Shiyao Lu

Mesoporous Co3V2O8 nanoparticles grown on reduced graphene oxide as a high-rate and long-life anode material for lithium-ion batteries

Hierarchical hybrid nanostructures based on flexible graphene sheets and ternary transition metal oxides have attracted special attention as high-performance electrode materials for next-generation lithium-ion batteries (LIBs) yet their practical application is often beset with challenges. In this work, we report a hierarchical hybrid nanocomposite of reduced graphene oxide supported mesoporous Co3V2O8 nanoparticles (rGO@Co3V2O8 NPs) through a simple hydrothermal synthesis and post-calcination. This unique hybrid architecture when used as an anode in LIBs would effectively facilitate charge transfer, maintain structural integrity and accommodate the volume variation of the electrode materials during the repeated charge/discharge processes. As a result, the hybrid rGO@Co3V2O8 NPs manifest a very stable high reversible capacity of 1050 mA h g−1 over 200 cycles at a current density of 50 mA g−1 and excellent rate capability. Importantly, even when cycled at a higher current density of 200 mA g−1, a stable reversible capacity of 899 mA h g−1 and a remarkable cycling stability could also be achieved after 600 cycles. These results indicate the potential suitability of such mesoporous nanoparticles on graphene nanostructures for high-rate and long cycle life anode materials.

One-pot synthesis of carbon coated Fe3O4 nanosheets with superior lithium storage capability

Hybrid nanosheet structures based on carbon coated metal oxides still attract promising interest as high-performance electrode materials for next-generation lithium-ion batteries (LIBs). In this study, we develop a simple one-pot solution method to synthesize large-scale flat Fe3O4 nanosheet hybrid structures coated with an amorphous carbon overlayer (denoted as Fe3O4@C NSs) followed by a thermal annealing treatment. It is found that the refluxing temperature plays an important role in adjusting the morphology of the Fe3O4@C hybrid. Increasing the temperature from 140 °C to 200 °C will lead to flower-like hybrid structures constructed by Fe3O4 nanoflakes gradually growing, rupturing, and finally evolving into flat and completely separate nanoflakes with large size at 200 °C. When evaluated as an anode material for LIBs, the hybrid Fe3O4@C NSs demonstrate a high reversible capacity of 1232 mA h g−1 over 120 cycles at a current density of 200 mA g−1, and remarkable rate capability.

Construction of sandwich-type hybrid structures by anchoring mesoporous ZnMn2O4 nanofoams on reduced graphene oxide with highly enhanced capability

We have developed a sandwich-type hybrid nanostructure by anchoring foam-like zinc manganate (ZnMn2O4) on reduced graphene oxide (rGO) (rGO/ZnMn2O4 NFs) via a trisodium citrate (TSC) assisted solution reaction followed by a post-calcination treatment. The interconnected sheet-like ZnMn2O4 subunits have assembled into mesoporous nanofoams on rGO sheets with the beneficial help of TSC. When cycled at a current density of 180 mA g−1, the hybrid rGO/ZnMn2O4 NF anodes present a high discharge capacity of 945 mA h g−1 even after 150 cycles with long cycle durability and good rate capability. Such highly enhanced electrochemical performance is ascribed to the sandwich-type hierarchical foam structure effectively promoting the ion/charge transport whilst buffering volume variations upon continuous discharge/charge cycling. These results indicate that a porous anode scaffold with conductive connections is a promising structural design for rechargeable batteries with superior reversible lithium storage capability.

Quick one-pot synthesis of amorphous carbon-coated cobalt–ferrite twin elliptical frustums for enhanced lithium storage capability

Hybrid carbon-coated transition metal oxides (TMOs@C) offer enhanced lithium storage capabilities, but the facile formation of TMOs@C nanocomposites remains a great challenge. Herein, we report a novel hierarchical hybrid nanostructure of carbon-coated CoFe2O4 twin elliptical frustums (CoFe2O4@C TEFs) via a quick one-pot refluxing reaction in ethylene glycol (EG) followed by an annealing treatment. When evaluated as an anode in lithium-ion batteries (LIBs), the resultant CoFe2O4@C TEF hybrids demonstrate good electrochemical performance with high reversible specific capacity, excellent rate capability and super-long life cycle. After 600 cycles at a current density of 500 mA g−1, the resultant TEFs still deliver a stable reversible discharge capacity of 875 mA h g−1. This work demonstrates the extensive potential of such simple synthetic methods towards various carbon coated transition metal oxide composites for energy conversion and storage devices.

Ordered mesoporous carbon supported Ni3V2O8 composites for lithium-ion batteries with long-term and high-rate performance

Transition metal vanadates have gained significant attention as high performance anode materials for lithium ion batteries (LIBs). Herein, we successfully fabricated a novel hierarchical hybrid nanostructure of ordered mesoporous carbon (CMK-3) supported Ni3V2O8 composites (Ni3V2O8@CMK-3) through a facile hydrothermal method and a post-calcination process for the first time. Within such a hierarchical hybrid structure, short intercrossed Ni3V2O8 nanorods are firmly anchored onto the external surface of CMK-3 and ultrafine Ni3V2O8 nanoparticles are embedded in the internal channels of CMK-3. Benefitting from their robust porous structure and excellent conductive characteristic, the as-prepared hierarchical hybrid Ni3V2O8@CMK-3 composites exhibit long-term cycle stability with a high reversible capacity of 945.9 mA h g−1 after 200 cycles at a current density of 500 mA g−1 and superior high-rate capability (161.5 mA h g−1 when cycled at 20 A g−1) when used as a promising anode for LIBs.

A high-performance mesoporous carbon supported nitrogen-doped carbon electrocatalyst for oxygen reduction reaction.

Investigating low-cost and highly active electrocatalysts for oxygen reduction reactions (ORR) is of crucial importance for energy conversion and storage devices. Herein, we design and prepare mesoporous carbon supported nitrogen-doped carbon by pyrolysis of polyaniline coated on CMK-3. This electrocatalyst exhibits excellent performance towards ORR in alkaline media. The optimized nitrogen-doped mesoporous electrocatalyst show an onset potential (E onset) of 0.95 V (versus reversible hydrogen electrode (RHE)) and half-wave potential (E 1/2) of 0.83 V (versus RHE) in 0.1 M KOH. Furthermore, the as-prepared catalyst presents superior durability and methanol tolerance compared to commercial Pt/C indicating its potential applications in fuel cells and metal-air batteries.

Dielectric gels with ultra-high dielectric constant, low elastic modulus, and excellent transparency

We designed dielectric gels, a new type of polymer-based dielectric material. By using solvents with high dielectric constants, the gels achieve a unique combination of ultra-high dielectric constant, low elastic modulus, and excellent transparency, which are extremely challenging or impossible to realize with traditional polymer dielectrics. The gels exhibit high stretchability (stretch of approximately 10) and low mechanical hysteresis. We demonstrated the use of the dielectric gels by fabricating a bioinspired tunable lens, the focal length of which can be adjusted by varying the applied voltage. We believe that the dielectric gels, as a new type of polymer dielectric, offer new opportunities for soft robotics, sensors, electronics, optics, and biomimetics.Polymers: Super-insulating gels catch the eyeStretchy and see-through substances known as dielectric gels may find application in soft robotics due to their capabilities of controllable movement. Insulating membranes can be stimulated to squeeze like a muscle by applying voltage pulses. Shujiang Ding from Xi’an Jiaotong University, China, and co-workers have developed a material that reduces the typically high voltages needed for movement by 50% compared with a commercial membrane. They used ultraviolet polymerization to lock liquid molecules with high charge-storing properties within a hydrocarbon chain network, producing super-insulating gels that can be extended up to 10 times their original size without damage. A bioinspired lens was fabricated by sandwiching a liquid between two gel membranes. Voltage-tunable pressure from the gels squeezed the lens and changed its focal length, similar to the changes seen in the human eye when focusing.Dielectric gels, a new type of polymer-based dielectric material have been designed. The gels achieve a unique combination of ultra-high dielectric constant, low elastic modulus, and excellent transparency, which are extremely challenging or impossible to realize by traditional polymer dielectrics. We have demonstrated the use of the dielectric gel by fabricating a bioinspired tunable lens, the focal length of which can be adjusted by varying the applied voltage. Dielectric gels offer new opportunities for soft robotics, sensors, electronics, optics, and biomimetics.