RU2528634C1 - Method to produce electrolyte pellet for heat chemical current source - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: method implies hot pressing of electrolyte mixture powder based on eutectic of lithium and potassium chlorides, aluminium oxide powder thickener γ-Al₂O₃ in a mould under pressure ((200±20) MPa and the temperature of (100±20)°C and maturing under the said pressure for (20-30) s. Pellets moulded in such a way are dried under the temperature of (135-220)°C and vacuum gage pressure of at least 95 kPa for at least 150 minutes.

EFFECT: reduced process cycle of electrolyte pellet production and improved mechanical strength of the pellets at keeping low internal ohmic resistance.

Description

The present invention relates to the electrical industry and can be used in thermal chemical current sources.

A known method of manufacturing electrolyte tablets for a thermal chemical current source by filling in the mold powder of the electrolyte mixture and holding under pressure, the value of which depending on the strength requirements for the tablet and the composition of the electrolyte mass can be in the range from 3.5 to 450 MPa [Kukoz F.I. et al. Thermal chemical current sources, p. 98, Izd-vo Rostov University, 1989].

In the known method there is no specific exposure time of the powder of the electrolyte mixture in the mold under pressure. However, regardless of the exposure time, the electrolyte tablets obtained by this method have low mechanical strength and high internal ohmic resistance. A significant contribution to the increase in the ohmic resistance of an electrolyte tablet is made by moisture, which enters the electrolyte tablet during the pressing process. Drying the tablets after such pressing does not lead to proper results.

A known method of manufacturing electrolyte tablets by hot pressing in an mold powder of an electrolyte mixture based on a eutectic of lithium and potassium chlorides, a thickener of γ-Al ₂ O ₃ powder, pressure (200 ± 20) MPa and holding under this pressure at a temperature (60 ± 120) ° C for (60-120) s [USSR Author's Certificate No. 1840220, cl. HO1M 6/36, 06/16/1986, publ. 08/20/2006].

The disadvantage of this method is the duration of the manufacture of tablets due to the long exposure time under pressure. The tablets have low mechanical strength, fragility and increased warping. When assembling the block of electrodes, the tablets crack, which leads to instability of the discharge characteristics of thermal current sources.

The aim of the proposed technical solution is to reduce the technological cycle of manufacturing electrolyte tablets and increase their mechanical strength while maintaining low internal ohmic resistance.

To this end, a method for the manufacture of electrolyte tablets by hot pressing in an mold powder of an electrolyte mixture based on a eutectic of lithium and potassium chlorides, a thickener of alumina powder γ-Al ₂ O ₃ pressure (200 ± 20) MPa and holding at this pressure at a temperature (100 ± 20) ° C, characterized in that the exposure is carried out for (20-30) s, after which the tablets are dried at a temperature of (135-220) ° C and a vacuum pressure of at least 95 kPa for at least 150 minutes .

The parameters of the pressing force, holding time under pressure and drying of the pressed tablets are determined by the need to obtain electrolyte tablets with a density of (1.95 ± 0.15) g / cm ³ , which simultaneously provides high specific electrical characteristics of the current sources and mechanical strength of the tablets themselves.

The exposure time of a sample of the electrolyte mixture in the mold for less than 20 s does not provide the required mobility of the electrolyte particles relative to each other due to incomplete heating of the sample of the electrolyte mixture over the entire volume of the mold even at a temperature of 120 ° C. The exposure time of the sample over 30 s leads to an increase in the density of the tablets, a certain value (1.95 ± 0.15) g / cm ² , which leads to their cracking and increased warpage due to internal overvoltage.

Drying the tablets at temperatures above 220 ° C also leads to warping and cracking of the tablets. At a drying temperature below 135 ° C, the tablets do not completely dry, even with a drying time of more than 150 minutes.

The vacuum created for drying, equal to 95 kPa, is sufficient to ensure the required depth of drying of the tablets in the specified temperature range. When drying with tablets, the entire useful volume of the vacuum cabinet is filled, which, along with a decrease in the exposure time of the tablet during the pressing process, can significantly reduce the time of the technological cycle of tablet production.

The proposed method for the manufacture of electrolyte tablets allows, in comparison with the known technical solution, to reduce the technological production time by ~ 2.5 times. The waste of tablets in quality decreased by 3 times. Improved working conditions by reducing the temperature of pressing.

Electrolyte tablets obtained by the proposed manufacturing method were tested as part of a thermal chemical current source using the LiSi / KCl-LiCl / FeS ₂ electrochemical system.

Tests have shown that, in comparison with current sources collected on electrolyte pellets made by known technology, the internal ohmic resistance of the current source decreased and its discharge characteristics stabilized.

Claims (1)

A method of manufacturing electrolyte tablets for a thermal chemical current source by hot pressing in an mold powder of an electrolyte mixture based on a eutectic of lithium and potassium chlorides, a thickener of alumina powder γ-Al ₂ O _{3 with a} pressure of (200 ± 20) MPa and holding under this pressure at temperature (100 ± 20) ° C, characterized in that the exposure is carried out for (20-30) s, after which the tablets are dried at a temperature of (135-220) ° C and vacuum pressure of at least 95 kPa for at least 150 min