Spiral-wound batteries

This section reviews the state-of-the-art in battery separator technology for lithium-ion cells, with a focus on separators for spirally wound batteries in particular, button cells are not considered. 

Figure 1. Schematic of components for making spirally wound batteries.

FIGURE 6.13 Punched grid for spiral-wound battery. (Courtesy of Exide.)... 

Pure lead is generally too soft to be used as a grid material. Exceptions that use pure lead plates are some special, very thick plate Plants or pasted-plate batteries, some small spiral wound batteries, some valve regulated cells and batteries (see Fig. 23.12c) and a cylindrical cell. The latter were developed by Bell Laboratories (now part of Lucent Technologies) (see Fig. 23.36). "... 

To further reduce weight and improve energy density, several companies are developing thin lead film electrodes in a spiral-wound construction with glass fiber separators. Already on the market for cordless electric tools, this battery technology may eventually be used in electric vehicles. 

The requirements for a battery separator can best be understood in the context of how the separator is used. The conventional process (Fig. 1) for making spirally wound cells involves threading the separator (a) through a winding pin (b). 

The simulated short-circuit test was developed to characterize the response of the separator to a short circuit without the complications of battery electrodes. The separator was spirally wound between lithium foils and placed in an AA-size can. To avoid lithium dendrite formation, an alternating voltage was applied to the cell. The cell current and can temperature were monitored. Figure 6 shows the behavior of Celgard membranes. 

Figure 1. Typical battery configurations (a) button cell (b) stack lead acid (c) spiral wound cylindrical lithium ion (d) spiral wound prismatic lithium-ion.

A novel microporous separator using polyolefins has been developed and used extensively in lithium-ion batteries since it is difficult for conventional separator materials to satisfy the characteristics required in lithium-ion batteries. In lithium-ion batteries two layers of separators are sandwiched between positive and negative electrodes and then spirally wound together in cylindrical and prismatic configurations. The pores of the separator are filled with ionically conductive liquid electrolyte. 

Li-FeS2 cells were manufactured as button cells, and are now produced as spiral wound cylindrical cells (Fig. 4.28). The latter are currently being heavily marketed worldwide by the Eveready Battery Co, Inc. (especially... 

Fig. l.l. (a) Gaston Plante s cell and battery (b) flat plate (c) tubular positive plate (d) spiral-wound cell. 

The tests of additives in spirally wound VRLA batteries [18] also included a proprietary AD7 additive, which was chemically described as polyvinylsulfonic acid or its salts, called polyvinylsulfonates [85,86], together with crystal carbon fibres, polyester fibres and Sn02 powder. None of the additives were found to increase the initial discharge capacities compared with the control. The AD7 additive did, however, show significantly better maintenance of capacity during cycling than the control. It was further claimed [81,82] that typical additive concentrations of about... 

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