Design, solid electrolytes

The third aspect, the stability range of solid electrolytes, is of special concern for alkaline-ion conductors since only a few compounds show thermodynamic stability with, e.g., elemental lithium. Designing solid electrolytes by considering thermodynamic stability did lead to very interesting compounds and the discovery of promising new solid electrolytes such as the lithium nitride halides [27]. However, since solid-state reactions may proceed very slowly at low temperature, metasta-... 

A few key points emerge from this study first, the interpretation of the observed conductivity data is confirmed (as shown in Fig. 8.2.). Second, the results, both theoretical and experimental, show that ionic size may have a large effect on ionic conductivity and this factor should clearly be born in mind in designing solid electrolytes. The third point is that the results show the quantitative success of this class of defect calculation in treating a subtle effect. 

Four major aspects should be taken into consideration for the design of suitable solid electrolytes ... 

Some further important aspects for the design of solid electrolytes and solid electrodes for battery-type applications are the following ... 

When a solid electrolyte component is interfaced with two electronically conducting (e.g. metal) films (electrodes) a solid electrolyte galvanic cell is formed (Fig. 3.3). Cells of this type with YSZ solid electrolyte are used as oxygen sensors.8 The potential difference U R that develops spontaneously between the two electrodes (W and R designate working and reference electrode, respectively) is given by ... 

But all these are problems which can be overcome by appropriate catalyst-electrode design and by appropriate choice of the solid electrolyte and thus of the promoting species. 

From these simple phenomenological considerations, it is clear that the two dominant considerations in the design of a solid electrolyte are the creation of a temperature-independent (l — n ) with approaching its optimum value of 0.5 and a minimisation of the motional enthalpy AH and minimisation of the energy E appearing in an exponent must demand priority. 

Little practical success has been achieved up to now in the design and construction of SBs based on light metals, despite extensive work done in that direction. The only new SBs which are today under test for practical large-scale use are the ones based on the reversible reaction Na + S, with a solid electrolyte of the type NazOCAlzOa)ii, and the SB based on the reversible reaction of Li + in a molten chloride electrolyte. 

Almost all modern practical aqueous primaries are referred to as dry cells . This designation should not be confused with the rather specialized solid state cells which make use of the recently discovered true solid electrolytes. Rather, the term implies that the aqueous electrolyte phase has been immobilized by the use of gelling agents or by incorporation into microporous separators. Such procedures permit the cells to operate in any orientation and reduce the effects of leakage should the container become punctured. 

There are numerous designs for vacuum electrochemical cells, ranging from very simple to extremely complex. In operation, the vacuum electrochemical cell parts are first cleaned, washed with solvent, and dried in an oven at 200°C. The hot cell parts should then be quickly assembled and evacuated on the vacuum line for several hours or overnight. Once the electrochemical cell has been pumped down, it should be closed off and transferred to a dry box, where the air-sensitive sample and the electrolyte can be added to it. Alternatively, the solid electrolyte could be added into the electrochemical cell before assembly. 

At room temperature -> Nernstian slope (59 mV/decade of concentration change) is usually observed. Partial pressure can be derived by applying Henrys law. A catheter configuration suitable for measurements inside blood vessels has been described [ii]. Using other electrolyte constituents and membranes semipermeable for other types of gas sensors for other analytes were developed (including N02, S02, H2S, HF [iii]). Various CO2 sensors with galvanic solid electrolyte cells have been designed [iv]. 

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