School of Intelligent Manufacturing Ecosystem

1. Facile preparation of Co3O4 nanoparticles incorporating with highly conductive MXene nanosheets as high-performance anodes for lithium-ion batteries

Author:Zhao, YC;Liu, CG;Yi, RW;Li, ZQ;Chen, YB;Li, YQ;Mitrovic, I;Taylor, S;Chalker, P;Yang, L;Zhao, CZ


Abstract:There is considerable scientific interest in the newly available family of MXenes material. An analog as graphene, this two-dimensional (2D) layered material with the structure of transition metal carbides or nitrides exhibits superior electronic conductivity, large interlayer spacing for highly efficient lithium ions diffusion pathways and environmental benignity, making it useful as energy storage material. However, the inferior capability to store lithium ions impedes its wide application in lithium-ion batteries. Therefore, a facile strategy for preparing Co3O4 nanoparticles incorporated with MXene nanosheets on Ni foams has been developed. Small-size Co3O4 nanoparticles are uniformly distributed within the MXene nanosheets leading to the highly efficient lithium ions and electrons transmission, as well as the prevention for the restacking of MXene nanosheets and huge volume change of the Co3O4 nanoparticles. Under the cooperative effect of Co3O4 nanoparticles and MXene nanosheets, the Co3O4/MXene composite electrode with the mass ratio of Co3O4/MXene = 1:1 exhibits an excellent reversible capacity of 1005 mAh g(-1) after 300 cycles at the current density of 1 C, which significantly exceeds that of pristine Co3O4 electrode. Though the current density climbs to 5 C, the composite electrode remains a stable capacity of 307 mAh g(-1) after 1000 cycles. It is demonstrated that Co3O4/MXene composite electrode has the potential as an anode for the high-performance lithium-ion batteries. (c) 2020 Elsevier Ltd. All rights reserved.
2. Porous Activated Carbons Derived from Pleurotus eryngii for Supercapacitor Applications

Author:Yuan, YD;Yi, RW;Sun, Y;Zeng, JQ;Li, JQ;Hu, JH;Zhao, YC;Sun, W;Zhao, C;Yang, L;Zhao, CZ


Abstract:Varieties of natural biomass have been utilized to prepare porous carbon materials for supercapacitor applications. In this work, porous activated carbons derived from Pleurotus eryngii were prepared by carbonization and KOH activation. The activated carbons presented a large specific surface area of 3255 m(2).g(-1) with high porosity. The as-prepared electrode exhibited a maximal specific capacitance of 236 F.g(-1) measured in a three-electrode cell system. Furthermore, the assembled symmetric supercapacitor showed a specific capacitance of 195 F.g(-1) at 0.2 A.g(-1) and a superior specific capacitance retention of about 93%% after 15000 cycles. The desirable capacitive behavior suggests that Pleurotus eryngii is an attractive biomass source of carbon materials for the potential supercapacitor applications.
3. Fabrication of a Light-Weight Dual-Function Modified Separator towards High-Performance Lithium-Sulfur Batteries

Author:Yi, RW;Lin, XF;Zhao, YC;Liu, CG;Li, YQ;Hardwick, LJ;Yang, L;Zhao, CZ;Geng, XW;Zhang, Q


Abstract:A light-weight dual-functional modified separator for lithium-sulfur batteries is prepared through a physical blend and blade-coating approach. The separator is coated with carbon black/poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (CB/PEDOT:PSS), remarkably improving the utilization of sulfur by serving as the co-current collector. Moreover, the PEDOT:PSS effectively inhibits the diffusion of polysulfides and promotes the migration of lithium ions by providing chemical absorption and cation transport acceleration. When assembling this modified separator into the coin cell, an initial specific capacity of 1315 mAh g(-1) at 0.2 C is achieved with a capacity of 956 mAh g(-1) after 100 cycles, showing a superior performance compared to the cell without an interlayer. Meanwhile, the cell exhibits a rate capability with a discharge capacity of 699 mAh g(-1) at a current density of 2 C. Notably, the areal density of CB/PEDOT:PSS coating is as low as 0.604 mg cm(-2), bringing a specific electrode capacity of 522 mAh g(-1) at 1 C.
4. Alloyed Cu/Si core-shell nanoflowers on the three-dimensional graphene foam as an anode for lithium-ion batteries

Author:Liu, CG;Zhao, YC;Yi, RW;Sun, Y;Li, YQ;Yang, L;Mitrovic, I;Taylor, S;Chalker, P;Zhao, CZ


Abstract:In this study, we demonstrate a facile method to fabricate a flexible alloyed copper/silicon core-shell nanoflowers structure anchored on the three-dimensional graphene foam as a current collector. This combination provides flexible and free-standing structure and three-dimensional conductive network, allowing unique properties for current collection and transmission. The copper oxide nanoflowers are synthesized on the three-dimensional graphene foam by a simple electrodeposition and etching, which serves as an outstanding template to retard the stress effects during the lithiation/delithiation of silicon. After the silicon coating uniformly deposited on the copper oxide nanoflowers, a simple hydrogen annealing was applied to reduce copper oxide nanoflowers and form the copper/silicon alloy, remarkably enhancing the conductivity of silicon. Moreover, this structure can be directly assembled without any conductive additive or binder. In electrochemical testing, the resulting copper/silicon core-shell nanoflowered electrode demonstrates a high initial capacity of 1869 mAh g(-1) at 1.6 A g(-1), with a high retention rate of 66.6%% after 500 cycles. More importantly, at a high current density of 10 A g(-1), this anode still remains a high capacity retention >63%% (compared with the highest capacity 679 mAh g(-1)), offering enormous potential for energy storage applications. (c) 2019 Elsevier Ltd. All rights reserved.
5. A light-weight free-standing graphene foam-based interlayer towards improved Li-S cells

Author:Yi, RW;Liu, CG;Zhao, YC;Hardwick, LJ;Li, YQ;Geng, XW;Zhang, Q;Yang, L;Zhao, CZ


Abstract:A light-weight and free-standing graphene foam interlayer placed between sulfur cathode and separator is investigated to improve the electrochemical performance of lithium-sulfur batteries. The highly conductive and light-weight porous graphene foam not only increases the electron pathway of cathode, but also adsorbs the dissolved high-order lithium polysulfides during cycles, thus the loss of active materials is greatly avoided with only minimum mass addition approximately 0.3 mg cm(-2) on cathodic side. Additionally, the atomic layer deposition method is applied to deposit the zinc oxide nano-scale coating on graphene foam interlayer in order to chemically trap the polysulfides with minimized deterioration on conductivity of graphene foam. Among all the graphene foam, graphene foam@zinc oxide and graphene foam/graphene foam@zinc oxide interlayers, the graphene foam/graphene foam@zinc oxide exhibits the best electrochemical performance, delivering an initial specific capacity of 1051 mAh g(-1) at 0.5 C and retaining a reversible capacity of 672 mAh g(-1) after 100 cycles, while the cell without interlayer only shows 346 mAh g(-1). These results demonstrate the strategy of including a zinc oxide modified graphene foam interlayer as an effective light-weight interlayer for improving Li-S cell performance. (C) 2019 Elsevier Ltd. All rights reserved.
6. Enhanced electrochemical performance by GeOx-Coated MXene nanosheet anode in lithium-ion batteries

Author:Liu, CG;Zhao, YC;Yi, RW;Wu, H;Yang, WB;Li, YQ;Mitrovic, I;Taylor, S;Chalker, P;Liu, R;Yang, L;Zhao, CZ


Abstract:Here, we demonstrate a facile method to synthesize an amorphous GeOx-coated MXene nanosheet structure as the anode in lithium-ion batteries. By using the GeO32- as the precursor, NaBH4 as the reduction agent, we performed a one-pot in situ synthesis to prepare a composite of GeOx nanoparticles coated on MXene nanosheet. The size of the GeOx nanoparticles is approximately 50 nm, which offers abundant contact surface between active materials with the electrolyte, as well as fast pathways for Li-ion interaction. Moreover, the unique two-dimensional MXene nanosheet serves as the excellent conductive additives to improve the electrochemical stability and electrical conductivity of composite when used in LIBs. The results indicate that the GeOx/MXene nanosheet structure significantly improves the stability during the lithiation/delithiation processes, with the enhanced capacity through an improved kinetic process. Another attractive element of this novel anode is the flexibility to tune the electrochemical properties by using different combination of binder and solvent when the slurry is prepared for the electrode fabrication. The electrode prepared with polyvinylidene fluoride binder and N-methyl pyrrolidinone solvent exhibits an excellent sustainable capacity of 381 mAh gel at 15 A g(-1). By contrast, the electrode with lithium polyacrylate and de-ionized water delivers a reversible capacity of 950 mAh g(-1) at 0.5 A g(-1) after 100 cycles. These interesting results are ascribed to the inner characteristic structure of the two types of electrodes, which have been verified by electrochemical kinetics and scanning electron microscopic images. It also reveals that the different dispersion state is responsible to the difference of electrochemical properties, which highlights the importance of the electrode design for high-performance lithium-ion batteries. (C) 2020 Elsevier Ltd. All rights reserved.
7. Isothermal sulfur condensation into carbon nanotube/nitrogen-doped graphene composite for high performance lithium-sulfur batteries

Author:Geng, XW;Yi, RW;Yu, ZM;Zhao, CZ;Li, YQ;Wei, QP;Liu, CG;Zhao, YC;Lu, B;Yang, L


Abstract:Nitrogen-doped graphene (NG) is a promising material for fabricating high-performance lithium-sulfur batteries. Here a facile hydrothermal method was used to synthesize the NG and then the composite of NG and SWCNT (NG/SWCNT) was obtained by mixing with single-walled carbon nanotubes (SWCNT) via a simple ultrasonic method. Finally, the NG/SWCNT-sulfur composite (NG/SWCNT-S) is synthesized via an isothermal method that enables rapid vapor infiltration of sulfur into carbon nanotubes. The resulting sulfur-containing cathode shows a good capacity performance, reaching high initial capacities of 1199.6 mAh g(-1) at 0.1 C and 725.2 mAh g(-1) at 1 C. The optimized electrochemical performance can be attributed to the NG addition which leads to an effective improvement of sulfur utilization and seizing polysulfides during cycling. Moreover, we show that the vapor infiltration method based on the thermodynamics of capillary condensation on nanoscale surfaces offers a new idea for assembling cathode, compared to the traditional melt infiltration method.
8. Facile Fabrication of Porous Carbon Materials Derived from Pleurotus Eryngii for Supercapacitor Electrodes

Author:Yuan, Yudan ; Zhao, Cezhou ; Li, Jiaqi ; Hu, Jiahao ; Zhao, Yinchao ; Zhao, Chun ; Zhao, Cezhou

Source:2018 IEEE International Conference on Electron Devices and Solid State Circuits, EDSSC 2018,2018,Vol.

Abstract:Porous carbon materials derived from pleurotus eryngii were successfully synthesized by carbonization and activation. The specific surface area of the obtained porous carbons reached up to 3255 m2, g-1. The electrode exhibited a maximal specific capacitance of 236 Fg-1 and excellent long-term cycle stability with 94%% capacitance retention after 6000 cycles at the current density of 2Ag-1. Therefore, pleurotus eryngii is demonstrated as an attractive biomass precursor of carbon materials for supercapacitor applications. © 2018 IEEE.
9. 3D-structured multi-walled carbon nanotubes/copper nanowires composite as a porous current collector for the enhanced silicon-based anode

Author:Zhao, YC;Liu, CG;Sun, Y;Yi, RW;Cai, YT;Li, YQ;Mitrovic, I;Taylor, S;Chalker, P;Yang, L;Zhao, CZ


Abstract:In this study, multi-walled carbon nanotubes/Cu nanowires-coated on the copper foil used as a three-dimensional porous current collector for Si electrode has been developed to tackle the problems of silicon-based lithium-ion batteries. The highly conductive Cu nanowires cooperated with robust multi-walled carbon nanotubes not only improve the inferior electric conductivity of the Si anode but also strengthen the total frame stability. Furthermore, the three-dimensional structure creates numerous voids on the surface of Cu foils. Such porous structure of the modified current collector offers the flexible volume expansion during lithiation/delithiation process. Meanwhile, the core-shell structure of multi-walled carbon nanotubes/Si and Cu nanowires/Si minimizes the deformation strain and greatly improves the long-term cycling performance in a real battery. As a result, a high specific capacity of 1845 mAh g(-1) in a half cell at a current density of 3.5 A g(-1) after 180 cycles with a capacity retention of 85.1%% has been achieved without any conductive additives or binder. The demonstrated three-dimensional current collector coupled with Si anode might inspire new material development on high-performance of lithium-ion batteries. (C) 2019 Elsevier B.V. All rights reserved.
10. Improved pseudocapacitances of supercapacitors based on electrodes of nitrogen-doped Ti3C2Tx nanosheets with in-situ growth of carbon nanotubes

Author:Sun, Y;Yi, RW;Zhao, YC;Liu, CG;Yuan, YD;Geng, XW;Li, WX;Feng, ZC;Mitrovic, I;Yang, L;Zhao, CZ


Abstract:A facile strategy involving only liquid mixing, drying, and annealing processes has been designed to fabricate a new MXene-based material containing nitrogen-doped carbon nanotubes grown on the nitrogen-modified titanium carbides (NCMX). During the thermal treatment, the nitrogen doping is dually achieved in MXene nanosheets and carbon nanotubes while the in-situ growth of carbon nanotubes occurs. The NCMX electrode exhibits the well-designed structure with the promoted specific surface area and specific capacitance. More attractively, the resultant NCMX-4 material shows extraordinary improved electrochemical capacitances of 299.52 F g(-1) at the scan rate of 2 mV s(-1) in the 3 M H2SO4 electrolyte, which is remarkably more superior than those of the pure un-doped one (74.98 F g(-1)). It delivers an excellent capacitance retention capability of 84.2%% after 10,000 cycles. Our results highlight that the strategy of fabricating novel NCMX materials here can be readily applied to a large industrial scale for improving the pseudocapacitance of supercapacitors. (C) 2020 Elsevier B.V. All rights reserved.
11. TCAD Simulation of Dual-Gate p-GaN/AlGaN/GaN HEMT Bidirectional Switch


Source:2021 18th China International Forum on Solid State Lighting and 2021 7th International Forum on Wide Bandgap Semiconductors, SSLChina: IFWS 2021,2021,Vol.

Abstract:The bidirectional switch has great potential in AC-AC matrix converter and other power electronics areas. In this work, the TCAD simulation of p-GaN/AlGaN/GaN High Electron Mobility Transistor (HEMT)dual-gate bidirectional switch is systematically carried out. The static I-V characteristics and the bidirectional conduction ability are presented to prove the successful establishment of our model. These results are consistent with the trends from previous literature. By changing the separation distance between two gates when the device's total size remains the same, the off-state breakdown voltage is improved to 1571V under gate voltage of 0V. The simulation points out the direction to improve the performance of monolithic GaN bidirectional switches in high voltage applications.
12. Threshold Voltage Instability in D-mode AlGaN/GaN MIS-HEMTs with Al2O3 Gate Dielectric


Source:2021 International Conference on IC Design and Technology, ICICDT 2021,2021,Vol.

Abstract:In this paper, D-mode MIS-HEMTs with 24 nm ALD-Al2O3 gate dielectric are studied. The electrical parameters, such as threshold voltage (Vth), drain current (Ids), on-resistant (Ron), sub-threshold swing (SS), and gate leakage current (Ileak) are investigated during the gate stress phase and recovery phase at room temperature. It is found that, during the stress phase, Vth and Ron show positive shifts while Ids show negative shifts. It is because channel electrons are trapped by the dielectric/III-nitride interface layer and by the bulk traps in the gate dielectric. However, these electrical parameter changes cannot be fully recoverable at the end of the recovery phase, followed by 30 mins thermal de-trapping. It may be caused by (1) positive gate bias induced unrecoverable defects in the dielectric layer. (2) bulk trap has a relatively large emission constant. (3) AlGaN barrier exists between the channel and dielectric/III-nitride interface layer, make the electrons hard to exchanges.
13. Monolithic si-based AlGaN/GaN MIS-HEMTs comparator and its high temperature characteristics


Source:Applied Sciences (Switzerland),2021,Vol.11

Abstract:Monolithic GaN High Electron Mobility Transistor (HEMT)-integrated circuits are a promis-ing application of wide band-gap materials. To date, most GaN-based devices behave as NMOS-like transistors. As only NMOS GaN HEMT is currently commercially available, its control circuit re-quires special design if monolithic integration is desired. This article analyzes the schematics of a GaN-based comparator, and three comparator structures are compared through ADS simulation. The optimal structure with the bootstrapped technique is fabricated based on AlGaN/GaN Metal– Insulator–Semiconductor (MIS) HEMT with the recessed gate method. The comparator has excellent static characteristics when the reference voltage increases from 3 V to 8 V. Dynamic waveforms from 10 kHz to 1 MHz are also obtained. High-temperature tests from 25◦ C to 250◦ C are applied upon both DC and AC characteristics. The mechanisms of instability issues are explained under dynamic working condition. The results prove that the comparator can be used in the state-of-art mixed-signal circuits, demonstrating the potential for the monolithic all-GaN integrated circuits.
14. A high conductive TiC-TiO2/SWCNT/S composite with effective polysulfides adsorption for high performance Li-S batteries

Author:Geng, XW;Yi, RW;Lin, XF;Liu, CG;Sun, Y;Zhao, YC;Li, YQ;Mitrovic, I;Liu, R;Yang, L;Zhao, CZ


Abstract:Lithium-sulfur (Li-S) batteries have attracted more and more attention in recent years, as their theoretical capacity is several times larger than conventional lithium-ion batteries and they have a high energy density in secondary battery systems. In our work, a titanium carbide - titanium dioxide/single-walled carbon nanotube/sulfur (TiC-TiO2/SWCNT/S) cathode with high conductivity and effective polysulfides adsorption is prepared by a facile method for fabricating Li-S batteries. The batteries with this composite cathode show a good performance at 0.1 C due to relatively high utilization of sulfur, reaching 1338.6 mAh.g(-1) specific capacity at first cycle and retaining 802.5 mAh.g(-1) after 100 cycles. Meanwhile, it presents an excellent rate performance with 711.2 mAh.g(-1) at 4 C, and recovers to 1006.9 mAh.g(-1) when the current returns to 0.1 C. Also a slow capacity decay (0.045%% decay rate per cycle) is observed at 1 C. These results suggest that a small amount of SWCNT can increase the conductivity of the whole composite to a great extent, and the strong adsorption ability of TiO2 increases the cycle life. This work offers an efficient and low-cost strategy to obtain high performance batteries with great potential for commercial applications. (C) 2020 Elsevier B.V. All rights reserved.
Total 14 results found
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