Preparation of ionic liquids based on boron clusters
Electrolytes and electrochemical cells include a novel ionic liquid having a quaternary cation and a boron cluster anion. In some versions, the boron cluster anion will be a functionalized or unfunctionalized icosahedral boranyl or carboranyl anion. Electrochemical cells have an electrolyte including the ionic liquid. In some versions, the ionic liquid is used as a solvent to dissolve an ionic shuttle salt for transport of active material, with an optional co-solvent. Methods to synthesize the ionic liquid include contacting a boron cluster salt with a quaternary salt to form the ionic liquid by a metathesis reaction.
1. A method for synthesizing an ionic liquid, the method comprising:
contacting a quaternary salt with a boron cluster salt in a metathesis solvent in which the ionic liquid is insoluble at a temperature above a melting temperature of the ionic liquid to form the ionic liquid via a salt metathesis reaction and as an immiscible liquid layer, the quaternary salt comprising a quaternary cation comprising at least one of:
an ammonium cation having a structure:
and
a phosphonium cation having a structure:
wherein R 1 , R 2 , R 3 , and R 4 is each, independently, selected from a group consisting of:
C2-C12 alkyl; and
poly(ethylene glycol) methyl ether having from 1-20 ethylene glycol subunits.
2. The method as recited in claim 1 , wherein the boron cluster salt comprises an alkali metal cation.
3. The method as recited in claim 1 , wherein the boron cluster salt comprises a boron cluster anion having a formula [B y H (y-z-i) R z X i ] 2− , [CB (y-1) H (y-z-i) R z X i ] − , [C 2 B (y-2) H (y-t-j-1) R t X j ] − , [C 2 B (y-3) H (y-t-j) R t X j ] − , or [C 2 B (y-3) H (y-t-j-1) R t X j ] 2−, and wherein:
y is an integer within a range of 6 to 12;
(z+i) is an integer within a range of 0 to y;
(t+j) is an integer within a range of 0 to (y-1);
X is F, Cl, Br, I, or a combination thereof; and
R is a substituent comprising any of:
group (i): a linear, branched-chain, or cyclic C1-C18 alkyl, perfluoroalkyl, or partially fluorinated alkyl group;
group (ii): a C6-C14 aryl, perfluoroaryl, or partially fluorinated aryl group;
group (iii): a linear, branched-chain, or cyclic C1-C18 alkoxy, perfluoroalkoxy, or partially fluorinated alkoxy group;
group (iv): a C6-C14 aryloxy, perfluoroaryloxy, or partially fluorinated aryloxy group; and
group (v): a substituent that combines moieties defined by two or more of groups (i)-(iv).
4. The method as recited in claim 1 , wherein the boron cluster salt comprises at least one boron cluster anion selected from a group consisting of closo-[B 12 H 12 ] 2− , closo-[CB 11 H 12 ] − , and closo-[C 2 B 10 H 11 ] − .
5. The method as recited in claim 1 , further comprising extracting the immiscible liquid layer with a solvent in which the immiscible liquid layer is soluble.
6. The method as recited in claim 1 , further comprising purifying the ionic liquid by a procedure selected from a group consisting of:
contacting the ionic liquid with an adsorbent;
contacting the ionic liquid with a highly water-reactive metal; and
placing the ionic liquid under vacuum at a temperature up to 100° C.
7. A method for synthesizing an ionic liquid, the method comprising:
contacting a quaternary salt with a boron cluster salt comprising an alkali metal cation in a metathesis solvent in which the ionic liquid is insoluble at a temperature above a melting temperature of the ionic liquid to form the ionic liquid via a salt metathesis reaction and as an immiscible liquid layer, the quaternary salt comprising a quaternary cation comprising at least one of:
an ammonium cation having a structure:
and
a phosphonium cation having a structure:
wherein R 1 , R 2 , R 3 , and R 4 is each, independently, selected from a group consisting of:
C2-C12 alkyl; and
poly(ethylene glycol) methyl ether having from 1-20 ethylene glycol subunits.
8. The method as recited in claim 7 , wherein the boron cluster salt comprises a boron cluster anion having a formula [B y H (y-z-i) R z X i ] 2− , [CB (y-1) H (y-z-i) R z X i ] − , [C 2 B (y-2) H (y-t-j-1) R t X j ] − , [C 2 B (y-3) H (y-t-j) R t X j ] − , or [C 2 B (y-3) H (y-t-j-1) R t X j ] 2− , and wherein:
y is an integer within a range of 6 to 12;
(z+i) is an integer within a range of 0 to y;
(t+j) is an integer within a range of 0 to (y-1);
X is F, Cl, Br, I, or a combination thereof; and
R is a substituent comprising any of:
group (i): a linear, branched-chain, or cyclic C1-C18 alkyl, perfluoroalkyl, or partially fluorinated alkyl group;
group (ii): a C6-C14 aryl, perfluoroaryl, or partially fluorinated aryl group;
group (iii): a linear, branched-chain, or cyclic C1-C18 alkoxy, perfluoroalkoxy, or partially fluorinated alkoxy group;
group (iv): a C6-C14 aryloxy, perfluoroaryloxy, or partially fluorinated aryloxy group; and
group (v): a substituent that combines moieties defined by two or more of groups (i)-(iv).
9. The method as recited in claim 7 , wherein the boron cluster salt comprises at least one boron cluster anion selected from a group consisting of closo-[B 12 H 12 ] 2− , closo-[CB 11 H 12 ] − , and closo-[C 2 B 10 H 11 ] − .
10. The method as recited in claim 7 , further comprising extracting the immiscible liquid layer with a solvent in which the immiscible liquid layer is soluble.
11. The method as recited in claim 7 , further comprising purifying the ionic liquid by a procedure selected from a group consisting of:
contacting the ionic liquid with an adsorbent;
contacting the ionic liquid with a highly water-reactive metal; and
placing the ionic liquid under vacuum at a temperature up to 100° C.
12. A method for synthesizing an ionic liquid, the method comprising:
contacting a quaternary salt with a boron cluster salt in a metathesis solvent in which the ionic liquid is insoluble at a temperature above a melting temperature of the ionic liquid to form the ionic liquid via a salt metathesis reaction and as an immiscible liquid layer, the quaternary salt comprising a quaternary cation comprising at least one of:
an ammonium cation having a structure:
and
a phosphonium cation having a structure:
wherein R 1 , R 2 , R 3 , and R 4 is each, independently, selected from a group consisting of:
C2-C12 alkyl; and
poly(ethylene glycol) methyl ether having from 1-20 ethylene glycol subunits; and
extracting the immiscible liquid layer with a solvent in which the immiscible liquid layer is soluble.
13. The method as recited in claim 12 , wherein the boron cluster salt comprises an alkali metal cation.
14. The method as recited in claim 12 , wherein the boron cluster salt comprises a boron cluster anion having a formula [B y H (y-z-i) R z X i ] 2− , [CB (y-1) H (y-z-i) R z X i ] − , [C 2 B (y-2) H (y-t-j-1) R t X j ] − , [C 2 B (y-3) H (y-t-j) R t X j ] − , or [C 2 B (y-3) H (y-t-j-1) R t X j ] 2− , and wherein:
y is an integer within a range of 6 to 12;
(z+i) is an integer within a range of 0 to y;
(t+j) is an integer within a range of 0 to (y-1);
X is F, Cl, Br, I, or a combination thereof; and
R is a substituent comprising any of:
group (i): a linear, branched-chain, or cyclic C1-C18 alkyl, perfluoroalkyl, or partially fluorinated alkyl group;
group (ii): a C6-C14 aryl, perfluoroaryl, or partially fluorinated aryl group;
group (iii): a linear, branched-chain, or cyclic C1-C18 alkoxy, perfluoroalkoxy, or partially fluorinated alkoxy group;
group (iv): a C6-C14 aryloxy, perfluoroaryloxy, or partially fluorinated aryloxy group; and
group (v): a substituent that combines moieties defined by two or more of groups (i)-(iv).
15. The method as recited in claim 12 , wherein the boron cluster salt comprises at least one boron cluster anion selected from a group consisting of closo-[B 12 H 12 ] 2− , closo-[CB 11 H 12 ] − , and closo-[C 2 B 10 H 11 ] − .
16. The method as recited in claim 12 , further comprising purifying the ionic liquid by a procedure selected from a group consisting of:
contacting the ionic liquid with an adsorbent;
contacting the ionic liquid with a highly water-reactive metal; and
placing the ionic liquid under vacuum at a temperature up to 100° C.