Surface Modification and Fabrication of Li-ion Battery Components for by xfo14057


									 Surface Modification and Fabrication of Li-ion Battery        offers some unique advantages over other welding
    Components for Plug-in Hybrid Electric Vehicle             processes with the high energy concentration of the beam
                                                               for reduced heat input to the joint. Several important
Ben Luan, Glen Campbell, Xing Yang Liu, John Nagata,           processing parameters were investigated for laser welding
          Maxime Gauthier, *Isobel Davidson                    of battery tabs, such as power level, travel speed, and
                                                               depth of penetration (Figures 2, 3 & 4).
 800 Collip Circle, London, Ontario, Canada, N6G 4X8,
              Industrial Materials Institute                   3.    Fabrication and Surface Modification of Current
           National Research Council Canada                          Collectors
     75 boulevard de Mortagne, Boucherville, QC, Canada,       The performance of current collectors is an important
                          J4B 6Y4                              issue related to not only the electrical conductivity but
                Industrial Materials Institute                 also the cycling kinetics of the battery. This research
             National Research Council Canada                  focuses on the fabrication of anodic and cathodic current
                                                               collectors with increased specific surface area and
 *M-12, 1200 Montreal Road, Ottawa, Ontario, Canada,
                                                               improved retention of active materials. Various
                     K1A 0R6
                                                               fabrication technologies are investigated including
     Institute for Chemical Processes and Environmental        powder metallurgy and electrochemical methodologies.
              National Research Council Canada

          This research addresses an important issue for
the practical application of lithium ion batteries in PHEV.
Since its revolutionary introduction into the portable
electronics market by Sony in 1991, lithium ion cells have
enjoyed a constantly increasing market share. This raised
the expectations for its implementation in PHEV,
particularly with the heightened needs for alternative
energy and environment protection. However, even
though the basic chemistry and design of Li-ion PHEV
cells are quite similar to those of small consumer cells,
the major challenge for PHEV cells is the demand for                 Figure 1 SEM Images and Elemental Mapping for
much higher power performance. Furthermore, this                              Uncoated and Coated Separator
demand is also linked to the safety/abuse resistance,
operating life (including calendar life and cycle life), and
cost of manufacturing. Li-ion battery components such as
separators, current collectors and battery tabs are
important components related to the power performance,
cyclic kinetics, and cycle life. This paper presents results
on the surface modification and fabrication of separators,
current collectors and laser welding of battery tabs.
                                                                    Figure 2 SEM Image showing the Laser Fusion Zone
Results and Discussion
1.    Surface Modification of Separators
          An important issue for battery performance and
safety is related to the separator. Unexpected short-
circuits across the separator induces hot spots where
thermal runaway may breakout. Internal short-circuits are
believed to occur either by protrusions on the electrode        Figure 3 SEM Image of the Interfacing of substrate and
surface or by shrinkage of the separator upon heating.                           the fusion zone
One way to prevent this from happening is to coat the
polymeric separator with ceramic coating.
         Several simple immersion methodologies using
various precursors and/or solvents were experimented
with some results shown in Figure 1. All these
methodologies demonstrated promising results.

2.    Laser Welding of Battery Tabs
                                                               Figure 4 EDX Mapping of fusion zone (Fe-left; Ni-right)
          Joining of battery leads and tabs is the basis of
the electrical connection between cells, current-collectors
and cell-cans. The main drivers in joining of the battery
leads and tabs are energy transfer capabilities, joint         This research addresses important issues related to the
reliability and manufacturing costs.                           fabrication and modification of key battery components
                                                               (separator, tab welding, and current collectors). Promising
        The laser process is a non-contact process that
                                                               results are shown to improve the performance of Li-ion
produces high quality joints, excellent repeatability and

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