Thermal reserve batteries

Theoretical capacity (of batteries) - capacity Thermal battery - reserve battery Thermal cell - thermocell... 

Reserve batteries have been developed for appHcations that require a long inactive shelf period foUowed by intense discharge during which high energy and power, and sometimes operation at low ambient temperature, are required. These batteries are usually classified by the mechanism of activation which is employed. There are water-activated batteries that utilize fresh or seawater electrolyte-activated batteries, some using the complete electrolyte, some only the solvent gas-activated batteries where the gas is used as either an active cathode material or part of the electrolyte and heat-activated or thermal batteries which use a soHd salt electrolyte activated by melting on appHcation of heat. 

Thermal batteries are a special class of reserve batteries which take advantage of the long-term stability intrinsic to many interfaces when both the active material and the electrolyte are solid state, at least until activation. The stability is attributable to the very low diffusion coefficients of electrolyte ions in the solid state for the chosen electrolyte systems. These batteries are fully assembled with electrolyte present, but the electrolyte remains a solid nonconductor until it is melted by rapid heating from a pyrotechnic heat source. 

Thermal batteries represent another type of primary reserve battery distinguished by the feature that they are activated by heating to a high temperature by internal... 

Reserve Batteries with Molten Electrolyte (Thermal Batteries)... 

In Section 4.5.3, reserve-type thermal batteries were mentioned that are activated after an instantly melting solid-state salt electrolyte. In this section more details about these batteries are described. 

Kiieger, F. C. Miniaturized Thermal Reserve Battery, Proc. 38th Annual Power Sources Conference, U.S. Army CECOM/ARL, Cherry HiU, NJ, pp. 231-234, 1998. 

Thermal batteries are primary reserve batteries that employ inorganic salt electrolytes. These electrolytes are relatively nonconductive solids at ambient temperatures. Integral to the thermal battery are pyrotechnic materials scaled to supply sufficient thermal energy to melt the electrolyte. The molten electrolyte is highly conductive, and high currents may then be drawn from the cells. 

H ig h-tem peratu re thermally activated primary reserve batteries... 

Ifigh meltii pc ts - This leads to high viscosity and can be a problem in that low temperature operation may be poor, or even non-existent if the melt freezes. However, it also offers the prospect of excellent shelf life in thermally activated reserve batteries, which are of interest for many mifitary purposes. More importantly, many ionic liquids remain liquid weU below the -20°C requirement for normal consumer batteries. Some have temperature ranges from -40 to +200°C [4] l-n-butyl-3-methylimidazolium tetrafiuoroborate remains liquid down to -82°C [22]. 

Various problems related to the construction and performances of these batteries, such as changes in materials of membranes and additives both to the electrode materials and to the electrolyte, were studied in recent years. Some instability of the silver electrode during such storage period and the ways of avoiding these difficulties were studied and discussed [347]. Reserve activated silver oxide-zinc cells were constructed [348] with synthetic Ag20 and Pb-treated zinc electrodes were produced by a nonelec-trolytic process. The cells were tested before and after thermally accelerated aging. 

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