Alumina sodium-sulfur battery

Electrophoretic casting (38,59) is accompHshed by inducing controUed migration of charged particles under an appHed electric field to deposit on a mandrel. Thin tubular shapes and coatings of limited thickness are formed using this technique. Electrophoretic deposition (EPD) is also used to manufacture thin waU, soHd P -alumina [12005-16-2] NaAl Og, electrolytes for sodium—sulfur batteries. 

The high ionic conductivity of sodium (3"-alumina suggested that it would form a suitable electrolyte for a battery using sodium as one component. Two such cells have been extensively studied, the sodium-sulfur cell and the sodium-nickel chloride (ZEBRA) cell. The principle of the sodium-sulfur battery is simple (Fig. 6.13a). The (3"-alumina electrolyte, made in the form of a large test tube, separates an anode of molten sodium from a cathode of molten sulfur, which is contained in a porous carbon felt. The operating temperature of the cell is about 300°C. 

As with the sodium-sulfur battery, the extraordinary conductivity of the (3"-alumina electrolyte, due to the defect structure of the conduction layer, is key to this device. 

Fig. 7.18 Sodium/sulfur battery with a sodium beta alumina solid electrolyte.

Ionic conductivity is used in oxygen sensors and in batteries (qv). Stabilized zirconia, Zy Ca 02 has a very large number of oxygen vacancies and very high O2- conductivity. P-Alumina [12005-48-0], NaAl11017, is an excellent cation conductor because of the high mobility of Na+ ions. Ceramics of p-alumina are used as the electrolyte in sodium-sulfur batteries. 

The jS-aluminas have been extensively used as permeable membranes in sodium-sulfur batteries since they provide the unique properties of allowing sodium transport but neither sulfur nor electron conduction and they are not attacked by molten sodium or sulfur. 

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. 

Since the principle of the sodium sulfur battery was established in 1967, it has been under development throughout the world. The schematic set-up of a sodium sulfur battery, operated at 300 350 °C, is shown in Figure 22. Molten sodium, the anode active material, is placed in a sintered S-alumina solid electrolyte tube, and molten sulfur impregnated in the porous graphite cathode, outside. The... 

FIGURE 17.10 In a sodium-sulfur battery, Na ions migrate through beta-alumina to the cathode to equalize the charge as electrons flow spontaneously from the anode to the cathode through the external circuit. 

Metallic sodium, or sodium hydroxide and sulfur, may also be extracted from flue gas by electrolysis of molten sodium sulfide (produced in the gas desulfurization process) by application of the charging reaction of the sodium-sulfur battery. This could conceivably be converted to a power-producing system if oxygen can be reduced at the cathode without severe polarization. Again, a beta-alumina diaphragm must be used to separate the sodium sulfide from the sodium hydroxide. 

Fig. 4. Construction of a sodium—sulfur battery. A, Negative terminal B, springs plus graphite felt C, sulfur D, carbon E, sodium reservoir F, positive terminal G, insulator H, aluminum sealing gaskets I, steel case J, film of sodium K, p-alumina tube L, carbon felt M, wick N, aluminum can (67).

The sodium/sulfur battery operates around 570-620 K and consists of a molten sodium anode and a liquid sulfur cathode separated by a solid P-alumina electrol5he (see Section 27.3). The cell reaction is ... 

Current developments in battery technology, electrochromic devices (see Box 22.4) and research into electrically powered vehicles make use of solid electrolytes (see Box 10.3). The sodium/sulfur battery contains a solid 3-alumina electrolyte. The name (3-alumina is misleading since it is prepared by the reaction of Na2C03, NaN03, NaOH and AI2O3 at 1770K and is a non-stoichiometric compound of approximate... 

Another example is P-alumina, Na20 AI2O3, and derivatives. It consists of aluminum oxide layers separated by intermediate layers of sodium and oxygen ions. The sodium ions are partially located on interstitials in channels with high mobility at ambient temperatures. The conductivity of sodium ions is of the order of 0.2 S cm at 3(X) °C. The conductivity in some derivatives can be 2S cm at 300 °C. The temperature dependence is shown in Figure 1.20. In the development of a sodium-sulfur battery P-alumina was used as the electrolyte membrane separating sulfur and liquid sodium. 

High-Temperature Sodium-Sulfur Battery This battery employs the ionic conductivity of P-alumina, that acts as a diaphragm containing liquid sodium which serves as the negative pole of the battery (Figure 7.12). The steel casing, which usually is... 

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... 

Minck, R. W. (1982) Corrosion problems of the sodium-sulfur battery. DOEMeetingonHigh TemperatureCorrosionProblems in Battery Systems, London, 13-14 July 1982 Minck, R. W. (1983) Practical experiences with beta-alumina. Research Assistance Task Force Meeting en Beta-Alumina for Sodium-SulfurCells, Oak Ridge,Tennessee, USA 8-10March 1983... 

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