Starved electrolyte

Lithium Iron Sulfide (High Temperature). High-temperature molten salt Li—Al/LiCl— KCl/FeS - cells are known for their high energy density and superior safety. At one point they were being actively pursued for electric vehicle and pulse-power applications. Historically, boron nitride (BN) cloth or felt has been used as the separator in flooded-electrolyte cells, while MgO pressed-powder plaques have been used in starved-electrolyte cells. 

Button, cylindrical and prismatic sealed cells are similar in design to the starved-electrolyte configuration of nickel-cadmium cells. A schematic diagram of a six-cell battery is shown in Fig. 6.11. Because of the slightly... 

Flooded battery — A battery (or a cell) containing an excess of electrolytic solution (in contrast to starved electrolyte batteries). Usually relevant to rechargeable -> lead-acid and -> nickel-cadmium batteries. Flooded battery design is typically applicable for heavy duty batteries, equipped with a vent valve that releases pressure buildup due to gas evolution. The excess electrolyte affects more sturdy batteries to become less susceptible to damage due to overcharge. In addition, the thermal conductivity of the electrolyte affords more efficient heat dissipation and thus higher -> power densities. 

Starved electrolyte battery — A -> battery with minimum amount of -> electrolyte. The electrolyte in starved electrolyte cells or batteries exists in the porous structure of the - electrodes and absorbed in the separator, so it contains little or no free fluid electrolytic solution. This type of batteries is used in certain constructions of sealed - lead-acid and -> nickel-cadmium batteries that rely on gas diffusion and recombination on the electrodes during charging or overcharging in order to maintain maintenance-free conditions, and to suppress pressure buildup. Starved electrolyte batteries benefit from larger - energy density due to the reduced amount of electrolyte. This design may suffer from poor heat dissipation compared with -> flooded batteries, thus for high power applications this point has to be taken into account. 

The amount of electrolyte is limited, that is, the cell is of starved type rather than the flooded type for vented batteries. The starved electrolyte can facilitate the oxygen transfer process. 

In the case of battery materials, the interparticle diffusion effects within a normally starved electrolyte cell design force standard voltammetric or coulometric experiments to be extremely time consuming. However, when working with small... 

A separator permeable to oxygen is used so that oxygen can pass through the separator to the negative electrode. Also, a limited amount of electrolyte is used (starved electrolyte system) as this facilitates the transfer of oxygen. This process is illustrated in Fig. 28.1. 

An aqueous solution of potassium hydroxide is the major component of the electrolyte. A minimum amount of electrolyte is used in this sealed cell design, with most of the Uquid absorbed by the separator and the electrodes. This starved-electrolyte design, similar to the one in sealed nickel-cadmium batteries, facilitates the diffusion of oxygen to the negative electrode at the end of the charge for the oxygen-recombination reaction. This is essentially a dry-cell construction, and the cell is capable of operating in any position. 

The oxygen gas diffuses through the separator to the negative electrode, the diffusion facilitated by the starved-electrolyte design and the selection of an appropriate separator system. 

An important feature of the electrolyte is related to fill fraction. Essentially all NiMH batteries are of the sealed, starved electrolyte design. As with NiCd batteries, the electrodes are nearly saturated with electrolyte, while the separator is only partially saturated to allow for rapid gas transport and recombination. 

Starved Electrolyte Cell A cell containing little or no free fluid electrolyte. This enables gases to reach electrode surfaces during charging and facilitates gas recombination. 

In the Gates cell, the closely spaced plates are separated by a glass mat separator, which is composed of fine glass strands in a porous structure. The cell is filied with only enough electrolyte to coat the surfaces of the plates and the individual glass strands in the separator, thus creating ihe starved electrolyte condition. This condition allows for homogeneous gas transfer between the plates, which is necessary to promote the recombination reactions. 

B. Hariprakash, S.K. Martha, M.S. Hegde and A.K. Shukla, A sealed, starved-electrolyte nickel-iron battery,. Appl. Electrochem. 35,2005,27-32. 

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