RESUMO
In this paper, a carbon nanofiber (CNF) hybrid nanomaterial composed of MnO-Sn cubes embedding in nitrogen-doped CNF (MnO-Sn@CNF) is synthesized through electrospinning and post-thermal reduction processes. It exhibits good electrochemical lithium-ion storage performance as the anode, such as high reversible capacity, outstanding cycle performance (754 mAh g-1at 1 A g-1after 1000 cycles), and good rate capability (447 mAh g-1at 5 A g-1). The excellent electrochemical properties are derived from a unique nanostructure design. MnO-Sn@CNF has a three-dimensional conductive network with a stable core-shell structure, which improves the electrical conductivity and mechanical stability of the materials. In addition, the mesopores on the surface of carbon fibers can shorten the diffusion distance of lithium ions and promote the combination of active sites of the material with lithium ions. The internal MnO and Sn form a heterostructure, which enhances the stability of the physical structure of the electrode material. This material design method provides a reference strategy for the development of high-performance lithium-ion batteries anode.
RESUMO
Engineering materials nanostructures is key for developing renewable energy technologies for lithium-ion batteries (LIBs) but remains a long-term research challenge. In this paper, heterostructured NiO/NiCo2O4 nanoprisms with a hierarchically hollow cavity and porous framework are rationally designed and further encapsulated in graphene oxide (NiO/NiCo2O4@GO) as a highly efficient anode nanomaterial for LIBs. Heterostructured NiO/NiCo2O4 hollow/porous nanoprisms are derived by the ionic exchange of Ni precursors with [Co(CN)6]3- (CoNi-metal-organic framework (MOF)) and then annealed under air. The encapsulation is achieved by fast assembly of GO and NiO/NiCo2O4. Thanks to hierarchically hollow and porous nanostructure, heterostructured NiO/NiCo2O4, and overcoated GO, the NiO/NiCo2O4 electrode shows excellent electrochemical performance toward lithium storage, disclosing a large rate capacity of 468 mA h g-1 at 3.0 A g-1 and a good capacity retention of 561 mA h g-1 at 1 A g-1 after 800 cycles. This work paves a facile ionic exchange method for the controllable construction of hierarchically hollow MOFs and their derived composite nanomaterials for various energy-related applications.
RESUMO
A novelty roasting method with manganese carbonate (MnCO3) as additive was carried out to separate and recover vanadium from high chromium vanadium slag (HCVS) efficiently. Vanadium tailings containing chromium was detoxified by carbon reduction and smelting to form Fe-Cr alloy. The whole process of HCVS utilization was analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). 89.37% of vanadium and 0.10% of chromium was leached when MnCO3 was added to HCVS at the mole ratio of MnO in MnCO3 and V2O3 in HCVS (n(MnO)/n(V2O3)) of 2.0 and heating at 850⯰C for 120â¯min, then leached under the pH value at 2.5. 99.19% of vanadium was precipitated by (NH4)2SO4 and V2O5 with a purity of 99.28% was prepared. More than 84% of manganese addictive was recovered after manganese precipitation by carbonization with CO2 discharged from manganese carbonate roasting, which could be used as the raw addictive for roasting. The wastewater after vanadium and manganese extraction could be circulated as leaching medium. Three circulation routes realized the closed-circuit circulation of raw materials and products, saving the production costs and avoiding the environmental pollution. Fe-Cr alloy with 67.35% of Fe and 13.28% of Cr was obtained from chromium-containing vanadium tailings, which could be returned to the steelmaking process.
