Clad Material for Battery Current Collector Pinhole Prevention
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Solution Overview
Problem
The existing clad materials for battery current collectors face issues with pinhole formation and metal dissolution due to the exposure of intermetallic compounds when the thickness is reduced to 50 μm or less, leading to reduced mechanical strength and electrical conductivity.
Innovation Solution
A clad material with a thickness of 50 μm or less, comprising a first layer of Al or Al alloy and a second layer of Ni, Ni alloy, or Fe alloy, with an intermetallic compound layer of Al and Ni or Al and Fe, formed between the layers to prevent pinhole formation and maintain mechanical strength, and the intermetallic compound layer is controlled to have a thickness of 0.1 μm to 1 μm to minimize exposure and ensure bonding strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the thickness of the clad material is reduced to 50 μm or less, then the weight and size of the battery current collector are reduced, but pinholes are easily formed due to breaking of the second layer during rolling
Solution Approach 1:
The patent changes the material parameter of the second layer from Cu to Ni or Fe, which have higher mechanical strength and hardness. This parameter change allows the clad material to be reduced to 50 μm or less without forming pinholes during rolling, as Ni and Fe are less likely to break compared to Cu
Solution Approach 2:
The patent applies preliminary annealing treatment at an annealing temperature equal to or higher than the recrystallization temperature of Ni or Fe before rolling to reduce the thickness to 50 μm or less. This preliminary softening action makes the material more ductile and less likely to break during the subsequent rolling process
2Ease of manufacture
If annealing is performed at an annealing temperature equal to or higher than the recrystallization temperature of Ni or Fe before rolling to 50 μm or less, then the Ni or Fe is softened to perform rolling, but intermetallic compounds are exposed on the outer surface and fall off forming pinholes
Solution Approach 1:
The patent applies local quality by creating a three-layer structure where the first layer (Al or Al alloy) serves as a protective outer layer that prevents intermetallic compounds from being exposed on the surface. This local protective quality ensures that even when annealing exposes intermetallic compounds, they remain covered and do not fall off to form pinholes
Solution Approach 2:
The patent uses a composite clad material structure consisting of an Al or Al alloy layer combined with Ni or Fe layer. This composite structure leverages the protective properties of Al while maintaining the mechanical strength of Ni or Fe, and the intermetallic compound layer formed at the interface enhances bonding between the layers
3Reliability
If another metal layer such as SUS or Ti is provided between Al and Ni or Fe to prevent intermetallic compound formation, then pinhole formation is reduced, but the thickness reduction to 50 μm or less becomes difficult
Solution Approach 1:
The patent changes the material composition parameters by using specific Al alloy compositions (containing Si, Mn, Mg, etc.) combined with Ni or Fe, which controls the formation and characteristics of the intermetallic compound layer. This parameter optimization allows the intermetallic layer to remain within the Al layer without requiring additional protective layers, enabling thickness reduction to 50 μm or less
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 solution effectively reduces pinhole formation and metal dissolution, maintaining mechanical strength and electrical conductivity, even at reduced thicknesses, by controlling the intermetallic compound layer's thickness and forming it in a discontinuous manner to prevent excessive exposure and bonding strength loss.
Implementation Method 1
an intermetallic compound layer constituted by an intermetallic compound containing Al and Ni or an intermetallic compound containing Al and Fe is formed between the first layer and the second layer
Implementation Method 2
annealing is performed on an intermediate clad material at an annealing temperature equal to or higher than the recrystallization temperature of Ni or Fe before rolling
Data Source
AI summary
A clad material for a battery current collector includes a pinhole due to falling off of an intermetallic compound containing Al and Ni or an intermetallic compound containing Al and Fe from an outer surface of a first layer. A clad material for a battery current collector includes a clad material obtained by bonding a first layer made of Al or an Al alloy and a second layer made of any one of Ni, a Ni alloy, Fe, and a Fe alloy by rolling. The clad material has a thickness of 50 μm or less. In the clad material, an intermetallic compound layer constituted by an intermetallic compound containing Al and Ni or an intermetallic compound containing Al and Fe, the intermetallic compound layer having a thickness of 0.1 μm or more and 1 μm or less, is formed between the first layer and the second layer.