Sodium-sulfur cell development

The ZEBRA cell, which is under development by the General Electric Co., uses a molten-sodium anode and a solid p,p"-alumina solid electrolyte as in the sodium-sulfur cell, but the positive electrode is large-surface-area nickel rather than molten sulfur with a large-surface-area current collector. The electrolyte on the cathode side of the ZEBRA solid electrolyte is an aqueous NaAlCLt containing NaCl and Nal as well as a little FeS. The FeS and Nal are added to limit growth of the Ni particles and to aid the overall cathode reaction, which is... 

Numerous other types of cells exist such as zinc-air, aluminum-air, sodium sulfur, and nickel-metal hydride (NiMH). Companies are on a continual quest to develop cells for better batteries for a wide range of applications. Each battery must be evaluated with respect to its intended use and such factors as size, cost, safety, shelf-life, charging characteristics, and voltage. As the twenty-first century unfolds, cells seem to be playing an ever-increasing role in society. Much of this is due to advances in the consumer electronics and the computer industry, but there have also been demands in numerous other areas. These include battery-powered tools, remote data collection, transportation (electric vehicles), and medicine. 

Among the various electrolytes, yttrium stabilized zirconia (YSZ) has been developed, for use in high-temperature fuel cells and oxygen sensors similarly, various S( S")-alumina materials are in development for sodium sulfur batteries. 

Once the principles of operating in a molten salt environment have been grasped, suitable extrapolations or interpolations of materials requirements and cell and equipment designs can be made between different systems. In bringing a molten salt process into commercial operation, unique materials problems requiring special solutions often limit its progress, but practically never prevent it. Thus, if a desired result may not be achieved for theoretical reasons in any alternative electrolyte, because of electrochemical instability, for example, then initial development costs and difficulties become inconsequential. Such has been the case with thermal batteries, " sodium-sulfur batteries, molten fluoride nuclear reactors, and molten carbonate fuel... 

The principle of operation is illustrated on Figure 4. The fast ion conductor 3-aluminium has been developed as the basic component of the sodium sulfur battery cell. Whether it will give birth to a new technological process is too early to predict. 

A new generation of batteries is under development that has distinct advantages over the traditional lead-sulfuric acid batteries both in terms of weight and energy density, and which can be adapted to road or rail transport. Most attention to date has been applied to the sodium-sulfur battery, in which liquid sodium and liquid sulfur are separated by a diaphragm of )8-alumina. The cell is operated at 300-350°C, and the cell reaction is... 

The 40 Ah sodium-sulfur (NajS) battery cell was developed for space applications by EaglePicher. Following are the typical performance characteristics ... 

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