meeting report

24th International Power Sources Symposium

Brighton, UK

April 19-21, 2005

• by Austin Attewell
• Past Editor, Symposium Proceedings

The first International Power Sources Symposium was held 47 years ago, inspired by the annual conferences then sponsored by the U.S. Army, Fort Monmouth, New Jersey. These British events are organised by a board consisting of influential figures in academia, industry and government. Known colloquially as the ìBrighton Conferences,î after the city on the southeast coast of England where the majority of these biennial gatherings are held, they have been held in recent years in The Netherlands and Manchester, England, but for 2005 it was held in its ìtraditionalî city.

Brighton was made famous in the late 18th century as the summer watering place of Britainís Prince Regent, son of King George III. Here he built an architecturally lavish pavilion, and this yearís Symposium was held in the Brighton Corn Exchange, part of the Pavilion complex.

The mandate for these symposia is to present papers on the research, development and exploitation of non-mechanical power sources, so inevitably papers on all aspects of batteries and fuel cells predominate. To broaden the appeal and technical base of the 2005 event, the IPSS board teamed up with Franceís CEA-GENEC organisation.

The largest groups of delegates were from North America and the U.K., but most countries in the European Union, the Near and Far East and Australia were well represented.

Traditionally, these symposia, unlike most, took pride in providing delegates with a hard copy of the full text of the papers. In this, and subsequent years, registered delegates may download the texts from the Syposiumís web site. A CD is available, which includes the final version of the proceedings, plus a transcription of the question and answer sessions and most of the presentations themselves.

Another tradition, whereby whole days or half days were set aside for discrete battery or fuel cell systems, was not followed. So, because of the dominance of lithium-based rechargeable systems, they were covered every day.

Andrew Ritchie, lately of QinetiQ, a recently privatised arm of a British Government organisation, gave a review which updated the one he presented in Amsterdam at the 2003 Symposium. He dealt mainly with the use of lithium-ion systems, stressing the need to produce cheaper cathodes than the present widely used lithium cobalt oxide. Nano composites, such as L₁₄T₁₃O₁₁, promise longer cycle life whilst anode improvements may result from the incorporation of carbon fibres in excess to improve safety during overcharge.

One paper, which is bucking the almost universal interest of intercalated lithium electrode research, was that on a lithium sulfur system. Constrained by company privacy, Gleb Ivanov of Intellikraft (UK) Ltd. did not reveal the electrolyte used or the cathode makeup but, furthering the initial work done by The British Atomic Energy Authority, he claimed that his system is safe and gives 350-450Wh/kg, twice that of lithium polymer. Capacity loss is a problem, but 200 cycles have been achieved. End-of-live occurs when the sulfur is immobilised as insoluble sulfides. The system discharges in two steps at 2.2 and 2.0 volts, an end of life cathode achieving Li₂S₈. However, Ivanov showed no hardware to enable the audience to judge the maturity of his physical design, and while presenting the impressive technical possibilities of a metallic anode system he did not minimise the difficulties arising from the propensity of Li and S to indulge in a bewildering array of non-electrochemical reactions. One recalls the rapid demise of Moli Energyís well-engineered LiMoS₂ system after following just one major incident, and hopes that such will not be the fate of this intriguing chemistry.

Sandia National Laboratory has an impressive record of high quality research on many battery systems and Ganesan Nagasubramanian pursued a theme started at previous symposia. This is the solid electrolyte system Li: PEO-polymer/organic-inorganic conducting composite. In coin cells, he claimed that nanostructures reduced the operating temperature of polyelectrolytes.

With what was perhaps the most ìprofessionalî presentation of the whole Symposium, Prof. Ian Ward described work sponsored by the U.K. Dept. of Trade and Industry at University of Leeds to produce novel PVDF polymer gel electrolytes in sheet form and ship them to Spectra Power in the USA for incorporation into cells, which presently are giving 185Wh/kg^-1 and 400Wh/kg dm³.

The IPSS Board has the discretion to present medals to those they judge have made significant contributions to electrochemical research and technology. Last April two medals were presented, the first to Öistein Hasvold, who heads a team in the Norwegian DOD that is responsible for the design and development of power sources. He has presented many papers at previous Symposia, notably on systems that exploit the dissolved oxygen in seawater. This year he broadened his brief to describe an EU-funded survey of all available and potentially usable electrochemical systems for electric road vehicles. He emphasised that the survey was three pronged: to assess from technical, environmental and economic viewpoints.

The other medal recipient was Robert Hamlen, lately head of the Power Sources Branch of the U.S. Army RD and E Center at Fort Monmouth. He also gave the Bourner lecture, an event each year that commemorates Sheila Bourner, who for more than 20 years, was the Symposiumís secretary. His chosen theme was the ever-increasing demand for man-portable electrical power required by the 21st century soldier.

The medals were presented at the gala dinner held in the Brighton Thistle, a five-star hotel on the sea front of this famous south coast resort.

After the formal session on Tuesday, Gerry Woolf, charismatic editor of the British Batteries and Energy Storage Technology (BEST) magazine, hosted a lively discussion that inevitably focused upon the perennial problem ñ how to educate engineers and equipment designers about the niceties and intricacies of selecting and using the correct batteries for their applications. This is an uphill struggle because electrochemical technology sits uneasily between electrical and mechanical engineering as well as chemistry. In these three disciplines, students should be made aware of the theoretical and practical implications of electrochemical conversion.

Angel Kirchev of the Bulgarian Academy of Sciences gave the Dave Rice Memorial Lecture, pursuing the kinetics of the oxygen cycle that is fundamental to the operation of valve regulated lead-acid batteries. Dave Rice, technical manager of VRLA at Energys, was an active member of the IPSS board until his sudden death in 2003.

Fuel cells have spawned many conference papers over the last 40 or so years, such as cost-was-no-object alkaline fuel cells for the moon landing programme, and the technical breakthrough from the use of polymer electrolyte membranes that has led to many experimental applications, including portable designs for man packs using methanol fuel capsules.

Various ways of efficient storage or on-site production of hydrogen provided several papers this year, including a summary of their present programs by Ashok Patel of U.S. Army RD and E Center at Fort Belvoir, Virginia; Raadschelders of the Dutch MOD, and from the British Defence Science and Technology Laboratory on lithium borohydride for H₂ generation. This latter group also gave us glimpses of their research on a semi-fuel cell. Designated a carbon air fuel cell (CAFC) because of its use of carbon in the anode, its aim is for a specific energy of 3kWh/kg^-1, 30 times that of lithium-ion.

A decade ago, nano compounds were emerging from the depths of fundamental research. Now they are impinging upon electrochemical power supplies. Fundamental work on nanoscale Cu₆Sn₅ particles as insertion hosts for lithium electrodes was presented by Mladenov of the Bulgarian Academy of Sciences, while Ritchie, in his review mentioned lithiated nano-tin and titanium oxides as possible routes to a higher capacity insertion electrodes.

The high temperature sodium-sulfur battery emerged some 30 years ago. Passing through several design iterations, it has now been virtually eclipsed by the sodium/nickel chloride ZEBRA couple for vehicle applications, although MW installations are in use for load levelling in Japan. Tony Donaldson of the Naval Marine Division of Rolls Royce presented a feasibility study of ZEBRA batteries for submarine propulsion. Although providing a zero maintenance regime, it seemed that the release of crew members from the present need to attend to lead-acid batteries was not a major feature for considering the new system.

Anthony Green can be relied upon to present succinctly SAFTís thinking on battery applications. This year, he outlined their change from flooded nickel-cadmium batteries to no-maintenance nickel-metal hydride for stand-alone photovoltaic applications, bypassing the semi-sealed NiCad system. A huge 920Ah system has been installed in the USA.

An early paper on the first morning was intriguingly titled: ìPower Sources Compared: The Ultimate Truth.î Given by Bas Flipsen from the Dutch University of Delft, he put many energy-producing techniques into perspective, from carbon fibre springs built into shoes to fuel cells and lithium batteries. Via piezo devices and thermoelectrics, each was summarised and given its place on a necessarily busy Ragonne plot.

With the massive investments that the U.K. and other European countries are making in wind farms, it was understandable that several presentations covered the integration of storage batteries with the output from wind turbines. Papers from John Barton of Loughborough University, Mary Black of the Manchester Centre for Electrical Energy and Jim McDowall of SAFT, USA, all discussed the best mix of wind power to storage capacity.

Advanced Battery for Low-cost Renewable Energy (ABLE) was the topic discussed by Elisabeth Lemaitre- Potteau CEA-GENEC, a project funded by the European Union. She described multi-national work on an advanced VRLA system optimised for very good reliability and low cost and intended for small- and medium-sized photovoltaic systems. The fully integrated regulator includes an algorithm for energy management that uses battery history from the past eight days.

Looking towards the next generation of systems, Marion Perrin, also of CEA-GENEC, gave an excellent presentation on lithium-ion. Working with SAFT, cell sizes up to 50Ah have been tested giving up to 97% watt-hour efficiency in a photovoltaic regime.

Inevitably, the perennial topic of state-of-charge determination was well covered. Ever more sophisticated computer modelling and programmes are the norm and papers from Canada (Ian Hill, Defence R&D, lead-acid) and Pritpal Singh (a regular presenter at Brighton Symposia), with his fuzzy logic based meter for lithium-ion batteries, were two of the themes discussed.

Decades ago, before the introduction of lithium-based systems, papers on primary cells with aqueous-based electrolytes were common. Nowadays this is a rare topic, but in 2005 one paper from the Niru Manufacturing Co. of Iran was about the effect of surfactants on the performance of alkaline manganese cells. Unfortunately neither of the authors (Ghavami and Rafiee) could attend and, as is traditional, the paper was presented by one of the Symposium organisers.

Paul Skarstad of Medtronics and a previous Booth Medallist can be relied upon to present papers dealing with the meticulously researched and engineered batteries that are needed to power implantable medical devices. In previous lectures he has described cathode chemistries based upon pure vanadium compounds, but this year he introduced a mixed cathode of silver vanadium oxide with polycarbon monofluoride, i.e. CF_x : Ag₂V₄O₁₁, combining the high energy of the fluoride with the good power capability of the oxide. Another advantage of this system is that it gives a two-step discharge ñ a built-in ìgas gaugeî. The original lithium system with iodine is still in use, 10 million having been made over the past 20 years. However, the mixed cathode gives 40 times more power density for little over half the weight of Li-I₂.

Continuing the polycarbon monofluoride theme, Emmanuel Eweka of QinetiQ described early work on a version of the BA 5590 U.S. Army man pack battery that uses their pocket design of flattened spirally wound cell. He claimed 500Wh kg^-1 was achieved from a 25Ah cell against a target of 740Wh kg^-1.

The specialised topic of reserve batteries for missiles was the theme of Joe Wellís talk. Eagle Picher has developed reserve type, high-power, lithium thionyl chloride for interceptor kill vehicles where low skin temperatures preclude the use of thermal batteries and where cost is secondary. 100Wh kg^-1 is achievable and Wells presented data showing that the batteries are safe during various hazard test regimes.

The Brighton Conference ñ the International Power Sources Symposium ñ may not attract as many delegates these days as it did in the heady years of the 1970s when it and the U.S. Army Power Sources Conference were the only two regular and international battery/fuel cell meetings. But it remains a truly international affair, this year with authors from 18 nations. Supported internationally by manufacturers and user organisations, a comprehensive display by battery and test equipment makers is traditional

The CD mentioned earlier is available for £40.00, plus £12.50 postage and packing, from Symposium Secretary Bob Bailey at ipss@marketdevelopco.demon.co.uk or via the web site, www.ipss.org.uk

The next meeting is scheduled for the spring of 2007at a venue in the U.K.

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