31 results found
© 2018 We present an all-fiber flexible supercapacitor with composite nanofiber electrodes made via electrospinning and an electrospun separator. With the addition of manganese acetylacetonate (MnACAC) to polyacrylonitrile (PAN) as a precursor for the electrospinning process and subsequent heat treatment, the performance of pure PAN supercapacitors was improved from 90 F g −1 to 200 F g −1 (2.5 mV s −1 ) with possible mass loadings of MnACAC demonstrated as high as 40 wt%. X-ray diffraction measurements showed that after thermal treatment, the MnACAC was converted to MnO, meanwile, the thermal decomposition of MnACAC increased the graphitic degree of the carbonised PAN. Scanning electron microscopy and image processing showed that static electrospinning of pure PAN and PAN-Mn resulted in fiber diameters of 460 nm and 480 nm respectively after carbonisation. Further analysis showed that the fiber orientation exhibited a slight bias which was amplified with the addition of MnACAC. Use of focused ion beam scanning electron microscopy tomography also showed that MnO particles were evenly distributed through the fiber at low MnACAC concentrations, while at a 40 wt% loading the MnO particles were also visible on the surface. Comparison of the electrospun separators showed improved performance relative to a commercial Celgard separator (200 F g −1 vs 141 F g −1 ).
Merla Y, Wu B, Yufit V, et al., 2018, An easy-to-parameterise physics-informed battery model and its application towards lithium-ion battery cell design, diagnosis, and degradation, Journal of Power Sources, Vol: 384, Pages: 66-79, ISSN: 0378-7753
© 2018 Elsevier B.V. Accurate diagnosis of lithium ion battery state-of-health (SOH) is of significant value for many applications, to improve performance, extend life and increase safety. However, in-situ or in-operando diagnosis of SOH often requires robust models. There are many models available however these often require expensive-to-measure ex-situ parameters and/or contain unmeasurable parameters that were fitted/assumed. In this work, we have developed a new empirically parameterised physics-informed equivalent circuit model. Its modular construction and low-cost parametrisation requirements allow end users to parameterise cells quickly and easily. The model is accurate to 19.6 mV for dynamic loads without any global fitting/optimisation, only that of the individual elements. The consequences of various degradation mechanisms are simulated, and the impact of a degraded cell on pack performance is explored, validated by comparison with experiment. Results show that an aged cell in a parallel pack does not have a noticeable effect on the available capacity of other cells in the pack. The model shows that cells perform better when electrodes are more porous towards the separator and have a uniform particle size distribution, validated by comparison with published data. The model is provided with this publication for readers to use.
Trogadas P, Cho JIS, Neville TP, et al., 2018, A lung-inspired approach to scalable and robust fuel cell design, ENERGY & ENVIRONMENTAL SCIENCE, Vol: 11, Pages: 136-143, ISSN: 1754-5692
Chen X, Liu X, Childs P, et al., 2017, A Low Cost Desktop Electrochemical Metal 3D Printer, ADVANCED MATERIALS TECHNOLOGIES, Vol: 2, ISSN: 2365-709X
Gupta G, Wu B, Mylius S, et al., 2017, A systematic study on the use of short circuiting for the improvement of proton exchange membrane fuel cell performance, INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, Vol: 42, Pages: 4320-4327, ISSN: 0360-3199
Liu X, Wu B, Brandon N, et al., 2017, Tough Ionogel-in-Mask Hybrid Gel Electrolytes in Supercapacitors with Durable Pressure and Thermal Tolerances, ENERGY TECHNOLOGY, Vol: 5, Pages: 220-224, ISSN: 2194-4288
Wu B, Myant C, Weider SZ, 2017, The value of additive manufacturing: future opportunities, Briefing paper, 2
The global additive manufacturing (AM) – 3D printing – industr y was valued at $6 billion for 2016, and is predicted to grow to more than $26 billion by 20221. This rapid growth has arisen mainly because of the evolution of AM from primarily a prototyping tool to a useful end-product fabrication method in some high-value manufacturing applications (e.g., in the aerospace, medical device and automotive industries).• AM has the potential to offer many economic, technical and environmental advantages over traditional manufacturing approaches, including decreased production costs and times, the possibility of flexible and bespoke production, as well as a reduction in energy usage and waste. To realise these benefits, however, several barriers – across the entire AM process chain – need to be overcome. For example, improved design software, faster printing technology, increased automation and better industry standards are required.• To realise a more-efficient and more-profitable industr y, ‘game-changing’ AM research breakthroughs are thus required. Involving more researchers – from a wide array of scientific and engineering backgrounds – will be beneficial, as will a closer working relationship between academia and industr y.• The concept of molecular science and engineering2 – melding a deep understanding of molecular science with an engineering mind-set – provides an excellent framework for the ‘cross pollination’ of research ideas. In the pursuit of solving some of the biggest needs in AM, scientists and engineers – from a range of disciplines – can be brought together to communicate and collaborate at all stages of the AM research-to-final-product chain. In this way, costly late-stage changes can be avoided and the route to final, functional end-use products can be rapidly optimised. In addition, a new generation of scientists and engineers can be trained in a transdi
Wu B, Offer G, 2017, Environmental impact of hybrid and electric vehicles, Environmental Impacts of Road Vehicles : Past, Present and Future, Editors: Harrison, Hester, Publisher: Royal Society of Chemistry
Hybrid and electric vehicles play a critical role in reducing global greenhouse gas emissions, with transport estimated to contribute to 14% of the 49 GtCO2eq produced annually. Analysis of only the conversion efficiency of powertrain technologies can be misleading, with pure battery electric and hybrid vehicles reporting average efficiencies of 92% and 35% in comparison with 21% for internal combustion engine vehicles. A fairer comparison would be to consider the well-to-wheel efficiency, which reduces the numbers to 21–67%, 25% and 12%, respectively. The large variation in well-to-wheel efficiency of pure battery electric vehicles highlights the importance of renewable energy generation in order to achieve true environmental benefits. When calculating the energy return on investment of the various technologies based on the current energy generation mix, hybrid vehicles show the greatest environmental benefits, although this would change if electricity was made with high amounts of renewables. In an extreme scenario with heavy coal generation, the CO2eq return on investment can actually be negative for pure electric vehicles, highlighting the importance of renewable energy generation further. The energy impact of production is generally small (∼6% of lifetime energy) and, similarly, recycling is of a comparable magnitude, but it is less well studied.
Ibrahim KA, Wu B, Brandon NP, 2016, Electrical conductivity and porosity in stainless steel 316L scaffolds for electrochemical devices fabricated using selective laser sintering, MATERIALS & DESIGN, Vol: 106, Pages: 51-59, ISSN: 0264-1275
Li J, wu BILLY, Myant CONNOR, 2016, The Current Landscape for Additive Manufacturing Research
Merla Y, Wu B, Yufit V, et al., 2016, Novel application of differential thermal voltammetry as an in-depth state-of-health diagnosis method for lithium-ion batteries, JOURNAL OF POWER SOURCES, Vol: 307, Pages: 308-319, ISSN: 0378-7753
Merla Y, Wu B, Yufit V, et al., 2016, Extending battery life: A low-cost practical diagnostic technique for lithium-ion batteries, JOURNAL OF POWER SOURCES, Vol: 331, Pages: 224-231, ISSN: 0378-7753
Patsios C, Wu B, Chatzinikolaou E, et al., 2016, An integrated approach for the analysis and control of grid connected energy storage systems, JOURNAL OF ENERGY STORAGE, Vol: 5, Pages: 48-61, ISSN: 2352-152X
Wu B, Parkes MA, de Benedetti L, et al., 2016, Real-time monitoring of proton exchange membrane fuel cell stack failure, JOURNAL OF APPLIED ELECTROCHEMISTRY, Vol: 46, Pages: 1157-1162, ISSN: 0021-891X
Dewage HH, Wu B, Tsoi A, et al., 2015, A novel regenerative hydrogen cerium fuel cell for energy storage applications, JOURNAL OF MATERIALS CHEMISTRY A, Vol: 3, Pages: 9446-9450, ISSN: 2050-7488
Lomberg M, Boldrin P, Tariq F, et al., 2015, Additive manufacturing for solid oxide cell electrode fabrication, Pages: 2119-2127, ISSN: 1938-5862
© The Electrochemical Society. Additive manufacturing can potentially offer a highly-defined electrode microstructure, as well as fast and reproducible electrode fabrication. Selective laser sintering is an additive manufacturing technique in which three-dimensional structures are created by bonding subsequent layers of powder using a laser. Although selective laser sintering can be applied to a wide range of materials, including metals and ceramics, the scientific and technical aspects of the manufacturing parameters and their impact on microstructural evolution during the process are not well understood. In the present study, a novel approach for electrode fabrication using selective laser sintering was evaluated by conducting a proof of concept study. A Ni-patterned fuel electrode was laser sintered on an yttria-stabilized zirconia substrate. The optimization process of laser parameters (laser sintering rate and laser power) and the electrochemical results of a full cell with a laser sintered electrode are presented. The challenges and prospects of using selective laser sintering for solid oxide cell fabrication are discussed.
Wu B, Brandon NP, Yufit V, et al., 2015, HYBRID ELECTROCHEMICAL ENERGY DEVICE, WO/2015/150784
The present invention generally relates to the field of devices which are capable of storing and delivering electricity. In particular, the invention relates to a hybrid redox flow battery (HyRFB) capable of operating in a power delivery mode in which it generates electrical power by the reaction of electrochemically active species at a first and second electrode and in an energy storage mode in which it consumes electrical power to generate at least one electrochemically active species, the HyRFB comprising: • a reversible first electrode in a first electrode compartment containing a first aqueous electrolyte, • a reversible second electrode in a second electrode compartment containing a second aqueous electrolyte; and • a conduit arrangement configured, in said power delivery mode, for carrying electrochemically active species to the first electrode and, in an energy storage mode, for carrying generated electrochemically active species away from the first electrode; wherein the second electrode comprises a material that is capable of reversibly taking up and releasing alkali metal ions or alkaline earth metal ions during the said modes of operation, and wherein the second electrolyte comprises the alkali metal ions or the alkaline earth metal ions.
Wu B, Yufit V, Merla Y, et al., 2015, Differential thermal voltammetry for tracking of degradation in lithium-ion batteries, Journal of Power Sources, Vol: 273, Pages: 495-501, ISSN: 1873-2755
Monitoring of lithium-ion batteries is of critical importance in electric vehicle applications in order to manage the operational condition of the cells. Measurements on a vehicle often involve current, voltage and temperature which enable in-situ diagnostic techniques. This paper presents a novel diagnostic technique, termed differential thermal voltammetry, which is capable of monitoring the state of the battery using voltage and temperature measurements in galvanostatic operating modes. This tracks battery degradation through phase transitions, and the resulting entropic heat, occurring in the electrodes. Experiments to monitor battery degradation using the new technique are compared with a pseudo-2D cell model. Results show that the differential thermal voltammetry technique provides information comparable to that of slow rate cyclic voltammetry at shorter timescale and with load conditions easier to replicate in a vehicle.
Tariq F, Yufit V, Eastwood DS, et al., 2014, In-Operando X-ray Tomography Study of Lithiation Induced Delamination of Si Based Anodes for Lithium-Ion Batteries, ECS ELECTROCHEMISTRY LETTERS, Vol: 3, Pages: A76-A78, ISSN: 2162-8726
Troxler Y, Wu B, Marinescu M, et al., 2014, The effect of thermal gradients on the performance of lithium-ion batteries, JOURNAL OF POWER SOURCES, Vol: 247, Pages: 1018-1025, ISSN: 0378-7753
Wu B, Brandon NP, Yufit V, et al., 2014, A segmented fuel cell-battery passive hybrid system, WO/2014/195736
An apparatus for supplying electrical energy to a varying load is disclosed. The apparatus comprises fuel cells and energy storage devices. A fuel cell subset comprises one or a plurality of series-connected ones of the fuel cells, having a first no-load open- circuit potential thereacross and is connected in parallel with an energy storage device subset comprising one or a plurality of series-connected ones of the energy storage devices, having a second no-load open-circuit potential thereacross, to form a unit. The unit cell is connected in series or parallel with at least one other unit cell. The fuel cells in the unit cell and the at least one other unit cell are fuel cells of the same fuel cell stack. The arrangement is such that first no-load open-circuit potential and the second no-load open circuit potential are substantially balanced.
Wu B, Parkes MA, Yufit V, et al., 2014, Design and testing of a 9.5 kWe proton exchange membrane fuel cell-supercapacitor passive hybrid system, INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, Vol: 39, Pages: 7885-7896, ISSN: 0360-3199
Marinescu M, Wu B, Von Srbik M, et al., 2013, The effect of thermal gradients on the performance of battery packs in automotive applications, IET Conference Publications, Vol: 2013
Thermal gradients arising inside a battery pack for automotive applications are calculated for 200 A discharge via a multiparticle thermal-electrochemical coupled high fidelity model for a 12P7S 4.8 Ah cell pack. The effect of such gradients at the cell level are studied in a first approximation under a corresponding discharge at 15 A, by discretising the cell into units at fixed temperatures throughout the discharge. The immediate time evolution of load distribution through the various parts of the cell shows a complex behaviour, dependent on parameters such as temperatures, state of charge and load characteristics.
Wu B, Yufit V, Campbell J, et al., 2013, Simulated and experimental validation of a fuel cell-supercapacitor passive hybrid system for electric vehicles, IET Conference Publications, Vol: 2013
The concept of a fuel cell-supercapacitor hybrid system involves the direct coupling of the two devices to achieve the same benefits of hybridisation but without the need for costly DCDC converters. Using an experimentally validated steady state fuel cell model and a transmission line based supercapacitor model, it has been shown that the passive hybridisation allows for efficiency gains of approximately 16% compared to a pure fuel cell system. Under load, the supercapacitors meets the peak power requirement due to their lower impedance giving the FC time to ramp up. Under no load conditions, the fuel cell gradually charges the supercapacitors back to the steady state thermodynamic equilibrium potential. A fast fourier transform analysis of the respective loads under an automotive drive cycle showed that the supercapacitors act as a low pass filter, reducing the magnitude of load oscillations from the fuel cell. This therefore addresses two of the main modes of fuel cell degradation in automotive applications: rapid power cycling and no load idling.
Wu B, Yufit V, Marinescu M, et al., 2013, Coupled thermal-electrochemical modelling of uneven heat generation in lithium-ion battery packs, JOURNAL OF POWER SOURCES, Vol: 243, Pages: 544-554, ISSN: 0378-7753
Offer GJ, Yufit V, Howey DA, et al., 2012, Module design and fault diagnosis in electric vehicle batteries, JOURNAL OF POWER SOURCES, Vol: 206, Pages: 383-392, ISSN: 0378-7753
Wu B, Matian M, Offer GJ, 2012, Hydrogen PEMFC system for automotive applications, International Journal of Low-Carbon Technologies, Vol: 7, Pages: 28-37, ISSN: 1748-1317
A balance of plant (BOP) system for a 9.5-kWe Nedstack P9.5-75 low-temperature proton exchange membrane fuel cell (FC) stack was tested up to a power of 2 kWe. The system has been designed to act as a range extender for a series hybrid electric vehicle driven under urban duty cycles. Vehicle simulations have estimated that an average gross power requirement of 4 kWe is needed from the FC, whilst simulations of the FC stack and BOP components have allowed for characterisation of transient behaviour and performance degradation. © The Author 2012. Published by Oxford University Press. All rights reserved.
Wu B, Offer GJ, Yufit V, et al., 2012, Fault analysis in battery module design for electric and hybrid vehicles
In this paper systems integration issues, such as electrical and thermal design and management of full battery packs - often containing hundreds of cells - are discussed. The design and construction of a 9 kWh battery pack for a motorsports application is used as an example. The pack contained 504 lithium cells arranged into 2 sidepods, each containing 3 modules, with each module in a 12P7S configuration. This paper focuses on describing problems related to cells being connected in parallel, known as massively parallel packs. We also demonstrate how a full vehicle test can be used to identify malfunctioning strings of cells for further investigation. It is shown that normal inter-cell contact resistances can cause currents to flow unevenly within the pack, leading to cells being unequally worked. This is supported by a Matlab/Simulink model of one battery module, including contact resistances, which was able to reproduce the results that were seen in experimental tests. Over time the unequal current flowing through cells can lead to significant differences in cells' state of charge and open circuit voltages, large currents flowing between cells even when the load is disconnected, and ultimately, some cells discharging and aging more quickly than others and jeopardising the energy storage capacity and lifetime of the entire pack.
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