Tin and tin-zinc plated substrates to improve Ni-Zn cell performance
View Patent ↗An improved Ni—Zn cell with a negative electrode substrate plated with tin or tin and zinc during manufacturing has a reduced gassing rate. The copper or brass substrate is electrolytic cleaned, activated, electroplated with a matte surface to a defined thickness range, pasted with zinc oxide electrochemically active material, and baked. The defined plating thickness range of 40-80 μIn maximizes formation of an intermetallic compound Cu 3 Sn that helps to suppress the copper diffusion from under plating layer to the surface and eliminates formation of an intermetallic compound Cu 6 Sn 5 during baking to provide adequate corrosion resistance during battery operation.
1. A nickel zinc battery cell comprising:
(a) a negative electrode layer comprising a current collector and a zinc oxide based electrochemically active layer;
(b) a positive electrode layer comprising nickel; and
(c) a separator layer to separate the positive and negative electrode layers;
wherein the current collector comprises a copper or brass substrate and a single intermetallic compound layer consisting essentially of Cu 3 Sn and 10% or less Cu 6 Sn 5 .
2. The nickel zinc battery cell of claim 1 , wherein the intermetallic compound layer is made by:
(a) plating about 40-80 μIn of tin on the copper or brass substrate;
(b) pasting the copper or brass substrate with a layer of zinc oxide based electrochemically active material; and
(c) baking the copper or brass substrate.
3. The nickel zinc battery cell of claim 2 , wherein the baking operation comprises maintaining the copper or brass substrate at a temperature of about 200-350° C. for a period of about 30 minutes to 2 hours.
4. A nickel zinc battery cell comprising:
(a) a negative electrode layer comprising a current collector and a zinc oxide based electrochemically active layer;
(b) a positive electrode layer comprising nickel; and
(c) a separator layer to separate the positive and negative electrode layers;
wherein the current collector comprises a copper or brass substrate and a single intermetallic compound layer comprising predominately Cu 3 Sn and 10% or less Cu 6 Sn 5 .
5. The nickel zinc battery cell of claim 4 , wherein the intermetallic compound layer is made by:
(a) plating about 40-80 μIn of tin on the copper or brass substrate;
(b) pasting the copper or brass substrate with a layer of zinc oxide based electrochemically active material; and
(c) baking the copper or brass substrate.
6. The nickel zinc battery cell of claim 5 , wherein the baking operation comprises maintaining the copper or brass substrate at a temperature of about 200-350° C. for a period of about 30 minutes to 2 hours.