Guozhao Fang

Two-dimensional hybrid nanosheets of few layered MoSe2 on reduced graphene oxide as anodes for long-cycle-life lithium-ion batteries

A rational design of two-dimensional (2D) hybrid materials between transition metal dichalcogenides (TMDs) and graphene has received great attention because of their promising applications in the energy field. Herein, we report the synthesis of novel 2D hybrid nanosheets constructed by few layered MoSe2 grown on reduced graphene oxide (rGO). As a proof-of-concept application, the 2D MoSe2/rGO nanosheets exhibit excellent electrochemical performance as anodes for lithium ion batteries, demonstrating outstanding cycling stability (up to 1000 cycles), and high-rate capability.

PVP-assisted synthesis of MoS2 nanosheets with improved lithium storage properties

An efficient and scalable strategy has been developed for the synthesis of MoS2 nanosheets employing PVP as a surfactant. The MoS2 nanosheets exhibit an enhanced lithium intercalation capacity, cyclic stability and rate capability.

Ultrathin Na1.1V3O7.9 Nanobelts with Superior Performance as Cathode Materials for Lithium-Ion Batteries

The Na1.1V3O7.9 nanobelts have been synthesized by a facile and scalable hydrothermal reaction with subsequent calcinations. The morphologies and the crystallinity of the nanobelts are largely determined by the calcination temperatures. Ultrathin nanobelts with a thickness around 20 nm can be obtained, and the TEM reveals that the nanobelts are composed of many stacked thinner belts. When evaluated as a cathode material for lithium batteries, the Na1.1V3O7.9 nanobelts exhibit high specific capacity, good rate capability, and superior long-term cyclic stability. A high specific capacity of 204 mA h g(-1) can be delivered at the current density of 100 mA g(-1). It shows excellent capacity retention of 95% after 200 cycles at the current density of 1500 mA g(-1). As demonstrated by the ex situ XRD results, the Na1.1V3O7.9 nanobelts have very good structural stability upon cycling. The superior electrochemical performances can be attributed to the ultra-thin nanobelts and the good structural stability of the Na1.1V3O7.9 nanobelts.

Metal–organic framework-templated two-dimensional hybrid bimetallic metal oxides with enhanced lithium/sodium storage capability

Two-dimensional (2D) porous hybrid bimetallic transition metal oxide (TMO) nanosheets demonstrated promising applications in the energy field due to their large surface areas, porous structure, and synergistic effects. However, the synthesis of these materials is still a big challenge. In this study, we rationally designed a facile strategy to prepare 2D porous hybrid bimetallic TMO (Co3O4/ZnO) nanosheets with novel structural and electrochemical synergistic effects. Derived from bimetallic MOF nanosheets, the porous hybrid nanosheets possess high surface areas and large pore volume. In particular, they are rich in oxygen vacancies, which provide more active sites for electrochemical reaction. Moreover, the harmonious multi-step conversion reaction between Co3O4 and ZnO was helpful for volume buffering, leading to an outstanding cyclic stability. With remarkable structural features and harmonious electrochemical behaviors, the Co3O4/ZnO hybrids exhibit excellent electrochemical performances as anodes for both lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). This study also introduces a new strategy to prepare 2D porous hybrid bimetallic TMO nanosheets, which can find wide applications in energy storage, catalysis, sensors, and information storage devices.

Hydrothermal synthesis of Ag/β-AgVO3 nanobelts with enhanced performance as a cathode material for lithium batteries

An efficient and scalable strategy has been developed for the synthesis of Ag nanoparticles anchored on β-AgVO3 nanobelts via a template-free hydrothermal reaction. The Ag/β-AgVO3 nanobelts demonstrate enhanced lithium intercalation capacity, rate capability and cyclic stability.

Nb2O5 quantum dots embedded in MOF derived nitrogen-doped porous carbon for advanced hybrid supercapacitor applications

Hybrid supercapacitors (HSCs), which are expected to possess the good characteristics of both lithium batteries and supercapacitors, have become a hot research topic in recent years for catering to the growing market for electric vehicles (EVs) and hybrid electric vehicles (HEVs). Herein, we demonstrate an advanced hybrid material construction by the orthorhombic Nb2O5 quantum dots embedded in nitrogen-doped porous carbon derived from ZIF-8 dodecahedrons, referred to as NQD–NC. Then the applications of this material in LIBs and HSCs are studied in-depth. The LIB test reveals that the novel Nb2O5-based material shows excellent high-rate capability and long-term cyclic stability. Importantly, by assembling a HSC device using a NQD–NC anode and a commercial activated carbon cathode with an organic electrolyte, the HSC shows superior electrochemical performance including ultra-high energy and power density (76.9 W h kg−1 and 11 250 W kg−1, respectively) and superior cyclic stability (capacity retention of ∼85% at 5 A g−1 after 4500 cycles in a voltage range of 0.5–3.0 V). The excellent electrochemical performance of the HSCs indicates combining the advantages of lithium-ion batteries and supercapacitors, which is promising for the next generation of energy storage systems.

General synthesis of three-dimensional alkali metal vanadate aerogels with superior lithium storage properties

Three-dimensional (3D) aerogel materials assembled from simplex nanostructures have many advantages in the energy field, but the synthesis of alkali metal vanadate aerogels remains challenging. Herein, we demonstrate a general method for the preparation of a series of 3D alkali metal vanadate aerogels, including NaV3O8, NaV6O15, and K0.25V2O5. The aerogels with a large porous structure built from cross-linked ultra-long nanofibers can be prepared via the hydrothermal self-assembly route followed by a freeze-drying process. The resulting aerogels, e.g. NaV3O8, NaV6O15, and K0.25V2O5, exhibit excellent Li+ storage properties in terms of high specific capacity, good rate capability, and outstanding cyclic stability as cathodes for lithium batteries. Importantly, the NaV3O8 aerogel demonstrates an excellent long-life cyclic performance of 600 cycles at 1000 mA g−1 with no capacity fading. To account for the mechanisms that affect the electrochemical properties, a systematic study is conducted. The superior performances may be due to the superior mechanical stability, good reversibility of lithium insertion/de-insertion and excellent interior structural stability. It is believed that our strategy could probably be extended to prepare other metal vanadate aerogel materials with great promise for various applications.

Template-free synthesis of highly porous V2O5 cuboids with enhanced performance for lithium ion batteries

Highly porous hierarchical V2O5 cuboids have been synthesized by a template-free PVP-assisted polyxol method and the formation mechanism is studied. The cuboids are assembled from numerous mesoporous nanoplates and the preferred orientation of each single nanoplate exposes the 〈110〉 facets, facilitating lithium-ion diffusion by offering a prior channel. This material exhibits a high capacity of 143 mA h g(-1), high rate capacity of 10 C and long life cycling performance up to 1000 cycles. The excellent electrochemical performance of V2O5 cuboid electrodes is due to its unique porous cuboid morphology and optimized structural stability upon cycling. This research provides an effective route to the construction of complex porous architectures assembled from nanocrystals through a surfactant-assisted synthesis method.

Nb2O5 microstructures: a high-performance anode for lithium ion batteries.

We report the synthesis of three-dimensional (3D) urchin-like Nb2O5 microstructures by a facile hydrothermal approach with subsequent annealing treatment. As anode materials for lithium-ion batteries, the 3D urchin-like Nb2O5 microstructures exhibit superior electrochemical performance with excellent rate capability as well as long-term cycling stability. The electrode delivers high capacity of 131 mA h g-1 after 1000 cycles at a high current density of 1 A g-1. The excellent electrochemical performance suggests the 3D urchin-like Nb2O5 microstructures may be a promising anode candidate for high-power lithium ion batteries.

Metal-organic framework-derived porous shuttle-like vanadium oxides for sodium-ion battery application

Vanadium oxides with a layered structure are promising candidates for both lithium-ion batteries and sodium-ion batteries (SIBs). The self-template approach, which involves a transformation from metal-organic frameworks (MOFs) into porous metal oxides, is a novel and effective way to achieve desirable electrochemical performance. In this study, porous shuttle-like vanadium oxides (i.e., V2O5, V2O3/C) were successfully prepared by using MIL-88B (V) as precursors with a specific calcination process. As a proof-of-concept application, the asprepared porous shuttle-like V2O3/C was used as an anode material for SIBs. The porous shuttle-like V2O3/C, which had an inherent layered structure with metallic behavior, exhibited excellent electrochemical properties. Remarkable rate capacities of 417, 247, 202, 176, 164, and 149 mAh·g−1 were achieved at current densities of 50, 100, 200, 500, 1,000, and 2,000 mA·g−1, respectively. Under cycling at 2 A·g−1, the specific discharge capacity reached 181 mAh·g−1, with a low capacity fading rate of 0.032% per cycle after 1,000 cycles. Density functional theory calculation results indicated that Na ions preferred to occupy the interlamination rather than the inside of each layer in the V2O3. Interestingly, the special layered structure with a skeleton of dumbbell-like V–V bonds and metallic behavior was maintained after the insertion of Na ions, which was beneficial for the cycle performance. We consider that the MOF precursor of MIL-88B (V) can be used to synthesize other porous V-based materials for various applications.