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Development of a high-power lithium-ion battery.

Description: Safety is a key concern for a high-power energy storage system such as will be required in a hybrid vehicle. Present lithium-ion technology, which uses a carbon/graphite negative electrode, lacks inherent safety for two main reasons: (1) carbon/graphite intercalates lithium at near lithium potential, and (2) there is no end-of-charge indicator in the voltage profile that can signal the onset of catastrophic oxygen evolution from the cathode (LiCoO{sub 2}). Our approach to solving these safety/life problems is to replace the graphite/carbon negative electrode with an electrode that exhibits stronger two-phase behavior further away from lithium potential, such as Li{sub 4}Ti{sub 5}O{sub 12}. Cycle-life and pulse-power capability data are presented in accordance with the Partnership for a New Generation of Vehicles (PNGV) test procedures, as well as a full-scale design based on a spreadsheet model.
Date: September 2, 1998
Creator: Jansen, A. N.
Partner: UNT Libraries Government Documents Department

Comparative costs of flexible package cells and rigid cells for lithium-ionhybrid electric vehicle batteries.

Description: We conducted a design study to compare the manufacturing costs at a level of 100,000 hybrid vehicle batteries per year for flexible package (Flex) cells and for rigid aluminum container (Rigid) cells. Initially, the Rigid cells were considered to have welded closures and to be deep-drawn containers of about the same shape as the Flex cells. As the study progressed, the method of fabricating and sealing the Rigid cells was expanded to include lower cost options including double seaming and other mechanically fastened closures with polymer sealants. Both types of batteries were designed with positive electrodes containing Li(Ni{sub 1/3}Co{sub 1/3}Mn{sub 1/3})O{sub 2} and graphite negative electrodes. The use of a different combination of lithium-ion electrodes would have little effect on the difference in costs for the two types of cells. We found that 20-Ah cells could be designed with excellent performance and heat rejection capabilities for either type of cell. Many parts in the design of the Flex cells are identical or nearly identical to those of the Rigid Cell, so for these features there would be no difference in the cost of manufacturing the two types of batteries. We judged the performance, size and weight of the batteries to be sufficiently similar that the batteries would have the same value for their application. Some of the design features of the Flex cells were markedly different than those of the deep-drawn and welded Rigid cells and would result in significant cost savings. Fabrication and processing steps for which the Flex cells appear to have a cost advantage over these Rigid cells are (1) container fabrication and sealing, (2) terminal fabrication and sealing, and (3) intercell connections. The costs of providing cooling channels adjacent to the cells and for module and battery hardware appear to favor Rigid cell batteries slightly. Overall, ...
Date: November 28, 2006
Creator: Nelson, P. A. & Jansen, A. N.
Partner: UNT Libraries Government Documents Department

Electrochemical studies of Mg-doped Li{sub 4}Ti{sub 5}O{sub 12} anodes.

Description: Commercial lithium-ion batteries use carbon as the material of choice for the anode. However, because lithiated carbon has a voltage very close to the potential of metallic lithium, there are concerns about the safety of fully-charged carbon electrodes. The safety issue can be addressed by using a material that intercalates lithium at a higher voltage. A promising material is the lithium-titanium-oxide spinel material Li{sub 4}Ti{sub 5}O{sub 12} which can accommodate 3 Li{sup +} ions per formula unit (corresponding to 175 mAh/g) in a two-phase reaction at approximately 1.5 V versus lithium. One of the drawbacks of this system is that the end-member Li{sub 4}Ti{sub 5}O{sub 12} is electronically insulating, which limits electron transfer at the electrode surface. By doping this material with magnesium, Li{sub 4{minus}x}Mg{sub x}Ti{sub 5}O{sub 12}, we introduced mixed-valent Ti{sup 4+}/Ti{sup 3+} into the stoichiometric spinel structure and thereby increased the electronic conductivity by several orders of magnitude without sacrificing electrochemical performance. In this presentation we will provide data on the extent of the solid solution in Li{sub 4{minus}x}Mg{sub x}Ti{sub 5}O{sub 12}, the variation of electronic conductivity as a function of dopant concentration and the rate capability of the doped material.
Date: July 19, 1999
Creator: Chen, C. H.; Jansen, A. N. & Vaughey, J.
Partner: UNT Libraries Government Documents Department

Modification of LiCl-LiBr-KBr electrolyte for LiAl/FeS{sub 2} batteries

Description: The bipolar LiAl/FeS{sub 2} battery is being developed to achieve the high performance and long cycle life needed for electric vehicle application. The molten-salt (400 to 440 C operation) electrolyte composition for this battery has evolved to support these objectives. An earlier change to LiCl-LiBr-KBr electrolyte is responsible for significantly increased cycle life (up to 1,000 cycles). Recent electrolyte modification has significantly improved cell performance; approximately 50% increased power, with increased high rate capacity utilization. Results are based on power-demanding EV driving profile test at 600 W/kg. The effects of adding small amounts (1--5 mol%) of LiF and LiI to LiCl-LiBr-KBr electrolyte are discussed. By cyclic voltammetry, the modified electrolytes exhibit improved FeS{sub 2} electrochemistry. Electrolyte conductivity is little changed, but high current density (200 mA/cm{sup 2}) performance improved by approximately 50%. A specific feature of the LiI addition is an enhanced cell overcharge tolerance rate from 2.5 to 5 mA/cm{sup 2}. The rate of overcharge tolerance is related to electrolyte properties and negative electrode lithium activity. As a result, the charge balancing of a bipolar battery configuration with molten-salt electrolyte is improved to accept greater cell-to-cell deviations.
Date: June 1, 1996
Creator: Kaun, T.D.; Jansen, A.N.; Henriksen, G.L. & Vissers, D.R.
Partner: UNT Libraries Government Documents Department

Low-cost flexible packaging for high-power Li-Ion HEV batteries.

Description: Batteries with various types of chemistries are typically sold in rigid hermetically sealed containers that, at the simplest level, must contain the electrolyte while keeping out the exterior atmosphere. However, such rigid containers can have limitations in packaging situations where the form of the battery is important, such as in hand-held electronics like personal digital assistants (PDAs), laptops, and cell phones. Other limitations exist as well. At least one of the electrode leads must be insulated from the metal can, which necessitates the inclusion of an insulated metal feed-through in the containment hardware. Another limitation may be in hardware and assembly cost, such as exists for the lithium-ion batteries that are being developed for use in electric vehicles (EVs) and hybrid electric vehicles (HEVs). The large size (typically 10-100 Ah) of these batteries usually results in electric beam or laser welding of the metal cap to the metal can. The non-aqueous electrolyte used in these batteries are usually based on flammable solvents and therefore require the incorporation of a safety rupture vent to relieve pressure in the event of overcharging or overheating. Both of these features add cost to the battery. Flexible packaging provides an alternative to the rigid container. A common example of this is the multi-layered laminates used in the food packaging industry, such as for vacuum-sealed coffee bags. However, flexible packaging for batteries does not come without concerns. One of the main concerns is the slow egress of the electrolyte solvent through the face of the inner laminate layer and at the sealant edge. Also, moisture and air could enter from the outside via the same method. These exchanges may be acceptable for brief periods of time, but for the long lifetimes required for batteries in electric/hybrid electric vehicles, batteries in remote locations, and those in satellites, ...
Date: June 18, 2004
Creator: Jansen, A. N.; Amine, K. & Henriksen, G. L.
Partner: UNT Libraries Government Documents Department

Development of a high-rate, rechargeable bipolar LiAl/FeS{sub 2} battery

Description: Materials refinements have improved bipolar Li-Al/FeS{sub 2} batteries for power-demand applications. Current technology uses a two-phase Li-alloy cathode, LiCl-LiBr-KBr electrolyte, and an upper-plateau (UP) FeS{sub 2} anode for a battery operated at 440 C; the battery is in sealed bipolar form. The two-phase Li alloy ({alpha}+{beta} Li-Al and Li{sub 5}Al{sub 5}Fe{sub 2}) cathode provides in situ overcharge tolerance that makes the bipolar design viable. The use of LiCl-rich LiCl-LiBr-KBr electrolyte in ``electrolyte-starved`` cells achieves low-burdened cells with low area-specific impedance, with MgO powder separator. Combining dense UP FeS{sub 2} electrodes with a CuFeS{sub 2} additive and a LiI-modified electrolyte produces a stable and reversible couple, with high power capabilities. Long cycle life depends on peripheral seals for each cell in the bipolar stack. Seal composition is based on stable sulfide ceramic/sealant materials that produce strong bonds between metals and ceramics. Using these seals, bipolar Li-Al/FeS{sub 2} cells and four-cell stacks are being built and tested (25 Ah, 13-cm dia). Adding 5 mol% LiI to the electrolyte increased specific energy by 50% under a 140 W/kg, constant power C/1 rate and a 544 W/kg power pulse (8-s) schedule. Cell capacity under the high-power pulse-demand approximates the C/3 rate discharge capacity. Cell specific energy is 155 Wh/kg at the C/3 rate.
Date: June 1, 1996
Creator: Kaun, T.D.; Jansen, A.N.; Hash, M.C.; Prakash, J.; Turner, R.L. & Henriksen, G.L.
Partner: UNT Libraries Government Documents Department