Supercapacitor with hexacyanometallate cathode, activated carbon anode, and non-aqueous electrolyte
A supercapacitor is provided with a method for fabricating the supercapacitor. The method provides dried hexacyanometallate particles having a chemical formula A m M1 x M2 y (CN) 6 .pH 2 O with a Prussian Blue hexacyanometallate, crystal structure, where A is an alkali or alkaline-earth cation, and M1 and M2 are metals with 2+ or 3+ valance positions. The variable m is in the range of 0.5 to 2, x is in the range of 0.5 to 1.5, y is in the range of 0.5 to 1.5, and p is in the range of 0 to 6. The hexacyanometallate particles are mixed with a binder and electronic conductor powder, to form a cathode comprising A m M1 x M2 y (CN) 6 .pH 2 O. The method also forms an activated carbon anode and a membrane separating the cathode from the anode, permeable to A and A′ cations. Finally, an electrolyte is added with a metal salt including A′ cations. The electrolyte may be aqueous.
1. A method for fabricating a supercapacitor, the method comprising:
providing dried hexacyanometallate particles having a chemical formula A m M1 x M2 y (CN)6•pH 2 O with a Prussian Blue hexacyanometallate crystal structure, wherein A-ions are deinserted and inserted, respectively, during supercapacitor charge and discharge cycling;
where A is selected from a group consisting of alkali and alkaline-earth cations;
where M1 is a metal selected from a group consisting of 2+ and 3+ valance positions;
where M2 is a metal selected from a group consisting of 2+ and 3+ valance positions;
where m is in a range of 0.5 to 2;
where x is in a range of 0.5 to 1.5;
where y is in a range of 0.5 to 1.5;
where p is in a range of 0 to 6;
mixing the hexacyanometallate particles with a binder and electronic conductor powder;
forming a cathode comprising A m M1 x M2 y (CN) 6 •pH 2 O;
forming an activated carbon anode capable of physically adsorbing and deadsorbing cations, respectively, during supercapacitor charge and discharge cycling;
forming a membrane separating the cathode from the anode, permeable to A and A′ cations; and,
adding a non-aqueous electrolyte with a metal salt including A′ cations.
2. The method of claim 1 wherein mixing the hexacyanometallate particles with a binder and electronic conductor powder includes:
mixing in a low boiling point solvent, forming a mixture;
drying the mixture, forming a A m M1 x M2 y (CN) 6 .pH 2 O paste; and,
pressing the paste to a metal current collector, to increase the density of the hexacyanometallate particles.
3. The method of claim 1 wherein mixing the hexacyanometallate particles with a binder and electronic conductor powder includes:
pressing the mixture to form a self-supporting plate; and,
locating a metal current collector adjacent to, and in contact with the plate.
4. The method of claim 1 wherein A cations are selected from a first group consisting of Li + , Na + , K + , Mg 2+ , NH 4 + , and Ca 2+ ; and,
wherein A′ cations are selected from a first group consisting of Li + , Na + , K + , Mg 2+ , NH 4 + , and Ca 2+ .
5. The method of claim 1 wherein the M1 metal is selected from a group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ca, and Mg; and,
wherein the M2 metal is selected from a group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ca, and Mg.
6. The method of claim 1 wherein the M1 metal is selected from a group consisting of the same metal as the M2 metal and a different metal than the M2 metal.
7. The method of claim 1 wherein providing the dried hexacyanometallate particles includes providing particles having a size in a range of 5 nanometers (nm) to 10 microns.
8. The method of claim 1 wherein mixing the hexacyanometallate particles with the binder and electronic conductor powder includes mixing with a binder selected from a group consisting of polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF).
9. The method of claim 1 wherein mixing the hexacyanometallate particles with the binder and electronic conductor powder includes mixing with an electronic conductor powder selected from a group consisting of carbon black, carbon nanotubes, carbon nanowire, and grapheme, having a particle size in a range of 5 nm to 10 microns.
10. The method of claim 1 wherein mixing the hexacyanometallate particles with the binder and electronic conductor powder includes forming a paste with 40 to 95 weight (wt) % A m M1 x M2 y (CN) 6 .pH 2 O, 0 to 50 wt % electronic conductor powder, and 1 to 30 wt % binder.
11. The method of claim 1 wherein forming the activated carbon anode includes:
mixing activated carbon, a binder, and an electronic conductor powder with a low boiling point solvent to form a paste;
pressing the paste to a metal current collector to increase the density of the activated carbon.
12. The method of claim 11 wherein forming the activated carbon anode includes forming a paste with 40 to 95 weight (wt) % activated carbon, 0 to 50 wt % electronic conductor powder, and 1 to 30 wt % binder.
13. The method of claim 1 wherein forming the activated carbon anode includes:
mixing activated carbon, a binder, and an electronic conductor powder;
pressing the mixture to form a plate; and,
locating a metal current collector adjacent to, and in contact with plate.
14. The method of claim 1 wherein the A cations are selected from a group consisting of the same material as the A′ cations and a different material than the A′ cations.
15. A method for using a supercapacitor, the method comprising:
providing a cathode with hexacyanometallate particles overlying a current collector, the hexacyanometallate particles having a chemical formula A m M1 x M2 y (CN) 6 .pH 2 O, and having a Prussian Blue hexacyanometallate crystal structure;
where A cations are selected from a group consisting of alkali and alkaline-earth cations;
where M1 is a metal selected from a group consisting of 2+ and 3+ valance positions;
where M2 is a metal selected from a group consisting of 2+ and 3+ valance positions;
where m is in a range of 0.5 to 2;
where x is in a range of 0.5 to 1.5;
where y is in a range of 0.5 to 1.5;
where p is in a range of 0 to 6;
the supercapacitor further comprising a non-aqueous electrolyte with a metal salt including A′ cations, an activated carbon anode, and a membrane separating the cathode from the anode, permeable to A and A′ cations;
charging the supercapacitor as follows:
at the cathode, deinserting A-ions
A m M1 x M2 y (CN) 6 .p H 2 O→( m− 1)A + +AM1 x M2 y (CN) 6 .p H 2 O+( m− 1) e − ;
at the anode, physically adsorbing cations
( m− 1)A + +( m− 1) e − +□→( m− 1)A + // − ;
□=activated carbon.
16. The method of claim 15 wherein the A cations are selected from a first group consisting of Li + , Na + , K + , Mg 2+ , NH 4 + , and Ca 2+ ; and,
wherein the A′ cations are selected from a first group consisting of Li + , Na + , K + , Mg 2+ , NH 4 + , and Ca 2+ .
17. The method of claim 15 wherein the M1 metal is selected from a group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ca, and Mg; and,
wherein the M2 metal is selected from a group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ca, and Mg.
18. The method of claim 15 wherein the M1 metal is selected from a group consisting of the same metal as the M2 metal and a different metal than the M2 metal.
19. The method of claim 15 wherein the A cations are selected from a group consisting of the same material as the A′ cations and a different material than the A′ cations.
20. The method of claim 15 further comprising:
discharging the supercapacitor as follows:
at the anode, physically deadsorbing cations
( m− 1)(A + )//□ − →( m− 1)A + +( m− 1) e − +□;
□=Activated carbon;
at the cathode, inserting A-ions
( m− 1)A + +AM1 x M2 y (CN) 6 .p H 2 O+( m− 1) e − →A m M1 x M2 y (CN) 6 .p H 2 O.