Dr Foivos Markoulidis


Faraday Institution Research Fellow
B.Eng. (Hons), M.Sc., Ph.D. (Surrey)

Biography

Foivos is a Faraday Institution Research Fellow based across two departments in the Faculty of Engineering and Physical Sciences (FEPS), researching and developing cathode materials for lithium-sulfur batteries as part of project LiSTAr. He completed the MSc in 'Advanced Materials', here, at the University of Surrey and stayed on to conduct postgraduate research in FEPS, under a European Commission-funded PhD programme. His area of research was the fabrication, processing and testing of supercapacitors for electric vehicles. He carried out further, post-doctoral research on supercapacitors and graphene electrochemistry, at Imperial College London. Having also worked in the pharmaceutical industry, Foivos re-joined FEPS in late-2018 to conduct lithium-ion battery research.

University roles and responsibilities

  • Electrochemistry Instruments Manager (12AZ02, 20AZ02)
  • Panel Member of Health & Safety Forum (Area 8)
  • Glovebox Manager (20AZ02)

My qualifications

Nanomaterials Safety and Handling
Compressed Gases & Cylinder Safety
Safe Use of Lasers
Radiation Protection
Fire Extinguisher Training
Microscopy Silver User: FESEM/EDS/WDS/BSD
MSSU | University of Surrey

Research projects

My publications

Highlights

Markoulidis, F., Bates, J., Lekakou, C., Slade, R., & Laudone, G. M. (2020). Supercapacitors with lithium-ion electrolyte: An experimental study and design of the activated carbon electrodes via modelling and simulations. Carbon. https://doi.org/10.1016/j.carbon.2020.04.017

Markoulidis, F., Lei, C., Lekakou, C., Duff, D., Khalil, S., Martorana, B., & Cannavaro, I. (2014). A method to increase the energy density of supercapacitor cells by the addition of multiwall carbon nanotubes into activated carbon electrodes. Carbon68, 58–66. https://doi.org/10.1016/j.carbon.2013.08.040

Markoulidis, F., Lei, C., & Lekakou, C. (2017). Investigations of Activated Carbon Fabric-based Supercapacitors with Different Interlayers via Experiments and Modelling of Electrochemical Processes of Different Timescales. Electrochimica Acta249, 122–134. https://doi.org/10.1016/j.electacta.2017.07.182

Markoulidis, F., Lei, C., Lekakou, C., Figgemeier, E., Duff, D., Khalil, S., & Cannavaro, I. (2012). High-performance Supercapacitor cells with Activated Carbon/MWNT nanocomposite electrodes. In IOP Conference Series: Materials Science and Engineering (Vol. 40). https://doi.org/10.1088/1757-899X/40/1/012021

Woodward, R. T., Markoulidis, F., De Luca, F., Anthony, D. B., Malko, D., McDonald, T. O., & Bismarck, A. (2018). Carbon foams from emulsion-templated reduced graphene oxide polymer composites: Electrodes for supercapacitor devices. Journal of Materials Chemistry A6(4), 1840–1849. https://doi.org/10.1039/c7ta09893f

De Marco, M., Markoulidis, F., Menzel, R., Bawaked, S. M., Mokhtar, M., Al-Thabaiti, S. A., & Shaffer, M. S. P. (2016). Cross-linked single-walled carbon nanotube aerogel electrodes: Via reductive coupling chemistry. Journal of Materials Chemistry A4(15), 5385–5389. https://doi.org/10.1039/c5ta10311h

Lei, C., Amini, N., Markoulidis, F., Wilson, P., Tennison, S., & Lekakou, C. (2013). Activated carbon from phenolic resin with controlled mesoporosity for an electric double-layer capacitor (EDLC). Journal of Materials Chemistry A1(19), 6037–6042. https://doi.org/10.1039/c3ta01638b

Rocha, V. G., García-Tuñón, E., Botas, C., Markoulidis, F., Feilden, E., D’Elia, E., & Saiz, E. (2017). Multimaterial 3D Printing of Graphene-Based Electrodes for Electrochemical Energy Storage Using Thermoresponsive Inks. ACS Applied Materials and Interfaces9(42), 37136–37145. https://doi.org/10.1021/acsami.7b10285

Lei, C., Markoulidis, F., Ashitaka, Z., & Lekakou, C. (2013). Reduction of porous carbon/Al contact resistance for an electric double-layer capacitor (EDLC). Electrochimica Acta92, 183–187. https://doi.org/10.1016/j.electacta.2012.12.092

Lei, C., Markoulidis, F., Wilson, P., & Lekakou, C. (2016). Phenolic carbon cloth-based electric double-layer capacitors with conductive interlayers and graphene coating. Journal of Applied Electrochemistry46(2), 251–258. https://doi.org/10.1007/s10800-015-0909-x

Markoulidis, F., Lei, C., & Lekakou, C. (2013). Fabrication of high-performance supercapacitors based on transversely oriented carbon nanotubes. Applied Physics A: Materials Science and Processing111(1), 227–236. https://doi.org/10.1007/s00339-012-7471-8

Fields, R., Lei, C., Markoulidis, F., & Lekakou, C. (2016). The Composite Supercapacitor. Energy Technology4(4), 517–525. https://doi.org/10.1002/ente.201500328

Markoulidis, F., Todorova, N., Grilli, R., Lekakou, C. & Trapalis C. (2019). Composite Electrodes of Activated Carbon and Multiwall Carbon Nanotubes Decorated with Silver Nanoparticles for High Power Energy Storage. Journal of Composites Science3(4), 97. https://doi.org/10.3390/jcs3040097

Publications

F. Markoulidis (2006). Evaluation of Computing Requirements for Rolls-Royce Whole Engine Finite Element Models
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The fundamental endeavour of this project was to establish the feasibility and the equivalent computational requirements for running a full thermal simulation of a Rolls Royce Trent 900 gas turbine. Three finite element models had to be simulated: a two dimensional shaft/disk cut-out (2D tutorial file), a 3D shaft/disk model and the Trent 900 module 04. The Trent 900 finite engine model was a standard size module 04 model utilised, nowadays, by Rolls Royce. This model had undergone a full thermal analysis; without the need of providing any data as input, since the model itself included a materials and cycle definitions database. The CPU time and RAM memory usage throughout the process was noted. Then, the re-meshing process of the two dimensional and three dimensional tutorial files was initiated; with the primary concern lying on the three dimensional part. Hence, the three dimensional model was re-meshed in various configurations, up to a point where the mesh reached a maximum level of fineness; approximately half a million of tetrahedral elements. Each mesh configuration was subjected to a separate thermal analysis, which provided various CPU time and RAM memory values. The results were plotted into graphs against the number of elements for each mesh arrangement (CPU time vs. number of elements, RAM vs. number of elements). Moreover, a forecast on the computational requirements of a WEM1 (between 5 to 100 million tetrahedral elements) was completed successfully. Equivalently, between 6 to 392 days will be needed to effectively run such thermal simulations, using the existing software and facilities.
F. Markoulidis (2006). Hot-Wire Constant Temperature Anemometry in a Turbulent Mixing Layer
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The aim for this experiment was the implementation of basic understanding of turbulent flow and the creation of profiles of mean and root mean square velocities in a 2D turbulent mixing layer. Analogue measurements were solely utilised and Constant temperature hot-wire anemometry was the main approach.
F. Markoulidis (2007). Maximum Range Calculations for a Gulfstream GVI Business Jet
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The main objective of this this project was the calculation of maximum range, on various cruise conditions, for a highly popular business jet, the Gulfstream IV. The specifications for the respective cruise conditions, plus other essential data and numerical information were provided through an exercise and were tabulated in detai. Chiefly, four different analyses were required and thus, four different cruise conditions were investigated.
F. Markoulidis (2007). Review of Membrane Airfoils & Wings
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The most significant task of this project was to approach and thoroughly explain,through the appropriate scientific literature and bibliography, the various aerodynamic performance considerations and concepts associated with “membrane wings”. The fundamental motivation behind this entire work was mainly associated with the great demand in studying such types of lift generating mechanisms, in both academic and industrial organisations. Such an interest was fuelled by a wide spectrum of applications that were found to utilize the aforementioned concept, ranging from lightweight/fabric sails for various sea vessels, windmill applications, hot gas air balloons, parachutes and last but not least the presently ever so developing area of Micro Air Vehicles (MAVs). The topic areas addressed covered a preliminary membrane analysis which would introduce the fundamentals of membranes and their aerodynamic properties. Then there was a more thorough consideration of membrane aerodynamics, with small camber and angle of attack, where specific properties of the particular airfoil theory were presented and analysed both mathematically and physically. That was followed by a discussion and critical review on the various theoretical assumptions and experimental methods for membranes. Moreover, two highly important topic areas were investigated (much like case studies) and explained through the previously analysed theory. The first one was related with Flexible sails, while the second one highlighted some important aspects of the membrane aerodynamics and their progressive utilisation on MAVs.
F. Markoulidis (2009). A Review on Surface Analysis Techniques
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A focused review on the fundamentals of Surface Analysis and related characterisation techniques. Topics covered include: X-ray Photoelectron Spectroscopy (XPS) and imaging, Auger Electron Spectroscopy (AES), Secondary Ion mass Spectroscopy (SIMS) and imaging. Technique Comparisons are also covered, namely Sputter Depth Profiling with XPS vs. AES and dynamic SIMS vs. XPS & AES. Special focus is given to XPS and SIMS including time of flight detectors (ToF-SIMS) and discussion on their utilisation.
F. Markoulidis (2009). A Review on the Science of Adhesion and Characterisation Techniques
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A focused review on the fundamentals of the Science of Adhesion as well as relevant characterisation techniques. Topics covered include: Surface and Interfacial Free Energy, Surface Analysis & Adhesion and Inverse Gas Chromatography.
F. Markoulidis (2010). Materials processing, Fabrication and Testing of Carbon Nanotube-based Supercapacitors
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During the course of this work the performance of supercapacitors with nanotube-based electrodes was evaluated. Three different fabrication methods were followed: Drop Casting, Transfer Printing and Electrophoretic deposition. Various supercapacitor specifications were tried and tested and their impact on cell performance was experimentally and critically approached. Two types of electrode separators were employed: glass microfibre and lens tissue. Moreover two electrolyte types were fabricated and tested: a polymer gel electrolyte (PEO-EC-LiCLO4) and a liquid, salt-based electrolyte (TEABF4-PC). Supercapacitor performance was evaluated with a multi-channel analyser which carried out cyclic voltammetry, charge-discharge and impedance spectroscopy tests. Nanotube dispersion was done mechanically and then observed via scanning electron microscopy (SEM). Moreover certain samples that underwent EPD were observed with a high-magnification, scanning transmission electron microscope (STEM). Transparency testing was also completed and specimen transmittance was noted, with an indium tin oxide specimen with deposited carbon nanotubes achieving the highest transparency. It was shown that drop-casting fabrication process provided the highest performing supercapacitor.
C. Lekakou, O. Moudam, F. Markoulidis, T. Andrews, J. F. Watts, G. T. Reed (2011). Carbon-Based Fibrous EDLC Capacitors and Supercapacitors
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This paper investigates electrochemical double-layer capacitors (EDLCs) including two alternative types of carbon-based fibrous electrodes, a carbon fibre woven fabric (CWF) and a multiwall carbon nanotube (CNT) electrode, as well as hybrid CWF-CNT electrodes. Two types of separator membranes were also considered. An organic gel electrolyte PEO-LiCIO4-EC-THF was used to maintain a high working voltage. The capacitor cells were tested in cyclic voltammetry, charge-discharge, and impedance tests. The best separator was a glass fibre-fine pore filter. The carbon woven fabric electrode and the corresponding supercapacitor exhibited superior performance per unit area, whereas the multiwall carbon nanotube electrode and corresponding supercapacitor demonstrated excellent specific properties. The hybrid CWF-CNT electrodes did not show a combined improved performance due to the lack of carbon nanotube penetration into the carbon fibre fabric.
F. Markoulidis, C. Lei, C. Lekakou, A. Sorniotti (2012). Supercapacitors: Materials, Fabrication and Testing
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Supercapacitors are electrochemical capacitors that function under the principle of double-layer capacitance. They can be alternatively termed as ‘Electric, Double-Layer Capacitors’ (EDLCs). During the course of this work supecapacitor cell specimens were successfully fabricated and tested. All cells utilised a salt-based, organic electrolyte, porous separator and various carbon-based electrode materials. Special focus was given to the electrode fabrication process and electrolyte selection, given that certain environmental and structural conditions had to be met. Electrode surface topography was also investigated with two different approaches: scanning electrode microscopy (SEM) and transmission electrode microscopy (TEM). The generated images led to conclusions about sample preparation, material selection and specimen quality. Supercapacitor performance was evaluated with a multi-channel potentiostat/galvanostat/impedance analyser. Thus, three types of electrochemical tests were completed: Cyclic Voltammetry (CV), Charge-Discharge and Electrochemical Impedance Spectroscopy (EIS). Useful data and figures for all three aforementioned tests were successfully produced, thus specific power and energy density values were obtained.
C. Lei, F. Markoulidis, P. Wilson, C. Lekakou (2012). Reduction of the Internal Resistance of Carbon Electrodes for an Electric Double-layer Capacitor (EDLC)
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Carbonaceous materials are commonly used to fabricate electrodes for electric double-layer capacitors (EDLCs) or supercapacitors. The internal resistance of the carbon electrode comes from the carbon material itself, carbon particle-particle contact, and carbon-current collector contact. The high internal resistance of the carbon electrode can decrease capacitor energy and power performance, and reduce the lifetime of the capacitor. In this report, the sources of carbon based EDLC internal resistance were explored using electrochemical impedance spectroscopy (EIS). A generalized equivalent circuit model was coupled with the EIS for the analyses. The EDLC cells were made from symmetric carbon/Al electrodes and operated in organic electrolyte. The analysis results showed the effects of the current collector, amount of polymer binder Poly(vinylidene fluoride) (PVDF) and carbon particle sizes on the internal resistance of the electrode.
E. C. Vermisoglou, N. Todorova, G. Pilatos, G. E. Romanos, V. Likodimos, N. Boukos, C. Lei, F. Markoulidis, C. Lekakou, C. Trapalis (2012). Few layer graphene decorated with silver nanoparticles
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Graphite oxide (GO) powder was irradiated in a microwave oven and lightweight expanded graphite oxide (EGO) powder with high BET surface area 1316 m2/g was obtained. Activation of EGO was performed by impregnation in KOH solution and high temperature treatment under Ar flow, followed by annealing in vacuum (t-EGO). KOH acted more as a reducing agent diminishing the defects than as a surface modifier for high porosity. EGO and t-EGO were further decorated with Ag nanoparticles (~40 nm) applying solar light irradiation. Along with Ag deposition the structural defects of the graphene were reduced upon photo-irradiation. It was established that among the bare graphenes the EGO exhibited the highest capacitance. From the Ag-containing composites, the KOH activated EGO acted as a supercapacitor, while the non-activated EGO as a resistant.
C. Lekakou, F. Markoulidis, C. Lei, A. Sorniotti, J. Perry, C. Hoy, B. Martorana, I. Cannavaro, M. Gosso (2012). Meso-nano and micro-nano ion transport in porous carbon composite electrodes for energy storage applications
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In energy storage devices carbonaceous composite electrodes are a popular choice, consisting of activated carbon (AC), conductive additives and a polymeric binder matrix. The active electrode components are in the form of ac particles, ac fibres, or ac monolith combined with conductive additives such as carbon black. Activated carbon plays the most important role for storing a large amount of energy in the form of ions contained in the carbon nanopores. This study considers a modelling approach to the meso-nano and micro-nano infiltration of ions into the porous carbon structure during the operation of the energy storage device. Depending on the pore size, ion size and solvent molecule size, ions may be solvated or unsolvated as they move, where ions are solvated in meso-pores for most cases. Molecular model simulations have been performed to determine the values of the geometrical parameters of different ions, solvated and unsolvated in various solvents. A meso-nano and micro-nano ion infiltration model has been developed in this study under both steady state and dynamic conditions.
M. Weil, H. Dura, B. Simon, M. J. Baumann, B. M. Zimmermann, S. Ziemann, C. Lei, F. Markoulidis, C. Lekakou, M. Decker (2012). Ecological assessment of nano-enabled supercapacitors for automotive applications
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New materials on nano scale have the potential to overcome existing technical barriers and are one of the most promising key technologies to enable the decoupling of economic growth and resource consumption. Developing these innovative materials for industrial applications means facing a complex quality profile, which includes among others technical, economic, and ecological aspects. So far the two latter aspects are not sufficiently included in technology development, especially from a life cycle point of view. Supercapacitors are considered a promising option for electric energy storage in hybrid and full electric cars. In comparison with presently used lithium based electro chemical storage systems supercapacitors possess a high specific power, but a relatively low specific energy. Therefore, the goal of ongoing research is to develop a new generation of supercapacitors with high specific power and high specific energy. To reach this goal particularly nano materials are developed and tested on cell level. In the presented study the ecological implications (regarding known environmental effects) of carbon based nano materials are analysed using Life Cycle Assessment (LCA). Major attention is paid to efficiency gains of nano particle production due to scaling up of such processes from laboratory to industrial production scales. Furthermore, a developed approach will be displayed, how to assess the environmental impact of nano materials on an automotive system level over the whole life cycle.
F. Markoulidis, C. Lei, C. Lekakou, E. Figgemeier, D. Duff, S. Khalil, B. Martorana, I. Cannavaro (2012). High-performance Supercapacitor cells with Activated Carbon/MWNT nanocomposite electrodes
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The purpose of this work was to investigate and improve the performance of supercapacitor cells with carbon-based nanocomposite electrodes. The electrode structure comprised activated carbon (AC), four types of multi-wall nanotubes (MWNTs) and two alternative polymer binders, Polyvinyl alcohol (PVA) or Polyvinylidene fluoride (PVDF). Electrode fabrication involved various stages of mixing and dispersion of the AC powder and carbon nanotubes, rolling and coating of the AC/MWNT/binder paste on an aluminium substrate which also served as current collector. The organic electrolyte utilised was 1M tetraethylammonium tetrafluoroborate (TEABF4) fully dissolved in propylene carbonate (PC). All devices were of the electrochemical double layer capacitor (EDLC) type, incorporating four layers of tissue paper as separator material. The surface topography of the so fabricated electrodes was investigated with scanning electrode microscopy (SEM). Overall cell performance was evaluated with a multi-channel potentiostat/galvanostat/impedance analyser. Each supercapacitor cell was subjected to Cyclic Voltammetry (CV) at various scan rates from 0.01 V/s to 1 V/s, Charge-Discharge at a fixed current steps (2 mA) and Electrochemical Impedance Spectroscopy (EIS) with frequency range from 10 mHz to 1 MHz. It was established that an AC-based supercapacitor with 0.15%w/w MWNT content and 30 μm roll-coated, nanocomposite electrodes provided superior energy and power and energy densities while the cells was immersed in the electrolyte; well above those generated by the AC-based EDLC cells.
C. Lekakou, F. Markoulidis, C. Lei, A. Sorniotti (2012). Nanomaterials and Nanocomposites for High Energy/High Power Supercapacitors
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This study includes nanomaterials and nanocomposites for the fabrication of supercapacitor cells aiming at both high power and high energy densities. Activated carbon powder, multi-wall carbon nanotubes and graphene are considered as electrode materials. Electrochemical double layer supercapacitor cells (EDLCs) have been fabricated and tested to a maximum voltage of 3 V, where TEABF4 solution has been used as the organic electrolyte. The supercapacitors are proposed for applications of personal electronics, EV and HEV, and displays, depending on their maximum frequency of operation.
E. C. Vermisoglou, D. Petridis, G. Pilatos, G. E. Romanos, V. Likodimos, C. Lei, F. Markoulidis, C. Lekakou, C. Trapalis (2012). Iron carbide–graphene hybrid nanostructures
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A European Conference/Workshop on the Synthesis, Characterization and Apllications of Graphene (GrapHEL). Mykonos, Greece
N. Todorova, E. C. Vermisoglou, T. Giannakopoulou, C. Lei, F. Markoulidis, C. Lekakou, C. Trapalis (2012). Simultaneous photoreduction and silver decoration of graphitic materials
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A European Conference/Workshop on the Synthesis, Characterization and Apllications of Graphene (GrapHEL). Mykonos, Greece
F. Markoulidis, C. Lei, C. Lekakou, A. Sorniotti, B. Martorana, I. Cannavaro (2013). Improving the Performance of Supercapacitors with Activated Carbon/Multiwall Carbon Nanotube Electrodes
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Recent developments in nanomaterials have enabled improvements in supercapacitor performance by incorporating porous electrodes with high specific surface area (SSA). The investigated supercapacitors featured carbonaceous electrodes with activated carbon (AC), multi-wall nanotubes (MWNTs) and two polymer binder options. The electrode fabrication process involved various stages of mixing and dispersion of the nanotubes and then rolling and coating of the AC/MWNT/binder slurry on two different substrates, which served as current collector. Tetraethylammonium tetrafluoroborate (TEABF4) was used as electrolyte, fully dissolved in acetonitrile (AN). All supercapacitors incorporated a cellulose-based separator film between both carbonaceous electrodes. The surface topography of the so fabricated electrodes was investigated with scanning electrode microscopy (SEM). The generated micrographs led to conclusions about sample preparation improvement, material selection and specimen quality. The overall cell performance was evaluated with a multi-channel, electrochemical analyser. Each supercapacitor was subjected to electrochemical impedance spectroscopy (EIS) with frequency range from 10 mHz to 1 MHz, cyclic voltammetry (CV) at various scan rates (0.01 – 1 V s-1) and Galvanostatic Charge-discharge (GCD) from 0 to 3 V, at various current densities (2 - 100 mA). Ragone plots based on GCD data were derived. The addition of MWNTs improved the supercapacitor performance, compared to plain AC-based cells (for both current collector options). Moreover, the utilisation of conductive PVDF binder and aluminium carbide (Al4C3) nano-whisker foil, also provided additional improvements in performance.
C. Lei, F. Markoulidis, Z. Ashitaka, C. Lekakou (2013). Reduction of porous carbon/Al contact resistance for an electric double-layer capacitor (EDLC)
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Carbonaceous materials are commonly used to fabricate electrodes for electric double-layer capacitors (EDLCs) or supercapacitors. The high contact resistance between the carbon active layer and the Al current collector can decrease capacitor energy and power performance, and shorten the lifetime of the capacitor. In this report, the sources of carbon based EDLC internal resistance were explored using electrochemical impedance spectroscopy (EIS). An equivalent circuit model was coupled with the EIS data for the analyses. The EDLC cells were made from symmetric carbon/Al electrodes and operated in organic electrolyte. The analysis results showed the effects of pressure and modified Al on the contact resistance, where a novel, carbon modified Al collector with Al4C3 nano whiskers greatly reduced the contact resistance. Finally the effect of scale-up on the internal resistance was discussed.
C. Lei, N. Amini, F. Markoulidis, P. Wilson, S. R. Tennison, C. Lekakou (2013). Activated carbon from phenolic resin with controlled mesoporosity for an electric double-layer capacitor (EDLC)
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Activated carbon materials are prepared from phenolic resin precursors by physical activation to fabricate electrodes for electric double-layer capacitors (EDLCs). Pore size and surface area of the carbon materials are controlled during the synthesizing process and after the carbonization through activation in a CO2 atmosphere to different levels of burn-off. The resultant carbon materials were evaluated as EDLC electrodes, using electrochemical impedance spectroscopy (EIS) and galvanostatic charge–discharge (GCD) measurements with the organic electrolyte of spiro-(1,1′)-bipyrrolidinium tetrafluoroborate in propylene carbonate, SBPBF4/PC. The results of the study showed that the capacitance of carbon materials, as well as energy density of the EDLC cells, increased by increasing the level of burn-off (activation). The 46% activated carbon gave a capacitance of 160 F g−1 and an energy density of 35 W h kg−1, at a current density of 1 mA cm−2. The long term cycling tests showed high cycling stability of these carbon materials.
F. Markoulidis, C. Lei, C. Lekakou (2013). Fabrication of high-performance supercapacitors based on transversely oriented carbon nanotube
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High-performance supercapacitors with organic electrolyte 1 M TEABF4 (tetraethyl ammonium tetrafluoroborate) in PC (propylene carbonate) were fabricated and tested, based on multiwall carbon nanotubes (MWNTs) deposited by electrophoresis on three types of alternative substrates: aluminium foil, ITO (indium tin oxide) coated PET (polyethylene terephthalate) film and PET film. In all cases, SEM (scanning electron microscopy) and STEM (scanning transmission electron microscopy) micrographs demonstrated that protruding, transversely oriented MWNT structures were formed, which should increase the transverse conductivity of these MWNT electrodes. The best supercapacitor cell of MWNT electrodes deposited on aluminium foil displayed good transverse orientation of the MWNT structures as well as an in-plane MWNT network at the feet of the protruding structures, which ensured good in-plane conductivity. Capacitor cells with MWNT electrodes deposited either on ITO-coated PET film or on PET film demonstrated lower but still very good performance due to the high density of transversely oriented MWNT structures (good transverse conductivity) but some in-plane inhomogeneities. Capacitor cells with drop-printed MWNTs on aluminium foil, without any transverse orientation, had 16–30 times lower specific capacitance and 5–40 times lower power density than the capacitor cells with the electrophoretically deposited MWNT electrodes.
C. Lekakou, F. Markoulidis (2013). Development of high Energy/high Power Density Supercapacitors for Automotive Applications
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Supercapacitors are essential in electric vehicles for supplying power during acceleration and recovering braking energy. High power and sufficient energy density are required for both an effective power system but also to reduce weight. We are aiming at developing supercapacitors of both high power and high energy density at affordable levels by the automotive industry, and of higher sustainability than many current electrochemical storage devices.
C. Trapalis, E. C. Vermisoglou, N. Todorova, T. Giannakopoulou, G. E. Romanos, F. Markoulidis, C. Lei, C. Lekakou (2013). Graphene-based Materials for Supercapacitor Applications
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High quality graphene sheets with superior physical properties such as large surface area and high electrical conductivity allowed the development of new engineered carbons for energy storage devices. Towards this goal, high surface area graphene oxide materials were prepared using various pristine graphite and oxidation methods. Natural graphite with different sizes and microwave expanded graphite were oxidized using modified Staudemayer or Hammers methods. The resulting graphite oxide paper was exfoliated and reduced via microwave treatment leading to few layers graphene/graphene oxide nanostructures (EGO). Impregnation in KOH and high temperature treatment in vacuum was also applied to increase the porosity and diminish the oxygen content in the final materials (t-EGO). The obtained materials were further processed to create metal and metal oxide/graphene heterostructures [1, 2]. Graphene-based materials were either decorated with silver (Ag) nanoparticles or intercalated with iron carbide (Fe3C) nanostructures. The structural, morphological and electrical properties of the bare and composite graphitic materials were investigated. The XRD and TEM analysis confirmed the oxidation of graphite and further exfoliation to few layers graphene, respectively. It was also established that the oxidation route and especially the type of the pristine graphite (flake size, pretreatment) influence significantly the level of oxidation, the specific surface area and the electrical properties of the produced graphene. Liquid N2 adsorption-desorption isotherms demonstrated that small flakes (100 mesh) natural graphite and expanded graphite resulted in large specific surface area (>900 m2/g up to ~2400 m2/g) of the prepared EGO. The use of larger flakes (10 mesh) natural graphite led to lower BET surface but higher capacitance (~629 F/g) assessed by CV measurements. The Raman results revealed that KOH acted more as a reducing agent diminishing the defects than as surface modifier for high porosity. It was also established that the decoration of EGO and t-EGO with Ag nanoparticles (~40 nm) trough photo-deposition decreased the structural defects of the graphene. However, the procedure did not improve the capacitance of the resulting materials. The activated t-EGO/Ag composite exhibited supercapacitor’s behavior with lower capacitance than the bare graphene, while the non-activated EGO/Ag acted as a resistant. The outcome was related with the deposition of Ag not between but onto the surface and the edges of the graphene layers and the decrease of the materials porosity. In the case of graphene oxide/Fe3C hybrids it was established that the immobilization of Fe-based intercalant (IFe) was governed by the pH of the aqueous graphite oxide dispersion following nucleophilic substitution or ion exchange path. Subsequent thermal annealing resulted in formation of pillaring Fe3C nanoparticles encapsulated in a graphite shell. It is suggested that the graphite shell prevent the aggregation between both adjacent Fe3C nanoparticles, and bundles of neighboring multi-layer graphenes. The exhibited properties of the obtained hybrid materials make them appropriate for magnetic and supercapacitor applications. These materials have also the advantage of being low cost, low toxicity and environmentally friendly.
H. Dura, J. Perry, C. Lekakou, F. Markoulidis, S. Khalil, M. Decker, M. Weil (2013). Cost Analysis of Supercapacitor Cell Production
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A life cycle costing (LCC) is to be performed complementary to the ongoing research on an enhanced supercapacitor pouch cell, in order to provide additional decision support on the best cell chemistry from the economic point of view. Due to the early stage of the project so far merely the production phase is considered. The detailed cost calculation method was chosen and complemented with a scale up using dimension analysis and analogy analysis, in order to be able to utilize this method since available data is either scarce or refers to laboratory scale. It was found that the researched cells are within the lower margin of costs reported in literature. Also the relative contribution of material and production costs as well as energy consumption was in the same range as stated in literature. Although these comparisons should be handled with care as they do not always refer to the exact same item. Further, we concluded that the developed approach provides a sound basis for a reproducible calculation of production costs for technologies at an early research stage.
F. Markoulidis (2013). Multiwall Carbon Nanotubes in Supercapacitor Electrodes
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Multiwall carbon nanotubes (MWNTs) were added in coatings based on activated carbon powder from natural sources and a polymer binder, such as PVDF. Coatings with AC carbon powder derived from natural sources and 5 wt% PVDF reached a powder density of 18 kW/kg and an energy density of 18 Wh/kg. MWNTs were added at different concentrations in coating manufactured by the doctor blade coating technique. Very low MWNT concentrations raised both powder and energy density performance of the EDLC cells to a maximum tested 40 kW/kg and 27 Wh/kg, respectively. Work continues using different electrode manufacture methods, such as spraying. There are different issues associated with the spraying of coating: we were able to spray 95 wt% MWNT coating but generally at low areal loading below 1 mg/cm2, whereas areal loadings around 4 mg/cm2 were achieved with > 70 wt% AC, 5 wt% PVDF and the rest MWNTs. ELDC supercapacitor cells achieved a maximum tested energy density of 36 Wh/kg and a maximum tested power density of 40 kW/kg (the cells were not tested at higher powers, although it might have been possible to exceed 40 kW/kg).
M. Weil, H. Dura, B. Simon, M. J. Baumann, B. M. Zimmermann, S. Zimmann, C. Lei, F. Markoulidis, C. Lekakou, M. Decker (2013). Ecological Assessment of Nano Materials for the Production of Electrostatic/Electrochemical Energy Storage Systems
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Electrochemical double layer capacitors, also known as supercapacitors are considered as a promising option for stationary or mobile electric energy storage. At present lithium ion and nickel metal hydride batteries are used for automotive applications. In comparison to this type of batteries supercapacitors possess a high specific power, but a relatively low specific energy. Therefore, the goal of ongoing research is to develop a new generation of supercapacitors with high specific power and high specific energy. To reach this development goal particularly nano materials are under investigation on cell level. In the presented study the ecological implications (regarding known environmental effects) of carbon based nano materials are analysed using Life Cycle Assessment (LCA). Major attention is paid to efficiency gains of nano material production due to scaling up of such processes from laboratory to industrial production scales. Furthermore, a developed approach will be displayed, how to assess the environmental impact of nano materials on an automotive system level over the whole life cycle.
F. Markoulidis, C. Lei, C. Lekakou, D. Duff, S. Khalil, B. Martorana, I. Cannavaro (2014). A method to increase the energy density of supercapacitor cells by the addition of multiwall carbon nanotubes into activated carbon electrodes
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The performance of supercapacitor cells with activated carbon (AC) electrodes was improved by adding a small amount of multiwall carbon nanotubes (MWCNTs). The electrode structure investigated comprised AC, four different types of MWCNTs and two polymer binders, polyvinylidene fluoride or polyvinyl alcohol. All fabricated devices were of the electrochemical double layer capacitor type. The organic electrolyte used was tetraethyl ammonium tetrafluoroborate (TEABF4) in two different solvents: propylene carbonate or acetonitrile (AN). The electrodes were characterised with scanning electron microscopy and tested for their specific surface area and pore size distribution. The electrode fabrication process was fine-tuned by investigating the effect of the coating thickness on the supercapacitor cell performance. It was established that an AC/MWCNT-based supercapacitor with 30 μm thick roll-coated, composite electrodes of just 0.15%w/w MWCNT content provided superior tested power and energy densities of 38 kW/kg and 28 W h/kg, respectively, compared to 18 kW/kg and 17 W h/kg for AC only–based cells in a 1.5 TEABF4/AN electrolyte. The increased energy density was attributed to a fine lace of MWCNTs covering the AC microparticles with visible 20–30 nm lace pores and to the high specific area of micropores.
F. Markoulidis, C. Lei, P. Wilson, C. Lekakou, A. Sorniotti (2014). Electrode Fabrication and Manufacturing of high Energy Density/high Power Density Supercapacitors
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Supercapacitors are essential in electric vehicles for supplying power during acceleration and recovering braking energy. High power and sufficient energy density are required for both an effective power system but also to reduce weight. Supercapacitors of the symmetric, electrochemical double layer capacitor (EDLC) type are presented for automotive, grid, electrical, electronic and optoelectronic applications. The emphasis in our research is to increase not only power density but also energy density for these supercapacitors. Two types of porous electrode materials have been investigated: activated carbon (AC) fabrics and coatings.
F. Markoulidis (2014). Materials and Processing Techniques for the Fabrication of Supercapacitors for Automotive Applications
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This thesis investigated materials and processing techniques for the fabrication of supercapacitors utilised in automotive applications, which required energy densities higher than 10 Wh kg-1, cell efficiencies rated at 95% and power densities higher than 10 kW kg-1. In addition, there was particular interest in relevant material properties at the nanometre level, their micro-structure, as well as their impact in different combinations, on the electrochemical (EC) performance of prospective supercapacitor cells. The literature survey covered first principles to current theories and research in the field of materials for electric double-layer capacitors (EDLCs). Simulations of the relation between electrode pore size and electrolyte ion size, coupled with predictions for capacitance were also completed, highlighting the role of micro-pores (< 2 nm) in maximising capacitance. Experimental analysis included electrochemical impedance spectroscopy (EIS) at frequencies ranging from 10 mHz and up to 1 MHz. Cyclic voltammetry was carried out at scan rates between 0.01 and 1 V s-1, while galvanostatic charge-discharge (GCD) was completed at current densities ranging from 1 up to 150 mA cm-2. Powder and coating characterisation included BET/BJH analysis via nitrogen adsorption determining the surface area and pore size distribution, respectively. Microscopy techniques investigated the micro-structure of different types of carbonaceous electrodes. Two major types of EDLCs were fabricated: AC fabric-based (ACF) and AC coating-based cells. Phenolic-derived ACF-based electrodes with a BET surface area of 2,000 m2 g-1 and combined with 1.5M tetraethylammonium tetrafluoroborate (TEABF4) dissolved in acetonitrile (AN) as electrolyte, yielded cells with about 140 F g-1 of specific capacitance, 42 Wh kg-1 of energy density, 11 kW kg-1 of power density, about 0.5 Ω οf internal resistance and 95% of energy efficiency. Phenolic-derived AC coatings, with powder BET surface area of about 1,200 m2 g-1, as well as 0.15 wt% additions of MWNTs and 5 wt% polyvinylidene fluoride (PVDF) binder, provided optimum cell performance. The same coatings, when incorporated in an ELDC with 1.5M spiro-(1,1′)-bipyrrolidinium tetrafluoroborate (SBPBF4) salt dissolved in AN as electrolyte, 0% R.H., aluminium carbide-based Al foil current collectors and cellulose paper separator, achieved maximum specific electrode capacitance of 105 F g-1, energy density of 30 Wh kg-1, power density of about 37 kW kg-1, internal resistance of 0.8 Ω and energy efficiency of 94%. Lab-scale results showed than the three main thesis goals were met. Pilot-level cell fabrication and predictions indicated that stacking thirty devices in-parallel would in fact meet the required automotive application target.
C. Lekakou, B. Lindsey, G. Rebord, P. Wilson, O. Moudam, F. Markoulidis, T. Andrews, J. F. Watts, G. Reed (2015). Processing of conductive polymers & nanocomposites and fabrication of devices with conductive, transparent, optoelectronic, energy harvesting, energy storage and electromechanical functionalities
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Overview of research activities and project outcomes at the 9th annual and final conference of the Innovative electronics Manufacturing Research Centre at Sir Denis Rooke, Holywell Park, Loughborough University.
C. Lekakou, A. Sorniotti, C. Lei, F. Markoulidis, P. C. Wilson, A. Santucci, S. R. Tennison, N. Amini, C. Trapalis, G. Carotenuto, S. Khalil, B. Martorana, I. Cannavaro, M. Gosso, J. Perry, C. Hoy, M. Weil, H. Dura, F. Viotto (2015). AUTOSUPERCAP: Development of High Energy and High Power Density Supercapacitor Cells
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The study focuses on the materials and small supercapacitor cells manufactured in the first period of AUTOSUPERCAP project. The supercapacitor cells presented in this paper are of the type of symmetrical, electrochemical double layer capacitor (EDLC) cells with organic electrolyte TEABF4 dissolved in propylene carbonate (PC) or acetonitrile (AN). Different active electrode materials have been investigated, including novel activated carbon, graphene and carbon nanotubes produced in this project, as well as combinations of these materials. Supercapacitor cells of 2–4 cm2 area were fabricated and tested in impedance spectroscopy, cyclic voltammetry and charge-discharge tests. Ragone plots of energy density against power density were constructed from the charge-discharge test data at different current densities. Furthermore, the results of a cost analysis are presented for the main types of supercapacitors investigated.
H. Dura, B. M. Zimmermann, M. Decker, C. Lekakou, F. Markoulidis, C. Lei, P. Wilson, R. Fields, J. Perry, B. Martorana, M. Weil (2015). Life Cycle Costing of a supercapacitor for automotive application, in early development stage
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Supercapacitors are one of the most promising energy storage systems, particularly in automotive applications. The EU Project AutoSupercap aimed at developing the next generation supercapacitor with enhanced power and energy performance, while reducing weight and costs. A life cycle costing was performed complementary to the development to provide additional decision support to technology developers from an economic viewpoint. As the use and end of life phases of supercapacitors are still very uncertain, the cost assessment focused on the production phase.
C. Lei, F. Markoulidis, P. Wilson, C. Lekakou (2015). Phenolic carbon cloth-based electric double-layer capacitors with conductive interlayers and graphene coating
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Phenolic resin-derived activated carbon (AC) cloths are used as electrodes for large-scale electric double-layer capacitors or supercapacitors. To increase the energy and power density of the supercapacitor, the contact resistance between the carbon cloth and the aluminium foil current collector is reduced by modifying the Al current collectors. Different modified Al current collectors, including Toyal-Carbo®(surface-modified Al), DAG® (deflocculated Acheson™ graphite) coating and poly(3,4-ethylenedioxythiophene) (PEDOT) coating, have been tested and compared. The use of modified Al current collectors are shown to greatly reduce the contact resistance between the AC cloth and the Al foil. Another solution investigated in this study is to coat AC cloth with graphene through electrophoretic deposition (EPD). The graphene coated AC cloth is shown increased the capacitance and greatly reduced internal resistance.
R. Fields, C. Lei, F. Markoulidis, C. Lekakou (2016). The Composite Supercapacitor
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Inspired by the design of composite materials, we propose a new composite supercapacitor that comprises an integrated cell with high‐power‐ and high‐energy‐related electrode materials. The composite electrochemical double‐layer capacitor (EDLC) is the equivalent circuit of a high‐power EDLC of power P1 and energy E1 and a high‐energy EDLC of power P2 and energy E2 connected in parallel. A methodology is proposed and validated in this study for the design of an application‐specific composite supercapacitor of power P and energy E with P1/E1>P/E>P2/E2. The methodology was tested successfully in medium‐ and large‐sized application‐specific composite supercapacitors, which were fabricated in the form of pouch cells using an organic electrolyte. The application‐specific composite supercapacitors offered weight reductions of 40–60 % compared with supercapacitors based on the high‐power‐ or on high‐energy‐related electrode materials only.
M. De Marco, F. Markoulidis, R. Menzel, S. Bawaked, M. Mokhtar, S. Al-Thabaiti, S. N. Basahel, M. S. P. Shaffer (2016). Cross-linked single-walled carbon nanotube aerogel electrodes: Via reductive coupling chemistry
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Single-walled carbon nanotube (SWCNT) anions can be cross-linked by a dielectrophile to form covalent, carbon-bonded organogels. Freeze-drying produces cryogels with low density (2.3 mg cm−3), high surface area (766 m2 g−1), and high conductivity (9.4 S m−1), showing promise as supercapacitor electrodes. Counterion concentration controls debundling, grafting ratio, as well as all the resulting properties.
E. G. Tunon, V. G. Rocha, E. Feilden, E. D'Elia, F. Markoulidis, M. S. P. Shaffer, E. Saiz (2016). 3D printing components for energy storage devices
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As new technologies in key areas such as energy and medicine develop, the demand for state-of-the art fabrication to create complex multifunctional devices also grows. An emerging group of techniques known as Additive Manufacturing (AM) are based on making a 3D solid object of virtually any shape from a digital model. An ‘addition process’, where objects are usually built layer-by-layer following a computer design. The freedom of creating completely new designs is what makes AM technologies - for some considered the next industrial revolution - so attractive. However, the challenge of making this prediction a reality demands a major effort in material development, since the commercial applications in AM are now mostly limited to a number of metals and polymers. On the other hand graphene - with its two dimensional structure and unique combination of properties - is the ‘wonder’ material with promising applications. But to actually exploit all the advantages of this fascinating material, it is necessary to develop manufacturing routes to create graphene 3D components and integrate them into practical devices while preserving its multi-functionalities at the macro scale. We have developed ink formulations for AM using responsive building blocks approaches. These formulations are water based, flexible and easily scalable up. They allow us to design 3D-inks for different materials, from ceramics and metals to chemically modified graphene, enabling the printing of multi material devices. I will present the processing approach, the rheological behavior of our inks to satisfy the demands for direct ink writing, the printing and characterization of different structures as well as introducing a proof of concept of graphene based devices for supercapacitors.
R. Woodward, F. Markoulidis, D. W. H. Fam, T. O. Mcdonald, F. De Luca, M. S. P. Shaffer, A. Bismarck (2016). Carbon Foams from Polyhipe/Reduced Graphene Oxide Composites and Their Performance As Electrodes in Supercapacitor Devices
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Carbon foams were produced from composites of macroporous poly(divinylbenzene) (poly(DVB) and reduced graphene oxide (rGO). Poly(DVB) was synthesized by polymerizing the continuous phase of water-in-oil high internal phase emulsions (HIPEs) stabilized at the interface by amphiphilic rGO, employed as a particulate emulsifier. The use of rGO as an emulsifier allows for the synthesis of stable macroporous composites of poly(DVB)HIPEs with a percolating network of rGO at the surface of the material. Both permeable and non-permeable carbon foams, or ‘carboHIPEs’, could be prepared by carbonization of these macroporous composites at 800 °C. The resulting carboHIPEs gave yields as high as 26 wt.% of the original material. Furthermore, carboHIPEs retain the pore structure of their macroporous precursor, while also producing a newly-formed microporous structure, leading to hierarchical porosity and huge increases in surface area upon carbonization. Surface areas of up to 1800 m2/g and excellent electrical conductivities of up to 270 S/m are achievable, among the highest reported within the fields of both polyHIPEs and carboHIPEs. Using an rGO emulsifier when creating these structures allows for the production of true ‘all-carbon’ foams upon carbonization. These polyHIPE composites do not require modification, such as additional crosslinking, prior to carbonization, due to the inherently crosslinked structure of poly(DVB). It is demonstrated that the rGO derived carboHIPEs are good candidates as electrodes in supercapacitor applications such as electrical double-layer capacitor (EDLC) devices, where carboHIPEs derived from more conventional silica-stabilized HIPEs perform poorly. The use of a pourable, aqueous emulsion-template enables simple moulding, minimizes waste and avoids the strong acid treatments used to remove many conventional solid-templates. The capability of producing monolithic, porous carbon foams allows for the production of binderless devices, potentially simplifying the production process of supercapacitors. Devices demonstrated maximum specific electrode capacitance to the tune of 26 F g-1 at 10 mV s-1, 5.2 Wh kg-1 of energy density, 280 W kg-1 of power density and coulombic efficiency of up to 99.6 %. In short, the carbonization of rGO-poly(DVB)HIPE composites enables the production of hierarchically porous carboHIPEs, suitable for a wide range of applications as sorbents and electrodes.
V. G. Rocha, E. G. Tunon, C. Botas, F. Markoulidis, E. Feilden, E. D'Elia, N. Ni, M. S. P. Shaffer, E. Saiz (2017). Multimaterial 3D Printing of Graphene-Based Electrodes for Electrochemical Energy Storage Using Thermoresponsive Inks
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The current lifestyles, increasing population and limited resources result in energy research being at the forefront of worldwide grand challenges, increasing the demand for sustainable and more efficient energy devices. In this context, Additive Manufacturing brings the possibility of making electrodes and electrical energy storage (EES) devices in any desired 3D shape and dimensions, while preserving the multifunctional properties of the active materials in terms of surface area and conductivity. This paves the way to optimized and more efficient designs for energy devices. Here we describe how three-dimensional (3D) printing will allow the fabrication of bespoke devices - with complex geometries, tailored to fit specific requirements and applications - by designing water-based thermo-responsive inks to 3D-print different materials in one step. For example, printing the active material precursor (Chemically Modified Graphene, rCMG) and the current collector (copper) for supercapacitors or anodes for Lithium-ion batteries (LIBs). The formulation of thermo responsive inks using Pluronic F127 provides an aqueous-based, robust, flexible and easy scalable-up approach. The devices are designed to provide low resistance interface, enhanced electrical properties, mechanical performance, packing of rCMG and low active material density while facilitating the post-processing of the multicomponent 3D printed structures. The electrode materials are selected to match post-processing conditions. The reduction of the active material (rCMG) and sintering of the current collector (Cu) take place simultaneously. The electrochemical performance of the rCMG-based self-standing binder-free electrode and the two-materials rCMG/Cu printed prove the potential of multi-material printing in energy applications.
F. Markoulidis, C. Lei, C. Lekakou (2017). Investigations of Activated Carbon Fabric-Based Supercapacitors with Different Interlayers Via Experiments and Modelling of Electrochemical Processes of Different Timescales
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This study includes a novel approach of applying an equivalent electric circuit model of two resistors and three constant phase elements (CPEs) to the galvanostatic charge-discharge of supercapacitors which provides virtual monitoring of the electrochemical processes taking place in parallel at different timescales and offers remarkable insights into the coexistence composition and cascade of such processes during the charge-discharge of cells at different current densities. This modelling method has been applied to analyse the performance of high energy density supercapacitors based on a microporous, phenolic-derived, activated carbon fabric (ACF) with different interlayers with the current collector (CC). Associated experimental studies deal with the challenge of overcoming the high contact resistance between the ACF and the current collector (CC) by employing innovative interlayers containing conductive features or structures to fill or bridge the interface gaps between the ACF fibers and the CC foil and the pores of the activated carbon (AC) fiber surface. Such interlayers involve tree-like microstructures of carbon black nanoparticles or deflocculated graphite platelets or multiwall carbon nanotubes (MWCNTs) deposited electrophoretically on the aluminium foil and the ACF. The use of PEDOT:PSS binder in such interlayer raises performance to maximum 44 Wh/kg and 9 kW/kg for electrolyte 1.5 M TEABF4/AN. These are further raised by 17% and 13%, respectively, using electrolyte 1.5 M SBPBF4/AN, and by 19% (both) using a thin polyolefinic separator against the thicker, cellulose-based separator.
R. Woodward, F. Markoulidis, F. De Luca, D. V. Anthony, D. Malko, T. O. Mcdonald, M. S. P. Shaffer, A. Bismarck (2018). Carbon foams from emulsion-templated reduced graphene oxide polymer composites: Electrodes for supercapacitor devices
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Amphiphilic reduced graphene oxide (rGO) is an efficient emulsifier for water-in-divinylbenzene (DVB) high internal phase emulsions. The polymerisation of the continuous DVB phase of the emulsion template and removal of water results in macroporous poly(divinylbenzene) (polyDVB). Subsequent pyrolysis of the poly(DVB) macroporous polymers yields ‘all-carbon’ foams containing micropores alongside emulsion templated-macropores, resulting in hierarchical porosity. The synthesis of carbon foams, or ‘carboHIPEs’, from poly(DVB) produced by polymerisation of rGO stabilised HIPEs provides both exceptionally high surface areas (up to 1820 m2/g) and excellent electrical conductivities (up to 285 S/m), competing with the highest figures reported for carboHIPEs. The use of a 2D carbon emulsifier results in the elimination of post-carbonisation treatments to remove standard inorganic particulate emulsifiers, such as silica particles. It is demonstrated that rGO containing carboHIPEs are good candidates for supercapacitor electrodes where carboHIPEs derived from more conventional polymerised silica-stabilised HIPEs perform poorly. Supercapacitor devices featured a room-temperature ionic liquid electrolyte and electrodes derived from either rGO- or silica-containing poly(DVB)HIPEs and demonstrated a maximum specific capacitance of 26 F g-1, an energy density of 5.2 Wh kg-1 and a power density of 280 W kg-1.
F. Markoulidis (2018). The Challenges of Lithium-Sulfur Battery Development
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This presentation outlines the R&D Impetus, desired metrics and challenges in developing Li-S batteries. We explain the key features of the Li-S chemistry, also focusing on batteries with Li2S cathodes and underlining the related, real-wold complexities. Problems in realising applications are listed together with a focus on Li-S battery self-discharge. The lithium polysulfide (LiPS) shuttle effect is explained together with methodologies in limiting said LiPS shuttling. Development strategies are openly proposed, outlining challenges ahead.
F. Markoulidis (2018). Validation, Qualification and the GMP Laboratory
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A brief overview of Validation, Qualification and their relevance, role in the GMP laboratory.
F. Markoulidis (2018). Manufacturing high-quality Battery slurries and Electrodes: Challenges in Scaling-up
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This presentation addressed processing aspects of battery manufacturing as well as the big picture in the field. Slurry processing as per a ‘standard route’ (planetary/vacuum mixing with optional homogeniser) was evaluated. Further analysis was carried out on an ‘enhanced route’ via conventional methodology plus commercial, pre-dispersed carbon/PVdF dispersions, as well as a ‘sufficiently prudent route for R&D’, the use of a THINKY mixer/degasser or equivalents. Further comments were made on scale-up as well as incorporating Quality by Design aspects in the Battery processing industry. Finally, coating challenges were briefly outlined.
F. Markoulidis, N. Todorova, R. Grilli, C. Lekakou, C. Trapalis (2019). Composite Electrodes of Activated Carbon and Multiwall Carbon Nanotubes Decorated with Silver Nanoparticles for High Power Energy Storage
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Composite materials in electrodes for energy storage devices can combine different materials of high energy density, in terms of high specific surface area and pseudocapacitance, with materials of high power density, in terms of high electrical conductivity and features lowering the contact resistance between electrode and current collector. The present study investigates composite coatings as electrodes for supercapacitors with organic electrolyte 1.5 M TEABF4 in acetonitrile. The composite coatings contain high surface area activated carbon (AC) with only 0.15 wt% multiwall carbon nanotubes (MWCNTs) which, dispersed to their percolation limit, offer high conductivity. The focus of the investigations is on the decoration of MWCNTs with silver nanoparticles, where smaller Ag crystallites of 16.7 nm grew on carboxylic group-functionalized MWCNTs, MWCNT–COOH, against 27–32 nm Ag crystallites grown on unfunctionalized MWCNTs. All Ag-decorated MWCNTs eliminate the contact resistance between the composite electrode and the current collector that exists when undecorated MWCNTs are used in the composite electrodes. Ag-decorated MWCNT–COOH tripled the power density and Ag-decorated MWCNT additive doubled the power density and increased the maximum energy density by 6%, due to pseudocapacitance of Ag, compared to composite electrodes with undecorated MWCNTs.
J. Bates, C. Lekakou, Q. Cai, F. Markoulidis, R. Slade, G. Hinds (2019). Modelling and Simulations of Energy Storage Devices
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In electrochemistry, numerical models are used to predict the activity of energy storage devices such as batteries and supercapacitors. Novel battery technologies, such as lithium-sulphur batteries, benefit from simulation studies in optimising their materials, and more specifically in this study, their porous cathodes. Porous carbon is typically used as the electrode in different supercapacitor configurations, as well as the cathode structural material in Li-S batteries. Previous models in the literature simulate the porous electrodes with a single uniform pore size. In this project a novel model has been devised, incorporating multiple pore sizes of the electrode material, determined from a pore size distribution.
F. Markoulidis, J. Bates, C. Lekakou, R. Slade, G. M. Laudone (2020). Supercapacitors with lithium-ion electrolyte: An experimental study and design of the activated carbon electrodes via modelling and simulations
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Electrochemical double layer capacitors (EDLCs) are investigated with activated carbon electrodes and a lithium-ion electrolyte, in anticipation of potential future applications in hybridised battery-supercapacitor devices and lithium ion capacitors. An experimental study of a symmetric electrochemical double layer capacitor (EDLC) with activated carbon (AC) electrodes on aluminium foil current collectors and electrolyte 1 M LiPF6 in EC:EMC 50:50 v/v concludes a stability window to a maximum potential of 3 V, an equivalent in series resistance of 48 Ω for 1 cm² cell area (including the contact resistance between electrode and current collector) and an average specific electrode capacitance of 50.5 F g⁻¹. Three AC electrode materials are assessed via computer simulations based on a continuum ion and charge transport model with volume-averaged equations, considering the pore size distribution for each electrode material and, depending on pore size, transport of tetrahedral solvated or flat solvated Li⁺ ions and solvated or desolvated PF6⁻ ions. The computer simulations demonstrate that the best electrode material is an AC coating electrode with a hierarchical pore size distribution measured in the range of 0.5–180 nm and bimodal shape, and specific surface area BET = 808 m² g⁻¹.
C. Lekakou, J. P. Baboo, F. Markoulidis, R. C. T. Slade (2019). Increasing Energy Density and Power Density in Hybridised Supercapacitor-Battery Devices
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The first stage of our study is focused on demonstrating homogeneous and deep sulphur impregnation of porous carbonaceous material to create cathodes with more than 50 wt% sulphur in a supercapacitor-type, porous, host matrix. Repeated discharges are carried out after which we have achieved the theoretical specific capacity of sulphur at first discharge (cumulative curve in Figure 1). We shall continue with parametric studies to investigate the effect of different amounts of sulphur in the composite cathode on the pore size distribution and discharge capacity. The second part of this study includes the investigations into lithium battery-supercapacitor cells hybridised at electrode material level, in combinations of parallel and in series material parts in equivalent circuit models. The effect of the supercapacitor porous carbonaceous electrode materials on the voltage of the cell in galvanostatic charge-discharge curves will be presented in experimental investigations for half-cells of both sides and full cells. Some novel cell architectures will be presented aiming at minimising any detrimental reactions in the supercapacitor materials within the battery cell window.
F. Markoulidis, P. Wilson, C. Lei, C. Lekakou (2014). Inkjet printed carbon-nanotube containing polymer-based photovoltaic cells
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11th International Conference on Nanosciences & Nanotechnologies NN14