Graduate Student Highlight: Yao Lu

Yao Lu-Photo (1)

Name:  Yao Lu

Degree Program:  PhD in Fiber and Polymer Science

Advisor(s):  Prof. Xiangwu Zhang

Degrees you have:  MS in Textile Engineering, BS in Textile Engineering

Where are you from?  Yangquan City, Shanxi Province, China

What is your town / country like?   My hometown, Yangquan, is the third largest city in Shanxi Province, China. Yangquan is famous for its abundant mineral and tourist resources.

Why did you decide to pursue your degree at NC State University?  Wilson College of Textiles in NC State University is known to be the best around the world and the 3 + X program offered by NC State University and Donghua University provided great opportunity for me to purse graduate degrees.

Give a short description of your research:  My research is mainly focused within two areas: (i) fabrication of polymer, carbon, ceramic and composite nanofibers and microfibers using advanced spinning technologies; and (ii) synthesis of energy storage materials for batteries and supercapacitors.

How does your research impact the world? Nanofibers and microfibers are currently widely used in various fields including filtration, textile, medicine, composite and energy.  My research in nanofiber/microfiber fabrication can help advance the production of “fine” fibers. Recently, rechargeable batteries and supercapacitors become important energy storage devices in consumer electronics, electric vehicles and large-scale grids, and my research can help make high-performance materials for energy storage purpose.

Have you published your work yet and/or received any awards?  If you have published, please provide the citation and an abstract appropriate at the high school science level:

  1. Yao Lu, Meltem Yanilmaz, Chen Chen, Mahmut Dirican, Yeqian Ge, Jiadeng Zhu, Xiangwu Zhang (2015), Centrifugally Spun SnO2 Microfibers Composed of Interconnected Nanoparticles as the Anode in Sodium-Ion Batteries. ChemElectroChem, DOI: 10.1002/celc.201500367.

Abstract: SnO2 microfibers were synthesized by centrifugal spinning technology and were evaluated as the anode in sodium-ion batteries. The as-prepared SnO2 microfibers are composed of interconnected nanoparticles with small interparticle opening. The 1-demensionalfibrous morphology, fine particle size and open pore structure together result in reduced electrochemical impedance and enhanced electrochemical performance. The highest capacity achieved is 567 mAh g-1 at 20 mA g-1. At a much higher current density of 640 mA g-1, the microfiber electrode still retains a high capacity of 158 mAh g-1 after 50 cycles. The SnO2 microfibers also demonstrate good rate performance in a current range of 20 – 640 mA g-1. The results demonstrate that SnO2 microfibers are potential anode material candidate for sodium-ion batteries and centrifugal spinning offers a feasible solution of large-scale production of fibrous electrode materials.

  1. Yao Lu, Meltem Yanilmaz, Chen Chen, Yeqian Ge, Mahmut Dirican, Jiadeng Zhu, Yongqiang Li, Xiangwu Zhang (2015), Lithium-substituted sodium layered transition metal oxide fibers as cathodes for sodium-ion batteries. Energy Storage Materials 1, 74-81.

Na layered transition metal oxide fibers with/without partial Li substitution were prepared by the combination ofanovelcentrifugalspinningmethodandthermaltreatment.ComparedtotheLi-free fibers, the Li-substituted Na layered transition metal oxide fiber cathodes exhibit higher capacities, better cycling stability and enhanced rate capability. Among the studied Li substituted Na layered transition metal oxide fibers, Na0.8Li0.4Ni0.15Mn0.55Co0.1O2 demonstrates the best overall electrochemical performance. The highest capacity of 138 mAhg-1 is achieved at 15 mA g-1. As the current density increased to 75 and 300 mA g-1, Na0.8Li0.4Ni0.15Mn0.55Co0.1O2 fibers still deliver high capacities of 113 and 94 mAh g-1, respectively. This specific fiber composition also yields stable cycling performance and superior rate performance at various current densities between 15–600 mA g-1. The results suggest that partial Li substitution is an effective method to stabilize the structure of the Na layered transition metal oxide cathodes and hence enhance the electrochemical performance. It is also demonstrated that centrifugal spinning can be an attractive technology for mass production of micro-sized, fibrous electrodes.

  1. Yao Lu, Chen Chen, Xiangwu Zhang (2015), Functional Nanofibers for Energy Storage. Handbook of Smart Textiles, 513-547.

Abstract: Among a variety of current energy storage technologies, rechargeable lithium-ion batteries are considered to be an effective solution to the ever-growing demand for high-power and high-energy electrochemical power sources. Novel nanofiber preparation technologies, such as electrospinning, offer a great opportunity to design new materials for advanced lithium-ion batteries. This chapter addresses developing novel nanofiber-based anode, cathode, and separator materials for lithium-ion batteries. The discussion focuses on the preparation, structure, and performance of nanofiber-based anode materials such as carbon nanofiers (CNFs), tin antimony alloy/CNFs, silicon/CNFs, and manganese oxide/CNFs; cathode materials including lithium cobalt oxide nanofibers, lithium manganese oxide nanofibers, lithium iron phosphate/CNFs, lithium manganese silicate/CNFs, as well as separators such as lithium lanthanum titanate/ polyacrylonitrile composite nanofiber separators. By employing the nanofiber structure, the nanofiber anodes and cathodes exhibit high capacity and stable cycling performance, while the nanofiber separators show improved electrolyte uptake, high ionic conductivity, low interfacial resistance, and enhanced capacity and cycling stability in lithium-ion batteries. These results suggest that electrospinning is a promising technology to fabricate nanofiber-based anode, cathode, and separator materials for rechargeable lithium-ion batteries.

  1. Yao Lu, Kun Fu, Shu Zhang, Ying Li, Chen Chen, Jiadeng Zhu, Meltem Yanilmaz, Mahmut Dirican, Xiangwu Zhang (2015), Centrifugal spinning: A novel approach to fabricate porous carbon fibers as binder-free electrodes for electric double-layer capacitors. Journal of Power Sources 273, 502-510.

Abstract: Carbon nanofibers (CNFs), among various carbonaceous candidates for electric double-layer capacitor (EDLC) electrodes, draw extensive attention because their one-dimensional architecture offers both shortened electron pathways and high ion-accessible sites. Creating porous structures on CNFs yields larger surface area and enhanced capacitive performance. Herein, porous carbon nanofibers (PCNFs) were synthesized via centrifugal spinning of polyacrylonitrile (PAN)/poly(methyl methacrylate) (PMMA) solutions combined with thermal treatment and were used as binder-free EDLC electrodes. Three precursor fibers with PAN/PMMA weight ratios of 9/1, 7/3 and 5/5 were prepared and carbonized at 700, 800, and 900°C, respectively. The highest specific capacitance obtained was 144 F g-1 at 0.1 A g-1 with a rate capability of 74% from 0.1 to 2 A g-1 by PCNFs prepared with PAN/PMMA weight ratio of 7/3 at 900°C. These PCNFs also showed stable cycling performance. The present work demonstrates that PCNFs are promising EDLC electrode candidate and centrifugal spinning offers a simple, cost-effective strategy to produce PCNFs.

  1. Yao Lu, Shu Zhang, Ying Li, Leigang Xue, Guanjie Xu, Xiangwu Zhang (2014), Preparation and characterization of carbon-coated NaVPO4F as cathode material for rechargeable sodium-ion batteries. Journal of Power Sources 247, 770-777.

Abstract: Sodium vanadium fluorophosphate (NaVPO4F), a material candidate for sodium-ion battery cathodes, was synthesized via a high-temperature solid-state reaction approach. Different amounts of carbon coating were introduced in NaVPO4F to improve its electrochemical performance. The structure and morphology of the resultant cathode materials were examined by scanning electron microscopy and X-ray diffraction. The effects of carbon coating on the electrochemical performance were evaluated by cyclic voltammetry, charge-discharge curve, cycling performance and electrochemical impedance spectroscopy. The highest capacity achieved for this material was 97.8 mAh g-1 and the best capacity retention was 89% at the 20th cycle. Results demonstrated that appropriate amount of carbon coating could effectively improve the electrochemical performance of NaVPO4F, and carbon-coated NaVPO4F could offer promising future for sodium-ion battery cathode materials.

  1. Yao Lu, Ying Li, Shu Zhang, Guanjie Xu, Kun Fu, Hun Lee, Xiangwu Zhang (2013), Parameter study and characterization for polyacrylonitrile nanofibers fabricated via centrifugal spinning process. European Polymer Journal 49 (12), 3834-3845.

Abstract: Electrospinning is currently the most popular method for producing polymer nanofibers. However, the low production rate and safety concern limit the practical use of electrospinning as a cost-effective nanofiber fabrication approach. Herein, we present a novel and simple centrifugal spinning technology that extrudes nanofibers from polymer solutions by using a high-speed rotary and perforated spinneret. Polyacrylonitrile (PAN) nanofibers were prepared by selectively varying parameters that can affect solution intrinsic properties and operational conditions. The resultant PAN nanofibers were characterized by SEM, and XRD. The correlation between fiber morphology and processing conditions was established. Results demonstrated that the fiber morphology can be easily manipulated by controlling the spinning parameters and the centrifugal spinning process is a facile approach for fabricating polymer nanofibers in a large-scale and low-cost fashion.

What is your favorite thing about TECS / NC State?  TECS department has the best faculty and staff team which definitely makes my graduate life easier. All the professors are so kind and willing to discuss and share knowledge, while the great staff team is always there to help.

Who has influenced you most during your research here and how?  Prof. Xiangwu Zhang, my advisor for Master and Ph.D. study, has influenced my research most. Prof. Zhang has offered me great chance to learn and work with him, and during my five-year research, his guidance, encouragement and support help develop my research, writing and presentation skills and also help me become a confident and energetic researcher.

What do you find most exciting about your field of study?  All scientific research help advance the society in one way or another. What my field of study excites me most is that the materials I made can store energy, and maybe, a lot of energy. If my fellow researchers and I can prepare materials that are capable of storing more energy, people can use cellphones or cameras with longer endurance or drive electric cars that run farther before recharging, and this can happen in very near future.