Part I

There were over 400 attendees at this year’s show, and despite a little rain a first it was a great success. As might be suspected from the large number of Li-ion battery recalls in 2006, a major theme was safety. Another was the expectation for implementing Li-ion batteries in HEV applications.

As usual, the Seminar provided an excellent overview of the global battery market, an update on the performance capabilities of the various battery chemistries, recent developments in materials research, and a preview of some new, emerging technologies.

Preceding the main conference were two excellent tutorials. The first, “Review on the Status and Prospects for Fuel Cells for Portable Applications,” was given by Dr. Frank Gibbard of Gibbard Research and Development Corp. He provided an overview of the different types of fuel cells, the different fuels, the key developers of fuel cell technology, and the current status of development. The second tutorial, “Worldwide Market Update on NiMH, Li-ion and Polymer Batteries for Portable Applications and HEVs,” was given by Hideo Takeshita from the Institute of Information Technology, Ltd. This tutorial has become an annual event at the conference and provides invaluable information on the state-of-health of the battery industry, market statistics, market trends, and technology trends.

Following are summaries of some key presentations made at the rest of the meeting.

Regulatory Update on Batteries and Fuel Cells

Richard Stern of the U.S. Consumer Product Safety Commission provided information on battery investi-gations and recalls. CPSC-announced battery recalls over the past four years are summarized as follows:

FY2004: 5 recalls, 250,500 units, 33 incidents
FY2005: 10 recalls, 1,317,075 units, 82 incidents
FY2006: 12 recalls, 4,579,300 units, 110 incidents
FY2007: 4 recalls, 345,800 units, 9 incidents (Oct06- Jan07)

Bob Richard of DOT’s Pipeline and Hazardous Materials Safety Administration (PHMSA) provided an update on the incidents they have encountered and recent changes to the regulations. Since 1991, there have been a total of 75 battery related incidents in aviation. Fortunately, most were detected on the ground, thereby avoiding any major catastrophes. However, there have been far too many close calls and an enterprise group is being assembled to study the problem in more detail.

Regulations are also being updated in an effort to enhance passenger safety. Proposed changes to the UN Model Regulations (15th Edition Amendments to be implemented January 1, 2009) include new names to distinguish between lithium metal and Li-ion batteries, required watt hour markings on battery packaging, and some packaging, marking, and documentation enhancements. Proposals by the International Civil Aviation Organization (ICAO) include prohibition of certain primary lithium batteries on passenger aircraft, removal of the passenger exception for batteries containing 8-25 grams of lithium, required reporting of all battery incidents for all battery types, and prohibition of transport of damaged batteries.

PHMSA is also taking proactive steps to educate the public on battery safety and to work with the airlines, battery manufacturers, and device manufactures to reduce the risk of battery incidents. A useful website to obtain information on what can be carried on commercial aircraft and what can be put into checked baggage is http://SafeTravel.dot.gov.

Other presentations on recent battery transportation incidents and proposed changes to industry standards to enhance safety and minimize risk were given by Marvin Sudduth of FedEx Express and George Kerchner of the Portable Rechargeable Battery Association.

Transportation regulations are just as important for fuel cells as they are for batteries and approvals are needed to be able to ship fuel cells and to carry fuel cartridges and electronic devices containing fuel cells onto commercial aircraft. Anna Stukas from Angstrom provided an update on the status of regulatory approvals for micro fuel cell systems. New and separate UN numbers have now been obtained for fuel cell cartridges involving flammable liquids (methanol, etc.), water reactive substances (borohydrides, etc.), corrosive substances (borohydrides, formic acid, etc.), and hydrogen stored in metal hydrides. Fuel cell cartridges containing flammable liquids have been approved for transport as cargo on passenger and cargo aircraft, and passenger cabin exceptions have been received for fuel cell cartridges containing flammable liquids (including methanol), formic acid, and butane. International safety standards are nearing completion and should be approved for all fuels onboard aircraft by 2009.

Li-ion Battery Safety and Reliability

Brian Barnett of TIAX discussed field failures of Li-ion batteries and how they differ from abusive failures. Field failures occur during normal use of batteries and devices, are unpredictable, have a low frequency of incidence (ppm level), don’t usually show up until the battery has been cycled many times, are generally caused by internal short circuits, and occur in cells made by the best manufacturers in the world. The most prevalent causes of the internal short circuits have been manufacturing defects, the presence of foreign metal particles, and the formation of lithium dendrites. During an internal short, localized temperatures can rise above 200C in less than one second, and general abusive safety features such as PTCs, CIDs, shutdown separators, and electronic controls are ineffective in preventing subse-quent thermal runaway. Thus, even if a cell has high abuse tolerance, it could react violently during a field failure.

To date, the focus has been on reducing the frequency of field failure occurrences through improved manufacturing and quality control practices. However, since the causes of field failures can never be completely eliminated, it is important to also pursue methods to reduce the severity of the failures when they do occur. This will require a thorough understanding of the kinetics of the exothermic decomposition reactions that occur along with methods to control the reaction kinetics and maintain them at safe levels. To this end, TIAX is pursuing a three-pronged approach: (1) the development of improved methods of materials characterization, including the use of the Accelerating Rate Calorimeter (ARC) and MMC, a new instrument being developed by TIAX that combines the best features of ARC and DSC and which can accurately measure self-heating rates up to 1000C/minute; (2) development of FEA models that can simulate internal short circuits and can be used to evaluate a wide range of cell design parameters and materials properties; and (3) development of methods to induce field failures in cells as a means to test theories and validate the FEA model results. An FEA model of an 18650 Li-ion cell has been successfully developed and was demonstrated in the presentation showing the temperature distributions and heat release profiles during an internal short circuit.

Christina Lampe-Onnerud of Boston Power Inc., a two-year-old start-up, outlined their whole systems approach to achieving greater performance, reliability, and safety in lithium-ion batteries. The industry focus in recent years has been to increase first cycle capacity, but this is often achieved at the expense of cycle life. Boston Power’s goals are to:

• Enable fast recharge capability (80% in 30 minutes)

• Deliver run-time that lasts the life of the notebook computer (e”1,000 cycles)

• Improved safety features – safety is non-negotiable

• Ensure reliability and consistency

• Provide a roadmap for continuous improvement

• Produce environmentally sound products

Their approach to achieve these goals includes: the use of a prismatic can sized to replace two side-by-side 18650 cells in a battery pack. This has the advantage of simplifying the battery pack and making cell balancing easier by eliminating parallel cells, improving heat dissipation, and better utilizing the space in the battery container, thereby allowing the use of lower packing density in the cells to improve safety and cycle life without loss of capacity compared to an 18650-based battery; improved safety components including lower temperature pressure vents, lower temperature CIDs, and lower impedance PTCs; a unique cathode formulation that is more thermally stable than LiCoO2; a tailored anode composition; and a unique approach to mass production in China emphasizing training, a 6-sigma manufacturing strategy, Boston Power on-site production, quality, and engineering managers, full materials and processing traceability, an automated production line with rapid QC feedback, and stringent supply chain management for all components and materials. Their new technology is called “Sonata” and has demonstrated good safety and performance capabilities, including a cycle life of 1200 cycles. Although its starting capacity is slightly less than competing 18650-based batteries, it catches up after 20- 40 cycles due to the more rapid fade in the conventional batteries. Also, Sonata batteries are environmentally friendly and have been approved for Ecolabel.

Because of their low frequency and unpredictability, determining the root cause of a field failure of a lithium-ion battery pack is often an overwhelming task, but one that is absolutely crucial. Troy Hayes outlined the systematic methodology that has been developed at Exponent Inc. to pinpoint the exact location and cause of cell and battery failures. This methodology has been used to successfully investigate hundreds of battery failures and involves the following steps:

I. Identify the location of the failure:

   A. Photograph battery pack

   B. X-ray battery pack and the individual cells

   C. Dot computer topography (CT) scans of the cells:

      1. This powerful technique provides a series of hundreds of cross-sectional images of the jellyroll from the top to the bottom of the cell

   D. Unroll the electrode assembly of incident cells:

      1. Use X-ray mapping to look for foreign elements in area of failure

II. Examine undamaged battery packs and cells from the same production lots to identify/verify the cause of failure:

   A. Impedance spectroscopy (for detection of microshorts)

   B. Cross-sectional analysis of jellyroll to detect manufacturing defects and/or the presence of foreign materials (metal particles, etc.)

III. Conduct statistical analysis to define the time frame of production cells that are affected

A case study involving analysis of a notebook computer battery failure incorporating 18650 Li-ion cells was presented.

Nickel-Metal Hydride Technology for Portable Devices

This marked Mike Fetcenko’s 20th year of presenting at this conference, providing annual updates on Ovonic’s NiMH technology. Over those 20 years, it has been interesting to witness the continuing growth of Ovonic licensees and the continuing evolution of the nickel-metal hydride technology. Today, Ovonics has 100 issued U.S. patents, 200 issued foreign patents, and 34 licensees. AA-cell performance is used as the benchmark and has progressed from 1100mAh, 54Wh/kg and 190Wh/L in 1991 to 2660 mAh, 110Wh/kg, and 433Wh/L today. Long charge retention cells are also being introduced by a number of manufacturers. These improvements now position NiMH as a viable alternative to traditional alkaline cells in many high-drain applications, and NiMH’s market share as an alkaline replacement is projected to be growing at 30-40% per year. Ovonics believes the NiMH is far from a mature technology and expects continued, significant improvements in the future. The next milestone is to achieve a 3000mAh AA cell with 120Wh/kg and 490Wh/L. Other areas of development include increased energy and power levels, the merger of high energy and high power into a single design, improved shelf and cycle life, and reduced cost.

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Hirohito Teraoka of Sanyo presented an update on their ENELOOP low self-discharge NiMH battery technology. Rechargeable batteries account for only 1% of battery usage in Japan and the major complaints against them are: too expensive, inability to use if stored for extended length of time (high self-discharge rate), not knowing which applications to use rechargeables for, and too difficult to use. The ENELOOP technology addresses the second concern, providing a rechargeable NiMH battery that comes charged, ready to use right out of the package. This technology uses a super-lattice hydrogen-absorbing alloy for the negative electrode to reduce dissolution of Co, Mn, and other elements, additives to increase the oxygen overvoltage at the positive electrode, use of a sodium-rich electrolyte solution in place of a potassium-rich solution to reduce the self-decomposition of the charged positive electrode, and a hydrophilic treatment of the separator to capture nitrogen-containing contaminants which can react and deplete energy from both electrodes. In addition to dramatically reducing self-discharge rates, the ENELOOP technology also provides longer cycle life over conventional NiMH cells. However, this longer cycle life was achieved at the cost of a 20% reduction in capacity due to the use of a thicker separator.

Continued in June 2007 ABT.