochemical performance of Ti_(3)C_(2)supercapacitors in KOH electrolyte

Two-dimensional(2D)carbide Ti_(3)C_(2)was synthesized by exfoliating Ti_(3)AlC_(2)in HF solution and used for supercapacitive performance investigation in 3 M KOH electrolyte.The specific surface area(SSA)of as-synthesized Ti_(3)C_(2)was 22.35 m^(2)/g.Ti_(3)C_(2)-based supercapacitor electrodes exhibited good energy storage ability and had a volumetric capacitance 119.8 F/cm^(3)at the current density of 2.5 A/g.Moreover,the addition of carbon black into Ti_(3)C_(2)powders greatly improved the performance of Ti_(3)C_(2)-based capacitors because carbon black restrained the preferred orientation of 2D Ti_(3)C_(2),providing fast ion transport channels,and in turn,decreasing electrical resistance from 16.7Ωto 3.5Ω.