Browsing by Subject "lithium ion batteries"

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    Beyond Lithium Ion: Lithium Metal Batteries with High Specific Energy and Long Cycle Life
    (Office of the Vice Chancellor for Research, 2014-04-11) Xie, Jian
    The lithium ion battery industry has been rapidly growing and now dominating in many power source sectors such as automotive industries, portable devices, and aerospace applications. Lithium ion batteries currently being implemented in electric vehicle (EV) and hybrid electric vehicle (HEV) are not efficient enough to outperform gas combustion vehicles on the road today, which is limited by the theoretical specific energy of cathode (intercalation oxides) and anode (graphite) materials for lithium ion batteries. The next phase in the advancement of the lithium battery technology relies very much on replacing the intercalation electrodes which has limited theoretical specific capacity. Metallic lithium is a good candidate for the anode, since it has a very high theoretical specific capacity which is more than 10 times than graphite. However, the formation of dendrites affects the charge efficiency of this type of electrode, which can be very dangerous, even fatal at time. In our approach, functionalized carbon black (FCB) coating was implemented onto the separator to eliminate the hazard of dendrite formation. Furthermore, the lithium metal batteries with our technology offered much higher specific energy and power, and improved cycle life.
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    Geometric characteristics of 3D reconstructed anode electrodes of lithium ion batteries
    (Office of the Vice Chancellor for Research, 2014-04-11) Lim, Cheolwoong; Yan, Bo; Yin, Leilei; Zhu, Likun
    The realistic 3D microstructure of lithium ion battery electrodes plays a key role in studying the effects of inhomogeneous microstructures on the performance of LIBs. However, the complexity of realistic microstructures implements significant computational cost on numerical simulation of large size samples. In this work, we used tomographic data obtained for a commercial lithium ion battery graphite electrode to evaluate the geometric characteristics of the reconstructed electrode microstructure. Based on the analysis of geometric properties, such as porosity, specific surface area, tortuosity, and pore size distribution, a representative volume element that retains the geometric characteristics of the electrode material was obtained for further numerical studies. In this work, X-ray micro-CT with 0.56 μm resolution was employed to capture the inhomogeneous porous microstructures of lithium ion battery anode electrodes. The Sigmoid transform function was employed to convert the initial raw tomographic images to binary images. Moreover, geometric characteristics of an anode electrode after 2400 1 C charge/discharge cycles were compared with those of a new anode electrode to investigate morphological change of the electrode. In general, the cycled electrode shows larger porosity, smaller tortuosity, and similar specific surface area compared to the new electrode.