RU2555369C1 - Meltable electrolyte for chemical source of current - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: electrolyte additionally contains lithium molybdate with the following component ratio, wt %: potassium bromide 6.4-7.4, potassium methavanadate 64.6-66.8, potassium molybdate 15.5-16.7, lithium molybdate 11.3-12.2.

EFFECT: electrolyte has low specific enthalpy and melting temperature.

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Description

The invention relates to the field of the electrical industry, in particular to the development of compositions comprising bromides, metavanadates, potassium and lithium molybdates, which are used as molten electrolytes in chemical current sources.

A known electrolyte for chemical current sources containing lithium fluoride and molybdate, metavanadate and potassium molybdate with a melting point of 421 ° C and a specific melting enthalpy of 184 J / g (I.K. Garkushin, E.I. Sorokina, T.V. Gubanova , VG Bamburov, Phase equilibria and chemical interaction in multicomponent systems of lithium and potassium salts (monograph) - Ekaterinburg: Ural Branch of the Russian Academy of Sciences, 2012. - 98 p. The disadvantage of this composition is the relatively high specific enthalpy and melting point.

The closest to the claimed composition in temperature and components is the low-melting composition of the KCl-KVO ₃ - (K ₂ MoO ₄ · Li ₂ MoO ₄ ) system (Malysheva E.I., Gubanova T.V., Garkushin I.K., Frolov E .I. Stable triangles KCl-KVO _3- LiKMoO ₄ , KCl-LiVO _3- LiKMoO ₄ (Li ₂ MoO ₄ ) of a four-component reciprocal system of lithium and potassium chlorides, metavanadates and molybdates. Condensed Matter and Interphase Boundaries. - 2011 . - T. 13. - No. 4. S.460-466).

The specific enthalpy of melting was 276 J / g at a melting point of the eutectic alloy 388 ° C.

The present invention allows to reduce specific enthalpy and melting point.

The novelty of the proposed composition compared to the known ones is that in order to reduce the specific enthalpy and the melting temperature, lithium molybdate is additionally introduced in the following ratio of components, wt.%: In the electrolyte containing bromide, metavanadate and potassium molybdate

potassium bromide 6.4 ... 7.4 potassium metavanadate 64.6 ... 66.8 potassium molybdate 15,5 ... 16,7 lithium molybdate 11.3 ... 12.2

Examples of specific performance:

Example 1

Anhydrous salts of 0.66 g (6.6 wt.%) Potassium bromide + 6.57 g (65.7 wt.%) Potassium metavanadate + 1.6 g (16.0 wt.%) Molybdate are remelted in a shaft-type furnace. potassium + 1.17 g (11.7 wt.%) lithium molybdate. The melting point of the mixture is 366 ° C, the specific enthalpy of melting is 117 J / g.

The melting enthalpy of the compositions was measured by us by the method of quantitative DTA. Three cooling and heating curves were studied for the studied eutectic composition and reference substance (KNO ₃ , melts at a temperature of 338 ° C, 115.8 J / g). The peak areas of the differential curves in the diagrams were limited in accordance with the recommendations of the International Committee for Standardization in thermal analysis.

The calculation of the specific enthalpy of melting of the composition was carried out according to the formula:

,

,

where Δ _t H _et - specific enthalpy of the phase transition of the reference substance, close in temperature to the phase transition to the composition under study, J / g;

S _E, S _et - peak areas of differential curves corresponding to the melting of the eutectic structure and the phase transition of the reference material, respectively; T _E , T _et - the melting temperature (K) of the eutectic composition and phase transition of the reference substance, respectively.

Example 2

According to the conditions of example 1, anhydrous salts are melted 0.65 g (6.5 wt.%) Potassium bromide + 6.46 g (64.6 wt.%) Potassium metavanadate + 1.67 g (16.7 wt.%) Molybdate potassium + 1.22 g (12.2 wt.%) lithium molybdate. The melting point of the mixture is 366 ° C, the specific enthalpy of melting is 141 J / g.

Example 3

According to the conditions of example 1, anhydrous salts are melted 0.64 g (6.4 wt.%) Potassium bromide + 6.68 g (66.8 wt.%) Potassium metavanadate + 1.55 g (15.5 wt.%) Molybdate potassium + 1.13 g (11.3 wt.%) lithium molybdate. The melting temperature of the mixture is 366 ° C, the specific enthalpy of melting is 146 J / g.

Example 4

According to the conditions of example 1, anhydrous salts are re-melted 0.74 g (7.4 wt.%) Potassium bromide + 6.51 g (65.1 wt.%) Potassium metavanadate + 1.59 g (15.9 wt.%) Molybdate potassium + 1.16 g (11.6 wt.%) lithium molybdate. The melting temperature of the mixture is 364 ° C, the specific enthalpy of melting is 127 J / g.

Beyond the indicated concentration limits, the compositions are non-phase due to an increase in the melting temperature other than eutectic.

The table shows the comparative characteristics of the physico-chemical properties of the proposed composition and the composition selected as a prototype.

Compositions The composition of the mixture, wt.% Specific enthalpy of melting, J / g Melting point, ° C KBr KVO ₃ K ₂ MoO ₄ Li ₂ MoO ₄ Prototype 11.0 84.7 4.3 - 235 430 Proposed one 6.6 65.7 16,0 11.7 117 366 2 6.5 64.6 16.7 12,2 141 366 3 6.4 66.8 15,5 11.3 146 366 four 7.4 65.1 15.9 11.6 127 364

From the results of the table it is seen that the proposed composition has a melting point of 64-66 ° C lower and the specific enthalpy of melting is 89-118 J / g less than the prototype, which significantly reduces the energy consumption for melting the composition and bringing it into working condition, and also expands the range of use of the composition in temperature.

Claims (1)

A molten electrolyte for a chemical current source, including bromide, metavanadate, potassium molybdate, characterized in that it additionally contains lithium molybdate in the following ratio, wt.%:
potassium bromide 6.4 ... 7.4 potassium metavanadate 64.6 ... 66.8 potassium molybdate 15,5 ... 16,7 lithium molybdate 11.3 ... 12.2