Lithium Ion Battery Current Collector Surface Roughness
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Solution Overview
Problem
Conventional current collectors for lithium ion secondary batteries often fail to enhance electroconductivity between the electrode mixture layer and the current collector, leading to decreased rate characteristics, especially when using active materials with small particle sizes.
Innovation Solution
A current collector with a three-dimensional center plane average roughness (SRa) of at least 0.10 µm and a ratio of actual surface area to geometric area (B/A) between 6 µm^-1 and 15 µm^-1, achieved through surface roughening and controlled electrolytic processing, to ensure high adhesion and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the thickness of the electrode mixture layer is increased to increase energy density, then the energy density is improved, but the electrode mixture layer can be readily removed from the current collector and the rate characteristic is decreased
Solution Approach 1:
The current collector surface is pre-treated with roughening and oil component attachment before the electrode mixture layer is applied. This preliminary surface preparation creates a foundation that prevents subsequent delamination, allowing thicker electrode layers to be used without adhesion failure.
Solution Approach 2:
The surface properties of the current collector are modified locally through roughening and selective oil component attachment. This creates specific local characteristics on the surface that enhance adhesion, enabling the electrode mixture layer to maintain strong bonding even at increased thickness.
2Quantity of substance
If the particle size of the active material is decreased to increase energy density, then the energy density is improved, but the rate characteristic decreases more noticeably
Solution Approach 1:
The surface roughness parameters (Ra and Rz) of the current collector are specifically controlled within defined ranges. This parameter optimization creates an ideal surface morphology that maintains electroconductivity even when small particle size active materials are used, thereby preserving rate characteristics while enabling higher energy density.
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
This configuration results in a current collector with excellent adhesion and rate characteristics, maintaining performance even with small particle-sized active materials, thereby improving the battery's energy density and stability.
Implementation Method 1
a current collector having high adhesion with the electrode mixture layer
Implementation Method 2
the amount of an oil component attached to the roughened surface of the foil being in an amount within the range of 50 to 1,000 μg/m2
Data Source
Figure 1
Figure 2
Figure 3(a)~3(b)
AI summary
A current collector for a lithium ion secondary battery, on which an electrode mixture layer is formed, satisfies A ≥ 0.10 µm and 6 ≤ (B/A) ≤15 when assuming that a three-dimensional center plane average roughness SRa of a surface of at least one side of the current collector on which the electrode mixture layer is formed is A and a ratio of an actual surface area of the surface of at least one side of the current collector to a geometric area of the surface of at least one side of the current collector, which is (actual surface area)/(geometric area), is B.