Publications
107 results found
Wu B, Merla Y, 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: 1873-2755
Understanding and tracking battery degradation mechanisms and adapting its operation have become a necessity in order to enhance battery durability. A novel use of differential thermal voltammetry (DTV) is presented as an in-situ state-of-health (SOH) estimator for lithium-ion batteries.Accelerated ageing experiments were carried on 5Ah commercial lithium-ion polymer cells operated and stored at different temperature and loading conditions. The cells were analysed regularly with various existing in-situ diagnosis methods and the novel DTV technique to determine their SOH. The diagnosis results were used collectively to elaborate the degradation mechanisms inside the cells. The DTV spectra were decoupled into individual peaks, which each represent particular phases in the negative and positive electrode combined. The peak parameters were used to quantitatively analyse the battery SOH.A different cell of the same chemistry with unknown degradation history was then analysed to explore how the cell degraded. The DTV technique was able to diagnose the cell degradation without relying on supporting results from other methods nor previous cycling data.
Parkes MA, Chen T, Wu B, et al., 2015, “can” you really make a battery out of that?, Journal of Chemical Education, Vol: 93, Pages: 681-686, ISSN: 1938-1328
This classroom activity introduces students to battery electrochemistry through the construction of a simple battery made from household products. Students will use a set of simple design rules to improve the performance of the battery, and power a light emitting diode. The electrochemical performance of the batteries is characterized using potentiostatic cyclic voltammetry and chronoampometry, and suggestions for implementing this activity into a high school teaching environment are presented. Designed for United Kingdom secondary schools and exam boards, the supplementary teaching package contains problem sheets and activities appropriate for students age 14 and up.
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, 2015, A review of: Electrochemical Power Sources: Batteries, Fuel Cells, and Supercapacitors, A review of: Electrochemical Power Sources: Batteries, Fuel Cells, and Supercapacitors, Publisher: Johnson Matthey Technology Review
Electrochemical Power Sources: Batteries, Fuel Cells,and Supercapacitors” is a comprehensive textbookcovering materials, applications and prospects ofthe aforementioned devices. The high level overviewprovided makes this book an excellent resource forreaders new to electrochemical devices as it avoidsgoing into excessive detail of each material, whilstproviding an overall perspective and outlook. The bookwas edited by Alexander Skundin and Yury Volfkovichin honour of the late Vladimir Bagotsky, who is widelyrecognised for his scientifi c activities in electrochemistryand for his textbooks on this subject. Skundin andVolfkovich themselves are the chief scientists at theA.N. Frumkin Institute of Physical Chemistry andElectrochemistry of the Russian Academy of Sciencesand are two of the leading experts in batteries andsupercapacitors in Russia with over 200 peer reviewedarticles between them. The book covers three general topics: batteries,fuel cells and supercapacitors, with each sectiondiscussing fundamental operating principles, materialconsiderations and technology prospects.
Lomberg M, Boldrin P, Tariq F, et al., 2015, Additive manufacturing for solid oxide cell electrode fabrication, ECS Conference on Electrochemical Energy Conversion & Storage with SOFC-XIV, Publisher: Electrochemical Society, Pages: 2119-2127, ISSN: 1938-6737
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.
Hewa Dewage HARINI, wu BILLY, Tsoi ANTHONY, 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: 2050-7496
A novel regenerative hydrogen cerium fuel cell is presented which has the potential to deliver both low cost and high performance. A 5 cm2 prototype is demonstrated, achieving 148 mW cm−2 when fully charged. Rate determining processes within the cell are identified.
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: 0378-7753
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.
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.
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, Electrochemistry Letters, Vol: 3
Silicon-Lithium based rechargeable batteries offer high gravimetric capacity. However cycle life and electrode microstructure failure mechanisms remain poorly understood. Here we present an X-ray tomography method to investigate in-operando lithiation induced stress cracking leading to the delamination of a composite Si based electrode. Simultaneous voltage measurements show increased cell resistance correlating with severe delamination and microstructural changes. 3D analysis revealed 44.1% loss of the initial electrode-current collector area after 1 hour of operation at 2.4 mA/cm2 and a 21.2% increase in new anode surface area. The work represents a new basis for future investigation of Si based anodes.
Wu B, Parkes MP, 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
The design and test of a 9.5 kWe proton exchange membrane fuel cell passively coupled with a 33 × 1500 F supercapacitor pack is presented. Experimental results showed that the system reduced dynamic loads on the fuel cell without the need for additional DC/DC converters. Fuel efficiency gains of approximately 5% were achieved by passive hybridisation in addition to addressing two main operational degradation mechanisms: no-load idling and rapid load cycling.Electrochemical Impedance Spectroscopy measurements indicated that the supercapacitor capacitance dropped with decreasing cell voltage and suggested that operation below 1.3 V is not recommended. Knee-frequency measurements suggested little benefit was gained in using passive systems with load cycles that have frequency components above 0.19 Hz. Analysis of system sizing suggested using the minimum number of supercapacitors to match the open circuit voltage of the fuel cell to maximise load buffering.
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
Abstract In battery packs with cells in parallel, the inter-cell connection resistances can cause unequal loads due to non-uniform interconnect overpotentials and consequentially lead to non-uniform heating. This article explores how load imbalances are generated in automotive applications, by describing a battery pack with finite interconnect resistances. Each cell inside the pack is represented by a pseudo 2D electrochemical model coupled with a lumped thermal model. Increasing the number of cells in parallel results in a linear increase in load non-uniformity, whilst increasing the ratio of interconnect to battery impedance results in a logarithmic increase in load non-uniformity, with cells closest to the load points experiencing the largest currents. Therefore, interconnect resistances of the order of mΩ can have a significant detrimental impact. Under steady state discharge the cell impedance changes until the loads balance. This process, however, can take hundreds of seconds and therefore may never happen under dynamic load cycles. Cycling within a narrow state-of-charge range and pulse loading are shown to be the most detrimental situations. Upon load removal, re-balancing can occur causing further heating. Simulation of a 12P7S pack under a real world load cycle shows that these effects could cause localised thermal runaway.
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.
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.
Troxler Y, Wu B, Marinescu M, et al., 2013, The effect of thermal gradients on the performance of lithium ion batteries, Journal of Power Sources, Pages: accepted-accepted, ISSN: 0378-7753
Abstract An experimental apparatus is described, in which Peltier elements are used for thermal control of lithium-ion cells under isothermal and non-isothermal conditions, i.e. to induce and maintain thermal gradients. Lithium-ion battery packs for automotive applications consist of hundreds of cells, and depending on the pack architecture, individual cells may experience non-uniform thermal boundary conditions. This paper presents the first study of the impact of artificially induced thermal gradients on cell performance. The charge transfer resistance of a 4.8 Ah is verified to have a strong temperature dependence following the Arrhenius law. Thermal cycling of the cell, combined with slow rate cyclic voltammetry, allows to rapidly identify phase transitions in electrodes, due to the thermal effect of entropy changes. A cell with a temperature gradient maintained across is found to have a lower impedance than one held at the theoretical average temperature. This feature is attributed to details of the inner structure of the cell, and to the non-linear temperature dependence of the charge transfer resistance.
Offer GJ, Yufit V, Howey DA, et al., 2012, Module design and fault diagnosis in electric vehicle batteries, Journal of Power Sources
Systems integration issues, such as electrical and thermal design and management of full battery packs–often containing hundreds of cells–have been rarely explored in the academic literature. In this paper we discuss the design and construction of a 9 kWh battery pack for a motorsports application. The pack contained 504 lithium cells arranged into 2 sidepods, each containing 3 modules, with each module in a 12P7S configuration. This paper focuses particularly on testing the full battery pack and diagnosing subsequent problems related to cells being connected in parallel. We demonstrate how a full vehicle test can be used to identify malfunctioning strings of cells for further investigation. After individual cell testing it was concluded that a single high inter-cell contact resistance was causing 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. 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, cells discharging and aging more quickly than others, and jeopardise capacity and lifetime of the pack.
Wu B, Offer GJ, Yufit V, et al., 2012, Fault analysis in battery module design for electric and hybrid vehicles, Power Electronics, Machines and Drive
Wu B, Matian M, Offer GJ, 2012, Hydrogen PEMFC system for automotive applications, International Journal of Low Carbon Technologies
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.
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.