Jingli Xu

Facile synthesis of CuO nanoparticles as anode for lithium ion batteries with enhanced performance

Particle size effects on the electrochemical performance of the CuO particles toward lithium are essential. In this work, a low-cost, large-scale production but simple approach has been developed to fabricate CuO nanoparticles with an average size in ~ 130 nm through thermolysis of Cu(OH)2 precursors. As anode materials for lithium ion batteries (LIBs), the CuO nanoparticles deliver a high reversible capacity of 540 mAh g-1 over 100 cycles at 0.5 C. It also exhibits a rate capacity of 405 mAh g-1 at 2 C. These results suggest that the facile synthetic method of producing the CuO nanoparticles can enhance cycle performance, superior to that of some different sizes of the CuO nanoparticles and many reported CuO-based anodes.

High performance Na3V2 (PO4)3/C composite electrode for sodium-ion capacitors

Sodium-ion capacitors were assembled with Na3V2(PO4)3/C composite cathode and activated carbon (AC) anode. In this work, Na3V2(PO4)3 (NVP) and NVP/C have been investigated as electrode materials in sodium ion capacitors for the first time. Electrochemical tests, such as cyclic voltammetry (CV), chronopotentiometry, and cycling were also performed to study the behavior of NVP and NVP/C. The specific capacitance and energy density of NVP/C composite electrode are as high as 51.0xa0Fxa0g−1 and 15.9xa0Whxa0kg−1. The optimized voltage range of sodium-ion capacitors is from 0 to 1.5xa0V. NVP/C composite demonstrates that it retained up to 80xa0% of the initial capacitance after 100xa0cycles. The outperforming results could be ascribed to the NVP/C composite, which indicates that NVP/C composite is more suitable as cathodematerials for sodium-ion capacitors.

Flexible and free-standing ternary Cd2GeO4 nanowire/graphene oxide/CNT nanocomposite film with improved lithium-ion battery performance

To realize flexible lithium-ion batteries (LIBs), the design of flexible electrode/current collector materials with high mechanical flexibility, superior conductivity and excellent electrochemical performance and electrical stability are highly desirable. In this work, we developed a new ternary Cd2GeO4 nanowire/graphene oxide/carbon nanotube nanocomposite (Cd2GeO4 NW/GO/CNT) film electrode. Benefiting from the efficient combination of GO and Cd2GeO4 NWs, our Cd2GeO4 NW/GO/CNT composite film exhibits a capacity of 784 mA h g(-1) after 30 cycles at 200 mA g(-1), which is 2.7 times higher than that of Cd2GeO4 NW/CNT film (290 mA h g(-1)). At a higher rate of 400 mA g(-1) and 1 A g(-1), the Cd2GeO4 NW/GO/CNT film delivers a stable capacity of 617 and 397 mA h g(-1), respectively. Even at 2.5 A g(-1), it still exhibits a high rate capacity of 180 mA h g(-1). The flexible Cd2GeO4 NW/GO/CNT film clearly demonstrates good cycling stability and rate performance for anode materials in LIBs. This route may be extended to design other flexible free-standing metal germanate nanocomposite anode materials.

Electrochemical performances of Na2MnSiO4 as an energy storage material in sodium-ion capacitors

In this work, we report the synthesis of Na2MnSiO4 via high-temperature solid-state chemical reaction method. The crystal structure and morphology of the synthesized Na2MnSiO4 material prepared at different temperatures (600, 700, 800, and 900u2009°C) were characterized using X-ray diffraction (XRD) and field emission scanning electron microscopy. The XRD patterns indicate that high-purity Na2MnSiO4 was obtained at the annealing temperature above 700u2009°C. The morphology observed by SEM shows that the particle size of the material increased with the increase of annealing temperature. Electrochemical energy storage performance of the material measured by galvanostatic charge–discharge reveals that the material prepared at 800u2009°C demonstrated the best energy storage capability with a specific capacitance of 123.8xa0Fxa0g−u20091 at 0.5xa0Ag−u20091. In addition, the material shows relatively good stability and 82% of initial capacitance was retained after 1000 charge–discharge cycles. Further testing by electrochemical impedance spectroscopy shows that the synthesized Na2MnSiO4 electrode has low series resistance (1.3xa0Ω) and charge transfer resistance (7.4xa0Ω), favoring the delivery of electrical power at a fast rate. These results suggest that the synthesized Na2MnSiO4 material has great potential for application in sodium-ion capacitors.Graphical Abstract

Facile synthesis of magnetic resorcinol–formaldehyde (RF) coated carbon nanotubes for methylene blue removal

In this paper, magnetic resorcinol–formaldehyde (RF) resin coated carbon nanotubes were synthesized from hydrophilic magnetic carbon nanotubes (CNTs) with the extended Stober method. Firstly, magnetic CNT composites (CNTs@Fe3O4) were synthesized by the high temperature decomposition process using the iron acetylacetonate as raw materials. Then the resorcinol–formaldehyde polymer can be easily coated on the magnetic CNTs with the extended Stober method. Finally, numerous of gold nanoparticles were assembled on the surface of CNTs@Fe3O4@RF by reducing Au3+ between the RF shell and HAuCl4 solution; meanwhile, the mesoporous carbon coated CNTs@Fe3O4 can also be obtained by calcinations of the CNTs@Fe3O4@RF composites in nitrogen atmosphere. The resulting CNTs@Fe3O4@RF@Au or CNTs@Fe3O4@C composites show not only a magnetic response to an externally applied magnetic field, but also can be a kind of catalyst or adsorbent to catalyze or adsorb the methylene blue (MB), in the ambient temperature.

Tailoring the nickel nanoparticles anchored on the surface of Fe3O4@SiO2 spheres for nanocatalysis

Herein, we report an efficient and universal strategy for synthesizing a unique triple-shell structured Fe3O4@SiO2@C-Ni hybrid composite. Firstly, the Fe3O4 cores were synthesized by hydrothermal reaction, and sequentially coated with SiO2 and a thin layer of nickel-ion-doped resin-formaldehyde (RF-Ni2+) using an extended Stöber method. This was followed by carbonization to produce the Fe3O4@SiO2@C-Ni nanocomposites with metallic nickel nanoparticles embedded in an RF-derived thin graphic carbon layer. Interestingly, the thin SiO2 spacer layer between RF-Ni2+ and Fe3O4 plays a critical role on adjusting the size and density of the nickel nanoparticles on the surface of Fe3O4@SiO2 nanospheres. The detailed tailoring mechanism is explicitly discussed, and it is shown that the iron oxide core can react with the nickel nanoparticles without the SiO2 spacer layer, and the size and density of the nickel nanoparticles can be effectively controlled when the SiO2 layer exits. The multifunctional composites exhibit a significantly enhanced catalytic performance in the reduction of 4-nitrophenol (4-NP).

Zn0.5Co0.5O Solid Solution Nanoparticles with Durable Life for Rechargeable Lithium-ion Batteries

Zn0.5Co0.5O solid solution materials have been extensively studied for possible spintronic applications, however, there are only a few reports using Zn0.5Co0.5O nanostructures for energy storage. Here, we report the preparation of Zn0.5Co0.5O nanoparticles with the average particle size 10 nm and their application as anode material for rechargeable Li-ion batteries (LIBs). Electrochemical measurements demonstrate that the Zn0.5Co0.5O solid solution nanoparticles deliver a stable reversible capacity of 309 mA h g-1 up to 250 cycles at 1 C rate. These results show higher-rate capability and better cycle durability compared with those of the reported ZnO or ZnO-based anodes.

Design of Rugby-Like GeO2 Grown on Carbon Cloth as a Flexible Anode for High-Performance Lithium-Ion Batteries

The new demands for energy storage systems have been placed with demands for flexible wearable electronics. Herein, rugby-like GeO₂ nanoparticles (NPs) have been directly grown on carbon cloth (GeO₂ NPs/CC) through a one-step hydrolysis process at room temperature, which can be used as a self-supporting flexible anode for lithium ion battery (LIBs). The rugby-like GeO₂ NPs/CC showed an improved lithium-storage performance with features of high reversible capacity ~2000 mA·h·g-1 even after 100 cycles and good cycling stability. Besides, its initial coulomb efficiency (79.1%) was also enhanced compared to that of some reported GeO₂-based materials.

TiO2 Nanotubes Array on Carbon Cloth as a Flexibility Anode for Sodium-Ion Batteries

In this work, three-dimensional (3D) TiO₂ nanotubes (NTs) on carbon cloth (CC) (TiO₂ NTs/CC) were synthesized by a method involving formation of a ZnO@TiO₂ nanorod (NRs) on CC (ZnO@TiO₂ NRs/CC) structure and a subsequent chemical etching process for ZnO NRs template. The 3D TiO₂ NTs/CC were applied as flexible anodes for sodium ion batteries (SIBs). The TiO₂ NTs/CC yielded high specific capacity and good cycling stability, superior to that of some reported TiO₂ nanocomposites. The TiO₂ NTs/CC delivered a reversible capacity of 260 mA·h·g-1 and 85.1% capacity retention over 150 cycles at current density of 0.25 C (1 C = 335 mA·g-1). It also exhibited high rate capacity of 200 mA·h·g-1 at 0.5 C. Even at a high rate of 1.0 C, the TiO₂ NTs/CC can still maintain a high capacity of 100 mA·h·g-1. Moreover, it was observed that the electrochemical performance for the TiO₂ NTs/CC was much better than that (150 mA·h·g-1 for up to 150 cycles) of a solid TiO₂ NRs/CC counterpart, which also demonstrated the capacity enhancement and good cycling stability.

A Novel V 2 AlC Electrode Material for Supercapacitors

A novel V2AlC electrode material for supercapacitors was investigated in this study. The structure and surface morphology were examined using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The formation of irregularly shaped V2AlC with different particle size distribution was confirmed by XRD and FESEM. The electrochemical measurements were performed by cyclic voltammetry (CV), galvanostatic charge discharge and electrochemical impedance spectroscopy (EIS). V2AlC electrode exhibited 27.6 F g–1 of specific capacitance at the current density of 0.5 A g–1. The specific capacitance of V2AlC electrode remained 93.8% of the first cycle after 2000 cycles. V2AlC has great potential for application in supercapacitors.