FR2516709A2 - Electrochemical generator with liquid negative electrode - uses alkali metal or alkaline earth in ammoniac liq. to form electrodes sepd. by iodide membrane - Google Patents

Abstract

The electrochemical generator has a negative electrode which is a solution of an alkaline metal, such as sodium, potassium, lithium; or an alkaline earth, such as calcium, in ammoniac liquid, which transforms into polysulphates during discharge. The solution impregnates a graphite pad. Positive and negative electrode structures are separated by a membrane which exchanges cations. The membrane is formed from an iodide soln. in an alkali metal or an alkaline earth, such as lithium iodide, sodium iodide, potassium iodide, or calcium iodide in an ammoniac liquid.

Description

Electrochemical generator with liquid negative electrode
The main patent describes an electrochemical generator comprising a negative electrode, a positive electrode and an electrolyte, a separator in which said negative electrode comprises an alkali or alkaline earth metal dissolved in liquid ammonia, said positive electrode being constituted of a solution, emulsion or suspension in ammonia of an electronic acceptor body chosen from chalcogens or a solid compound in the medium capable of interposing the alkali or alkaline earth metal of the negative electrode , said electrolyte comprising a solution of an iodide of an alkali or alkaline earth metal in said medium.

 It was also indicated that when the positive electrode included a solution of sulfur in ammonia the separator was advantageously constituted by a cation exchange membrane.

 The Applicant has sought to simplify the structure of generators having these latter characteristics.

 The invention relates to an electrochemical generator according to the main patent in which the separator is a cation exchange membrane, the positive electrode comprising, in the charged state of sulfur, transforming into polysulphides during discharge, characterized in that the electrolyte, which comprises a solution of an alkali or alkaline earth iodide in liquid ammonia, is located within said separator.

Other characteristics and advantages of the invention emerge from the description which follows, given by way of purely illustrative but in no way limiting, with reference to the appended drawing in which
FIG. 1 very schematically represents the structure of an experimental generator, according to the invention.

 FIG. 2 represents the performance of a generator according to the invention.

In FIG. 1, the negative electrode is referenced at 1 and the positive electrode at 2
The negative electrode 1 is a solution of an alkali metal, such as sodium, potassium, lithium, or of an alkaline earth metal, such as calcium, in liquid ammonia.
The positive electrode 2 is formed from a solution of sulfur in liquid ammonia which becomes polysulphides during the discharge.

This solution impregnates a graphite felt.

 References 5 and 6 designate the generator output terminals. According to the invention, the electrodes 1 and 2 are separated only by means of an exchange membrane 4 of the cationic type, impregnated with electrolyte, formed of an iodide solution of an alkali or alkaline earth metal. , such as LiI, Nal, KI, Cal2, in liquid ammonia.

 Such a generator operates between -700C and 500 C, and this under pressure.

 The advantages of such a generator are the same as those set out in the main patent.

 In particular, the negative electrode has excellent reversibility, hence the possibility of carrying out a large number of charge-discharge cycles having limited polarizations at low temperatures.

 On the other hand, the positive electrode also has great reversibility.

 By way of non-limiting example, an embodiment of a generator according to the invention will be given.

 The negative electrode includes potassium dissolved in liquid ammonia.

 The positive electrode contains 20% sulfur, in moles, also dissolved at room temperature and under pressure in liquid ammonia.

 These electrodes are separated by means of a cationic membrane with a surface area of 7 mm 2 of the LDE type. P2291, available under the brand name "Permion" and sold by the RAI Company. It is impregnated with KI dissolved in liquid ammonia. Its resistance is 600 ohms at - 40 C approximately. The current collectors are made of tungsten.

 Such a generator has a no-load voltage of the order of 2.3 volts, and a capacity of the order of 1'Ah.

 Figure 2 illustrates the characteristics of this generator at a temperature of -400 C. In this figure we have reported the voltage E, on the abscissa, in volts and the intensity I, on the ordinate, in microamps.

 The invention finds advantageous applications in the field of high power reversible generators operating at low temperature.

 Of course, the invention is in no way limited to the embodiment described and shown, but on the contrary covers all of its variants.

Claims (1)

CLAIM Generator according to claim 5 of the main patent in which the separator (4) is a cation-suspending membrane, the positive electrode (2) comprising, in the charged state of sulfur, transforming into polysulphides during discharge, characterized by the fact that the electrolyte, which comprises a solution of an alkali or alkaline earth iodide in liquid ammonia, is located within said separator (4).