Hollow Porous VOx/C Nanoscrolls as High-Performance Anodes for Lithium-Ion Batteries

Metal Oxide Nanosheet: Synthesis Approaches and Applications in Energy Storage Devices (Batteries, Fuel Cells, and Supercapacitors)

In recent years, the increasing energy requirement and consumption necessitates further improvement in energy storage technologies to obtain high cycling stability, power and energy density, and specific capacitance. Two-dimensional metal oxide nanosheets have gained much interest due to their attractive features, such as composition, tunable structure, and large surface area which make them potential materials for energy storage applications. This review focuses on the establishment of synthesis approaches of metal oxide nanosheets (MO nanosheets) and their advancements over time, as well as their applicability in several electrochemical energy storage systems, such as fuel cells, batteries, and supercapacitors. This review provides a comprehensive comparison of different synthesis approaches of MO nanosheets, as well their suitability in several energy storage applications. Among recent improvements in energy storage systems, micro-supercapacitors, and several hybrid storage systems are rapidly emerging. MO nanosheets can be employed as electrode and catalyst material to improve the performance parameters of energy storage devices. Finally, this review outlines and discusses the prospects, future challenges, and further direction for research and applications of metal oxide nanosheets.

Synthesis and Electrochemical Performance of KVO/GO Composites as Anodes for Aqueous Rechargeable Lithium-Ion Batteries

K_0.25V₂O₅ (KVO) and K_0.25V₂O₅/graphene oxide (KVO/GO) have been successfully synthesized by a chemical coprecipitation method and a subsequent calcination process. The structure and morphology of KVO and KVO/GO were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The as-obtained vanadate and vanadate modified by GO materials were used as anodes with LiMn₂O₄ as a cathode and saturated LiNO₃ as an electrolyte to assemble an aqueous rechargeable lithium-ion battery (ARLB). The cyclic voltammogram curves of both KVO and KVO/GO electrodes exhibited three pairs of redox peaks corresponding to charge/discharge platforms. We found that a small amount of graphene oxide added improved the electrochemical performance more significantly than excess graphene oxide. The as-prepared KVO/GO//LiMn₂O₄ could not only improve the initial discharge capacity but could also reduce the attenuation at a high current density. Furthermore, the ARLB with a KVO/GO anode exhibited an excellent rate performance and super long cycle life. These good electrochemical properties of this new ARLB system actually provided feasibility for application in large-scale power sources and energy storage devices.

Electronic Textiles Based on Highly Conducting Poly(vinyl alcohol)/Carbon Nanotube/Silver Nanobelt Hybrid Fibers

Highly stable conducting fibers have attracted significant attention in electronic textile (e-textile) applications. Here, we fabricate highly conducting poly(vinyl alcohol) (PVA) nanocomposite fibers with high thermal and chemical stability based on silver nanobelt (AgNB)/multiwalled carbon nanotube (MWCNT) hybrid materials as conducting fillers. At 20 vol % AgNB/MWCNT, the electrical conductivity of the fiber dramatically increased (∼533 times) from 3 up to 1600 S/cm after thermal treatment at 300 °C for 5 min. Moreover, PVA/AgNB/MWCNT fiber resists the harsh conditions of good solvents for PVA as well as high temperatures over the melting point of PVA, whereas pure PVA fiber is unstable in these environments. The significantly enhanced electrical conductivity and chemical stability can be realized through the post-thermal curing process, which is attributed to the coalescence between adjacent AgNBs and additional intensive cross-linking of PVA. These remarkable characteristics make our conducting fibers suitable for applications in e-textiles such as water leakage detectors and wearable heaters. In particular, heating behavior of e-textiles by Joule heating can accelerate the desorption of physically trapped moisture from the fiber surface, resulting in the fully reversible operation of water leakage monitoring. This smart e-textile sensor based on highly stable and conductive composite fibers will pave the way for diverse e-textile applications.

Metal-organic framework derived amorphous VOx coated Fe3O4/C hierarchical nanospindle as anode material for superior lithium-ion batteries

Lithium-ion batteries (LIBs) are widely regarded as a promising electrochemical energy storage device, due to their high energy density and good cycling stability. To date, the development of anode materials for LIBs is still confronted with many serious problems, and much effort is required for constructing more ideal anode materials. Herein, starting with metal-organic frameworks (MOFs), an amorphous VO_x coated Fe₃O₄/C hierarchical nanospindle has been successfully synthesized. The obtained Fe₃O₄/C@VO_x nanospindle has a uniform particle size of ∼100 nm in diameter and ∼400 nm in length and consists of ultrafine Fe₃O₄ nanoparticles (∼5 nm) embedded in a porous carbon matrix as the core and an amorphous VO_x layer as the shell. Notably, as the anode material for LIBs, Fe₃O₄/C@VO_x delivers a high coulombic efficiency (74.2%) and a large capacity of 845 mA h g^-1 after 500 cycles at 1000 mA g^-1. A prominent discharge reversible capacity of 340 mA h g^-1 is also still retained at 5000 mA g^-1. More importantly, the presented facile MOF-derived route could be easily extended to other functional materials for widespread applications.

Borax promotes the facile formation of hollow structure in Cu single crystalline nanoparticles for multifunctional electrocatalysis

Hollow Cu₂O and Cu are efficiently prepared using borax as structure-directing agent for electrocatalysis of glucose oxidation and H₂O₂ reduction.

Facile preparation of a V2O3/carbon fiber composite and its application for long-term performance lithium-ion batteries

A V₂O₃/carbon-nanofiber composite was initially synthesized, which exhibited large reversible capacity and excellent long-term cycling performance for lithium-ion batteries.