Electrolyte and surface-active additives for the electrochemical deposition of smooth, dense aluminum layers from ionic liquids

Abstract

The present invention relates to a process for the electrochemical deposition of aluminum, by means of which matt or shiny, dense aluminum layers can be obtained and which comprises the steps: (a) provision of an electrolysis apparatus having at least one anode and at least one cathode in an electrolysis space, (b) electrochemical deposition of aluminum on the at least one cathode of the electrolysis apparatus from an ionic liquid comprising anions and cations and also one or more metal salt(s) and one or more additive(s), wherein the current density at the at least one cathode is at least 50 A/m 2 .

1 . A process for the electrochemical deposition of aluminum, comprising
 electrochemically depositing aluminum on at least one cathode of an electrolysis apparatus comprising the at least one cathode and at least one anode and from an ionic liquid,   wherein:   current density at the at least one cathode is at least 50 A/m 2 ,   the ionic liquid comprises anions and cations, at least one metal salt, and at least one additive,   the amount of the at least one additive is from 0.1 to 10% by weight, based on the total amount of the ionic liquid, and   the at least one additive is selected from the group consisting of:   (a) a compound of the general formula (I):   
       
         
           
           
               
               
           
         
         wherein:
 X 1  and X 2  are each, independently of one another, N or CH, 
 X 3  is selected from the group consisting of NR 1 , O and S, 
 m is an integer from 0 to 4, 
 at least two of X 1 , X 2  and X 3  are heteroatoms selected from the group consisting of N, O and S, 
 R 1  is selected from the group consisting of H, alkyl, cycloalkyl, aralkyl, aryl, alkoxyaryl and heterocyclyl, where the alkyl, cycloalkyl, aralkyl, aryl, alkoxyaryl and heterocyclyl groups are optionally substituted by one or more substituents and the alkyl and cycloalkyl groups are optionally interrupted by from 1 to 3 heteroatoms or functional groups, and 
 the radicals R 2  are each, independently of one another, H, alkyl, cycloalkyl, aralkyl, aryl, alkoxyaryl or heterocyclyl, where the alkyl, cycloalkyl, aralkyl, aryl, alkoxyaryl and heterocyclyl groups are optionally substituted by one or more substituents and the alkyl and cycloalkyl groups are optionally interrupted by from 1 to 3 heteroatoms or functional groups, 
 
         (b) a compound of the general formula (I):
   R 3 N + (R 4 ) 3 HAI −   (II)
 
 
         wherein:
 R 3  is H, alkyl, cycloalkyl, aralkyl, aryl, alkoxyaryl or heterocyclyl, where the alkyl, cycloalkyl, aralkyl, aryl, alkoxyaryl and heterocyclyl groups are optionally substituted by one or more substituents and the alkyl and cycloalkyl groups are optionally interrupted by from 1 to 3 heteroatoms or functional groups, and 
 the radicals R 4  are each, independently of one another, H, alkyl, cycloalkyl, aralkyl, aryl, alkoxyaryl or heterocyclyl, where the alkyl, cycloalkyl, aralkyl, aryl, alkoxyaryl and heterocyclyl groups are optionally substituted by one or more substituents and the alkyl and cycloalkyl groups are optionally interrupted by from 1 to 3 heteroatoms or functional groups, and Hal is selected from the group consisting of fluorine, chlorine, bromine and iodine, and 
 
         (c) a compound of the general formula (III):
   R 5 SO 3   − M +   (III)
 
 
         wherein:
 R5 is alkyl, cycloalkyl, aralkyl, aryl, alkoxyaryl or heterocyclyl, where the alkyl, cycloalkyl, aralkyl, aryl, alkoxyaryl and heterocyclyl groups are optionally substituted by one or more substituents and the alkyl and cycloalkyl groups are optionally interrupted by from 1 to 3 heteroatoms or by functional groups, and 
 M +  is Na +  or K + . 
 
       
     
     
         2 . The process of  claim 1 , wherein the compound of the general formula (I) is selected from the group consisting of N-methylbenzothiazole, N-ethylbenzodiazole, benzooxazole, benzisooxazole, benzisothiazole and benzothiazole. 
     
     
         3 . The process of  claim 1 , wherein the compound of the general formula (II) is selected from the group consisting of hexadecyltrimethylammonium bromide and hexadecyltrimethylammonium chloride. 
     
     
         4 . The process of  claim 1 , wherein the compound of the general formula (III) is sodium laurylsulfate. 
     
     
         5 . The process of  claim 1 , wherein the cations of the ionic liquid comprise at least one cation selected from the group consisting of pyridinium, pyrrolidinium, pyrazolinium, pyrazolium, imidazolium and ammonium. 
     
     
         6 . The process of  claim 1 , wherein the anions of the ionic liquid comprise at least one anion selection from the group consisting of tetrachloroaluminate and heptachlorodialuminate. 
     
     
         7 . The process of  claim 1 , wherein the process is carried out at a temperature in the range from 20 to 120° C. 
     
     
         8 . The process of  claim 1 , wherein a current density of from 200 to 2000 A/m 2  is applied between the at least one anode and the at least one cathode. 
     
     
         9 . The process of  claim 1 , wherein the at least one metal salt is selected from the group consisting of AlCl 3 , AlBr 3 , AlI 3  and AlF 3 . 
     
     
         10 . The process of  claim 1 , wherein the at least one anode comprises a material selected from the group consisting of steel, stainless steel, nickel-based alloys, graphite, copper and aluminum. 
     
     
         11 . An electrolyte for the electrochemical deposition of aluminum comprising an ionic liquid comprising anions and cations, at least one metal salt, and at least one additive,
 wherein:   the at least one additive is selected from the group consisting of:   (a) a compound of the general formula (I):   
       
         
           
           
               
               
           
         
         wherein:
 X 1  and X 2  are each, independently of one another, N or CH, 
 X 3  is NR 1 , O or S, 
 m is an integer from 0 to 4, 
 at least two of X 1 , X 2  and X 3  are heteroatoms selected from the group consisting of N, O and S, 
 R 1  is selected from the group consisting of H, alkyl, cycloalkyl, aralkyl, aryl, alkoxyaryl and heterocyclyl, where the alkyl, cycloalkyl, aralkyl, aryl, alkoxyaryl and heterocyclyl groups are optionally substituted by one or more substituents and the alkyl and cycloalkyl groups are optionally interrupted by from 1 to 3 heteroatoms or functional groups, and 
 the radicals R 2  are each, independently of one another, H, alkyl, cycloalkyl, aralkyl, aryl, alkoxyaryl or heterocyclyl, where the alkyl, cycloalkyl, aralkyl, aryl, alkoxyaryl and heterocyclyl groups are optionally substituted by one or more substituents or are interrupted by from 1 to 3 heteroatoms or functional groups, 
 
         (b) a compound of the general formula (II):
   R 3 N + (R 4 ) 3 HAI −   (II)
 
 
         wherein:
 R 3  is H, alkyl, cycloalkyl, aralkyl, aryl, alkoxyaryl or heterocyclyl, where the alkyl, cycloalkyl, aralkyl, aryl, alkoxyaryl and heterocyclyl groups are optionally substituted by one or more substituents and the alkyl and cycloalkyl groups are optionally interrupted by from 1 to 3 heteroatoms or functional 20 groups, and 
 the radicals R 4  are each, independently of one another, H, alkyl, cycloalkyl, aralkyl, aryl, alkoxyaryl or heterocyclyl, where the alkyl, cycloalkyl, aralkyl, aryl, alkoxyaryl and heterocyclyl groups are optionally substituted by one or more 25 substituents or are interrupted by from 1 to 3 heteroatoms or functional groups, and Hal is selected from the group consisting of fluorine, chlorine, bromine and iodine, and 
 
         (c) a compound of the general formula (III):
   R 5 SO 3   − M +   (III)
 
 
         wherein:
 R5 is alkyl, cycloalkyl, aralkyl, aryl, alkoxyaryl or heterocyclyl, where the alkyl, cycloalkyl, aralkyl, aryl, alkoxyaryl and heterocyclyl groups are optionally substituted by one or more substituents and the alkyl and cycloalkyl groups are optionally interrupted by from 1 to 3 heteroatoms or by functional groups, and 
 M +  is Na +  or K + . 
 
       
     
     
         12 . The electrolyte of  claim 11 , wherein the at least one metal salt comprises AlCl 3 . 
     
     
         13 . (canceled) 
     
     
         14 . A process for electrochemical deposition of aluminum, the process comprising electrochemically depositing aluminum onto at least one cathode from the electrolyte of  claim 11 . 
     
     
         15 . The process of  claim 1 , wherein the at least one cathode comprises a material selection from the group consisting of steel, stainless steel, nickel-based alloys, graphite, copper and aluminum. 
     
     
         16 . The process of  claim 1 , wherein the at least one cathode and the at least one anode comprise a material selection from the group consisting of steel, stainless steel, nickel-based alloys, graphite, copper and aluminum. 
     
     
         17 . The electrolyte of  claim 11 , further comprising at least one solvent. 
     
     
         18 . The electrolyte of  claim 17 , wherein the at least one solvent is selected from the group consisting of toluene, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,3-dichlorobenzene, trichlorobenzene and xylene.