Electrodes bobbin construction

The cylindrical cells use a jellyroll construction similar to that already described for Li-FeS2 cells (Fig. 1). However, the cathode is typically thicker and embedded into a stainless steel Exmet screen rather than coated onto foil. Specialty versions of cylindrical cells using a bobbin construction are also manufactured these cells have higher capacity, but can only discharge at very low drain rates. Miniature cells use much of the same materials, but the electrodes are punched out and stacked together with a disk of separator material (Fig. 8). The 9 V battery uses a system of three unit cells wired in series using folded electrodes and a common case (Fig. 9). 

For example, two designs are used in cylindrical cells. One design known as the bobbin construction, is typical for zinc-carbon and alkaline-manganese dioxide cells. Here the electrodes are shaped into two concentric cylinders (Fig. 3.21a). This design maximizes the amount of active material that can be placed into the cylindrical can, but at the expense of surface area for the electrochemical reaction. 

A saturated salt sensor is constructed with an absorbent fabric bobbin covered with a bililar winding of inert electrodes and coated with a dilute solution of lithium chloride. Lithium chloride tLiCI) is often used as the saturating salt because of its hygroscopic nature, which permits application in relative humidities between 11 and 100%. 

Most primary or dry cells with aqueous electrolytes employ single, thick electrodes arranged in parallel or concentric configurations. Typical battery configurations are categorized as cylindrical, bobbins, buttons, or coin cells. Some primary cells are made in prismatic and thin, flat constructions to achieve the lowest volume. These form factors yield poor energy density and power capacity levels. 

Fabrication of a battery or a cell determines how the device will function and how much it will cost to construct it. Several primary cells with aqueous electrolytes seem to use a single electrodes arranged in parallel or concentric configuration. Specific construction of this type of cell includes cylindrical or bobbin button, and coin. Small secondary cells use a wound or jelly roll construction feature, in which long thin electrodes are wound into a cylinder and placed in a metallic housing or container. This particular cell construction yields higher power density, but it... 

Li/FeS2 batteries may be manufactured in a variety of designs, including the button and both bobbin and spiral-wound-electrode cylindrical cells. A bobbin constmction is most suitable for Ught-drain applications. The spiral-wound-electrode construction is needed for the heav-ier-drain applications, and it is this design that has been commercialized. 

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