Chromium-Rich Lead Tab Coating for Stronger Battery Welding
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Solution Overview
Problem
The bonding strength of lead tabs in secondary batteries is weakened by external forces, leading to potential ignition or explosion risks due to high current flow, especially when traditional chromium-based protective layers cause oxidation and reduce adhesion.
Innovation Solution
A lead tab design featuring a copper substrate with nickel-plated layers and a chromium-rich metal layer, formed through sputtering, enhances adhesion and welding strength to 48 kgf/mm² or more, reducing oxidation and improving corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a traditional chromium-based protective layer is applied to the lead tab, then corrosion resistance is improved, but adhesion and welding strength deteriorate due to oxidation
Solution Approach 1:
The protective layer is segmented into multiple functional layers: a bottom nickel-plated layer providing corrosion resistance and adhesion to the copper substrate, and a top chromium-rich metal layer providing enhanced corrosion resistance. This segmentation allows each layer to perform its specific function without compromising the other, achieving both adhesion and corrosion resistance.
Solution Approach 2:
The lead tab uses a composite structure combining copper substrate, nickel-plated layer, and chromium-rich metal layer. This composite material approach leverages the advantages of each material: copper for conductivity, nickel for adhesion and corrosion resistance, and chromium for enhanced corrosion resistance, while avoiding the oxidation problems of traditional single-layer chromium coatings.
2Reliability
If the bonding strength of the lead tab is increased to prevent cutoff under external force, then safety is improved, but manufacturing complexity increases
Solution Approach 1:
The invention optimizes the chromium content parameter in the metal layer to be 70-99.9 wt%, which balances corrosion resistance and adhesion properties. By controlling this compositional parameter within a specific range, the patent achieves high welding strength (48 kgf/mm² or more) without requiring complex multi-step manufacturing processes.
Solution Approach 2:
The patent replaces complex mechanical reinforcement methods with a metallurgical solution - using sputtering to create a chromium-rich metal layer that inherently provides both corrosion resistance and strong adhesion. This substitutes mechanical complexity with a controlled deposition process, simplifying overall manufacturing while achieving high bonding strength.
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 improved lead tab design significantly enhances bonding strength, preventing welding area cutoff and reducing ignition/explosion risks, while minimizing environmental and health hazards from hexavalent chromium.
Implementation Method 1
a metal layer on the nickel-plated layer, wherein the metal layer comprises 70 to 99.9 wt% of chromium
Data Source
Figure 1~2
Figure 3
AI summary
Another embodiment of the present invention provides a lead tab comprising: a metal substrate including copper; a nickel-plated layer disposed on both sides of the metal substrate; and a metal layer on the nickel-plated layer, wherein the metal layer comprises 70 to 99.9 wt% of chromium and wherein the lead tab has a welding strength of 48 kgf/mm2 or more.