Sodium cells

The main criteria for the selection of the current collector material in a central sulfur cell or for the cell case material in a central sodium cell are corrosion resistance to sulfur and sodium polysulfides, good electrical conductivity, and low costs. This cost argument has led to coated materials which have been compared with nickel—chromium alloys (Inconel 600). 

Gonzalez et al. first reported CoSn2 on metal foam obtained by electrodeposition of amorphous Co-Sn alloy and subsequent annealing [77]. It was observed that low current densities and short electrodeposition times favor the formation of discrete submicrometric particles (Volmer-Weber model] and the electrochemical behavior in lithium cell was very good, while the capacity in sodium cell was lower. 

Our experimental apparatus consists of a sodium containing heat-pipe cell with an active length of 20 cm the buffer gas is argon at a few torr pressure. The sodium density is in the range of 10 -10 cm". The dye laser is Hansch type and is pumped by a 30 kW peak power copper-halide laser with a 25 nsec duration pulse. The dye laser bandwidth is 0.5 cm . The laser beam is spatially filtered and focused into the sodium cell. The laser intensity at the focus is about 10 Mw/cm and is sufficient to form self-trapped filaments. The spectrum of the emission is monitored by 1.2 cm resolution McPearson 0.3m monochromator. The forward emission is photographed by an Alphax B216 camera placed after the sodium cell without any imaging optics. The laser beam is blocked with an on-axis disk. 

We have verified experimentally, that the ring emission is a surface radiation and occurs at the boimdary of self-trapped filaments, confirming that it is a Cherenkov type radiation. To this end, we examined the special coherence of the ring emission. The laser radiation was focused into the sodium cell by a cylindrical lens and the produced pattern is shown in Fig. 1. The off-axis ring emission preserves its symmetry around the laser axis, while the laser beam spot has an ellipse form. Should the ring emission be produced in the interior of the saturated filaments, where n=l, the interference between different filament emissions would result in a pattern representing the spatial distribution of the filaments, i.e. ellipse. We thus conclude, that the ring emission is produced mainly at the interior of the filaments. 

The experimental apparatus is discussed elsewhere. Briefly, a lOkW peak power Hansch-type dye laser with a 0.5 cm" bandwidth is focused into a sodium heat-pipe cell. The laser intensity at the focus is 10 Mw/cm. The sodium cell is 20 cm in length. Argon at a few torrs pressure is used as a buffer gas. 

Container. A major materials challenge associated with central sodium cells is the identification of a suitable sulfur container. The solution to this problem is difficult because the container must be very corrosion-resistant, have a surface with reasonable electrical conductivity, possess good mechanical properties, and yet be lightweight and inexpensive. Corrosion is detrimental not only because of its direct impact on the cell lifetime, but also because... 

Chlorine — 120-135 49-57 - E - - above sodium cell in fumes containing sodium oxychloride, sodium chloride, sodium oxide smoke and moist air. Alloy C = 0.1 mpy. 0.001 m max. pitting... 

Vandenberg CA (1987) Inward rectification of a potassium channel in cardiac ventricular cells depends on internal magnesium ions. Proc Natl Acad Sci USA 84 2560-2564 Whorton MR, MacKinnon R (2011) Crystal structure of the mammalian GIRK2 K" channel and gating regulation by G proteins, PIP2, and sodium. Cell 147 199-208... 

The last remark is about the future prospects. Most of the text presented here deals with lithium cells and lithium electrolytes. However one has to keep in mind that most of the knowledge earned on these systems can be transferred easily (if not directly sometimes) into different ones. A good example could be sodium cells. If one day humankind faces a scarcity of lithium (http //www.meridian-int-res.com/Projects/Lithium Problem 2. pdf) it will have to move towards sodium cells. However, the chemistry of lithium and sodium electrodes with liquid electrolytes is quite different. On the other hand aU the examination methods and experimental setups developed for dry polymer electrolytes apply to lithium as weU as sodium cells. There are also some common conclusions (West et al. 1989). At the time this book is being written, revival of research on sodium electrolytes and... 

WEST, K., ZACHAU-CHRISTIANSEN, B., JACOBSEN, T. and SKAARUP, S., 1989. Solid-State sodium cells - an alternative to lithium cells Journal of Power Sources, 26(3-4), 341-345. 

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