Electrochemical properties of bare and Ta-substituted Nb2O5 nanostructures

Nb3O7F mesocrystals: orientation formation and application in lithium ion capacitors

The formation mechanism of NOF-NCMs is the overlapping effect of etching action of HF and the aggregation of nanowires. Because of novel architecture, the NOF-NCMs possess enhanced kinetic properties and outstanding Li storage performance.

Electrospun Nb2O5 nanorods/microporous multichannel carbon nanofiber film anode for Na+ ion capacitors with good performance

For the disadvantages of both the slow reaction kinetics and the poor conductivity for Nb₂O₅ electrode materials as sodium-ion capacitors (SICs), Nb₂O₅ NRs/NMMCNF film electrode with good flexibility and high electrochemical property has been fabricated by electrospinning PAN/PMMA/H₂Nb₂O₆·H₂O homogeneous viscous suspension and followed by an annealing treatment, in which the precursor H₂Nb₂O₆·H₂O nanorods are obtained by grinding H₂Nb₂O₆·H₂O nanowires, and Nb₂O₅ nanorods are uniformly embedded in nitrogen doped microporous multichannel carbon nanofiber. Benefiting from the multichannel network structure, Nb₂O₅ NRs/NMMCNF film electrode delivers the fast kinetics of Na⁺-storage and the superior Na-ion storage performance, it delivers outstanding rate capability (101 mAh g^-1 at 4 A g^-1) and ultralong lifespan (91% capacity retention after 10,000 cycles at 2 A g^-1). A Nb₂O₅ NRs/NMMCNF//AC SIC based on the Nb₂O₅ NRs@NMMCNF fiber film anode and the AC cathode is assembled. The energy density of the as-assembled device is as high as 91 Wh kg^-1 and its maximum power density is 7499 W kg^-1. This work offers a new structure design strategy toward intercalation-type metal oxide electrodes for application in SICs.

Effects of Electrospun Carbon Nanofibers' Interlayers on High-Performance Lithium-Sulfur Batteries

Two different interlayers were introduced in lithium–sulfur batteries to improve the cycling stability with sulfur loading as high as 80% of total mass of cathode. Melamine was recommended as a nitrogen-rich (N-rich) amine component to synthesize a modified polyacrylic acid (MPAA). The electrospun MPAA was carbonized into N-rich carbon nanofibers, which were used as cathode interlayers, while carbon nanofibers from PAA without melamine was used as an anode interlayer. At the rate of 0.1 C, the initial discharge capacity with two interlayers was 983 mAh g⁻¹, and faded down to 651 mAh g⁻¹ after 100 cycles with the coulombic efficiency of 95.4%. At the rate of 1 C, the discharge capacity was kept to 380 mAh g⁻¹ after 600 cycles with a coulombic efficiency of 98.8%. It apparently demonstrated that the cathode interlayer is extremely effective at shutting down the migration of polysulfide ions. The anode interlayer induced the lithium ions to form uniform lithium metal deposits confined on the fiber surface and in the bulk to strengthen the cycling stability of the lithium metal anode.

Electrospinning of Nanofibers for Energy Applications

With global concerns about the shortage of fossil fuels and environmental issues, the development of efficient and clean energy storage devices has been drastically accelerated. Nanofibers are used widely for energy storage devices due to their high surface areas and porosities. Electrospinning is a versatile and efficient fabrication method for nanofibers. In this review, we mainly focus on the application of electrospun nanofibers on energy storage, such as lithium batteries, fuel cells, dye-sensitized solar cells and supercapacitors. The structure and properties of nanofibers are also summarized systematically. The special morphology of nanofibers prepared by electrospinning is significant to the functional materials for energy storage.

Li3V2(PO4)3 encapsulated flexible free-standing nanofabric cathodes for fast charging and long life-cycle lithium-ion batteries

Lithiated transition metal phosphates with large theoretical capacities have emerged as promising cathode materials for rechargeable lithium-ion batteries. However, the poor kinetic properties caused by their low intrinsic electronic and ionic conductivity greatly hinder their practical applications. In this work, we demonstrate a novel strategy to prepare monoclinic lithium vanadium phosphate nanoparticles implanted in carbon nanofibers as the cathodes of Li-ion cells with high capacity, flexibility, long cycle stability and significantly improved high-rate performance. The composite nanofibers were obtained by electrospinning using polyacrylonitrile and Li3V2(PO4)3 nanoparticles, followed by annealing and coating with a thin layer of carbon by plasma enhanced chemical vapor deposition. The Li3V2(PO4)3 nanocrystals with the monoclinic phase were uniformly distributed in the composite nanofibers. The electrochemical performances of the as-prepared binder-free fibrous cathodes were characterized by potentiostatic and galvanostatic tests. At the rate of 0.5 C in the range of 3.0-4.3 V, the composite displayed an initial discharge capacity of 128 mA h g(-1) (96.2% of the theoretical capacity). A discharge capacity of 120 mA h g(-1) was observed even at a high rate of 10 C, and a capacity retention of 98.9% was maintained after 500 cycles at 5 C, indicating excellent high-rate capability and capacity retention. Compared to the control samples without a carbon outer-layer, the composite nanofibers with carbon coating demonstrated much better electrochemical performances. It indicates that the carbon coating can further protect the structural integrity of nanofabric electrodes during the charge/discharge processes without hindering the Li-ion mobility and also can prevent undesired side reactions with an electrolyte, thus greatly improving the rate performance and cyclic stability of the cathode.

Comparison of amorphous, pseudohexagonal and orthorhombic Nb2O5 for high-rate lithium ion insertion

Amorphous, pseudohexagonal and orthorhombic Nb₂O₅ nanoparticles were synthesized by sol–gel process. The material characteristics and electrochemical performance of these polymorphs were compared.