Methods and electrolytes for electrodeposition of smooth films
Electrodeposition involving an electrolyte having a surface-smoothing additive can result in self-healing, instead of self-amplification, of initial protuberant tips that give rise to roughness and/or dendrite formation on the substrate and/or film surface. For electrodeposition of a first conductive material (C1) on a substrate from one or more reactants in an electrolyte solution, the electrolyte solution is characterized by a surface-smoothing additive containing cations of a second conductive material (C2), wherein cations of C2 have an effective electrochemical reduction potential in the solution lower than that of the reactants.
1. A method for improving surface smoothness during electrodeposition of a first conductive material (C1) on a substrate surface, the method comprising:
providing an electrolyte solution comprising reactants from which C1 is synthesized and a soluble, surface-smoothing additive comprising cations of a second conductive material (C2), wherein cations of C2 have a) a standard electrical reduction potential that is greater than an electrochemical reduction potential of the reactants and (b) an activity in solution such that an effective electrochemical reduction potential of the cations of C2 in the solution is lower than the electrochemical reduction potential of the reactants; and
applying an electrical potential that is less than the electrochemical reduction potential of the reactants and greater than the effective electrochemical reduction potential of the cations of C2, thereby reducing the reactants and forming C1 on the substrate surface.
2. The method of claim 1 , further comprising:
accumulating cations of C2 at protrusions on the substrate surface, thereby forming an electrostatically shielded region near each protrusion; and
temporarily repelling reactants from the electrostatically shielded region near each protrusion.
3. The method of claim 1 , wherein C1 is a metallic material and the reactants comprise cations of C1.
4. The method of claim 3 , wherein C1 is selected from a group consisting of Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba, Al, Ga, In, Tl, Ge, Sn, Pb, As, Sb, Bi, Se, Te, Bi, Po, Sc, Tl, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, W, Pt, Au, Hg, and combinations thereof.
5. The method of claim 3 , wherein C1 comprises Li.
6. The method of claim 1 , wherein C1 comprises an electronic conductive polymer and the reactants comprise monomers of the polymer.
7. The method of claim 1 , wherein the cations of C2 are metal cations.
8. The method of claim 7 , wherein the cations of C2 comprise a metal selected from a group consisting of Li, Cs, Rb, K, Ba, La, Sr, Ca, Ra, Zr, Te, B, Bi, Ta, Ga, Eu, S, Se, Nb, Na, Mg, Cu, Al, Fe, Zn, Ni, Ti, Sn, Sb, Mn, V, Ta, Cr, Au, Ge, Co, As, Ag, Mo, Si, W, Ru, I, Fc, Br, Re, Bi, Pt, Pd, and combinations thereof.
9. The method of claim 1 , wherein the cations of C2 have a concentration in the electrolyte solution that is less than 10% of that of the reactants.
10. The method of claim 1 , wherein the concentration of the cations of C2 have a concentration in the electrolyte solution that is lees than, or equal to, 5% of that of the reactants.
11. The method of claim 1 , wherein the surface-smoothing additive comprises an anion selected from a group consisting of PF 6 − , AsF 6 − , BF 4 − , N(SO 2 CF 3 ) 2 − , N(SO 2 F) 2 − , CF 3 SO 3 − , ClO 4 − , I − , Cl − , OH − , NO 3 − , SO 4 2− , and combinations thereof.
12. The method of claim 1 , wherein the substrate is an electrode.
13. The method of claim 12 , wherein the electrode comprises lithium.
14. The method of claim 12 , wherein the electrode comprises carbon.
15. A method for improving surface smoothness during electrodeposition of lithium on a substrate surface, the method comprising:
providing an electrolyte solution comprising lithium cations and a soluble, surface-smoothing additive comprising cations of a second conductive material (C2) selected from a group consisting of cesium, rubidium, potassium, strontium, barium, calcium, and combinations thereof, wherein cations of C2 have an activity in solution such that an effective electrochemical reduction potential of the cations of C2 is lower than an electrochemical reduction potential of the lithium cations;
applying an electrical potential that is less than the electrochemical reduction potential of the lithium cations and greater than the effective electrochemical reduction potential of the cations of C2, thereby reducing the lithium cations and forming lithium on the substrate surface;
accumulation cations of C2 at protrusions on the substrate surface, thereby forming an electrostatically shielded region near each protrusion; and
temporarily repelling the lithium cations from the electrostatically shielded region near each protrusion.
16. The method of claim 15 , wherein the cations of C2 have a concentration in the electrolyte solution that is less than 10% of that of the lithium cations.
17. The method of claim 15 , wherein the cations of C2 have a concentration in the electrolyte solution that is less than, or equal to, 5% of that of the lithium cations.
18. The method of claim 15 , wherein the surface-smoothing additive comprises an anion comprising PF 6 − anion.
19. The method of claim 15 , wherein the substrate is a battery anode comprising lithium or a battery anode comprising carbon.