Metal halogen electrochemical cell
AssigneeExxon Research & Engineering Co.
InventorsDaniel J. Eustace, Paul A. Malachesky
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Abstract
An improved aqueous metal-halogen electrochemical cell, particularly a zinc bromide cell, contains a water soluble tetraorgano-substituted ammonium salt in the electrolyte which forms a substantially water insoluble liquid complex with cathodic halogen thereby reducing self-discharge of the cell. Particularly preferred as the ammonium salt is N-ethyl, N-methyl morpholinium bromide.
Claims20
In an electrochemical cell having a metal anode selected from the group consisting of zinc and cadmium;
- a bromine cathode;
- and, an aqueous electrolyte containing a metal bromide, the metal bromide having the same metal as the metal of the anode, the improvement comprising:
- a bromine complexing agent in said aqueous metal bromide electrolyte consisting solely of a tetraorgano substituted ammonium salt, which salt is soluble in water and forms a substantially water immiscible liquid bromine complex at temperatures in the range of about 10.degree. C to about 60.degree. C and wherein the tetraorgano substituted ammonium salt is selected from asymmetric quaternary ammonium compounds having the formula:
- ##STR15## wherein the dangling valences of nitrogen indicates that the nitrogen is an endocyclic nitrogen atom connected to carbon atoms, thereby forming a ring structure selected from saturated five-membered ring structure and a saturated six-membered ring structure including an additional heteroatom and wherein X.sup.- is a halide selected from chloride and bromide, and R.sub.1 and R.sub.2 are selected from alkyl groups and haloalkyl groups of from 1 to 8 carbon atoms.
An aqueous metal halogen secondary battery including a plurality of electrochemical cells, said electrochemical cells comprising a metal anode selected from the group consisting of zinc and cadmium;
- an inert counterelectrode;
- and aqueous electrolyte, said aqueous electrolyte consisting essentially of an aqueous metal bromide solution in which the metal is the same as the metal of the anode and a cathodically active bromine complex which complex is a liquid at temperatures in the range of about 10.degree. C to about 60.degree. C and substantially water immiscible, said bromine complex being formed solely between bromine and a water soluble, asymmetric quaternary ammonium bromide having the general formula:
- ##STR18## wherein the dangling valences of the nitrogen indicate that the nitrogen is part of an endocyclic structure selected from five-membered structures and six-membered structures containing only carbon and hydrogen and another heteroatom and wherein R.sub.1 is selected from alkyl groups having from 1 to 8 carbon atoms and R.sub.2 is selected from alkyl groups and haloalkyl substituted groups having from 1 to 8 carbon atoms but different from R.sub.1.
An aqueous zinc bromide cell comprising a zinc anode;
- an inert electrode;
- and, an aqueous zinc bromine electrolyte containing a cathodically active bromine complex consisting solely of bromine and a water soluble asymmetric quaternary ammonium bromide having the general formula:
- ##STR22## wherein the dangling valences of nitrogen indicate that the nitrogen is an endocyclic nitrogen atom connected to carbon atoms, thereby forming a ring structure selected from saturated five-membered ring structures and a saturated six-membered ring structure including an additonal heteroatom and wherein R.sub.1 and R.sub.2 are selected from alkyl groups and haloalkyl groups of from 1 to 8 carbon atoms, said quaternary ammonium bromide being capable of forming a substantially water immiscible complex with bromine which complex is a liquid at temperatures ranging from about 10.degree. to about 60.degree. C.
Dependencies are inferred from the claim text.