Method to prepare a coated current collector electrode for a flow through capacitor using two solvents with different boiling temperature

1. A method to prepare a coated current collector electrode for a flow through capacitor, the method comprising:

preparing a coating paste comprising by weight %:

10-50 weight % of carbon having a specific surface area of at least 500 m 2 /g;

0.3-5 weight % of a binder;

10-50 weight % based on the total paste of a first solvent having a first boiling point; and

10-50 weight % based on the total paste of a second solvent having a second boiling point, the second boiling point being lower than the first boiling point;

applying the coating paste onto a current collector; and

allowing the second solvent in the coating paste applied on the current collector to evaporate at a temperature lower than the first boiling point, the first boiling point being larger than 120° C. at 1 atm.

2. The method according to claim 1 , wherein the first solvent is present in 20-40 weight %, based on the total paste.

3. The method according to claim 1 , wherein the first solvent is present in 25-35 weight %, based on the total paste.

4. The method according to claim 1 , wherein the first solvent comprises an alcohol.

5. The method according to claim 1 , wherein the first solvent comprises a polyol.

6. The method according to claim 1 , wherein the first solvent comprises a triol.

7. The method according to claim 6 , wherein the triol is glycerol.

8. The method according to claim 7 , wherein the glycerol is a food grade glycerol.

9. The method according to claim 1 , wherein the first solvent comprises a glycol.

10. The method according to claim 1 , wherein the second boiling point is 100° C. at 1 atm and the second solvent is water.

11. The method according to claim 1 , wherein the first boiling point is larger than 120° C. at 1 atm to ensure that enough of the first solvent will remain in the coated current collector to avoid cracking of the coated current collector during storage and/or transport.

12. The method according to claim 1 wherein the first boiling point is larger than 120° C. and below 350° C. at 1 atm.

13. The method according to claim 1 , wherein the coating paste is applied by paste-, blade-, dip- spray- or spin coating or by gravure roll coating, extrusion coating or by lamination or screen printing.

14. A coated current collector for a flow through capacitor obtained by the method according to claim 1 , the coated current collector having a dried, obtained coating comprising:

the carbon;

the binder; and

more than zero but less 50 weight % of the first solvent having the first boiling point larger than 120° C. at 1 atm.

15. An apparatus for removal of ions, the apparatus being provided with a housing, the apparatus comprising:

an inlet configured to let water enter an interior of the housing;

an outlet configured to let water out of the interior of the housing;

a first coated current collector and a second coated current collector; and

a spacer provided between the first and second coated current collectors and configured to allow water to flow in between the first and second coated current collectors,

wherein the first and/or second coated current collector is according to claim 14 .

16. The coated current collector of claim 14 , wherein the obtained coating comprises less than 10 weight % of the first solvent.

17. The coated current collector of claim 14 , further comprising a charge barrier membrane, the charge barrier membrane selective for either anions or cations.

18. The coated current collector of claim 14 , wherein the obtained coating comprises a polyelectrolyte.

19. The coated current collector of claim 14 , wherein the obtained coating has a thickness of at least 50 micrometers.

20. The coated current collector of claim 14 , wherein the obtained coating comprises at least 50 weight % of the carbon.