Ming Xu

Ming Xu


Postgraduate Research Student

Academic and research departments

Nanoelectronics Centre, Advanced Technology Institute.

About

My research project

Publications

Jinxin Bi, Shaoyin Li, Dongtao Liu, Bowei Li, Kai Yang, Ming Xu, Chaopeng Fu, Yunlong Zhao, Wei Zhang (2024)Highly Integrated Perovskite Solar Cells‐Based Photorechargeable System with Excellent Photoelectric Conversion and Energy Storage Ability, In: Energy & environmental materials (Hoboken, N.J.)7(5)e12728

Perovskite solar cells have emerged as a promising technology for renewable energy generation. However, the successful integration of perovskite solar cells with energy storage devices to establish high-efficiency and long-term stable photorechargeable systems remains a persistent challenge. Issues such as electrical mismatch and restricted integration levels contribute to elevated internal resistance, leading to suboptimal overall efficiency (ηoverall) within photorechargeable systems. Additionally, the compatibility of perovskite solar cells with electrolytes from energy storage devices poses another significant concern regarding their stability. To address these limitations, we demonstrate a highly integrated photorechargeable system that combines perovskite solar cells with a solid-state zinc-ion hybrid capacitor using a streamlined process. Our study employs a novel ultraviolet-cured ionogel electrolyte to prevent moisture-induced degradation of the perovskite layer in integrated photorechargeable system, enabling perovskite solar cells to achieve maximum power conversion efficiencies and facilitating the monolithic design of the system with minimal energy loss. By precisely matching voltages between the two modules and leveraging the superior energy storage efficiency, our integrated photorechargeable system achieves a remarkable ηoverall of 10.01% while maintaining excellent cycling stability. This innovative design and the comprehensive investigations of the dynamic photocharging process in monolithic systems, not only offer a reliable and enduring power source but also provide guidelines for future development of self-power off-grid electronics.

Ming Xu, Yuheng Liu, Kai Yang, Shaoyin Li, Manman Wang, Jianan Wang, Dong Yang, Maxim Shkunov, S. Ravi P. Silva, Fernando A. Castro, Yunlong Zhao (2024)Minimally invasive power sources for implantable electronics, In: Exploration4(1)20220106 Wiley

As implantable medical electronics (IMEs) developed for healthcare monitoring and biomedical therapy are extensively explored and deployed clinically, the demand for non‐invasive implantable biomedical electronics is rapidly surging. Current rigid and bulky implantable microelectronic power sources are prone to immune rejection and incision, or cannot provide enough energy for long‐term use, which greatly limits the development of miniaturized implantable medical devices. Herein, a comprehensive review of the historical development of IMEs and the applicable miniaturized power sources along with their advantages and limitations is given. Despite recent advances in microfabrication techniques, biocompatible materials have facilitated the development of IMEs system toward non‐invasive, ultra‐flexible, bioresorbable, wireless and multifunctional, progress in the development of minimally invasive power sources in implantable systems has remained limited. Here three promising minimally invasive power sources summarized, including energy storage devices (biodegradable primary batteries, rechargeable batteries and supercapacitors), human body energy harvesters (nanogenerators and biofuel cells) and wireless power transfer (far‐field radiofrequency radiation, near‐field wireless power transfer, ultrasonic and photovoltaic power transfer). The energy storage and energy harvesting mechanism, configurational design, material selection, output power and in vivo applications are also discussed. It is expected to give a comprehensive understanding of the minimally invasive power sources driven IMEs system for painless health monitoring and biomedical therapy with long‐term stable functions.

Y Zhang, M Xu, N Wang, J Li, P Chen, F Liang (2016)Compressing IP Forwarding Tables with Small Bounded Update Time, In: Computer Networks106pp. 77-90 Elsevier

With the fast development of the Internet, the size of Forwarding Information Base (FIB) maintained at backbone routers is experiencing an exponential growth, making the storage support and lookup process of FIBs a severe challenge. One effective way to address the challenge is FIB compression, and various solutions have been proposed in the literature. The main shortcoming of FIB compression is the overhead of updating the compressed FIB when routing update messages arrive. Only when the update time of FIB compression algorithms is small bounded can the probability of packet loss incurred by FIB compression operations during update be completely avoided. However, no prior FIB compression algorithm can achieve small bounded worst case update time, and hence a mature solution with complete avoidance of packet loss is still yet to be identified. To address this issue, we propose the Unite and Split (US) compression algorithm to enable fast update with controlled worst case update time. Further, we use the US algorithm to improve the performance of a number of classic software and hardware lookup algorithms. Simulation results show that the average update speed of the US algorithm is a little faster than that of the binary trie without any compression, while prior compression algorithms inevitably seriously degrade the update performance. After applying the US algorithm, the evaluated lookup algorithms exhibit significantly smaller on-chip memory consumption with little additional update overhead

Yuheng Liu, Ming Xu, Yunlong Zhao, Bahman Amini Horri (2023)Multi-doped ceria-based composite as a promising low-temperature electrolyte with enhanced ionic conductivity for steam electrolysis, In: Mol. Syst. Des. Eng Royal Society of Chemistry

Steam electrolysis is one of the most efficient approaches for producing green hydrogen. The method is based on the application of solid oxide electrolysis cells (SOECs) fabricated by functional ceramic composites for water splitting at high temperatures. Gadolinium doped ceria (GDC) is a promising electrolyte material for the fabrication of SOECs. However, the effective sintering temperature for GDC composite is usually above 1250 °C, which makes it impossible to use conventional supporting materials like ferritic steels for stack fabrication. In this work, for the first time, we have developed a lithium bismuth-copper co-doped GDC composite capable of sintering at ~750 °C. The physicochemical and electrochemical characteristics of the co-doped GDC electrolyte were systematically analysed using thermogravimetric analysis (TG/DTA), Raman spectroscopy, SEM/EDX, XRD, EIS, XPS and dilatometry analysis. The fabricated electrolyte pellets sintered at 750 °C for 6 hours in an inert atmosphere (argon) showed high densification, obtaining 96.70 % relative density. Also, the electrical conductivity obtained for the synthesised composite Ce0.712Gd0.178Li0.05Bi0.05Cu0.01O1.801 (sintered at 950 °C 6h) was 29.6 mS.cm-1 at 750 °C with activation energy as low as 0.13 eV. The result of this study helps to understand better the properties of co-doped electrolyte materials for the fabrication of more efficient steam electrolysers for environmentally-friendly hydrogen generation.

M Xu, T Chen, X Yang (2011)Optimal replacement policy for safety-related multi-component multi-state systems, In: Reliability Engineering and System Safety99(1)pp. 87-95 Elsevier

This paper investigates replacement scheduling for non-repairable safety-relatedsystems (SRS) with multiple components and states. The aim is to determine the cost-minimizing time for replacing SRS while meeting the required safety. Traditionally, such scheduling decisions are made without considering the interaction between the SRS and the production system under protection, the interaction being essential to formulate the expected cost to be minimized. In this paper, the SRS is represented by a non-homogeneous continuous time Markov model, and its state distribution is evaluated with the aid of the universal generating function. Moreover, a structure function of SRS with recursive property is developed to evaluate the state distribution efficiently. These methods form the basis to derive an explicit expression of the expected system cost per unit time, and to determine the optimal time to replace the SRS. The proposed methodology is demonstrated through an illustrative example.

Ganesh Chandrasekaran, Ning Wang, J Jun, M Xu, Rahim Tafazolli (2016)Towards D2D-based Opportunistic Data Relay Service in Partial Not-spots, In: Proceedings of WiMob'2016

With the recent development of Device-toDevice (D2D) communication technologies, mobile devices will no longer be treated as pure “terminals”, but they could become an integral part of the network in specific application scenarios. In this paper, we introduce a novel scheme of using D2D communications for enabling data relay services in partial Not-Spots, where a client without local network access may require data relay by other devices. Depending on specific social application scenarios that can leverage on the D2D technology, we consider tailored algorithms in order to achieve optimised data relay service performance on top of our proposed networkcoordinated communication framework. The approach is to exploit the network’s knowledge on its local user mobility patterns in order to identify best helper devices participating in data relay operations. This framework also comes with our proposed helper selection optimization algorithm based on reactive predictability of individual user. According to our simulation analysis based on both theoretical mobility models and real human mobility data traces, the proposed scheme is able to flexibly support different service requirements in specific social application scenarios.

Zhenhui Liu, Qiang Yu, Yunlong Zhao, Ruhan He, Ming Xu, Shihao Feng, Shidong Li, Liang Zhou, Liqiang Mai (2018)Silicon oxides: a promising family of anode materials for lithium-ion batteries, In: Chemical Society Reviews48(1)pp. 285-309

Silicon oxides have been recognized as a promising family of anode materials for high-energy lithium-ion batteries (LIBs) owing to their abundant reserve, low cost, environmental friendliness, easy synthesis, and high theoretical capacity. However, the extended application of silicon oxides is severely hampered by the intrinsically low conductivity, large volume change, and low initial coulombic efficiency. Significant efforts have been dedicated to tackling these challenges towards practical applications. This Review focuses on the recent advances in the synthesis and lithium storage properties of silicon oxide-based anode materials. To present the progress in a systematic manner, this review is categorized as follows: (i) SiO-based anode materials, (ii) SiO2-based anode materials, (iii) non-stoichiometric SiOx-based anode materials, and (iv) Si–O–C-based anode materials. Finally, future outlook and our personal perspectives on silicon oxide-based anode materials are presented.

Yi Gong, Jing Li, Kai Yang, Shaoyin Li, Ming Xu, Guangpeng Zhang, Yan Shi, Qiong Cai, Huanxin Li, Yunlong Zhao (2023)Towards Practical Application of Li-S Battery with High Sulfur Loading and Lean Electrolyte: Will Carbon-Based Hosts Win This Race? Nanomicro Lett

Acknowledgements: Y.Z. acknowledges support from EPSRC—New Investigator Award 2020 (EP/V002260/1), The Faraday Institute—Battery Study and Seed Research Project (FIRG052), The Royal Society—International Exchanges 2021 Cost Share (NSFC) (IEC\NSFC\211074). Y. G. thanks the China Scholarship Council (CSC, No. 201806130168). H. L. acknowledges the International Postdoctoral Exchange Fellowship Program (Grant No. PC2022020). Funder: Shanghai Jiao Tong University As the need for high-energy-density batteries continues to grow, lithium-sulfur (Li-S) batteries have become a highly promising next-generation energy solution due to their low cost and exceptional energy density compared to commercially available Li-ion batteries. Research into carbon-based sulfur hosts for Li-S batteries has been ongoing for over two decades, leading to a significant number of publications and patents. However, the commercialization of Li-S batteries has yet to be realized. This can be attributed, in part, to the instability of the Li metal anode. However, even when considering just the cathode side, there is still no consensus on whether carbon-based hosts will prove to be the best sulfur hosts for the industrialization of Li-S batteries. Recently, there has been controversy surrounding the use of carbon-based materials as the ideal sulfur hosts for practical applications of Li-S batteries under high sulfur loading and lean electrolyte conditions. To address this question, it is important to review the results of research into carbon-based hosts, assess their strengths and weaknesses, and provide a clear perspective. This review systematically evaluates the merits and mechanisms of various strategies for developing carbon-based host materials for high sulfur loading and lean electrolyte conditions. The review covers structural design and functional optimization strategies in detail, providing a comprehensive understanding of the development of sulfur hosts. The review also describes the use of efficient machine learning methods for investigating Li-S batteries. Finally, the outlook section lists and discusses current trends, challenges, and uncertainties surrounding carbon-based hosts, and concludes by presenting our standpoint and perspective on the subject.

Manman Wang, Zhibo Song, Jinxin Bi, Huanxin Li, Ming Xu, Yi Gong, Yundong Zhou, Yunlong Zhao, Kai Yang (2023)Probing interfacial electrochemistry by in situ atomic force microscope for battery characterization, In: Battery energy

Abstract Lithium‐ion batteries (LIBs) have been widely used in electric vehicles and energy storage industries. An understanding of the reaction processes and degradation mechanism in LIBs is crucial for optimizing their performance. In situ atomic force microscopy (AFM) as a surface‐sensitive tool has been applied in the real‐time monitoring of the interfacial processes within lithium batteries. Here, we reviewed the recent progress of the application of in situ AFM for battery characterizations, including LIBs, lithium–sulfur batteries, and lithium–oxygen batteries. We summarized advances in the in situ AFM for recording electrode/electrolyte interface, mechanical properties, morphological changes, and surface evolution. Future directions of in situ AFM for the development of lithium batteries were also discussed in this review.

Yi Gong, Jing Li, Kai Yang, Shaoyin Li, Ming Xu, Guangpeng Zhang, Yan Shi, Qiong Cai, Huanxin Li, Yunlong Zhao (2023)Towards Practical Application of Li-S Battery with High Sulfur Loading and Lean Electrolyte: Will Carbon-Based Hosts Win This Race?, In: Nano-micro letters15(1)150pp. 150-150 Springer Nature Singapore

A comprehensive discussion of the approaches for developing carbon-based sulfur hosts is presented, encompassing structural design and functional optimization. The recent implementation of effective machine learning methods in discovering carbon-based sulfur hosts has been systematically examined. The challenges and future directions of carbon-based sulfur hosts for practically application have been comprehensively discussed. A summary of the strengths and weaknesses, along with the outlook on carbon-based sulfur hosts for practical application has been incorporated. As the need for high-energy–density batteries continues to grow, lithium-sulfur (Li–S) batteries have become a highly promising next-generation energy solution due to their low cost and exceptional energy density compared to commercially available Li-ion batteries. Research into carbon-based sulfur hosts for Li–S batteries has been ongoing for over two decades, leading to a significant number of publications and patents. However, the commercialization of Li–S batteries has yet to be realized. This can be attributed, in part, to the instability of the Li metal anode. However, even when considering just the cathode side, there is still no consensus on whether carbon-based hosts will prove to be the best sulfur hosts for the industrialization of Li–S batteries. Recently, there has been controversy surrounding the use of carbon-based materials as the ideal sulfur hosts for practical applications of Li–S batteries under high sulfur loading and lean electrolyte conditions. To address this question, it is important to review the results of research into carbon-based hosts, assess their strengths and weaknesses, and provide a clear perspective. This review systematically evaluates the merits and mechanisms of various strategies for developing carbon-based host materials for high sulfur loading and lean electrolyte conditions. The review covers structural design and functional optimization strategies in detail, providing a comprehensive understanding of the development of sulfur hosts. The review also describes the use of efficient machine learning methods for investigating Li–S batteries. Finally, the outlook section lists and discusses current trends, challenges, and uncertainties surrounding carbon-based hosts, and concludes by presenting our standpoint and perspective on the subject.

Ganesh Chandrasekaran, Ning Wang, M. hassanpourasheghabadi, M. Xu, Rahim Tafazolli (2017)Mobility as a Service (MaaS): A D2D-based Information Centric Network Architecture for Edge-Controlled Content Distribution, In: IEEE Access6pp. 2110-2129 Institute of Electrical and Electronics Engineers (IEEE)

It has been envisaged that in future 5G networks user devices will become an integral part by participating in the transmission of mobile content traffic typically through Deviceto- device (D2D) technologies. In this context, we promote the concept of Mobility as a Service (MaaS), where content-aware mobile network edge is equipped with necessary knowledge on device mobility in order to distribute popular mobile content items to interested clients via a small number of helper devices. Towards this end, we present a device-level Information Centric Networking (ICN) architecture that is able to perform intelligent content distribution operations according to necessary context information on mobile user mobility and content characteristics. Based on such a platform, we further introduce device-level online content caching and offline helper selection algorithms in order to optimise the overall system efficiency. In particular, this paper sheds distinct light on the importance of user mobility data analytics based on which helper selection can lead to overall system optimality. Based on representative user mobility models, we conducted realistic simulation experiments and modelling which have proven the efficiency in terms of both network traffic offloading gains and user-oriented performance improvements. In addition, we show how the framework can be flexibly configured to meet specific delay tolerance constraints according to specific context policies.

Ming Xu, Yuheng Liu, Qiang Yu, Shihao Feng, Liang Zhou, Liqiang Mai (2021)Phenylenediamine-formaldehyde chemistry derived N-doped hollow carbon spheres for high-energy-density supercapacitors, In: Chinese chemical letters32(1)pp. 184-189 Elsevier

Porous carbon spheres represent an ideal family of electrode materials for supercapacitors because of the high surface area, ideal conductivity, negligible aggregation, and ability to achieve space efficient packing. However, the development of new synthetic methods towards porous carbon spheres still remains a great challenge. Herein, N-doped hollow carbon spheres with an ultrahigh surface area of 2044 m(2)/g have been designed based on the phenylenediamine-formaldehyde chemistry. When applied in symmetric supercapacitors with ionic electrolyte (EMIBF4), the obtained N-doped hollow carbon spheres demonstrate a high capacitance of 234 F/g, affording an ultrahigh energy density of 114.8 Wh/kg. Excellent cycling stability has also been achieved. The impressive capacitive performances make the phenylenediamine-formaldehyde resin derived N-doped carbon a promising candidate electrode material for supercapacitors. (C) 2020 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.

Qiyu Chen, Dunzhu Lu, Tianwei Qin, Xiao Luo, Ming Xu, Peining Li (2024)Optical nanoimaging of laser-switched phase-change plasmonic infrared antennas, In: Optics letters49(4)

We investigate the plasmonic properties of laser-printed chalcogenide phase-change material In SeTb (IST) antennas through near-field nanoimaging. Antennas of varying lengths were fabricated by laser switching an amorphous IST film into its crystalline metallic state. Near-field imaging elucidates the pronounced field confinement and enhancement at the antenna extremities along with the emergence of different ordered plasmonic modes with increasing length. Compared to gold antennas, the PCM antennas exhibit slightly lower but still substantial near-field enhancement with greater compactness. The interplay between antenna length, illumination angle, and excitation frequency enables versatile control over the resonant near-field distribution. Our work provides deeper understanding and tunable functionalities of laser-printed PCM nanoantennas for potential applications in compact, dynamically reconfigurable nanophotonic devices.

Xiaoqing Zhang, Wei Yuan, Honglin Huang, Ming Xu, Yu Chen, Bote Zhao, Xinrui Ding, Shiwei Zhang, Yong Tang, Longsheng Lu (2023)Rational design and low-cost fabrication of multifunctional separators enabling high sulfur utilization in long-life lithium-sulfur batteries, In: 极端制造(英文)5(1)pp. 265-280 School of Mechanical and Automotive Engineering,South China University of Technology,Guangzhou 510640,People's Republic of China%School of Environment and Energy,South China University of Technology,Guangzhou 510006,People's Republic of China

The lithium-sulfur(Li-S)battery with an ultrahigh theoretical energy density has emerged as a promising rechargeable battery system.However,the practical applications of Li-S batteries are severely plagued by the sluggish reaction kinetics of sulfur species and notorious shuttling of soluble lithium polysulfides(LiPSs)intermediates that result in low sulfur utilization.The introduction of functional layers on separators has been considered as an effective strategy to improve the sulfur utilization in Li-S batteries by achieving effective regulation of LiPSs.Herein,a promising self-assembly strategy is proposed to achieve the low-cost fabrication of hollow and hierarchically porous Fe3O4 nanospheres(p-Fe3O4-NSs)assembled by numerous extremely-small primary nanocrystals as building blocks.The rationally-designed p-Fe3O4-NSs are utilized as a multifunctional layer on the separator with highly efficient trapping and conversion features toward LiPSs.Results demonstrate that the nanostructured p-Fe3O4-NSs provide chemical adsorption toward LiPSs and kinetically promote the mutual transformation between LiPSs and Li2S2/Li2S during cycling,thus inhibiting the LiPSs shuttling and boosting the redox reaction kinetics via a chemisorption-catalytic conversion mechanism.The enhanced wettability of the p-Fe3O4-NSs-based separator with the electrolyte enables fast transportation of lithium ions.Benefitting from these alluring properties,the functionalized separator with p-Fe3O4-NSs endows the battery with an admirable rate performance of 877 mAh g-1 at 2 C,an ultra-durable cycling performance of up to 2176 cycles at 1 C,and a promising areal capacity of 4.55 mAh cm-2 under high-sulfur-loading and lean-electrolyte conditions(4.29 mg cm2,electrolyte/ratio:8 μl mg-1).This study will offer fresh insights on the rational design and low-cost fabrication of multifunctional separator to strengthen electrochemical reaction kinetics by regulating LiPSs conversion for developing efficient and long-life Li-S batteries.

Jiachen Li, Yuqiang Ma, Cong Zhang, Chi Zhang, Huijun Ma, Zhaoqi Guo, Ning Liu, Ming Xu, Haixia Ma, Jieshan Qiu (2023)Green electrosynthesis of 3,3'-diamino-4,4'-azofurazan energetic materials coupled with energy-efficient hydrogen production over Pt-based catalysts, In: Nature communications14(1) Nature Research

The broad employment of clean hydrogen through water electrolysis is restricted by large voltage requirement and energy consumption because of the sluggish anodic oxygen evolution reaction. Here we demonstrate a novel alternative oxidation reaction of green electrosynthesis of valuable 3,3'-diamino-4,4'-azofurazan energetic materials and coupled with hydrogen production. Such a strategy could greatly decrease the hazard from the traditional synthetic condition of 3,3'-diamino-4,4'-azofurazan and achieve low-cell-voltage hydrogen production on WS /Pt single-atom/nanoparticle catalyst. The assembled two-electrode electrolyzer could reach 10 and 100 mA cm with ultralow cell voltages of 1.26 and 1.55 V and electricity consumption of only 3.01 and 3.70 kWh per m of H in contrast of the conventional water electrolysis (~5 kWh per m ). Density functional theory calculations combine with experimental design decipher the synergistic effect in WS /Pt for promoting Volmer-Tafel kinetic rate during alkaline hydrogen evolution reaction, while the oxidative-coupling of starting materials driven by free radical could be the underlying mechanism during the synthesis of 3,3'-diamino-4,4'-azofurazan. This work provides a promising avenue for the concurrent electrosynthesis of energetic materials and low-energy-consumption hydrogen production.

Ruibin Gao, Jili Tao, Jingyi Zhang, Longhua Ma, Ming Xu (2023)Nsga-Iii-Sd Based Fuzzy Energy Management System Optimization for Lithium Battery/Supercapacitor Hev, In: SSRN Electronic Journal Elsevier BV
Yanchao He, Roberto Armellin, Ming Xu (2018)Bounded Relative Orbits in the Zonal Problem via High-Order Poincaré Maps, In: Journal of Guidance, Control, and Dynamics American Institute of Aeronautics and Astronautics

Searching for naturally bounded relative orbits in a zonal gravitational field is a crucial and challenging task in astrodynamics. In this work, a semi-analytical approach based on high-order Taylor expansions of Poincaré maps is developed. Entire families of periodic orbits, parameterized by the energy and the polar component of the angular momentum, are computed under arbitrary order zonal harmonic perturbations, thus enabling the straightforward design of missions with prescribed properties. The same technique is then proven effective in determining quasi-periodic orbits that are in bounded relative motion for long time and with very large aperture. Finally, an illustrative example on how to frame the design of bounded relative orbits with prescribed properties as an optimization problem is presented.

Roberto Armellin, Yanchao He, Ming Xu (2019)DESIGN AND CONTROL OF REPEAT GROUND TRACK ORBITS IN HIGH FIDELITY DYNAMICAL MODEL VIA HIGH ORDER POINCARÉ MAPPING, In: Advances in the Astronautical Sciences Univelt, Inc

A semi-analytical technique for both the design and control of repeat groundtrack (RGT) orbits in a high fidelity dynamical model, including non-conservative forces and accurate Earth orientation parameters, is introduced. The method is based on the use of high-order expansion of Poincaré maps to propagate forward in time regions of the phase space for one, or more, repeat cycles. This map provides the means to efficiently study the effect that an impulse, applied at the Poincaré section crossing, produces on the ground-track pattern, thus enabling highly accurate design and control. The approach is applied to the design and control of missions like TerraSAR-X, Landsat-8, SPOT-7, IRS-P6, and UoSAT-12.

M Xu, S Bhat, R Smith, G Stephens, J Sadhukhan (2009)Multi-objective optimisation of metabolic productivity and thermodynamic performance, In: COMPUTERS & CHEMICAL ENGINEERING33(9)pp. 1438-1450 PERGAMON-ELSEVIER SCIENCE LTD
Y He, M Xu, X Jia, Roberto Armellin (2017)High-Precision Repeat-Groundtrack Orbit Design and Maintenance for Earth Observation Missions, In: Celestial Mechanics and Dynamical Astronomy128(2)pp. 275-294 Springer Science+Business Media

The focus of this paper is the design and station keeping of repeat-groundtrack orbits for Sun-synchronous satellite. A method to compute the semimajor axis of the orbit is presented together with a station-keeping strategy to compensate for the perturbation due to the atmospheric drag. The results show that the nodal period converges gradually with the increase of the order used in the zonal perturbations up to J15. A differential correction algorithm is performed to obtain the nominal semimajor axis of the reference orbit from the inputs of the desired nodal period, eccentricity, inclination and argument of perigee. To keep the satellite in the proximity of the repeat-groundtrack condition, a practical orbit maintenance strategy is proposed in the presence of errors in the orbital measurements and control, as well as in the estimation of the semimajor axis decay rate. The performance of the maintenance strategy is assessed via the Monte Carlo simulation and the validation in a high fidelity model. Numerical simulations substantiate the validity of proposed mean-elements-based orbit maintenance strategy for repeat-groundtrack orbits.

Ming Xu, Qiang Yu, Zhenhui Liu, Jianshuai Lv, Sitian Lian, Bin Hu, Liqiang Mai, Liang Zhou (2018)Tailoring porous carbon spheres for supercapacitors, In: Nanoscale10(46)pp. 21604-21616 Royal Soc Chemistry

The last decade has witnessed significant breakthroughs in the synthesis of porous carbon spheres (PCSs). This Review provides an updated summarization on the controlled synthesis of PCSs for supercapacitors. The synthetic methodologies can be generally categorized into (i) hard templating, (ii) soft templating, (iii) the modified Stober method, (iv) hydrothermal carbonization (HTC), and (v) aerosol-assisted methods. The obtained PCSs include microporous/mesoporous/macroporous carbon spheres, single-/multi-shelled hollow carbon spheres, and yolk@shell carbon spheres. The structure-electrochemical performance correlation is discussed. Finally, the future research directions on the rational design of PCSs for supercapacitors are predicted.

Xinyuan Li, Zhenhui Liu, Congcong Cai, Qiang Yu, Wenting Jin, Ming Xu, Chang Yu, Shidong Li, Liang Zhou, Liqiang Mai (2021)Micropore-Rich Yolk-Shell N-doped Carbon Spheres: An Ideal Electrode Material for High-Energy Capacitive Energy Storage, In: ChemSusChem14(7)pp. 1756-1762 Wiley

Increasing the energy density of electrochemical double layer capacitors (EDLCs) can broaden their applications in energy storage but remains a formidable challenge. Herein, micropore-rich yolk-shell structured N-doped carbon spheres (YSNCSs) were constructed by a one-pot surfactant-free self-assembly method in aqueous solution. The resultant YSNCSs after activation possessed an ultrahigh surface area of 2536 m(2) g(-1), among which 80 % was contributed from micropores. When applied in EDLCs, the activated YSNCSs demonstrated an unprecedentedly high capacitance (270 F g(-1) at 1 A g(-1)) in 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]) ionic liquid, affording an ultrahigh energy density (133 Wh kg(-1) at 943 W kg(-1)). The present contribution provides insight into engineering porous carbons for capacitive energy storage.

Qiang Yu, Peipei Ge, Zhenhui Liu, Ming Xu, Wei Yang, Liang Zhou, Dongyuan Zhao, Liqiang Mai (2018)Ultrafine SiOx/C nanospheres and their pomegranate-like assemblies for high-performance lithium storage, In: Journal of materials chemistry. A, Materials for energy and sustainability6(30)pp. 14903-14909 Royal Soc Chemistry

The application of silicon oxide (SiOx)-based anode materials in lithium-ion batteries is hampered by their low conductivity and large volume expansion. To tackle both issues, ultrafine SiOx/C composite nanospheres with a uniform diameter of similar to 40 nm were fabricated through a tri-component co-assembly approach. The ultrafine SiOx/C nanospheres demonstrated a high specific capacity of 895 mA h g(-1) after 200 cycles at 200 mA g(-1). At a high current density of 1 A g(-1), a capacity of 828 mA h g(-1 )could be achieved after 1000 cycles. The ultrafine SiOx/C nanospheres were further assembled into pomegranate-like assemblies through spray drying. The resultant pomegranate-like structure manifested a discharge capacity of 1024 mA h g(-1 )after 200 cycles at 500 mA g(-1).

Qiang Yu, Jianshuai Lv, Zhenhui Liu, Ming Xu, Wei Yang, Kwadwo Asare Owusu, Liqiang Mai, Dongyuan Zhao, Liang Zhou (2019)Macroscopic synthesis of ultrafine N–doped carbon nanofibers for superior capacitive energy storage, In: Science bulletin (Beijing)64(21)pp. 1617-1624 Elsevier B.V

[Display omitted] Carbon nanofibers (CNFs) with excellent electric conductivity and high surface area have attracted immense research interests in supercapacitors. However, the macroscopic production of CNFs still remains a great challenge. Herein, ultrafine N–doped CNFs (N–CNFs) with a diameter of ∼20 nm are synthesized through a simple and scalable sol-gel method based on the self-assembly of phenolic resin and cetyltrimethylammonium bromide. When employed in aqueous supercapacitors, the obtained activated N–CNFs manifest a high gravimetric/areal capacitance (380 F g−1/1.7 F cm−2) as well as outstanding rate capability and cycling stability. Besides, the activated N–CNFs also demonstrate excellent capacitive performance (330 F g−1) in flexible quasi-solid-state supercapacitors. The remarkable electrochemical performance as well as the easy and scalable synthesis makes the N–CNFs a highly promising electrode material for supercapacitors.