Laser Cutting Lithium-Ion Battery Separators
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Solution Overview
Problem
Existing methods for forming lithium-ion battery separators often result in residues, contaminants, excessive heat affected zones, imprecise edges, and high production costs, which can impact the battery's power density and charge/discharge cycles.
Innovation Solution
A method involving a polymer film with a ceramic material on a porous polyolefin sheet, sandwiched between vitreous substrates with a sacrificial infrared radiation-absorbing layer, where an infrared laser generates heat at the sacrificial layer to cut the polymer film precisely without degrading it, minimizing the heat affected zone and avoiding residues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional cutting methods are used to form separators, then production cost is reduced, but residues and contaminants are generated on the separator surface
Solution Approach 1:
The patent replaces conventional mechanical cutting methods with a laser-based thermal processing system. The laser beam precisely heats and cuts the separator material without physical contact, eliminating mechanical residues and contaminants while maintaining cost-effectiveness through automated processing.
Solution Approach 2:
The laser cutting process utilizes phase transitions (melting and vaporization) of the separator material to achieve clean cutting. The controlled thermal energy causes the material to transition from solid to liquid and then to vapor, removing material without mechanical contact and leaving no residues on the separator surface.
2Productivity
If high power laser is used to cut the polymer film, then cutting speed is improved, but the polymer film is chemically degraded and carbonaceous residues are formed
Solution Approach 1:
The patent applies local quality by concentrating laser energy only at the specific cutting location rather than heating the entire polymer film. The laser beam is focused to a small spot size, creating high energy density locally at the cut line while the rest of the film remains unaffected, preventing chemical degradation and residue formation.
Solution Approach 2:
The laser cutting process uses periodic or pulsed action where the laser beam is applied in controlled pulses along the cutting path. This intermittent heating allows the material to be cut efficiently while preventing excessive heat accumulation that would cause chemical degradation and carbonaceous residue formation.
3Manufacturing precision
If laser heating is applied directly to the polymer film, then cutting precision is improved, but the heat affected zone is excessive and the polymer film is damaged
Solution Approach 1:
The patent introduces a sacrificial layer as an intermediary between the laser beam and the polymer film. The sacrificial layer absorbs the laser energy and undergoes controlled decomposition, acting as a buffer that protects the polymer film from direct laser heating. This intermediary approach maintains cutting precision while minimizing the heat affected zone and preventing polymer damage.
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 produces high-quality, precisely-cut separators that are free from residues and contaminants, with improved power density and charge/discharge cycles, while being economical and scalable for mass production.
Implementation Method 1
applying an infrared laser to the cutting stack through the first vitreous substrate to generate heat at the sacrificial layer
Implementation Method 2
applying an infrared laser to the cutting stack through the first vitreous substrate to generate heat at the sacrificial layer
Implementation Method 3
transferring heat from the sacrificial layer to the polymer film to thereby cut out a portion of the polymer film and form the separator
Implementation Method 4
The sacrificial layer may be formed from an infrared electromagnetic radiation-absorbing material
Data Source
AI summary
A method of forming a separator for a lithium-ion battery includes arranging a polymer film in contact with a sacrificial layer to form a cutting stack. The method includes disposing the cutting stack between a first vitreous substrate and a second vitreous substrate. The method includes applying an infrared laser to the cutting stack through the first vitreous substrate to generate heat at the sacrificial layer. The method also includes transferring heat from the sacrificial layer to the polymer film to thereby cut out a portion of the polymer film and form the separator. A method of cutting a polymer film and a cutting system are also explained.