Charge-voltage characteristics

Figure 51.29 Standard charging voltage characteristics of a Yuasa RSF sealed nickel-cadmium battery at 20-25°C (Courtesy of Yuasa)...

Rubber separators have good voltage characteristics, the ability to retard antimony transfer, properties to retard dendrite growth, and good electrochemical compatibility. Due to the hydrophilic properties of the rubber composition, the separators are highly wettable and renewable for the dry-charging process. Paik et al. showed that AGE-SIL (sulfur cured, hard rubber) separators performed well in industrial stationary or traction batteries. FLEX-SIL (electron-beam-cured. flexible rubber separator) separators are suited for deep-cycling batteries, and MICROPOR-... 

Cheng et al. carried out the impedance study on a foam-type NiMH battery with nonwoven PP separator to determine the main causes of early cycle deterioration. Their data indicated that the decrease in the voltage characteristic of the battery was due to drying out of the separator that increases the ohmic resistance of the battery and that decay of the total discharge capacity is due to an inactive surface that increases the charge-transfer of the battery. 

Sodium contamination and drift effects have traditionally been measured using static bias-temperature stress on metal-oxide-silicon (MOS) capacitors (7). This technique depends upon the perfection of the oxidized silicon interface to permit its use as a sensitive detector of charges induced in the silicon surface as a result of the density and distribution of mobile ions in the oxide above it. To measure the sodium ion barrier properties of another insulator by an analogous procedure, oxidized silicon samples would be coated with the film in question, a measured amount of sodium contamination would be placed on the surface, and a top electrode would be affixed to attempt to drift the sodium through the film with an applied dc bias voltage. Resulting inward motion of the sodium would be sensed by shifts in the MOS capacitance-voltage characteristic. 

Fig. 7. Theoretical current-voltage characteristics of thick carrier membranes with different charge concentrations c = Z/CISn. The values for c are arbitrary and increase from curve A to D (for details see [55]).

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