Jinzhi Sheng

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.

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.

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.

Three-dimensional porous V2O5 hierarchical octahedrons with adjustable pore architectures for long-life lithium batteries

Three-dimensional (3D) porous V2O5 octahedrons have been successfully fabricated via a solid-state conversion process of freshly prepared ammonium vanadium oxide (AVO) octahedrons. The formation of AVO octahedrons is a result of the selective adsorption of capping reagents and the favourable supersaturation of growth species. Subsequently, 3D porous V2O5 octahedrons were obtained by simple thermolysis of the AVO octahedrons via a calcination treatment. As cathode material for lithium batteries, the porous V2O5 octahedron cathode exhibits a capacity of 96 mA·g−1 at high rate up to 2 A·g−1 in the rang of 2.4–4 V and excellent cyclability with little capacity loss after 500 cycles, which can be ascribed to its high specific surface area and tunable pore architecture. Importantly, this facile solid-state thermal conversion strategy can be easily extended to controllably fabricate other porous metal oxide micro/nano materials with specific surface textures and morphologies.

Copper Silicate Hydrate Hollow Spheres Constructed by Nanotubes Encapsulated in Reduced Graphene Oxide as Long-Life Lithium-Ion Battery Anode

Hierarchical copper silicate hydrate hollow spheres-reduced graphene oxide (RGO) composite is successfully fabricated by a facile hydrothermal method using silica as in situ sacrificing template. The electrochemical performance of the composite as lithium-ion battery anode was studied for the first time. Benefiting from the synergistic effect of the hierarchical hollow structure and conductive RGO matrix, the composite exhibits excellent long-life performance and rate capability. A capacity of 890 mAh/g is achieved after 200 cycles at 200 mA/g and a capacity of 429 mAh/g is retained after 800 cycles at 1000 mA/g. The results indicate that the strategy of combining hierarchical hollow structures with conductive RGO holds the potential in addressing the volume expansion issue of high capacity anode materials.

Three-Dimensional Interconnected Vanadium Pentoxide Nanonetwork Cathode for High-Rate Long-Life Lithium Batteries

Three-dimensional interconnected vanadium pentoxide nanonetworks as cathodes for rechargable lithium batteries are successfully synthesized via a quick gelation followed by annealing. The interconnected structure ensures the electron transport of each unit. And their inner porous structure buffer the volume change over long-term repeated lithium ion insertion/extraction cycles, leading to the high-rate long-life cycling performance.

Facile synthesis of reduced graphene oxide wrapped nickel silicate hierarchical hollow spheres for long-life lithium-ion batteries

Layered silicate is a new type of electrode material with high reversible capacity. However, its poor electrical conductivity leads to rapid capacity decay. To solve this problem, reduced graphene oxide (RGO) wrapped nickel silicate (NiSiO) hollow spheres are successfully synthesized. The hollow structure provides sufficient free space to accommodate the volume variation during lithiation/de-lithiation and the RGO improves the electrical conductivity. The resulting NiSiO/RGO delivers a capacity of 400 mA h g−1 at 500 mA g−1 after 1000 cycles, making the NiSiO/RGO composite a promising anode material for lithium-ion batteries.

A High-Rate V2O5 Hollow Microclew Cathode for an All-Vanadium-Based Lithium-Ion Full Cell

V2O5 hollow microclews (V2O5-HMs) have been fabricated through a facile solvothermal method with subsequent calcination. The synthesized V2O5-HMs exhibit a 3D hierarchical structure constructed by intertangled nanowires, which could realize superior ion transport, good structural stability, and significantly improved tap density. When used as the cathodes for lithium-ion batteries (LIBs), the V2O5-HMs deliver a high capacity (145.3 mAh g(-1)) and a superior rate capability (94.8 mAh g(-1) at 65 C). When coupled with a lithiated Li3VO4 anode, the all-vanadium-based lithium-ion full cell exhibits remarkable cycling stability with a capacity retention of 71.7% over 1500 cycles at 6.7 C. The excellent electrochemical performance demonstrates that the V2O5-HM is a promising candidate for LIBs. The insight obtained from this work also provides a novel strategy for assembling 1D materials into hierarchical microarchitectures with anti-pulverization ability, excellent electrochemical kinetics, and enhanced tap density.

Top-Down Strategy to Synthesize Mesoporous Dual Carbon Armored MnO Nanoparticles for Lithium-Ion Battery Anodes

To overcome inferior rate capability and cycle stability of MnO-based materials as a lithium-ion battery anode associated with the pulverization and gradual aggregation during the conversion process, we constructed robust mesoporous N-doped carbon (N-C) protected MnO nanoparticles on reduced graphene oxide (rGO) (MnO@N-C/rGO) by a simple top-down incorporation strategy. Such dual carbon protection endows MnO@N-C/rGO with excellent structural stability and enhanced charge transfer kinetics. At 100 mA g-1, it exhibits superior rate capability as high as 864.7 mAh g-1, undergoing the deep charge/discharge for 70 cycles and outstanding cyclic stability (after 1300 cyclic tests at 2000 mA g-1; 425.0 mAh g-1 remains, accompanying merely 0.004% capacity decay per cycle). This facile method provides a novel strategy for synthesis of porous electrodes by making use of highly insulating materials.

Hierarchical three-dimensional MnO nanorods/carbon anodes for ultralong-life lithium-ion batteries

MnO anode materials with high energy densities for lithium-ion batteries (LIBs) face significant challenges in avoiding inferior reversible capacity and fast capacity fading. Here we demonstrate a facile and scalable approach to realizing excellent performance, overcoming such disadvantages. A well-connected three-dimensional (3D) hierarchical porous-conducting framework, consisting of MnO nanorods conformally encapsulated by a nitrogen-doped carbon network, was synthesized via an in situ polymerization of polyaniline into manganese dioxide along with thermal calcination. Such a structure possesses a continuous electrically conductive carbon network with porous spaces for volume expansion of MnO rods, and the carbon coating on the nanorods further alleviates pulverization and self-aggregation of the active materials. As an anode, it demonstrates a reversible capacity as high as 798.6 mA h g−1 after 5 cycles at 50 mA g−1, beyond the theoretical capacity of MnO, and an extremely stable cycle life of 3000 cycles with ∼95% capacity retention, even at a high current density of 4000 mA g−1. Significantly, the electrochemical behavior of this novel material was also probed by an in situ XRD technique.