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Final Report: Nanomaterials in Secondary Battery Research and Development, July 1, 1995 - September 14, 1999

Description: We have been exploring the rate capabilities of nanostructured Li-ion battery electrodes. These nanostructured electrodes are prepared via the template method - a general procedure used to prepare nanomaterials pioneered in the P.I.'s laboratory. The nanostructured electrodes consist of nanofibers or tubules of the electrode material that protrude from a current-collector surface like the bristles of a brush. These nanostructured electrodes show dramatically improved rate capabilities relative to conventional electrode designs.
Date: January 31, 2000
Creator: Martin, Charles R.
Partner: UNT Libraries Government Documents Department

Effect on Performance of Composition of Li-Ion Carbon Anodes Derived from PMAN/DVB Copolymers

Description: The effects on electrochemical performance of the nitrogen content of disordered carbons derived from polymethacryonitrile (PMAN)-divinylbenzene (DVB) copolymers were examined in galvanostatic cycling tests between 2 V and 0.01 V vs. Li/Li+ in lM LiPF<sub>6</sub>/ethylene carbonate (EC)-dimethyl carbonate (DMC). The first-cycle reversible capacities and coulombic efficiencies increased with increase in the level of nitrogen for samples prepared at 700&deg;C. However, the degree of fade also increased. Similar tests were performed on materials that were additionally heated at 1,000&deg; and 1,300&deg;C for five hours. Loss of nitrogen, oxygen, and hydrogen occurred under these conditions, with none remaining at the highest temperature in all cases but one. The pyrolysis temperature dominated the electrochemical performance for these samples, with lower reversible and irreversible capacities for the first intercalation cycle as the pyrolysis temperature was increased. Fade was reduced and coulombic efficiencies also improved with increase in temperate. The large irreversible capacities and high fade of these materials makes them unsuitable for use in Li-ion cells.
Date: May 14, 1999
Creator: Even, William R. & Guidotti, Ronald A.
Partner: UNT Libraries Government Documents Department

Degradation Reactions in SONY-Type Li-Ion Batteries

Description: Thermal instabilities were identified in SONY-type lithium-ion cells and correlated with interactions of cell constituents and reaction products. Three temperature regions of interaction were identified and associated with the state of charge (degree of Li intercalation) of the cell. Anodes were shown to undergo exothermic reactions as low as 100&deg;C involving the solid electrolyte interface (SEI) layer and the LiPF<sub>6</sub> salt in the electrolyte (EC: PC: DEC/LiPF<sub>6</sub>). These reactions could account for the thermal runaway observed in these cells beginning at 100&deg;C. Exothermic reactions were also observed in the 200&deg;C-300&deg;C region between the intercalated lithium anodes, the LiPF<sub>6</sub> salt and the PVDF. These reactions were followed by a high- temperature reaction region, 300&deg;C-400&deg;C, also involving the PVDF binder and the intercalated lithium anodes. The solvent was not directly involved in these reactions but served as a moderator and transport medhun. Cathode exotherrnic reactions with the PVDF binder were observed above 200oC and increased with the state of charge (decreasing Li content). This offers an explanation for the observed lower thermal runaway temperatures for charged cells.
Date: May 4, 1999
Creator: Nagasubramanian, G. & Roth, E. Peter
Partner: UNT Libraries Government Documents Department

Optimization of Acetylene Black Conductive Additive andPolyvinylidene Difluoride Composition for High Power RechargeableLithium-Ion Cells

Description: Fundamental electrochemical methods were applied to study the effect of the acetylene black (AB) and the polyvinylidene difluoride (PVDF) polymer binder on the performance of high-power designed rechargeable lithium ion cells. A systematic study of the AB/PVDF long-range electronic conductivity at different weight ratios is performed using four-probe direct current tests and the results reported. There is a wide range of AB/PVDF ratios that satisfy the long-range electronic conductivity requirement of the lithium-ion cathode electrode; however, a significant cell power performance improvement is observed at small AB/PVDF composition ratios that are far from the long-range conductivity optimum of 1 to 1.25. Electrochemical impedance spectroscopy (EIS) tests indicate that the interfacial impedance decreases significantly with increase in binder content. The hybrid power pulse characterization results agree with the EIS tests and also show improvement for cells with a high PVDF content. The AB to PVDF composition plays a significant role in the interfacial resistance. We believe the higher binder contents lead to a more cohesive conductive carbon particle network that results in better overall all local electronic conductivity on the active material surface and hence reduced charge transfer impedance.
Date: July 1, 2007
Creator: Liu, G.; Zheng, H.; Battaglia, V.S.; Simens, A.S.; Minor, A.M. & Song, X.
Partner: UNT Libraries Government Documents Department

Conductive Carbon Coatings for Electrode Materials

Description: A simple method for optimizing the carbon coatings on non-conductive battery cathode material powders has been developed at Lawrence Berkeley National Laboratory. The enhancement of the electronic conductivity of carbon coating enables minimization of the amount of carbon in the composites, allowing improvements in battery rate capability without compromising energy density. The invention is applicable to LiFePO{sub 4} and other cathode materials used in lithium ion or lithium metal batteries for high power applications such as power tools and hybrid or plug-in hybrid electric vehicles. The market for lithium ion batteries in consumer applications is currently $5 billion/year. Additionally, lithium ion battery sales for vehicular applications are projected to capture 5% of the hybrid and electric vehicle market by 2010, and 36% by 2015 (http://www.greencarcongress.com). LiFePO{sub 4} suffers from low intrinsic rate capability, which has been ascribed to the low electronic conductivity (10{sup -9} S cm{sup -1}). One of the most promising approaches to overcome this problem is the addition of conductive carbon. Co-synthesis methods are generally the most practical route for carbon coating particles. At the relatively low temperatures (&lt;800 C) required to make LiFePO{sub 4}, however, only poorly conductive disordered carbons are produced from organic precursors. Thus, the carbon content has to be high to produce the desired enhancement in rate capability, which decreases the cathode energy density.
Date: July 13, 2007
Creator: Doeff, Marca M.; Kostecki, Robert; Wilcox, James & Lau, Grace
Partner: UNT Libraries Government Documents Department

Performance of Lithium Ion Cell Anode Graphites Under Various Cycling Conditions

Description: Graphites MCMB-2810 and OMAC-15 (made by Osaka Gas Inc.), and SNG12 (Hydro Quebec, Inc.) were evaluated (in coin cells with lithium counter electrodes) as anode materials for lithium-ion cells intended for use in hybrid electric vehicles. Though the reversible capacity obtained for SNG was slightly higher than that of OMAC or MCMB, its 1st cycle efficiency was lower. Voltage vs capacity plots of cycling data show that the discharge and charge limits shift to higher capacity values due to continuation of anode side reactions. Varying the cycle charge and discharge limits was found to have no significant effect on fractional capacity shift per cycle.
Date: June 15, 2009
Creator: Ridgway, Paul; Zheng, Honghe; Liu, Gao; Song, Xiangun; Guerfi, Abdelbast; Charest, Patrick et al.
Partner: UNT Libraries Government Documents Department

Thermal Instability of Olivine-Type LiMnP04 Cathodes

Description: The remarkable thermal stability of LiFePO{sub 4} and its charged counterpart, FePO{sub 4}, have been instrumental in its commercialization as a lithium ion battery cathode material. Despite the similarity in composition and structure, and despite the high thermal stability of the parent compound, LiMnPO{sub 4}, we find that the delithiated phase Li{sub y}MnPO{sub 4}, (which contains a small amount of residual lithium), is relatively unstable and reactive toward a lithium ion electrolyte. The onset temperature for heat evolution in the presence of 1M LiPF{sub 6} in 1:1 ethylene carbonate/propylene carbonate is around 150 C, and the total evolved heat is 884 J/g, comparable to that produced under similar conditions by charged LiCoO{sub 2} electrodes.
Date: July 7, 2009
Creator: Chen, Guoying & Richardson, Thomas J.
Partner: UNT Libraries Government Documents Department

Lithium-endohedral C{sub 60} complexes.

Description: High capacity, reversible, lithium intercalated carbon anodes have been prepared, 855 m.Ah/g, which exceed the capacity for stage 1 lithium intercalated carbon anodes, 372 mAh/g. Since there is very little hydrogen content in the high capacity anode, the fullerene C{sub 60} lattice is used to investigate the nature of lithium ion bonding and spacing between lithiums in endohedral lithium complexes of C{sub 60}. Three lithium-endohedral complexes have been investigated using ab initio molecular orbital calculations involving 2,3 and 5 lithium. The calculated results suggest that lithium cluster formation may be important for achieving the high capacity lithium carbon anodes.
Date: May 4, 1998
Creator: Scanlon, L. G.
Partner: UNT Libraries Government Documents Department

Recent Developments in Thin-Film Lithium and Lithium-Ion Batteries

Description: This report on recent developments in thin-film lithium and lithium-ion batteries displays experimental data related to high-rate deposition and annealing, metal foil substrates, tin and zinc nitride anodes, lithium plating (``lithium-free'' lithium cells), manufacturing and applications. Challenges and future work include improving the yield of batteries on metal foils by electrical isolation of anode current collector from substrate, and lowering manufacturing costs by increasing deposition and processing rates of electrolyte and cathode films.
Date: January 4, 1999
Creator: Bates, J.B.; Dudney, N.J. & Neudecker, B.J.
Partner: UNT Libraries Government Documents Department

Low Temperature Electrical Performance Characteristics of Li-Ion Cells

Description: Advanced rechargeable lithium-ion batteries are presently being developed and commercialized worldwide for use in consumer electronics, military and space applications. The motivation behind these efforts involves, among other things, a favorable combination of energy and power density. For some of the applications the power sources may need to perform at a reasonable rate at subambient temperatures. Given the nature of the lithium-ion cell chemistry the low temperature performance of the cells may not be very good. At Sandia National Laboratories, we have used different electrochemical techniques such as impedance and charge/discharge at ambient and subambient temperatures to probe the various electrochemical processes that are occurring in Li-ion cells. The purpose of this study is to identify the component that reduces the cell performance at subambient temperatures. We carried out 3-electrode impedance measurements on the cells which allowed us to measure the anode and cathode impedances separately. Our impedance data suggests that while the variation in the electrolyte resistance between room temperature and -20"C is negligible, the cathode electrolyte interracial resistance increases substantially in the same temperature span. We believe that the slow interracial charge transfer kinetics at the cathode electrolyte may be responsible for the increase in cell impedance and poor cell performance.
Date: April 29, 1999
Creator: Nagasubramanian, Ganesan
Partner: UNT Libraries Government Documents Department

Cyanoethylated Compounds as Additives in Lithium/Lithium Ion Batteries

Description: The power loss of lithium/lithium ion battery cells is significantly reduced, especially at low temperatures, when about 1% by weight of an additive is incorporated in the electrolyte layer of the cells. The usable additives are organic solvent soluble cyanoethylated polysaccharides and poly(vinyl alcohol). The power loss decrease results primarily from the decrease in the charge transfer resistance at the interface between the electrolyte and the cathode.
Date: May 8, 1998
Creator: Nagasubramanian, Ganesan
Partner: UNT Libraries Government Documents Department

Optical State-of-Change Monitor for Lead-Acid Batteries

Description: A method and apparatus for determining the instantaneous state-of-charge of a battery in which change in composition with discharge manifests itself as a change in optical absorption. In a lead-acid battery, the sensor comprises a fiber optic system with an absorption cdl or, alternatively, an optical fiber woven into an absorbed-glass-mat battery. In a lithium-ion battery, the sensor comprises fiber optics for introducing light into the anode to monitor absorption when lithium ions are introduced.
Date: July 24, 1998
Creator: Weiss, Jonathan D.
Partner: UNT Libraries Government Documents Department

Design and modeling of cylindrical and falt-wound lithium-ion cells for the PNGV application.

Description: In this study, 10-Ah cylindrical and flat-wound cells were designed and studied for use in batteries for the Partnership for a New Generation of Vehicles (PNGV). A low-cost current collection system was devised that results in a low resistance. Heat rejection from flat cells is much better than that from cylindrical cells and is an important safety factor. Very compact, powerful batteries of about 1.5 kW/L can be designed with wound lithium-ion cells.
Date: November 10, 2000
Creator: Nelson, P. A.; Henriksen, G. L. & Amine, K.
Partner: UNT Libraries Government Documents Department

A SYSTEMATIC STUDY OF INTERCALATION COMPOUNDS AS CATHODE MATERIALS FOR LITHIUM BATTERIES.

Description: Three types of intercalation Compounds, LiMn{sub 2}O{sub 4} with spinel structure, LiNiO{sub 2} and LiCoO{sub 2} with layered structure are widely studied as cathode materials for lithium-ion batteries. Among them, LiCoO{sub 2} is the most widely used cathode material in commercial lithium battery cells. LiNiO{sub 2} has same theoretical capacity as LiCoO{sub 2}, but is less expensive. However its application in lithium batteries has not been realized due to serious safety concerns. Substituting a portion of Ni in LiNiO{sub 2} with other cations has been pursued as a way to improve its safety characteristics. It was reported that Co doped LiNi{sub 0.8}Co{sub 0.2}O{sub 2} showed better thermal stability than pure LiNiO{sub 2}. Many new materials have been developed aimed in increasing the capacity and improving the thermal stability and cyclability. Most of these new materials are based on these three types of materials and modified their compositions and structures by doping. However, most of the efforts on developing new cathode materials have been done on the empirical base without guidelines from the systematic studies on the relationship between the performance and the structural changes of the cathode materials. Exploring this relationship is very important not only in guiding the development of new materials, but also in improving the performance and safety aspect for the existing cathode materials for lithium ion batteries. Using conventional x-ray source and a specially designed battery cell with beryllium windows, Dahn and co-workers have published several papers on the structural changes of LiNiO{sub 2} cathodes 1 and LiCoO{sub 2} cathodes 2 during charge. Unfortunately, the charging voltage was limited to below 4.3 V due to the problem of beryllium window corrosion at higher voltage. However, the voltage range between 4.3 V and 5.2 V is the most important region for studying the relationship between the thermal ...
Date: June 8, 2001
Creator: YANG,X.Q. & MCBREEN,J.
Partner: UNT Libraries Government Documents Department

The effects of silicon doping on the performance of PMAN carbon anodes in Li-ion cells

Description: Carbons derived from polymethylacrylonitrile (PMAN) have been studied for use as intercalation anodes in Li-ion cells. The effect of Si doping upon the electrochemical performance of PMAN carbons was studied using tetravinylsilane (TVS) and tetramethysilane (TMS) as sources of Si during the formation of the PMAN precursors. The carbons were characterized by galvanostatic cycling, cyclic voltammetry, and complex impedance. The presence of 9 to 11 w/o Si in the PMAN lattice greatly increased the irreversible capacity of these materials.
Date: May 1, 1996
Creator: Guidotti, R.A.; Johnson, B.J. & Even, W. Jr.
Partner: UNT Libraries Government Documents Department

Electrical and Electrochemical Performance Characteristics of Large Capacity Li-Ion Cells

Description: We are currently evaluating large capacity (20 - 40 Ah) Bluestar (cylindrical) and Yardney (prismatic) Li-ion cells for their electrical and electrochemical performance characteristics at different temperatures. The cell resistance was nearly constant from room temperature to -20{degrees}C but increased by over 10 times at -40{degrees}C. The specific energy and power as well as the energy density and power density are high and didn't reach a plateau even at the highest discharge rates tested. For example, the prismatic Li-ion cells gave close to 280 Wh l{sup -1} at 4-amp discharge and 249 Wh l{sup -1} at 20-amp discharge at room temperature. For the same current range the specific power values are 102 Wh kg{sup -1} and 91 Wh kg{sup -1}. Cycle life and other electrical and electrochemical properties of the cells will be presented.
Date: December 1, 1998
Creator: Doughty, I.D.; Hill, C.; Ingersoll, D.; Marsh, C.; Nagasubramanian, G. & Radzykewycz, D
Partner: UNT Libraries Government Documents Department