Composite Current Collector for Battery Electrode Deformation Control
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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 cause the active material layer to dislocate and peel off, affecting safety and cycle performance.
Innovation Solution
The electrochemical device incorporates a current collector with a first substrate and a second substrate stacked together, where the tensile strength difference (100 MPa ≤ Rm1 - Rm2 ≤ 400 MPa) and thickness ratio (0.5 ≤ d1/d2 ≤ 2.5) are optimized to suppress both elongation deformation and detachment of the active material layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-layer current collector is used, then the device structure is simple, but the active material layer detaches during cycling
Solution Approach 1:
The current collector uses a composite structure with a first substrate (alloy material with high tensile strength) and a second substrate (copper-based material with high electrical conductivity and ductility). This composite design allows the first substrate to prevent detachment while the second substrate maintains conductivity and accommodates expansion, resolving the contradiction between structural simplicity and reliability.
Solution Approach 2:
The current collector is divided into two distinct substrates with different material properties and functions. The first substrate (e.g., aluminum alloy) provides mechanical strength to prevent detachment, while the second substrate (e.g., copper) provides electrical conductivity and ductility. This segmentation allows each layer to optimize its specific function, solving the detachment problem without excessive complexity.
2Reliability
If the first substrate has high tensile strength to prevent detachment, then the active material layer remains attached, but the electrode plate elongates and deforms
Solution Approach 1:
The current collector has different material properties in different layers: the first substrate has high tensile strength to prevent detachment, while the second substrate has high ductility and electrical conductivity to accommodate expansion and maintain shape. This local differentiation of material properties allows simultaneous achievement of attachment reliability and shape stability.
Solution Approach 2:
The composite structure combines an alloy material (first substrate) with a copper-based material (second substrate). The alloy provides the necessary tensile strength to prevent detachment, while the copper layer's high ductility allows it to deform elastically during cycling, accommodating volume changes without causing permanent deformation to the overall electrode plate shape.
3Strength
If the current collector thickness is increased to reduce deformation, then the structural integrity improves, but the energy density decreases
Solution Approach 1:
The composite current collector uses thin layers of both substrates (total thickness 4-20 μm) to achieve the required mechanical strength. The first substrate thickness is 0.5-2.5 times the second substrate thickness, creating an optimized ratio that provides sufficient integrity while minimizing total thickness and maximizing energy density.
Solution Approach 2:
The invention optimizes the thickness parameters of both substrates within specific ranges. The first substrate thickness is controlled at 0.5-2.5 times the second substrate thickness, and the total thickness is maintained at 4-20 μm. These parameter optimizations ensure adequate mechanical strength while minimizing the current collector's volume fraction, thereby maximizing energy density.
Data Source
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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.