Temperature Effects on Conductivities and Association Constants of Lithium and Tetra-Ethylammonium Salts in Six Aprotic Solvents of Medium to High Permittivities from - 30 ºC to + 10 ºC

 

César A.N. Viana,^a Mavitidi Dilo,^a Manuel A.P. Segurado^b,*

 

Centro de Electroquímica e Cinética e Departamento de Química e Bioquímica da Universidade de Lisboa: ^a) Faculdade de Ciências, Rua Ernesto Vasconcelos, 1749-016 Lisboa, Portugal; ^(b) Faculdade de Farmácia, Av. das Forças Armadas, 1649-003 Lisboa, Portugal.

 

Received 12 February 2004; accepted 02 March 2004

 

 

Abstract

A few non-aqueous dipolar aprotic solvents of medium to high permittivities, low viscosities and large temperature intervals between freezing and boiling points have been used to prepare electrolyte solutions applicable to primary and rechargeable high energy batteries. Lithium perchlorate is a salt often chosen to obtain those systems.

In this work low temperature effects on conductivities and association constants of LiClO₄ and Et₄NBr in six different solvents have been analyzed, using the tetraethylammonium bromide salt for comparative reasons. The temperature interval was -30 ºC to 10 ºC. A few thermodynamic functions resulting from K_A, T variations were determined being the results discussed on this basis.

The accuracy and precision of results are high; whenever possible they are compared with others previously published.

 

Keywords: low temperature effects, limiting molar conductivity, association constants, electrolyte solutions, ionic associations.

 

 

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* Corresponding author. E-mail address: asegurado@ff.ul.pt