Batteries concentration cells

Battery Alkali battery, redox-flow battery, concentration cell, etc. 

In the final sections, we introduce several key electrochemical applications, such as the pH electrode (a type of concentration cell), nerve cells (which rely on junction potentials) and batteries. 

Fundamentally, the eel is simply a living battery. The tips of its head and tail represent the poles of the eel s battery . As much as 80 per cent of its body is an electric organ, made up of many thousands of small platelets, which are alternately super-abundant in potassium or sodium ions, in a similar manner to the potentials formed across axon membranes in nerve cells (see p. 339). In effect, the voltage comprises thousands of concentration cells, each cell contributing a potential of about 160 mV. It is probable that the overall eel potential is augmented with junction potentials between the mini-cells. 

Schematically speaking an elementary SOFC is composed of a solid oxide electrolyte, an oxygen electrode (cathode) and a fuel electrode (anode), as shown in Fig. 1. To form a battery, several elementary cells must be connected using an appropriate material. A SOFC may be considered as an oxygen concentration cell [6] of the following type...

Except for the need to take concentration overpotential into account in electroanalytical studies, it is an important factor for energy losses in electrochemical power sources (e.g., in -> batteries, fuel cells, etc.) and -> electrolysis (e.g., in electrochemical materials production, -> electroplating, etc.). Concentration overpotential is called also concentration polarization and mass transfer overpotential. 

Higgins cell — This was a chromic acid (carbon electrode) - zinc - battery constructed in such a way that the chromic acid electrolyte was stirred to reduce concentration polarization. See also -> chromic acid battery, -> Daniell cell, -> zinc, - Zn2+/Zn electrodes, -r Zn2+/Zn(Hg) electrodes, -> zinc-air batteries (cell), and - Leclanche cell. 

There are also batteries in which the sum of the two electrode half-reactions produces not a chemical reaction but the transfer of a species from one electrode to the other. Such cells are called concentration cells to distinguish them from those in which a chemical reaction takes place. 

Figures 13 and 14 display the discharge processes for the two kinds of lithium battery. During discharge at the anode the lithium ions are formed from the lithium metal or are released from an Li,A, B < host material at the cathode the lithium ions are inserted into the void spaces of the structure of the A B insertion material. The lithium-ion battery behaves almost like a concentration cell lithium ions move from a lithium-rich source toward the cathode, which acts as sink, while electrons flow through the external circuit from anode to the cathode.

The main effort as far as synthetic membranes are concerned is concentrated on the development of completely new membranes for processes such as pervap-oration, gas separation, membrane distillation, or as ion transferring separators in batteries, fuel cells or electrochemical production processes. Liquid membranes with selective carriers used today for the separation and concentration of heavy metal ions or certain organic compounds are being developed further to be used in gas separation. 

When one surface of an ion exchange membrane contacts a concentrated solution and the other a dilute one, a membrane potential is generated as explained in Chapter 2.4. For example, about 100 mV (unit pair)-1 of membrane potential is observed in seawater concentration to produce sodium chloride. Usage of the membrane potential as a battery has been studied in detail.281 Especially, detailed studies and analysis have been made by researchers in Israel due to the existence of salt lakes such as the Dead Sea.282 It was calculated that 1.08 X 106 m3/s of river water flows in seawater, which corresponds to about 2.43 X 1012 W of electricity if it is generated by a concentration cell using ion exchange membranes. This electric power is calculated to be larger than the electric power consumption of the world.283... 

The cell potential is about 2 V. A car battery consists of (usually) six cells in series (a battery of cells), to give 12 V. Sulphuric acid is used up during operation, so the state of charge of the battery can be estimated by measuring the concentration of the acid, usually via density. 

A wet cell battery has a liquid electrolyte. It is also called as flooded cell, since the liquid covers all internal parts. Wet cells were a precursor to dry cells and are commonly used as a tool for electrochemistry. A particular type of wet cell known as a concentration cell is important in imderstanding corrosion. Wet cells may be primary or secondary cells. Some other primary wet cells are the Leclanche cell. Grove cell, Bunsen cell, chromic acid cell, etc. Wet cells are used in automobile batteries and telecommunication. 

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