Tin-Plated Copper Substrate for Ni-Zn Battery Gassing Control
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Solution Overview
Problem
Current nickel zinc rechargeable battery cells face issues with high gassing rates due to the formation of intermetallic compounds like Cu6Sn5, which are brittle and less conductive, leading to corrosion and reduced performance.
Innovation Solution
A method involving electrolytic cleaning and electroplating a copper or brass substrate with a tin/copper alloy, followed by baking to form a preferred intermetallic compound layer of Cu3Sn, which suppresses copper diffusion and reduces gassing rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a copper substrate is used for the zinc negative electrode current collector, then high electrical conductivity is achieved, but high gassing rates occur due to formation of brittle intermetallic compounds like Cu6Sn5
Solution Approach 1:
The patent applies local quality by creating a non-uniform plating layer structure with different regions having different properties. The plating layer contains an intermetallic compound layer (Cu6Sn5) that is strategically positioned and controlled in thickness (1-10 μm) to provide local corrosion protection at the substrate interface, while the remaining thicker plating layer (tin-rich or tin-zinc alloy) provides overall gassing suppression. This localized differentiation allows the copper substrate to maintain conductivity while the controlled intermetallic layer prevents harmful gassing reactions.
Solution Approach 2:
The patent employs composite materials by creating a multi-layered plating structure consisting of a copper substrate combined with a tin or tin-zinc alloy plating layer that contains controlled amounts of intermetallic compounds. This composite structure integrates the high conductivity of copper with the corrosion resistance and gassing suppression properties of tin-based materials. The intermetallic compound layer acts as an intermediate phase that bonds the copper substrate to the tin-rich outer layer, creating a synergistic composite that achieves both electrical conductivity and low gassing rates.
2Reliability
If a thick tin plating layer is applied to suppress gassing, then corrosion resistance improves, but manufacturing cost and plating time increase
Solution Approach 1:
The patent applies parameter changes by precisely controlling the thickness and composition parameters of the plating layer. Instead of using uniformly thick tin plating, the invention specifies that the plating layer should be 40-80 μin thick with an intermetallic compound layer comprising 1-10 μm at the substrate interface. This parameter optimization allows sufficient corrosion protection while reducing total material usage and plating time compared to conventional thick uniform plating approaches.
Solution Approach 2:
The patent applies partial action by forming an intermetallic compound layer with specific thickness (1-10 μm) that is sufficient to provide corrosion protection at the critical substrate interface, rather than requiring excessive thick tin plating throughout. The remaining plating thickness (30-70 μm of tin-rich material) provides adequate gassing suppression without over-plating. This partial optimization of each layer's thickness reduces overall manufacturing cost while maintaining reliability.
3Reliability
If intermetallic compounds like Cu6Sn5 are formed to protect the copper substrate, then corrosion resistance improves, but the compounds become brittle and reduce electrical conductivity
Solution Approach 1:
The patent applies local quality by confining the intermetallic compound layer (Cu6Sn5) to a specific thin region (1-10 μm) at the substrate-plating interface, where it provides localized corrosion protection. The bulk of the plating layer (40-80 μin total thickness with 30-70 μm of tin-rich material) maintains high electrical conductivity and ductility. This spatial differentiation allows the brittle intermetallic to perform its protective function locally without compromising the overall electrical properties of the current collector.
Solution Approach 2:
The patent applies partial action by forming only the necessary minimum thickness of intermetallic compound layer (1-10 μm) required to provide corrosion protection at the substrate interface, rather than allowing excessive intermetallic formation throughout the plating. This controlled partial formation ensures adequate corrosion resistance while minimizing the negative impact on electrical conductivity and mechanical flexibility of the overall plating structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The approach results in a nickel zinc battery cell with reduced gassing rates and improved corrosion resistance, enhancing both low-rate and high-rate applications by avoiding the formation of detrimental intermetallic compounds like Cu6Sn5.
Implementation Method 1
electroplating 40-80 μIn (1-2 μm) of metal onto the strip in an electrolyte bath comprising tin ions and optionally zinc ions
Implementation Method 2
baking the plated substrate and paste by maintaining a higher than ambient temperature for a period of time to form an intermetallic compound layer
Implementation Method 3
baking the plated substrate and paste by maintaining a higher than ambient temperature for a period of time
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
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 In maximizes formation of an intermetallic compound Cu3Sn that helps to suppress the copper diffusion from under plating layer to the surface and eliminates formation of an intermetallic compound Cu6Sn5 during baking to provide adequate corrosion resistance during battery operation.