Tin-plated anode casings for alkaline cells
An anode casing having a bright tin or bright tin alloy surface layer at least on an inside surface of the casing, preferably on the entire surface of the anode casing, and to an electrochemical cell containing the anode casing. Methods for preparing anode casings and electrochemical cells containing the anode casings are disclosed. In a preferred embodiment, the anode casings are plated at high current density utilizing a variable contact rack plating process, wherein portions of a clamp assembly of the device variably or alternately contact different portions of the anode casing so the entire surface of the anode casing is plated. The bright tin-plated surface is a high hydrogen-overvoltage metal that reduces gassing in cells using the casings.
1. A method of manufacturing an electrochemical cell comprising the steps:
(a) providing a sheet comprising a steel layer as a substrate;
(b) forming a negative electrode casing from the substrate;
(c) electroplating a layer comprising bright tin and having an average thickness from 1 to 10 micrometers onto the substrate, using a rack plating process with variable contact holding of the negative electrode casing and an electroplating current density from 538 to 2691 amps per square meter;
(d) depositing a negative electrode material comprising zinc and an aqueous alkaline electrolyte in a concave portion of the negative electrode casing such that the negative electrode material is in contact with the tin layer on the negative electrode casing; and
(e) combining the negative electrode casing and the negative electrode material with a positive electrode and a positive electrode casing to form a sealed cell.
2. The method as defined in claim 1 , wherein the tin layer is electroplated using a current density from 807 to 2153 amps per square meter.
3. The method as defined in claim 1 , wherein the average thickness of the tin layer is from 2.5 to 9 micrometers.
4. The method as defined in claim 1 , wherein the substrate comprises an intermediate copper layer on at least part of the concave portion of the anode casing, and the copper layer is applied to the steel layer before the bright tin layer is electroplated onto the negative electrode casing.
5. The method as defined in claim 4 , wherein the copper layer is clad to the steel layer.
6. The method as defined in claim 4 , wherein the copper layer is electroplated onto the steel layer.
7. The method as defined in claim 6 , wherein the copper layer is a strike layer averaging from 0.2 to 2.0 micrometers thick.
8. The method as defined in claim 7 , wherein the copper layer is a strike layer averaging from 0.5 to 1.0 micrometers thick.
9. The method as defined in claim 8 , wherein the copper layer is electroplated using a rack plating process, with variable contact holding of the casing and an electroplating current density from 323 to 646 amps per square meter.
10. The method as defined in claim 8 , wherein the copper layer is electroplated using a plating solution comprising copper cyanide.
11. The method as defined in claim 6 , wherein the copper layer comprises a copper alloy.
12. The method as defined in claim 6 , wherein the copper layer is non-alloyed copper.
13. The method as defined in claim 6 , wherein the negative electrode casing is cleaned and then rinsed prior to electroplating the copper layer.
14. The method as defined in claim 1 , wherein the negative electrode casing has a maximum diameter or a maximum length dimension greater than 11.6 millimeters.
15. The method as defined in claim 1 , wherein the steel layer is a nickel plated steel layer.
16. The method as defined in claim 1 , wherein the steel layer comprises a mild steel layer.
17. The method as defined in claim 16 , wherein the steel layer is a nickel plated mild steel layer.
18. The method as defined in claim 1 , wherein the steel layer comprises a stainless steel layer.
19. The method as defined in claim 1 , wherein the average thickness of the tin layer is less than 5 micrometers, and the substrate comprises an intermediate copper layer on at least part of the concave portion of the anode casing before the bright tin layer is electroplated onto the negative electrode casing.
20. The method defined in claim 1 , wherein the tin in the layer comprising bright tin is an alloy including tin.
21. The method defined in claim 1 , wherein the tin in the layer comprising bright tin is unalloyed tin.
22. The method defined in claim 1 , wherein the surface of the layer comprising bright tin has a reflectance specular excluded Y parameter value from 1 to 40, when tested using a sphere spectrophotometer in the Reflectance Specular Excluded mode.
23. The method defined in claim 22 , wherein the Y parameter value is from 1 to 20.
24. The method defined in claim 23 , wherein the Y parameter value is from 1 to 15.
25. The method defined in claim 24 , wherein the Y parameter value is from 1 to 10.
26. The method as defined in claim 1 , wherein the cell has a prismatic shape.
27. The method as defined in claim 1 , wherein the cell has a catalytic electrode.
28. The method as defined in claim 27 , wherein the cell is a battery cell and comprises an aqueous alkaline electrolyte.
29. The method as defined in claim 28 , wherein the cell is a zinc-air battery cell.
30. A method of manufacturing an electrochemical battery cell comprising the steps:
(a) providing a sheet comprising a non-clad steel layer as a substrate;
(b) forming a negative electrode casing from the substrate;
(c) cleaning the negative electrode casing, and then rinsing the cleaned negative electrode casing;
(d) electroplating an intermediate strike layer having an average thickness from 0.5 to 1.0 micrometers and comprising copper on the cleaned and rinsed negative electrode casing using a rack process with variable contact holding of the negative electrode casing;
(e) electroplating a layer comprising bright tin and having an average thickness from 1 to 10 micrometers onto the substrate, using a rack plating process with variable contact holding of the negative electrode casing and an electroplating current density from 538 to 2691 amps per square meter;
(f) depositing a negative electrode material comprising zinc and an aqueous alkaline electrolyte in a concave portion of the negative electrode casing such that the negative electrode material is in contact with the tin layer on the negative electrode casing; and
(g) combining the negative electrode casing and the negative electrode material with a positive electrode and a positive electrode casing to form a sealed cell.
31. A method of manufacturing an electrochemical battery cell comprising the steps:
(a) providing a substrate comprising a sheet with a layer comprising copper clad to a layer of steel;
(b) forming a negative electrode casing from the substrate, with the layer comprising copper on a concave surface of the negative electrode casing;
(c) cleaning a surface of the layer comprising copper;
(d) electroplating a layer comprising bright tin and having an average thickness from 1 to 10 micrometers on the cleaned surface of the layer comprising copper, using a rack process with variable contact holding of the negative electrode casing and an electroplating current density from 538 to 2691 amps per square meter;
(e) depositing a negative electrode material comprising zinc and an aqueous alkaline electrolyte in a concave portion of the negative electrode casing such that the negative electrode material is in contact with the tin layer on the negative electrode casing; and
(f) combining the negative electrode casing and the negative electrode material with a positive electrode and a positive electrode casing to form a sealed cell.