Qiulong Wei

One-Pot Synthesized Bicontinuous Hierarchical Li3V2(PO4)3/C Mesoporous Nanowires for High-Rate and Ultralong-Life Lithium-ion Batteries

Lithium-ion batteries have attracted enormous attention for large-scale and sustainable energy storage applications. Here we present a design of hierarchical Li3V2(PO4)3/C mesoporous nanowires via one-pot synthesis process. The mesoporous structure is directly in situ carbonized from the surfactants (CTAB and oxalic acid) along with the crystallization of Li3V2(PO4)3 without using any hard templates. As a cathode for lithium-ion battery, the Li3V2(PO4)3/C mesoporous nanowires exhibit outstanding high-rate and ultralong-life performance with capacity retention of 80.0% after 3000 cycles at 5 C in 3-4.3 V. Even at 10 C, it still delivers 88.0% of its theoretical capacity. The ability to provide this level of performance is attributed to the hierarchical mesoporous nanowires with bicontinuous electron/ion pathways, large electrode-electrolyte contact area, low charge transfer resistance, and robust structure stability upon prolonged cycling. Our work demonstrates that the unique mesoporous nanowires structure is favorable for improving the cyclability and rate capability in energy storage applications.

Amorphous Vanadium Oxide Matrixes Supporting Hierarchical Porous Fe3O4/Graphene Nanowires as a High-Rate Lithium Storage Anode

Developing electrode materials with both high energy and power densities holds the key for satisfying the urgent demand of energy storage worldwide. In order to realize the fast and efficient transport of ions/electrons and the stable structure during the charge/discharge process, hierarchical porous Fe3O4/graphene nanowires supported by amorphous vanadium oxide matrixes have been rationally synthesized through a facile phase separation process. The porous structure is directly in situ constructed from the FeVO4·1.1H2O@graphene nanowires along with the crystallization of Fe3O4 and the amorphization of vanadium oxide without using any hard templates. The hierarchical porous Fe3O4/VOx/graphene nanowires exhibit a high Coulombic efficiency and outstanding reversible specific capacity (1146 mAh g(-1)). Even at the high current density of 5 A g(-1), the porous nanowires maintain a reversible capacity of ∼500 mAh g(-1). Moreover, the amorphization and conversion reactions between Fe and Fe3O4 of the hierarchical porous Fe3O4/VOx/graphene nanowires were also investigated by in situ X-ray diffraction and X-ray photoelectron spectroscopy. Our work demonstrates that the amorphous vanadium oxides matrixes supporting hierarchical porous Fe3O4/graphene nanowires are one of the most attractive anodes in energy storage applications.

Nanoscroll Buffered Hybrid Nanostructural VO2 (B) Cathodes for High‐Rate and Long‐Life Lithium Storage

Hybrid nanostructural VO2 (B) composed of nanoscrolls, nanobelts and nanowires is synthesized through a hydrothermal-driven splitting and self-rolled method. The hybrid nanostructure with nanoscroll buffered effect provides facile strain relaxation for swelling during lithiation/delithiation, resulting in the excellent structural stability and cyclability. The interior of nanoscrolls and the interconnected voids shorten the ion diffusion pathway, which greatly enhances the rate performance.

Porous One‐Dimensional Nanomaterials: Design, Fabrication and Applications in Electrochemical Energy Storage

Electrochemical energy storage technology is of critical importance for portable electronics, transportation and large-scale energy storage systems. There is a growing demand for energy storage devices with high energy and high power densities, long-term stability, safety and low cost. To achieve these requirements, novel design structures and high performance electrode materials are needed. Porous 1D nanomaterials which combine the advantages of 1D nanoarchitectures and porous structures have had a significant impact in the field of electrochemical energy storage. This review presents an overview of porous 1D nanostructure research, from the synthesis by bottom-up and top-down approaches with rational and controllable structures, to several important electrochemical energy storage applications including lithium-ion batteries, sodium-ion batteries, lithium-sulfur batteries, lithium-oxygen batteries and supercapacitors. Highlights of porous 1D nanostructures are described throughout the review and directions for future research in the field are discussed at the end.

Synergistic Effect of Hierarchical Nanostructured MoO2/Co(OH)2 with Largely Enhanced Pseudocapacitor Cyclability

Pseudocapacitors have demonstrated an ability to deliver high energy and power densities. The main limitation is their poor cyclability and for this reason the architectural design of electrode materials has attracted considerable attention. Here we report the synthesis of hierarchical nanostructured material by growing Co(OH)2 nanoflakes onto MoO2 thin film. The electrode material exhibits a high capacitance of 800 F g(-1) at 20 A g(-1) with only 3% capacitance loss after 5000 cycles and high rate capability with increasing current density from 2 to 40 A g(-1), which are better than those of individual component. The enhanced pseudocapacitor performances benefit from the synergistic effect of the hierarchical nanostructure: (1) faster ion diffusion and electron transport at electrode/electrolyte interface, and (2) mitigation of the electrode destruction caused by ion insertion/deinsertion during charge-storage process. This facile design and rational synthesis offers an effective strategy to enhance the electrochemical performance of pseudocapacitors and shows promising potential for large-scale application in energy storage.

Low-crystalline iron oxide hydroxide nanoparticle anode for high-performance supercapacitors

Carbon materials are generally preferred as anodes in supercapacitors; however, their low capacitance limits the attained energy density of supercapacitor devices with aqueous electrolytes. Here, we report a low-crystalline iron oxide hydroxide nanoparticle anode with comprehensive electrochemical performance at a wide potential window. The iron oxide hydroxide nanoparticles present capacitances of 1,066 and 716 F g−1 at mass loadings of 1.6 and 9.1 mg cm−2, respectively, a rate capability with 74.6% of capacitance retention at 30 A g−1, and cycling stability retaining 91% of capacitance after 10,000 cycles. The performance is attributed to a dominant capacitive charge-storage mechanism. An aqueous hybrid supercapacitor based on the iron oxide hydroxide anode shows stability during float voltage test for 450 h and an energy density of 104 Wh kg−1 at a power density of 1.27 kW kg−1. A packaged device delivers gravimetric and volumetric energy densities of 33.14 Wh kg−1 and 17.24 Wh l−1, respectively.

Hierarchical zigzag Na1.25V3O8 nanowires with topotactically encoded superior performance for sodium-ion battery cathodes

We report a facile method to topotactically synthesize Na1.25V3O8 nanowires with a novel hierarchical zigzag structure. The unique morphology can provide an increased electrode–electrolyte contact area and better strain accommodation; also the topotactic intercalation method can improve structure integrity and robustness. The as-synthesized material delivers a capacity of 172.5 mA h g−1 at 100 mA g−1, shows excellent cyclability with a capacity fading of only 0.0138% per cycle at 1 A g−1 for 1000 cycles, and high rate capability as a sodium-ion battery cathode. We propose that the novel morphology as well as intrinsically advantageous structural features can synergistically facilitate the kinetics and stability, resulting in superior electrochemical performance.

Hydrated vanadium pentoxide with superior sodium storage capacity

Sodium ion batteries (SIBs), as potential candidates for large-scale energy storage systems, have attracted great attention from researchers. Herein, a V2O5·nH2O xerogel composed of thin acicular interconnected nanowire networks has been synthesized via a facile freeze-drying process. The interlayer spacing of V2O5·nH2O is larger than that of orthorhombic V2O5 due to the intercalation of water molecules into the layer structure. As the cathode of a SIB, V2O5·nH2O exhibits a high initial capacity of 338 mA h g−1 at 0.05 A g−1 and a high-rate capacity of 96 mA h g−1 at 1.0 A g−1. On the basis of combining ex-situ XRD and FTIR spectroscopy, the Na+ ion intercalation storage reactions are discussed in detail. By modeling calculations, the pseudocapacitive behavior makes a great contribution to the high capacities. Our work demonstrates that V2O5·nH2O with large interlayer spacing is a promising candidate for high capacity sodium-based energy storage.

Nanoflakes-Assembled Three-Dimensional Hollow-Porous V2O5 as Lithium Storage Cathodes with High-Rate Capacity

Three-dimensional (3D) hollow-porous vanadium pentoxide (V2 O5 ) quasi-microspheres are synthesized by a facile solvothermal method followed by annealing at 450 °C in air. The interconnected hollow-porous networks facilitate the kinetics of lithium-ion diffusion and improve the performance of V2 O5 to achieve a high capacity and remarkable rate capability as a cathode material for lithium batteries.

Top-down fabrication of three-dimensional porous V2O5 hierarchical microplates with tunable porosity for improved lithium battery performance

Three-dimensional porous V2O5 hierarchical microplates have been fabricated by a one-step top-down strategy, and display an excellent rate capability and stable capacity of 110 mA h g−1 at 2000 mA g−1 after 100 cycles. We have demonstrated that the facile approach of a solid-phase conversion is promising for large-scale fabrication of highly porous micro/nano materials.