Surface-Modified Copper Foil Current Collector for Lithium Cells
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Solution Overview
Problem
The existing copper current collector foils in lithium-based batteries and capacitors have smooth surfaces that limit the adhesion and interaction of particulate electrode materials with the electrolyte, leading to restricted energy capacity and electrical resistance issues.
Innovation Solution
The surfaces of the copper foils are chemically modified to form integral, outwardly extending copper wires, creating a field of micro-scale structures that enhance adhesion and contact with electrode materials, allowing for thicker porous layers and improved electrical interaction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If smooth copper foil surfaces are used, then manufacturing simplicity is maintained, but adhesion of particulate electrode material and contact with electrolyte are limited
Solution Approach 1:
The patent transforms the flat copper foil surface into a three-dimensional structure with outwardly extending copper wires or protrusions. This curvature transformation increases the surface area and provides mechanical interlocking with electrode particles, significantly enhancing adhesion while maintaining manufacturing simplicity through chemical etching processes.
Solution Approach 2:
The patent creates a porous surface structure on the copper foil by forming arrays of copper wires with interstitial spaces. This porous morphology increases the contact area with both electrode material and electrolyte, improving adhesion and ionic conductivity without requiring complex multi-layer constructions.
2Reliability
If smooth copper foil surfaces are used, then electrical resistance is reduced in the bulk material, but interfacial resistance between electrode and current collector increases
Solution Approach 1:
The patent transitions from a two-dimensional flat surface to a three-dimensional structure with vertically extending copper wires. This dimensional change creates multiple contact points for electrode particles, reducing interfacial resistance by providing numerous parallel conduction pathways between the electrode and current collector.
3Quantity of substance
If thicker porous electrode layers are applied, then energy capacity increases, but adhesion to smooth surfaces becomes insufficient
Solution Approach 1:
The three-dimensional copper wire structures provide mechanical anchoring points that penetrate into thicker electrode layers, maintaining strong adhesion even when substantial amounts of electrode material are applied. The protruding wires act as anchors that secure the electrode material firmly to the current collector.
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 foils with copper wires increase the energy capacity and power performance by providing additional mechanical connectors and increased contact areas for the electrode materials, reducing interfacial resistance and enhancing the overall performance of lithium-based cells.
Implementation Method 1
The copper foil is immersed in an aqueous alkaline solution of an oxidizing agent and a hydroxide compound, and the copper surface is oxidized by the solution to form a field of copper oxide wires
Implementation Method 2
The copper oxide wires are reduced in a hydrogen atmosphere to form a field of copper wires extending outwardly from the surface of the copper foil
Data Source
AI summary
A copper foil, intended for use as a current collector in a lithium-containing electrode for a lithium-based electrochemical cell, is subjected to a series of chemical oxidation and reduction processing steps to form a field of integral copper wires extending outwardly from the surfaces of the current collector (and from the copper content of the foil) to be coated with a resin-bonded porous layer of particles of active electrode material. The copper wires serve to anchor thicker layers of porous electrode material and enhance liquid electrolyte contact with the electrode particles and the current collector to improve the energy output of the cell and its useful life.