Zinc electrode improvements
Disclosed are methods of making porous zinc electrodes. Taken together, the steps are: forming a mixture of water, a soluble compound that increases the viscosity of the mixture, an insoluble porogen, and metallic zinc powder; placing the mixture in a mold to form a sponge; optionally drying the sponge; placing the sponge in a metal mesh positioned to allow air flow through substantially all the openings in the mesh; heating the sponge in an inert atmosphere at a peak temperature of 200 to 420° C. to fuse the zinc particles to each other to form a sintered sponge; and heating the sintered sponge in an oxygen-containing atmosphere at a peak temperature of 420 to 700° C. to form ZnO on the surfaces of the sintered sponge. The heating steps burn out the porogen.
1. A method comprising:
forming a mixture comprising:
water;
a water-soluble compound that increases the viscosity of the mixture;
water-insoluble carboxymethyl cellulose resin porogen particles; and
metallic zinc powder;
placing the mixture in a mold to form a sponge;
optionally drying the sponge;
heating the sponge in an inert atmosphere at a temperature that fuses the zinc particles to each other to form a sintered sponge; and
heating the sintered sponge in an oxygen-containing atmosphere at a temperature that forms ZnO on the surfaces of the sintered sponge;
wherein the heating steps burn out the porogen.
2. The method of claim 1 , wherein the mixture further comprises an organic liquid.
3. The method of claim 1 , wherein the water-soluble compound is a water-soluble carboxymethyl cellulose resin.
4. The method of claim 1 , wherein the heating steps are performed with the sponge in a metal mesh positioned to allow air flow through substantially all the openings in the mesh.
5. The method of claim 4 ;
wherein the mesh is cylindrical in shape; and
wherein the mesh is placed horizontally on a substrate that touches the mesh at most on two lines along the length of the mesh.
6. The method of claim 5 , wherein heating the sponge in an inert atmosphere is performed at a peak temperature of 200 to 420° C.
7. The method of claim 5 , wherein heating the sintered sponge in an oxygen-containing atmosphere is performed at a peak temperature of 420 to 700° C.
8. A zinc electrode made by the method of claim 5 .
9. The zinc electrode of claim 8 , wherein the zinc electrode has a density of at least 1.0 g cm −3 .
10. The zinc electrode of claim 8 , wherein the zinc electrode comprises no more than 99 wt. % ZnO.
11. An electrochemical cell comprising:
an anode current collector;
the zinc electrode of claim 8 in electrical contact with the anode current collector;
an electrolyte;
a cathode current collector;
a cathode in electrical contact with the anode current collector; and
a separator between the zinc electrode and the cathode.
12. A method comprising:
providing a sponge comprising zinc particles and porogen particles;
placing the sponge in a cylindrical metal mesh positioned to allow air flow through substantially all the openings in the mesh;
wherein the mesh is placed horizontally on a substrate that touches the mesh at most on two lines along the length of the mesh;
heating the sponge in an inert atmosphere at a temperature that fuses the zinc particles to each other to form a sintered sponge; and
heating the sintered sponge in an oxygen-containing atmosphere at a temperature that forms ZnO on the surfaces of the sintered sponge;
wherein the heating steps burn out the porogen.
13. The method of claim 12 , wherein heating the sponge in an inert atmosphere is performed at a peak temperature of 200 to 420° C.
14. The method of claim 12 , wherein heating the sintered sponge in an oxygen-containing atmosphere is performed at a peak temperature of 420 to 700° C.
15. The method of claim 14 , wherein heating the sintered sponge produces a zinc electrode comprising no more than 99 wt. % ZnO.
16. A method comprising:
forming a mixture comprising:
water;
a water-soluble compound that increases the viscosity of the mixture;
water-insoluble porogen particles; and
metallic zinc powder;
placing the mixture in a mold to form a sponge;
optionally drying the sponge;
heating the sponge in an inert atmosphere at a temperature that fuses the zinc particles to each other to form a sintered sponge; and
heating the sintered sponge in an oxygen-containing atmosphere at a temperature that forms ZnO on the surfaces of the sintered sponge;
wherein the heating steps are performed with the sponge in a cylindrical metal mesh positioned to allow air flow through substantially all the openings in the mesh;
wherein the mesh is placed horizontally on a substrate that touches the mesh at most on two lines along the length of the mesh; and
wherein the heating steps burn out the porogen.
17. The method of claim 16 , wherein the mixture further comprises an organic liquid.
18. The method of claim 16 , wherein the water-soluble compound is a water-soluble carboxymethyl cellulose resin.
19. The method of claim 16 , wherein the porogen is corn starch.
20. The method of claim 16 , wherein heating the sponge in an inert atmosphere is performed at a peak temperature of 200 to 420° C.
21. The method of claim 16 , wherein heating the sintered sponge in an oxygen-containing atmosphere is performed at a peak temperature of 420 to 700° C.
22. A zinc electrode made by the method of claim 16 .
23. The zinc electrode of claim 22 , wherein the zinc electrode has a density of at least 1.0 g cm −3 .
24. The zinc electrode of claim 22 , wherein the zinc electrode comprises no more than 99 wt. % ZnO.
25. An electrochemical cell comprising:
an anode current collector;
the zinc electrode of claim 22 in electrical contact with the anode current collector;
an electrolyte;
a cathode current collector;
a cathode in electrical contact with the anode current collector; and
a separator between the zinc electrode and the cathode.