meeting report
26th International Battery Seminar & Exhibition
Ft. Lauderdale, Florida
March 16-19, 2009
- Bronxville, New York
The International Battery Seminar and Exhibit is organized by Dr. Sumner P. "Shep" Wolsky and Dr. A. Harry Taylor and is administered by Tom DeVita. The Battery Seminar was highly successful with presentations on a variety of important topics for approximately 360 attendees, 40 exhibitors and sponsors. Concurrently, the 13th International Battery Materials Recycling Seminar was held at the same location with about 200 attendees.
The Battery Seminar opened with two tutorials. The first was given by Prof. Andrew Burke of the University of California-Davis on lithium batteries and supercapacitors for vehicle applications: Device Test Data, Systems Design Considerations and Vehicle Simulations. Prof. Burke discussed a variety of energy storage options for propulsion of electric vehicles (EVs), hybrid electric vehicles (HEVs) and plug-in hybrid vehicles (PHEVs). He presented test data on a number of these systems. High-power ultracapacitors and lithium-ion batteries are now available for HEVs. Hybrid ultracapacitors offer significantly higher specific energy than those using carbons only. Combinations of batteries and ultracapacitors are feasible for use in micro-hybrids with lead-acid batteries and in PHEVs using lithium-ion batteries with the highest specific energy. Ultracapacitors alone should be considered for use in mild/moderate HEVs in the charge-sustaining mode. Cost factors for these systems were discussed in detail.
The second tutorial, entitled Worldwide Market Update on NiMH, Li-ion and Polymer Batteries for Portable and Future Applications, was given by Hideo Takeshita of the Institute for Information Technology of Japan. This presentation was Takeshita’s annual marketing update by market segment, cell technology and manufacturers. Particular emphasis this year was placed on batteries for electric vehicles and the emergence of South Korea as the source of these products.
Copies of both tutorials are available on CD from Florida Educational Seminars at www.PowerSources.net.
The first presentation at the seminar on Monday afternoon was given by Brian Barnett of TIAX and was entitled How to Mitigate/Prevent Safety Incidents in Lithium-ion Cells. Safety-related incidents with lithium ions occur in only one of 5 to 10 million cells produced and typically are caused by internal short circuits. TIAX has employed Finite Element Analysis to model the rapid temperature rise in 18650 cells and finds that there exist threshold levels of power and energy above which catastrophic failures occur. TIAX has also employed the JEIA internal short-circuit test in which metal particles are introduced into an 18650 cell which is then placed in an accelerating rate calorimeter (ARC) to simulate a field failure due to an internal short circuit. Using several methodologies and technologies, TIAX states that the development of a "fail-safe" lithium-ion battery is now possible.
Troy Hayes of Exponent-China made a presentation on The Use of CT Scanning for Defect Detection in Li-Ion Cells. Cross-sections of a typical 18650 cell may be obtained using CT scans which are 70 microns thick. Exponent has determined that foreign object defects of 20-100 microns lead to internal short circuits which typically occur between the aluminum cathode current collector and the anode. Other techniques to detect potential internal shorts include a Hi-Pot test of the dry cell and measuring the OCV of a fresh cell as a function of time. In addition, a case study in which cells subjected to repeated overcharges which resulted in cell leakage was presented. Poor registration of the electrodes during winding, resulting in cathode-anode contact, was identified as the cause of the problem.
Next, Kevin White of Exponent-USA spoke on Cell Overcharge in the Absence of Battery Management Unit Failure. He described a case study in which Li-ion battery packs were exhibiting zero volts after a few charge-discharge cycles even though the battery management unit was functioning flawlessly. The current interrupted devices were open. Gas analysis, cross-sectional analysis and energy-dispersive spectroscopy were carried out on the failed cells. Reference electrodes were also inserted in some cells to determine the voltage excursions of the anode and cathode during charge and discharge. The electrolyte was found to contain propylene carbonate (PC) which resulted in the formation of a thick layer on the anode, preventing normal intercalation and forcing the positive electrode to +4.7 volts. The overcharge of the LCO positive electrode resulted in structural degradation, oxygen evolution and decomposition of the electrolyte.
Next, E. Peter Roth of Sandia National Laboratory spoke on Abuse Response of HEV and PHEV Materials and Cells. Li-ion safety issues involve two failure modes: 1) field failure and 2) abuse failures. The materials studied were those employed in the DOE Advanced Technology Development (ATD) program. Thermal runaway conditions were characterized using accelerating rate calorimetry (ARC). Thermo-Gravimetric Analysis (TGA) was also carried out on numerous electrode materials. Decomposition of LFP does not occur until 360C. The LiPF6 SAIT salt was found to catalyze electrode decomposition around 150C. The highest abuse tolerance among cathode materials was found to be over-lithiated LNMC,>LMO>LFP. Separator failure has also caused cell failure under high-rate conditions. SNL has developed impedance during temperature ramp and DC resistance under high potential tests to detect separator failure modes.
This was followed by Daniel Derwey of the U.S. Department of Transportation (DOT) Office of Hazardous Materials Enforcement who spoke on Batteries and Regulations. DOT is aware of more than 96 air transport incidents which involve batteries or battery-powered devices which produced of tests and criteria (4th Revision-2003). New DOT regs which will require incident reporting, more detailed information on airway bills and eliminate the requirement to disconnect the terminals during shipment of wheelchairs and other electric vehicles have been delayed until January 1, 2010. The DOT safe travel program was also discussed.
top
This was followed by Regulatory and Legislative Update by George Kerschner of PRBA-The Rechargeable Battery Association. Several countries have adopted new regulations on lithium-ion cells and batteries and two, Japan and Korea, require in-country testing which is a violation of the World Trade Organization (WTO) agreement on technical barriers to trade. PRBA is working with the U.S. Trade Representative to resolve this issue. Consumer Safety Commission (CPSC) recalls in 2008 were reviewed. CPSC is particularly concerned about remote-controlled (R/C) toys and is working with ANSI and ASTM to develop regulations which are expected within two years. PRBA has been working with the UN Working Group to establish new definitions of "large" and "small" batteries, reduce the number of batteries and battery assemblies required for testing and eliminate the need for testing most discharged cells and batteries, effective in 2011. Changes to certain definitions and test procedures are also anticipated. PRBA is also working to harmonize ICAO and U.S. DOT shipping regulations. Effective January 14, 2009, new U.S. DOT regs require that "dry cell" batteries (NiCad, NiMH and alkaline) be shipped to prevent short-circuits and inadventant activation.
The last presentation on Monday was made by J.P. Wiaux of RECHARGE, The European Association of the Portable Rechargeable Battery Industry on The Impact of European Regulatory and Legislative Issues on the Rechargeable Battery Industry. By 2011, recycling goals have been established by weight for lead-acid (65%), nickel-cadmium (75%) and other batteries and accumulators (50%) in the E.U. The methodology used to calculate recycling efficiencies was discussed. Although the use of heavy metals in the E.U. is restricted by the RoHS Recycling Standards, these do not apply to batteries but the use of Cd and Hg in batteries is restricted. Detailed information on E.U. regulations may be found on the CD for the seminar.
The first talk on Tuesday morning was given by Yeugen Barshukov of Texas Instruments on Advantages and Challenges of System-Side Battery Fuel Gauge. Potential advantages of this approach in laptop computers and other devices include: 1) lower cost battery packs with protection electronics only; 2) many external packs can share one fuel gauge; 3) battery pack may be readily replaced if its life expires and 4) system can be developed faster without relying on pack manufacturers. Challenges with this approach include: 1) requirement for multiple cells in series; 2) requirement for interchangeability and support of packs from multiple suppliers; 3) the system fuel gauge requires high accuracy and battery state-of-health (SOH) indicator; 4) there may be insufficient capability in host CPU; and 5) system manufacturer may possess inadequate battery expertise. Methods for using host-side fuel gauging were delineated and their characteristics were discussed. Impedance tracking of the battery pack using the TI integrated circuit bq 2750x series was state to offer definite advantages for this approach and to offer SOH capability.
The following talk was given by Kamal Shah of Intel Corp. on User Perception of PC Battery Life. He detailed the results of a survey conducted by the Mobile PC Extended Life Working Group in 2008. The results of this survey indicate the following: 1) one out of three notebook PC users employ battery power more than 50% of the time; 2) users are moving towards more demanding applications and increased reliance on network connectivity which will require more battery life; 3) many users are unaware of the power management feature; and 4) battery life is the No. 1 or No. 2 concern of most users and they are willing to pay more for longer battery life.
Digatron booth
The following presentation was made by Dr. John Wozniak of Hewlett-Packard who discussed lithium-ion battery chemistries. Current batteries for laptop PCs and cellphones employ cobalt (LCO), manganese (LMO) or iron phosphate (LFP) as cathode materials. More recent developments include mixed oxides LNMC or LNCA and their advantages were delineated. Alternate technologies such as lithium-sulfur, silver-zinc and zinc-air were also discussed in the same context. The potential advantages of the Sonata® cell were also described. Next, Wozniak described the advantages of various form factors in laptop PCs. The cost of the various types is cylindrical > prismatic > pouch. The use of pouch cells is only justified in thin, light-weight notebook PCs. He concluded with a discussion of the common misconceptions about polymer-electrolyte pouch cells and the competitive edge their use may convey.
After the mid-morning break, Akira Kinoshita of Sanyo spoke on The Development of Sanyo Li-Ion Batteries. He discussed the growing demand for rechargeable batteries and the application they support. Sanyo has production capability of 700 million Li-ion cells per month and a 30% market share. Sanyo’s recent development efforts have emphasized higher capacity and power along with lower cost through the reduced use of cobalt. Sanyo’s current 18650 cylindrical cells provide 2.6Ah capacity but this is moving to 2.8Ah. Higher power cells are increasing in capacity from 1.2Ah to 1.6Ah. Cells with reduced CO content are also increasing capacity from 2.0Ah to 2.25Ah. Similar trends are occurring in prismatic cells. The use of an improved LCO cathode material containing Zr with the NMC oxide allows a higher charging voltage and provides higher capacity. Higher power prismatic cells under development employ a mixture of LMO and LNMC oxides.
The next presentation was made by Rick Chamberlain on Boston Power’s Sonata® Li-Ion Battery Technology. The Boston Power cell is comparable to two 18650 cells placed side-by-side but is wider with increased volume and provides a 4.4Ah capacity. It is also said to provide longer cycle life, faster charging, and greater safety than current Li-ion technology. The cell is housed in an aluminum case with two vents, an internal current-interrupter device (CID), and external PTC safety fuse and is said to be manufactured to six-sigma quality standards. Potential cost savings in pack assembly using the Boston Power cell were described.
The last talk of the Tuesday morning session was given by George Thomas of Tianj in Lishen Battery Co. on Li-Ion Power Batteries: Industry Trends and Applications. He discussed the use of various oxide cathode materials (LMO, LFP, LNMC and mixed LNMC-LMO) in high power application, particularly power tools (PT). Lishen manufacturers all of the above cylindrical, prismatic and foil laminate designs. Most PT products use LMO, mixed-oxide or LFP cathode-based cells. Cells LFP provide a long cycle life but LMO cells have cost and energy density advantages.
The first presentation of the Tuesday afternoon session was by Kenny Jeong of Samsung SDI America on Samsung Advanced Battery Solutions. Samsung-SDI is engaged in a joint venture to develop batteries for HEVs with Bosch. Jeong described Samsung-SDI’s development of the lithium-ion market where it projects a 22% market share in 2009 with a CAGI of 31%. Samsung-SDI uses LCO, NMC and mixtures of these as positive materials and graphite, silicon and their mixtures of these as positive materials and graphite, silicon and their mixtures as negatives to produce an 18650 cell with 2.8Ah capacity.
Robin Tichy of Micro Power Electronics next spoke about Battery Pack Design to Prevent Thermal Damage in Transient Thermal Conditions. Micro Power serves specialized battery markets including portable medical equipment and devices and develops custom hardware for these applications. This company uses a thermal network model to develop battery systems capable of withstanding transient high-temperature excursions. Mr. Tichy described the methodology used to carry out this process.
top
The final talk before the Tuesday afternoon break was given by David Tsai of Simplo Technology Co. in Taiwan on Challenges of Designing Battery Packs for Low Cost and Safety. He described the causes of Li-ion battery failures, most of which are caused by the cells (59%) or the battery management unit (BMU - 19%). This was followed by a case study in which electrolyte leakage resulted in a burnt battery and vented cells. Simplo’s approach to enhanced safety includes the use of double cell insulation and a BMU with reduced PCB layers conforming to JEITA standards with key component placement optimization. Their PMU incorporates a barrier wall design to prevent electrolyte ingress. Simplo selects cells for their packs based on OCV and impedance matching.
Following the mid-afternoon break on Tuesday, parallel sessions were held. One emphasized Large Format Systems while the other covered Battery materials and Processes. Selected presentations from each will be covered in this summary.
Bridget Deveney first spoke on SAFT’s Line of Lithium Iron Phosphate Cells and Beyond. SAFT initiated work on lithium iron phosphate (LFP) cells under sponsorship from the Army Research Laboratories (ARL) and it was continued under a MANTECH program. SAFT obtains its LFP from PhosTech which as licensed The Goodenough Patent. Development was carried out using SAFT’s high-power electrode technology and existing hardware from its NCA product line.
The LFP cells have lower capacity and power than NCA. the characteristics of SAFT’s FL 10 Fe 10Ah high-power and its VL 25 Fe 25Ah medium-power cells were described. The FL 10 Fe is capable of producing 6400w/kg under pulse-power conditions but has a specific energy of 54Wh/kg. The VL 25 Fe can produce 120 amps under continuous discharge and provides 89Wh/kg. Through optimization of electrode materials and electrolyte composition, SAFT’s LFP cells are capable of operation to -40C. Long cycle life is projected for the VL 10 Fe cell at 30C. High self-discharge rates are observed above 60C and impedance growth above 72C. This is believed to be caused by iron dissolution from the cathode, followed by reaction with the lithiated carbon anode. Safety testing at the cell level has been successful and prototype batteries have been built and tested.
Michael Fetchenko of ECD Ovonic then spoke on Ovonic NiMH Battery Technology. Nickel-metal hydride (NiMH) Technology has become a major factor in the commercial and vehicle battery markets. Commercial cells are available worldwide in sizes from AAA to F cells. Two million HEVs are on the road using NiMH batteries for energy storage. Improvements in this technology continue to develop, including new alloys and 50A nickel catalysts for positive electrode. Current AA cells provide 2.7Ah, 110Wh/kg and 459wh/L.
PHEVs using NiMH batteries have a 25-mile range in the pure electric mode at low speed. A custom Prius conversion to a PHEV is available for $12,500 with a three-year battery warranty. Large NiMH batteries for energy storage, telecommunications and UPS applications are now available although the initial cost is higher than lead-acid. Life-cycle cost is lower.
Dr. Franz Kruger of PowerGenix then spoke on Performance of Advanced Ni-Zn Cells and Batteries. PowerGenix has its headquarters in San Diego with a design center and a manufacturing partner in China. Kruger detailed the technical advantages of NiZn technology over other aqueous batteries and PowerGenix’s technology which uses a wicking separator and a microporous separator between the Ni foam and the Zn electrodes. The design of the spiral-wound, sealed cells was also described. Additives in the electrode and electrolyte are employed to inhibit Zn dendrite formation. Advances in the zinc electrode and separator enable high power and high cycle life. AA cells are available in a 1.5Ah consumer model and a 1.35Ah high-power OEM design. A 1.8Ah Sub-C cell is available for power tool applications and 6.5Ah and 8.0Ah D cells are under development. Battery packs have been assembled and tested for power tool usage.
The final presentation on Tuesday afternoon was made by Kurt Kelty of Tesla Motors who spoke on Safety Testing of Tesla’s 53KWh Li-ion Battery Pack." He described the characteristics of Tesla’s 2008 Roadster, including its 53KWh Li-ion battery pack which provides an EPA driving range of 244 miles. Battery safety and reliability are provided by: 1) a safe reliable cell designed to prevent the initiation and propagation of a thermal runway; 2) redundant monitoring and protection; 3) physical protection of the battery pack; and 4) extensive testing and validation. The results of safety testing, including a 50mph rear crash test on the Tesla Roadster, were shown.
