from June 2009 ABT

meeting report - part 2

26th International Battery
Seminar & Exhibition

Ft. Lauderdale, FL USA

March 16-19, 2009

Part 1 of this article appeared last month

The first talk on Wednesday morning was presented by Christophe Pillot of Avicenne-France on Electric, PHEV and Hybrid Vehicle Trends and Impact on the Battery Market. He gave his annual presentation on the market for HEVs and their batteries. Sales of HEVs were dominated by Toyota and fell slightly in 2008 with the U.S. being the largest consumer, followed by Japan and Europe. Due to favorable tax treatment, diesel cars are very popular and account for over half of the passenger vehicles sold. The various producers of batteries for HEVs and their relationship to the car manufacturers were discussed. By 2010, 70% of the NiMH batteries will be used by HEV.

Data on the relative costs of Lithium-ion and NiMH batteries at the cell and pack level currently and in the future were presented. By 2015, Pillot projects Lithium-ion will still cost nearly twice as much at the pack level based on dollars per KWh but will be comparable on a dollar per KWh basis.

Next Dr. Don Hillerand of Argonne National Laboratory spoke on Transforming Our Energy Economy: Reducing Oil Consumption and Greenhouse Gas Emissions from U.S. Transportation. The new administration in DC has initiated a paradigm shift in energy policy to reduce dependence on foreign oil and this will result in a shift away from vehicles powered by the ICE to ones powered by energy from a wide variety of domestic sources. This will be accomplished through increased MPG standards and tax credits to result in 15 million HEVs on the road by 2015.

DOE investments in HEVs and EVs have grown to $143 million in FY09. This is projected to increase to $2.5 billion under the economic stimulus package. Various DOE vehicle proposals were discussed as were other DOE initiatives to reduce oil imports and greenhouse gas emissions, including the clean cities program. A DOE generation capacity study indicates millions of PHEVs can be recharged using off-peak power. The DOE PHEV technology assessment program was also discussed.

Hillebrand’s closing remarks were that the cost of gasoline in the U.S. is currently too cheap and the cost of Lithium-ion batteries too high to achieve these objectives but policy innovation would spur industry innovation and break the current 15-year paradigm in the auto industry.

Then Dr. Ralph Brodd of Broddarp of Nevada discussed the National Alliance for Advanced Transportation Batteries (NAATBAT). He described the formation of this organization to develop the domestic battery industry for use in electric vehicles. Twenty-two organizations have joined at a cost of $10,000 per year. The organization is based on the SemiTec model for the semiconductor industry and will establish centers of excellence and development of prototype Lithium-ion cells and the manufacturing technology needed to produce them.

NAATBAT is seeking funding of $1.1 billion from the U.S. government in two tranches of $350 and $750 million. The first grant will be used to establish an initial production facility with four independent lines and the second for three additional production facilities. The objective is to capture 30% of the market for vehicle propulsion batteries by 2015.

Following the mid-morning break, Sven Bauer of BMZ Batterien-Montage-Zentrum in Germany and China spoke on New Lithium Technologies. He reviewed the market drivers that will lead to increased production of HEVs and the planned production of these vehicles by various manufacturers.

Incremental cost for various types of electric vehicles were estimated and the characteristics of batteries capable of meeting their requirements delineated. An economic analysis shows that the cost of electricity and depreciation on the battery is less than the cost of gasoline at $4.00 per gallon. When driving 15,000 miles per year and analysis of the technical and cost factors involved in the use of several battery materials ensued.

A discussion of various battery manufacturers and the supply and demand factors for battery materials followed. With current productions rates, the supply of lithium salts should be adequate for demand until 2017. If Bolivian production comes online, supply should last until 2030.

Next Dr. Mark Verbrugge of GM made a presentation on How Long Do Lithium-Ion Batteries Last? in conjunction with Y-T Cheng of The University of Kentucky. Verbrugge has developed a mathematical model of mechanical stress in the carbon anodes of Lithium-ion batteries during charge and discharge.

Battery failures normally occur either early in life or due to wear-out after long-term use.

One means to obtain a long useful life is to operate within a limited voltage range to limit reactivity of the electrodes with the electrolyte. The LFP-LTO battery provides 2.4V and achieves this objective in commercial Lithium-ion. Batteries, solvent reduction at the carbon anode and solvent oxidation at the cathode result in the formation of solid electrolyte interface (SEI) layers. During cycling, stress develops in the SEI due to expansion and contraction and the magnitude of this stress is related to the change in state-of-charge (SOC). As a result of this stress, new areas are exposed, leading to an increase in the amount of active material converted to SEI and even the isolation of active material from the electrode. Both effects result in a loss of capacity in the anode after long cycle life.

The final talk of the Wednesday morning session was given by Mohamed Alamgir of Compact Power/LG Chemical on Large-Format Li-Ion Polymer Battery for Automotive Applications. Compact Power (CPI) is a wholly owned subsidiary of LG Chemical (LG) in Korea and carries out battery pack designs, battery management systems development and battery pack production and support.

LG has developed a unique folded bi-cell configuration for its cell in an Al foil laminate package. This company employs a spinel-based chemistry with a proprietary separator coated in-house and either a graphite or amorphous carbon anode. The electrolyte contains Li PF6 in a gel-type polymer electrolyte. The cathode composition contains the spinel LMO plus an unspecified layered oxide which is stated to optimize its performance. The SRS™ separator incorporates a nano-scale ceramic coating on a microporous polyolefin film.

The results of safety tests have demonstrated abuse-tolerance for the LG cell. Performance targets include:

Testing to demonstrate these objectives is in progress. The prismatic cell allows a variety of pack architectures which incorporates an air gap for thermal management. The use of liquid or refrigerant cooling is also possible via active air cooling. The BMS uses an ASIC circuit and improved SOC and SOH functions.

The LG Chemical cell has been selected by GM for use in the Chevy Volt. CPI/LG will assemble initial packs but large-scale assembly will be carried out by GM.

The first presentation on Wednesday afternoon in the large format session was given by Dr. Klaus Brandt of Lithium Technology Corp./GAIA on Development of Lithium-Ion Batteries for Automotive Applications Using Large Format Cells. Brandt reviewed the battery requirements for use in the mild HEV, full HEV, PHEV and full EV. He then discussed DSC experiments on common cathode materials which show that lithium iron phosphate (LFP) is the most stable of those tested. LTC/GAIA cells using LFP possess the required power for HEVs but insufficient energy for EVs. At 100% DOD, DD-size LFP cells demonstrate longer cycle life than NCA cells. GAIA has available large cylindrical cells using LFP or NCA in high-energy and high-power designs with capacities from 6Ah to 60Ah.

Information on cost as a function of production rate was presented. Large-cell cost should be lower than small-cell cost at high production rates but both types must be in excess of 1BWh/yr to achieve the Argonne National Laboratory goal of about $240 per KWh. A comparison of a 24KWh battery composed of 18650 cells or 60Ah high-energy cells was presented. Currently such a battery using 18650 cells has cost and weight advantages based on cell properties only. However, Brandt presented information showing that a 24KWh battery using 60Ah cells has potential advantages in terms of safety, cycle-life at high DOD and high-rate capability. The requirements for thermal management and the BMS in electric vehicles were discussed and the design of a battery for a delivery vehicle presented.

In the battery material session, Prof. Robert Hamers and also CTO of SilaTronix gave a talk on Organo-silicon Electrolytes for Lithium-Ion Batteries. The potential advantages of organo-silicon (O-S) electrolytes relative to carbonate compounds were discussed. O-S electrolytes are stable to +6V and their use in Lithium-ion batteries results in a SEI layer formed from the salt, not the solvent. O-S compounds can be used with ionic liquids (ILs) as the salt.

The properties of several O-S compounds under development were discussed and the requirements for an electrolyte salt presented. Lithium bisoxalatoborate (LI BOB) has the most favorable characteristics for use with O-S compounds. Conductivity data shows these electrolytes possess conductivities of CA 2mS/cm at 25C using an O-S compound called 1NM3. Electrochemical data demonstrating the stability of these electrolytes was presented. The LI BOB salt forms a SEI layer which appears stable on long-term cycling tests. The use of ILs with O-S compounds shows improved conductivity at low temperature. The potential advantages of using these electrolytes in electric double-layer capacitors, Lithium-ion and lithium primary batteries were discussed.

The next talk in the materials session was given by Prof. Doron Aurbach of Bar-Ilian University in Israel on Advances in R&D on Electrolyte Solutions for Rechargeable Batteries. Discharge curves and DSC data were presented for four advanced cathode materials. The properties of known solvents and salts for electrolyte solutions were reviewed. The use of additives to the electrolyte solutions to improve their properties were discussed. Additives may be employed to 1) remove protic and acidic contaminants; 2) reduce flamability; 3) improve conductivity; and 4) provide overcharge protection.

The effects of two additives, vinylene carbonate (VC) and propargyl methyl sulfonate (PMS) on the properties of the EC-DMC-LiPF6 electrolytes were studied by electrochemical and spectroscopic techniques. The use of VC + PMS results in very low oxidative currents on Pt at +5V vs. Li for graphite on Ni electrodes. Research on ionic liquids as additives to carbonates has shown that they improve the oxidative stability of the cathode and allow the use of 5V cathodes. The properties of several ILs and the potential problems associated with their use defined. Some test data on rechargeable Mg batteries was also presented.

The first talk after the mid-afternoon break was given by Glenn Amatucci of Rutgers University on Pathways to High-Energy Electrodes Incorporating Fluoride and OxyFluoride Compounds. Prof. Amatucci discussed the properties of compounds such as Ferric Fluoride which can be converted to Fe + LiF in a two-step process and which provide a theoretical capacity of 820mAhlg and a specific energy of 1,783Wh/Kg. Although this material is an insulator, when prepared as nanoparticles, it becomes conductive. The two-step process involves intercation first producing LiFeF3 in a one-electron process followed by conversion to Fe and LiF in a two-electron step. The Rutgers Energy Storage Research Group has also developed a Ag Mo O3F3 compound which exhibits performance superior to that to silver vanadium oxide in lithium primary cells used in heart defibrillators. On discharge against Li, AgMoO3F3 exhibits plateaux at 3.6V (two electrons), 3.1V (one electron) and 2.1V (two electrons). the first two correspond to the reduction of silver species and the third to the reduction of Mo (VI) to Mo (IV).

Next Sebastien Martinet of Liten-CEA in France made a presentation on High-Energy Li-Ion Cells. Over-lithiated mixed metal oxides employing Mn and another transition metal oxide (Ni or Co) have achieved very high capacities but suffer from limited performance at high rates and low temperatures. A simplified mechanism for lithium insertion and extraction from these compounds was presented along with a route to their synthesis. Non-optimized compounds demonstrate a specific capacity above 200mAh/g for cycles between 4.8V and 3.0V. An optimized compound gave a specific capacity of 250mAh/g for 25 cycles. When used with a graphite anode, these oxides are projected to provide 250Wh/Kg at the cell level.

Silicon-graphite composite anodes have been synthesized and tested. Although these compounds suffer from a very high irreversible capacity loss, a reversible specific capacity of 1,000mAh/g was demonstrated for 45 cycles before further capacity loss occurred. Improved performance was seen with anodes with a higher Si/C ratio employing nano-Si particles.

Preliminary test data on prototype cells in a foil-laminate package with a NCA positive and graphite or SiC negatives was shown. Swelling of the cell with the Si-C negative was observed on cycling. The talk concluded with a summary of the specific energies for the cells tested. The use of a Si-C anode increases the specific energy significantly in LCO and LFP cells. A specific energy range of 280-320Wh/Kg is claimed for a cell employing the LMN cathode with a Si-C anode but the cycle life was not defined.

The first presentation in the materials session on Thursday morning was given by Kirby Beard of Porous Power Technologies (PPT) on Electrochemical, Thermal and Safety Characteristics on High Power High Efficiency Lithium-Ion Cells Constructed with Novel, High Performance Separators. The properties of a proprietary Symmetrix™ PVDF separator material were described. The high-power version is 80% porous, 25 micron thick with average pore diameters of 0.2 to 0.8 microns. The HPX version is reinforced with PET. Tests have been carried out in Li-ion pouch cells to compare the PPT separator with commercial products with respect to rate capability and cycle life. These products demonstrate improved performance at intermediate rates and long cycle life. Safety tests have been carried out by an independent laboratory in accord with UL-1642 requirements.

Pouch cells using the PPT HP and HPX separators passed the short circuit, crush, abnormal charge and heating tests, as did cells containing commercial separators. PPT states that the unique properties of their separators are the key to providing improved Lithium-ion cell performance.

The next presentation was made by Aron Newman of Physical Sciences Inc. (PSI) on Electroactive Polymer Separator for Overcharge Protection. PSI has developed a battery separator material containing an electroactive polymer to provide overcharge protection if the charging voltage exceeds 3.45V. These polymers employ polythiophene derivatives which are oxidized at +3.5V. The separator is a three-component material consisting of a structural component 5-20%), a polythiophene overcharge component (25-50%) and a lithium ion conductor (40-60%). Tests were carried out using coin cells with a LFP cathode, a graphite anode and a carbonate electrolyte. Impedance studies show higher resistance for the polythiophene separator. When charged at 0.55mA/cmsq., the voltage stabilizes at +3.45V after peaking at +3.5V.

The peak voltage and the overcharge voltage are both functions of the charging current. When cycled at the 2C rate and overcharged 150% the PSI separator performed well for 350 cycles. Some self-discharge is observed after a 24-hour stand. PSI attributes this to pinholes in the material. The rate-capacity of a polythiophene-free separator is comparable to commercial products and it exhibits good mechanical properties. Pouch cells have been Tested.

The subsequent talk in the large format session was given by Frank Zhao of Ampere Technologies Ltd. (ATL) on High-Power Nano Lithium Titanate-Based Battery for HEV Applications. Altair-Nano Inc. also contributed to this presentation. Zhao described the properties of LTO which make it an attractive anode material for use in low-voltage Lithium-ion batteries. It has a wider safety window, long cycle life, no volume change, faster charge and discharge and good low-temperature performance. It suffers from a low energy density and low voltage. Electrochemical tests show some irreversible capacity loss on the first cycle. A 3.5Ah HEV LMO-LTO cell has been developed. Impedance tests were carried on this foil-laminate cell and demonstrate a low impedance between 10% and 70% SOC. A discharge pulse-power of 3.7KW/Kg at 50% SOC was also shown. The cell also demonstrates high-rate cycling capability to 10C with high efficiency and show acceptable abuse performance but high-temperature storage capability needs to be improved.

Next John M. Miller of Maxwell Technologies made a presentation on Ultracapacitors Plus Lithium-Ion for PHEV: Technical and Economic Analysis. He presented a theoretical analysis of the potential advantages of using a Lithium-ion battery and ultracapacitors with a power convertor in PHEVs. In order to make this feasible economically, it will be necessary to optimize lithium-ion energy density and the ultracapacitor must have a high power density. Data on partitioning the power between the battery and the ultracapacitor for a Chevy Volt type PHEV was presented and a conceptual design of a fully hybridized battery pack shown.

The following talk in the materials session was given by Ivan Exnar of high-power lithium (HPL) in Switzerland on Lithium Manganese Phosphate Cathodes for High-Performance Lithium-Ion. He discussed the need to improve safety and lower cost in industrial markets for Lithium-ion batteries and then presented information on properties of lithium metal phosphates as offering a potential solution to these barriers. He believes the lithium manganese phosphate (LMP) offers the most ideal voltage of all the transition metal phosphates and that it provides advantages in cost and safety as well. It suffers from several disadvantages including low conductivity and density, however. The average discharge voltage is also lower than LFP despite the higher OCV. HPL states that its proprietary nano-structured synthesis with a carbon coating overcomes these disadvantages. Their synthesis produces LMP particle s which are 200nm long by 20nm thick. with a specific capacity of 150nAh/g at low rate. Electrodes using these materials show good rate capability and long cycle life.

DSC data shows a mall exotherm for LMP at 240C. HPL has produced prototype 18650 cells with a capacity of 0.96Ah and states that its technology has been validated by Toyota and Bosch. Prototype LMP-LTO cells have also been developed in pouch cells.

The next presentation was made by Ben Kaun of InvenTek Corp. on Rolled-Ribbon™ Large Format Battery Architecture. Using long (40m), thin (133mm) electrodes, InvenTek is producing Li-ion cells in a spiral-wound disk format so that these cells may be stacked in a bipolar-type configuration to produce a 12-cell 42V module. The edge of the current collector makes contact with the top or bottom of the case, obviating the need for tabs and providing a short current path to the case. This results in a lower DC impedance than conventional spiral-wound designs and provides higher capacity at high rates. InvenTek states that this design produces better energy efficiency and lower heat generation which may lead to enhanced safety.

In the final presentation of the conference, Dr. Frank Jamerson of The Electric Battery Bicycle Company spoke on Electric Bikes Worldwide-Electric Transportation Now. Jamerson described the development of the market for electric bikes and other light electric vehicles and the current status of this market. A copy of Jamerson’s annual report with Ed Benjamin on this market is available at
www.EBWR.com.

Copies of the CD for the two tutorials and both the battery and recycling seminars are available from Florida Educational Seminars at
www.POWERSOURCES.net.