Copper Foil Surface Modification for Battery Adhesion
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Solution Overview
Problem
Lithium secondary batteries face a challenge with metal-based anode active materials, which have a large volume expansion rate during charging and discharging, leading to separation from the copper foil, resulting in a shortened battery lifetime due to insufficient adhesive force.
Innovation Solution
A copper foil with an improved adhesive force is achieved by modifying its surface properties, including a protective layer with specific roughness, peak density, and oxygen atomic amount, and incorporating chromium, silane, or nitrogen compounds, along with a controlled manufacturing process to enhance yield strength and elongation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the surface roughness of copper foil is increased to improve adhesive force with metal-based active material, then the adhesive force is enhanced, but the surface becomes too rough causing poor coating uniformity and reduced battery performance
Solution Approach 1:
The patent applies parameter changes by precisely controlling the surface roughness of copper foil within a specific range (Rz: 0.5-3.0 μm, Rmax: 0.8-5.0 μm) and adjusting the electrolyte composition parameters (organic additive concentration: 5-50 ppm, temperature: 20-60°C, current density: 30-80 ASD) to achieve optimal coating uniformity and adhesive force simultaneously
Solution Approach 2:
The patent uses composite materials by incorporating organic additives (surfactants, polymers, or their mixtures) into the electrolyte solution, creating a composite electrolyte system that deposits copper with controlled surface morphology and improved adhesive properties while maintaining coating uniformity
2Quantity of substance
If metal-based active material is used to increase battery capacity, then the energy storage capacity is improved, but the large volume expansion rate causes separation from copper foil and shortened battery lifetime
Solution Approach 1:
The patent applies preliminary action by pre-modifying the copper foil surface through controlled roughness and organic additive treatment before applying the metal-based active material coating. This preliminary surface preparation creates optimal bonding conditions that prevent separation during subsequent volume expansion cycles
Solution Approach 2:
The patent changes physical parameters of the copper foil surface (roughness Rz: 0.5-3.0 μm, Rmax: 0.8-5.0 μm) and chemical parameters (oxygen atomic amount: 10-40 at%, organic additive residues) to enhance adhesive force, enabling the copper foil to withstand the mechanical stress of metal-based active material volume expansion
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 modified copper foil ensures a strong adhesive force with the active material, preventing separation and enhancing the durability and electrical performance of secondary batteries.
Implementation Method 1
a surface of the protective layer has a maximum height roughness (Rmax) of 0.6 μm to 3.5 μm, a peak density (PD) of 5 to 110, and an oxygen atomic amount of 22 at % (atomic %) to 67 at %
Data Source
AI summary
Provided is a copper foil. The copper foil includes a copper layer and a protective layer disposed on the copper layer, wherein a surface of the protective layer has a maximum height roughness (Rmax) of 0.6 μm to 3.5 μm, a peak density (PD) of 5 to 110, and an oxygen atomic amount of 22 at % (atomic %) to 67 at %.