Composite Current Collector Structure for Battery Electrode Elongation
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Solution Overview
Problem
Electrochemical devices, such as lithium-ion batteries, experience volume expansion during cycling, leading to elongation and deformation of the current collector, which can result in the detachment of the active material layer, affecting safety and cycle performance.
Innovation Solution
The electrochemical device incorporates a current collector with a first substrate of high tensile strength and a second substrate of lower tensile strength, stacked together with a bonding layer, where the tensile strength difference and thickness ratio between the substrates are optimized to suppress both elongation deformation and detachment of the active material layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a single-layer current collector is used, then the structure is simple and easy to manufacture, but the electrode plate undergoes significant elongation deformation during cycling
Solution Approach 1:
The current collector uses a composite structure consisting of a first substrate and a second substrate with different tensile strengths. The first substrate (e.g., aluminum foil with 80-150 MPa tensile strength) provides baseline structural support, while the second substrate (e.g., stainless steel foil with 200-400 MPa tensile strength) provides enhanced tensile strength to resist elongation deformation. This composite approach solves the contradiction by achieving high strength without excessive structural complexity.
Solution Approach 2:
The current collector is segmented into multiple functional layers: the first substrate, the second substrate, and optionally a bonding layer. Each layer has a specific function - the first substrate provides structural support, the second substrate provides tensile strength enhancement, and the bonding layer ensures strong adhesion between layers. This segmentation allows optimization of each layer's properties to collectively solve the elongation problem while maintaining manufacturing feasibility.
2Strength
If a current collector with high tensile strength is used, then elongation deformation is reduced, but the active material layer may peel off due to insufficient adhesion
Solution Approach 1:
The composite current collector structure is designed so that the second substrate (with higher tensile strength) is positioned adjacent to the active material layer, while the first substrate (with lower tensile strength) is on the opposite side. This arrangement ensures that the high-strength layer provides adhesion support where needed, while the overall composite structure maintains appropriate flexibility and bonding characteristics.
Solution Approach 2:
Different regions of the current collector have different tensile strength characteristics tailored to their specific functions. The second substrate with higher tensile strength is strategically positioned where adhesion and deformation resistance are most critical, while the first substrate with lower tensile strength is positioned where flexibility and bonding are prioritized. This local differentiation resolves the contradiction between strength and adhesion.
3Strength
If the current collector is made thicker to reduce deformation, then the tensile strength increases, but the device volume and energy density are reduced
Solution Approach 1:
The composite current collector achieves enhanced tensile strength through material composition rather than increased thickness. By combining a first substrate (6-12 μm thick) with a second substrate (3-8 μm thick), the structure achieves superior mechanical strength without proportionally increasing total thickness, thereby maintaining high energy density and compact device volume.
Solution Approach 2:
Instead of changing the thickness parameter to increase strength, the invention changes the material composition parameters - selecting specific materials with appropriate tensile strength ranges for each substrate layer. This parameter change approach achieves the desired strength improvement while minimizing volume increase, as the thickness increase is much smaller than the strength enhancement would require with a single thick layer.
Data Source
AI summary
An electrochemical device includes a first electrode plate. The first electrode plate includes a current collector and an active material layer. The current collector includes a first substrate and a second substrate that are stacked together. The second substrate is disposed between the first substrate and the active material layer. And 100 MPa≤Rm1−Rm2≤400 MPa, Rm1 is a tensile strength of the first substrate and Rm2 is a tensile strength of the second substrate. The current collector that includes the first substrate and the second substrate is adopted, thereby suppressing both the elongation deformation of the electrode plate and the detachment of the active material layer.