Electrodeposited Copper Foil with Localized Roughness for Battery Adhesion
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Solution Overview
Problem
Lithium-ion secondary batteries face issues with uneven electrode material distribution and reduced charge-discharge cycle life due to excessively rough copper foils used as current collectors, leading to inefficient lithium ion utilization and premature battery capacity attenuation.
Innovation Solution
An electrodeposited copper foil with specific puncture and tear strength ratios, surface roughness, and mass per unit area is developed, optimized through controlled electrochemical deposition processes and electrolyte composition, ensuring uniform grain structure and mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the surface of the copper foil is made rough to enhance adhesion with active material layer, then adhesion strength is improved, but the uniformity of negative electrode material coating deteriorates
Solution Approach 1:
The copper foil surface is designed with locally differentiated properties: the first surface (contacting active material) has controlled roughness (Ra: 0.5-3.0 μm) to enhance adhesion, while the second surface maintains smoothness for uniform coating application. This local quality differentiation resolves the contradiction between adhesion strength and coating uniformity.
2Strength
If the surface roughness is increased to improve adhesion, then binding strength is enhanced, but charge-discharge cycle life deteriorates due to material peeling
Solution Approach 1:
Different surface roughness characteristics are applied to different surfaces of the copper foil. The first surface has controlled roughness to provide binding strength, while the second surface remains smooth to prevent material peeling during cycling, thereby extending charge-discharge cycle life.
Solution Approach 2:
The surface roughness parameter is precisely controlled within specific ranges (Ra: 0.5-3.0 μm for the first surface) to optimize both adhesion strength and cycle stability. This parameter optimization prevents excessive roughness-induced peeling while maintaining sufficient binding strength.
3Strength
If the copper foil surface is made excessively rough to ensure adhesion, then adhesion is improved, but active material utilization efficiency deteriorates
Solution Approach 1:
The copper foil exhibits local quality differentiation where only the first surface has controlled roughness for adhesion, while the second surface remains smooth. This ensures active material is evenly distributed and utilized efficiently without the waste associated with excessive roughness.
4Strength
If the surface roughness is increased to enhance adhesion, then binding strength is improved, but negative electrode material uniformity deteriorates
Solution Approach 1:
The copper foil is designed with asymmetric surface properties: the first surface has controlled roughness to provide adhesion, while the second surface maintains smoothness to ensure uniform active material distribution and composition stability.
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 optimized copper foil enhances the charge-discharge cycle life and capacity of lithium-ion secondary batteries by maintaining uniform electrode material distribution and preventing material peeling, while avoiding excessive force during manufacturing.
Implementation Method 1
a cathode and an anode are placed in an electrolytic solution containing copper ions, a small amount of chromium trioxide, and a small amount of 3-S-isothiuronium propylsulfonate; direct current is applied to electrodeposit the copper ions on the cathode
Data Source
AI summary
The present disclosure provides an electrodeposited copper foil having a puncture strength value and a tear strength value. A ratio of the puncture strength value to the tear strength value is from 14 to 64. The present disclosure also provides a lithium-ion secondary battery. The lithium-ion secondary battery is manufactured by using the electrodeposited copper foil and has excellent charge-discharge cycle life.