meeting report
22nd International Seminar on Primary and Secondary Batteries
Fort Lauderdale, FL USA
March 14-17, 2005
- Broddarp of Nevada, Inc.
- Henderson, NV USA
The 22nd International Seminar on Primary and Secondary Batteries was held in Ft. Lauderdale, Florida, on March 14-17. There were over 400 attendees. Several summaries of the presentations at the meeting follow.
George Kershner and Saskia Mooney of Wiley, Rein and Fielding reviewed the shipping regulations and the actions of the U.S. Department of Transportation to further regulate the transport of lithium-ion and fuel cells. The two lithium fires at FedEx involving lithium primary medical batteries and lithium-ion cells for a hybrid car coupled with the LAX airport fire of lithium coin cells has caused DOT to open up a new study. A previous report from England showed that lithium fires were not extinguished by the Halon fire extinguishers used on aircraft. DOT has commissioned a study on Li-ion batteries to identify problems with extinguishing these fires on aircraft. DOT has long wanted to regulate Li-ion batteries as for lithium metal cell regulations. The battery industry prevailed, and DOT permits the carrying of a 96Wh battery pack on aircraft. The Portable Rechargeable Battery Association is pushing for a separate category for Li-ion batteries to help differentiate them from lithium metal batteries. They also are pushing for a 200Wh allowance to ship Li-ion batteries as non-hazardous cargo. In the past several years there have been incidents involving lead acid (20), NiCd and NiMH (4), lithium primary (5), lithium-ion (1), and dry cell (8) batteries. The DOT recently funded a study at the Rochester Institute of Technology to evaluate the E3 impact of methanol cartridges in transportation. A fallout from these studies may impact recycling efforts, if scrap batteries are reclassified as hazardous goods.
M. Sudduth of FedEx related their experience in shipping batteries. Because of the recent incidents, they require shippers of lithium batteries to go through a qualification process before accepting shipments from them. They accept only shipments from the qualified list, and they are taken as Class 9 hazardous goods. Their two recent incidents involved medical primary lithium batteries and 78 Li-ion batteries intended for HEV application. Both incidents were detected before the aircraft took off. The Li-ion cell fire melted the plastic shipping container. It was taken off the aircraft when a worker smelled smoke. It appeared that the cells were not packaged properly and were touching one another. The fire started in one cell and then spread domino fashion to nearby neighbors. He did not identify the source of the cells.
Brian Barnett of TIAX introduced the safety session with a brief description of the thermal runaway scenario. First the cell contents are heated, perhaps by an internal short or from a hot component in the electronic circuitry of a battery pack. As the cell warms up, the reaction of the cathode with the electrolyte increases. Once the point is reached where the heating from internal reactions is greater than the heat dissipated, the cell has reached a critical point/temperature where thermal runaway occurs with disastrous results. That temperature varies with the cathode composition and the electrolyte composition and is different for each cell manufacturer. To raise the temperature for thermal runaway, it will be necessary to engineer the kinetics of the decomposition reactions.
According to Jeff Dahn of Dalhousie University, the success of arriving at a ìdrug storeî battery will depend on the ability to develop a system whose safety is ìbulletproof,î whose cost performance is like NiCd or less ñ safe and does not require electronic circuitry for safety or cell management. Overcharge and overdischarge protection like the NiCd will require an internal redox material with the right potential. The cell includes a LiFePO4 cathode and a Li4/3Ti5/3O4 anode and adding a 2,5 diterbutyl 1,4 dimethoxybenzene as the overcharge/overdischarge protection shuttle. A very safe, long lasting cell can be produced. The cell can be overcharged continuously at moderate rates without overheating the cell.
Linda Nazar of Waterloo University discussed lithium iron phosphate as a cathode material. The ideal LiFePO4 material would have: a) small particle size to limit the path length inside the particle, and b) conductive surface network that does not impede the intercalation and deintercalation of lithium. The carbo-thermal process for producing LiFePO4 produces the conductive Fe2C on the surface of the LiFePO4 particle by a simple surface reduction process. The electronic conductivity of LiFePO4 is about 10-9S/cm and the diffusivity of the Li is about 10-15cm2/sec. This translates into fully charging a 50 nanometer particle will take about 1.75 hours. By comparison the Li diffusivity in LiCoO2 is about 10-10cm2/sec. Both the surface chemistry and the particle size are important in the use of LiFePO4 materials in batteries.
M. Broussely described the Saft lithium-ion (Li-ion) technology applied to a variety of stationary energy storage applications as replacements for lead acid and nickel metal hydride (NiMH). The advantages are very high energy storage (Wh/l and Wh/kg), high efficiency, and maintenance-free (sealed) with predictable end-of-life and state-of-charge characteristics. The Saft preference is for the stabilized lithium cobalt-nickel oxide cathode material, a natural graphite anode with hexafluorophosphate electrolyte with added VC. The cell design and cell balance depend on the application but are generally positive limited. On C/3 cycling to 80% depth of discharge (DOD) the cells show 13% capacity loss after 3200 cycles. On a simulated HEV test the cells cycled 50% state of charge and discharged at 2.2% DOD with 12 sec., 500 amp pulses; cells lost about 15% of their original capacity after 500,000 cycles. The cells have shown minimal degradation after 4.3 years of active life at 40C. A battery management system has been developed to increase safety and service life and controls on a cell-by-cell basis.
M. Fetcenko of Ovonic described their work to improve the performance of NiMH. The state-of-the-art systems now stand at over 100Wh/kg, 400Wh/l and up to 2000W/kg in commercial cells. They have developed a new modified AB2 alloy system with acceptable cycle life (400 cycled to 80%) but lower cost than the AB5 type alloys. The Ni(OH)2 materials have been developed with enhanced specific power and high temperature capability by incorporating nickel fibers and cobalt additions. Ovonics has found a way to enhance the capacity by stabilizing the charge and discharge of the nickel materials to the higher capacity alpha to gamma transition rather than the usual beta to beta for the charge-discharge regime. The smaller AA- and AAA-size cells are replacing alkaline primary cells in digital cameras, and all HEVs use the NiMH system as the power source.
Peter Guggenheim of Valence Technology Inc. discussed the performance and safety characteristics of phosphate-based Li-ion batteries as compared to metal-oxide batteries. The inherent properties of the cathode material itself define the ultimate safety of a power system. Phosphate-based cathodes possess a structural advantage that limits the likelihood of oxygen liberation and combustion, thereby translating into safer Li-ion batteries.
Their forecast of the Li-ion market is given in the table below:
| Lithium-Ion Market ($billion) | |||
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Valence makes both lithium iron phosphate and lithium vanadium phosphate batteries for various applications at their plant in China. They forecast a 10-year life at room temperature for the system. The Li-ion, with phosphate cathode materials, does not go into thermal runaway until above 250C. Theirs is viewed as being the safest Li-ion battery.
Norman Allen reviewed the UltraCell fuel cell technology development for notebooks and other applications. The technology is a spinoff from the Lawrence Livermore National Laboratory. The fuel is methanol but the system reforms methanol into hydrogen for use in the fuel cell. As a result, the cell can operate at higher current densities. UltraCell has developed a 45-watt unit for notebook computers. The unit is under test at several potential users. It will yield a 400Wh mission on a 200cc cartridge.
M. Holzapfel of Paul Scherrer Institute presented their work on silicon (Si) anodes for Li-ion cells. Si was vapor deposited onto a graphite substrate from silane in an argon carrier gas. The nano Si particles (size ca. 20nm) were homogeneously distributed over the surface of the graphite particle. To make an electrode, the nanocrystal particle of Si on graphite was mixed with TIMREX KS6 and carbon black, with 10% PVdF as the binder. The mix was cast onto a treated copper foil substrate as the current collector. The electrodes were highly reversible with a capacity of about 900-1000mAh/g. The electrodes had good cycle life and could deliver over 80% of their capacity at 8C discharge rate.
Kamel Urbal of Intel reviewed their efforts in funding new ventures to increase the run-time of batteries that power notebook computers. Notebooks are finally enabling the ìpersonalî of what is called personal computing, any time, anywhere. In 2001, 24 million notebooks were sold and last year the number rose to 47 million, of which 65% had wireless capability. That is expected to rise to 90% in 2005. Battery life is the often-heard complaint. Intel Capital has focused its investment activities into three thrusts to increase runtime: 1) increased battery capacity, 2) development of new higher energy chemistries, cell constructions and fuel cells, and 3) fast charging technologies, alternate charging algorithms, etc. Their goal is to balance a business relationship with a strategic financial investment. In 2004, Intel Capital participated in 1100 deals and invested $130 million of which 40% were outside the U.S.
Christophe Pillot of Avicenne presented their market forecasts and applications for small sealed cells. The following values were estimated from his charts.
| Cellular Phones | |||
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| Notebook Computers | |||
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| Camcorders | |||
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| The 2004 market was 2.5 billion cells | |||
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| Cell Usage | |||
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Christina Lampe-Onnerud reviewed the cost structure of Li-ion batteries. The cost of cobalt and nickel has varied widely over the past 10 years. Cobalt low and high were at $15.21/kg in 2002 and at $64.40 in 1995. It currently is $39.69/kg. This has led to a significant activity to develop lower cost cathode materials. Nickel has had a similar variation with a low of $4.63/kg and a high of $14.10/kg. It currently is at the high of $14.10/kg. This compares to a cost of $10/kg for the manganese compounds.The 1/3 mixed oxides currently come in at about $30/kg. The capacity of these compounds is similar to the cobalt material but the 1/3 compound discharges at a lower voltage. Cost is the only advantage of this material. The higher performance stabilized nickel-cobalt materials offer a way for higher capacity and lower cost with good safety characteristics.
Thomas Dougherty of Johnson Controls (JCI) described their work on developing NiMH and Li-ion batteries for automotive applications. JCI currently has the capability to produce over 86 million car batteries and has sales of about $2.3 billion. The hybrid system is more than a battery. It includes the electric motor, battery controller including cell balancing, wiring harness and hardware. Battery costs grow in proportion to the voltage as do warranty costs. JCI prefers a prismatic cell design with through-the-partition inter-cell connections to reduce cost and lower internal resistance. Long life requires a balance of energy, power and the proper state of charge operating window. Li-Ion has an advantage of significantly fewer cells and higher specific power than lead acid or NiMH for the same battery voltage. NiMH is the technology of today but Li-ion can replace it when cost and abuse tolerance are on a par with NiMH.
N. Yamamoto of Panasonic reported on their efforts to develop a nickel-manganese cathode material. They have developed a solid solution mixture of LiNiO2 and LiMn2O4. The new material has slightly higher capacity and superior rate capability than the cobalt materials with the thermal stability and safety of manganese.
U. Wietelmann of Chemetall gave an overview of the available information on the new lithium bisoxalato borate (LiBOB) electrolyte salt. Full registration as the chemical should be complete by May 2005 in Europe. The registration process is in progress in Japan and the U.S. It is neither corrosive nor mutagenic with an LD50 of 300 mg/kg. It will be classified as ìHarmful.î The formation process in LiBOB electrolytes differs from the formation in LiPF6 electrolytes. It will be necessary to have a careful balancing of the anode/cathode capacity balance. There is good performance with manganese spinel and phosphate cathode materials but is unstable at higher temperatures with cobalt materials. Tests show reduced manganese dissolution in contact with a LiBOB electrolyte than with a LiPF6 electrolyte.
M. Thackeray of Argonne National Laboratory described their work on manganese-based materials for Li-ion cells. They have been working with layered manganese compounds with other metals incorporated into the lattice, including cobalt and nickel. ìLayered-layeredîstructure of xLiMn-O3 ï (1-x) LiMO2 and ìlayered-spinelî xLi2MnO3 ï (10x)LMn2O4 electrodes with (M=Mn, Ni, Co) have incoherent composite structures. The inactive Li2MnO3 acts as a structural dopant to stabilize layered LMO2 and to reduce oxygen activity at the surface of charged electrode particles. Li2O removal during the initial charge increases MnO2 content and capacity of composite material. A rechargeable capacity of 250mAh/g or more can be achieved when charged to 5 volts.This is similar to the results of I. Davidson reported at IMLB-12 with chromium substitutions. The capacity of these materials is significantly higher than that of presently used cobalt cathode materials. These manganese materials have excellent safety characteristics and use electrolytic manganese dioxide (EMD) as the starting material. EMD sells for about $1/lb so the manganese materials will be significantly less expensive than the cobalt materials. EMD is a commodity on the world market and should not be subject to large swings in price. These materials could well be in the next round of service improvements.
Y. Gao of FMC introduced a new stabilized lithium metal powder (SLMP) for use in fabrication of lithium and Li-ion batteries. It can be handled in a regular dry room and coated on foils to form electrode structures. It has a particle size in the range of 10 to 50 microns. It can lithiate graphite when contacted with electrolyte and can be used to balance the first charge loss on formation of Li-ion cells. It can enable the use of low-cost cathode materials, such as EMD or other non-lithiated cathode materials. As an example, when used with heat-treated EMD as the cathode, it forms a spinel on charging with a capacity of 200mAh/g during first charge.