Cryogenic Rolling of Metal Thin Foils to Prevent Tearing
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Solution Overview
Problem
Current processes for producing thin metal-based foils, particularly those made from alkali and alkaline earth metals, face challenges such as high reactivity, mechanical ductility, adhesion issues, and difficulty in achieving foil thicknesses below 20 μm due to tearing and inhomogeneous thickness, leading to increased costs and complexity.
Innovation Solution
A process involving extrusion followed by cooling in a coolant bath, such as liquid nitrogen, to reduce ductility and susceptibility to tearing, allowing for higher-speed rolling with conventional rolls while maintaining homogeneity and precision, and optionally cooling the rolls to prevent overheating and adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If lithium is processed at room temperature, then it has high mechanical ductility and can be formed, but it has strong adhesion tendency and high reactivity making it difficult to handle
Solution Approach 1:
The patent applies parameter changes by cooling the lithium material to temperatures below -100°C (e.g., using liquid nitrogen at -196°C). This temperature parameter change fundamentally alters the material properties: lithium transitions from a ductile, adhesive state at room temperature to a brittle, non-adhesive state at cryogenic temperatures, enabling successful rolling and handling.
Solution Approach 2:
The patent employs an inert atmosphere by surrounding the lithium with nitrogen gas during the cooling and rolling processes. This inert environment prevents lithium from reacting with oxygen and moisture in the air, eliminating the harmful reactivity while the material is in its vulnerable thin-foil state.
2Ease of manufacture
If conventional rolling is used at room temperature, then the process is simple, but the foil thickness cannot be reduced below 20 μm due to tearing and inhomogeneous thickness
Solution Approach 1:
The patent changes the temperature parameter to cryogenic levels (-100°C or lower), which fundamentally alters the rolling characteristics. The cooled lithium becomes brittle and can be rolled to thicknesses of 5-50 μm with uniform thickness distribution, overcoming the 20 μm limitation of room temperature processing while maintaining a relatively simple rolling process.
3Manufacturing precision
If the foil is cooled to reduce ductility and prevent tearing, then thinner foils can be produced, but the material becomes more brittle and requires careful handling
Solution Approach 1:
The patent applies preliminary action by cooling the lithium foil to cryogenic temperatures before the rolling process begins. This pre-cooling ensures the material is in the optimal brittle state throughout the entire rolling operation, preventing tearing and enabling uniform thin foil production. The foil remains in this controlled brittle state until immediately after rolling is complete.
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
Enables the reliable production of foils with thicknesses as low as 5-50 μm, reducing material waste and costs by using conventional rolls and maintaining foil homogeneity and precision, suitable for applications like energy storage batteries.
Implementation Method 1
the preliminary foil is cooled in a coolant bath
Implementation Method 2
the coolant in the coolant bath is one of the following compounds or elements in liquid phase: nitrogen, ammonia, methane, hydrogen, oxygen, carbon dioxide, helium or another noble gas
Data Source
AI summary
A method for producing metal-based thin foils is provided, which includes the steps of extruding a metal through an extruder to form a preliminary foil, cooling the preliminary foil in a coolant bath, and rolling the preliminary foil in a rolling system containing at least two rollers to form a metal-based thin foil.