Porous Metal Foil Production via Patterned Rolling
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Solution Overview
Problem
Existing methods for producing porous metal foils, such as aluminum foils, for use in lithium ion batteries and capacitors fail to create sufficient fine pores to hold active materials while maintaining high mechanical strength, leading to inadequate energy density and poor mechanical properties.
Innovation Solution
A method involving a metal foil and a soft laminate sheet passing through a gap between a pattern roll with high-hardness fine particles and a hard metal roll, using a soft sheet with a hard plastic layer on the metal foil side to form fine pores without breaking the foil, utilizing a pattern roll with sharp-edged particles and a die steel roll body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If DC electrolytic etching is used to form pores in aluminum foil, then the foil can be processed, but the resulting pores have small inner diameters (0.2-5 μm) that cannot hold sufficient active material
Solution Approach 1:
The invention changes the pore formation mechanism from electrochemical etching to mechanical pressing, fundamentally altering the pore diameter parameter from micrometer scale (0.2-5 μm) to larger dimensions capable of holding active material. The pressing method with patterned rolls creates pores with diameters determined by the roll pattern geometry rather than electrochemical reaction limits.
Solution Approach 2:
The invention replaces the electrochemical etching system with a mechanical pressing system. Instead of using electrical current and chemical electrolytes to create pores, the patent uses patterned rolling mills with raised patterns that mechanically press pores into the aluminum foil during the rolling process, eliminating the need for subsequent chemical treatment.
2Quantity of substance
If chemical etching is used to enlarge pore diameters, then more active material can enter, but the mechanical strength of the foil deteriorates
Solution Approach 1:
The invention performs pore formation as a preliminary action during the foil manufacturing process itself, rather than as a subsequent treatment step. The patterned pressing is applied to the aluminum foil while it is still in the rolling mill, creating pores before the foil is removed for further processing. This eliminates the need for separate chemical etching steps that would weaken the foil.
Solution Approach 2:
The invention replaces chemical etching with mechanical pressing to create pores. The patterned rolling mill uses controlled mechanical pressure to form pores without the aggressive chemical reactions that would compromise foil strength. The mechanical process allows precise control of pore formation while maintaining the integrity and strength of the aluminum foil structure.
3Shape
If three-dimensional network structure foamed resin is used as substrate, then porous structure is achieved, but the production method becomes complicated and mechanical strength becomes poor
Solution Approach 1:
The invention extracts and eliminates the complex three-dimensional network structure from the substrate. Instead of using foamed resin with intricate internal networks, the patent uses simple aluminum foil with pores created by direct pressing. This removes the need for complex coating, impregnation, and heat treatment processes required to create and stabilize the foamed resin structure.
Solution Approach 2:
The invention replaces the multi-step chemical and thermal processes required for foamed resin substrate preparation with a single mechanical pressing operation. The patterned rolling mill directly creates the porous structure in the aluminum foil during normal rolling operations, eliminating the need for separate steps to form, coat, impregnate, and heat-treat a foamed resin substrate.
4Manufacturing precision
If fine particles with particle sizes of 50-500 μm are pressed into metal foil directly, then fine pores are formed, but the metal foil breaks
Solution Approach 1:
The invention introduces a soft laminate sheet as an intermediary between the patterned rolling mill and the metal foil. This intermediate layer acts as a cushion that distributes the pressing force uniformly across the foil surface, preventing localized stress concentrations that would cause foil breakage. The soft sheet deforms under pressure, allowing fine pores to form without transmitting damaging point loads to the metal foil.
Solution Approach 2:
The soft laminate sheet provides beforehand cushioning by being positioned between the patterned rolls and the metal foil before pressing begins. This protective layer absorbs and distributes the mechanical stress, preventing the foil from breaking during the pore-forming process. The cushioning effect allows the application of sufficient pressure to create fine pores while protecting the foil's structural integrity.
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 method efficiently produces porous metal foils with fine pores that can hold active materials, achieving high mechanical strength and suitable energy density for lithium ion batteries and capacitors, while being cost-effective and high-speed.
Implementation Method 1
causing a metal foil together with a soft sheet to pass through a gap between a pattern roll of a hard metal, which has high-hardness, fine particles having particle sizes of 50-500 μm on the surface, and a hard metal roll, to press the metal foil together with the soft sheet
Data Source
AI summary
A method for producing a porous metal foil comprising causing a metal foil together with a soft sheet to pass through a gap between a pattern roll of a hard metal, which has high-hardness, fine particles having particle sizes of 50-500 μm on the surface, and a hard metal roll opposing the pattern roll, to press the metal foil and the soft sheet, thereby forming fine pores in the metal foil; the soft sheet being a laminate sheet of a relatively hard plastic layer and a relatively soft plastic layer; and the pressing of the metal foil being conducted with the relatively hard plastic layer on the side of the metal foil, and the relatively soft plastic layer on the side of the hard metal roll.