Separator Cutting Method Preventing Powder Dropping
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Solution Overview
Problem
The existing methods for producing separators with a porous base material layer, a filler layer, and a resin layer suffer from powder dropping during cutting, which compromises the shutdown function and contaminates the device.
Innovation Solution
A method involving cutting the laminated porous film from the surface with the filler layer first, using a slit blade, to prevent powder dropping by reducing external force on the resin layer, thereby maintaining the structural integrity and functionality of the separator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the laminated porous film is cut from the resin layer side, then the cutting process is simple, but powder dropping occurs at the cut section
Solution Approach 1:
The patent applies inversion by reversing the conventional cutting approach. Instead of cutting from the resin layer side (which causes powder dropping), the cutting is performed from the filler layer side. This reversal of the cutting direction allows the resin layer to support the filler layer during cutting, preventing powder dropping while maintaining manufacturing simplicity
Solution Approach 2:
The resin layer acts as an intermediary that supports the filler layer during the cutting process. By cutting from the filler layer side, the resin layer serves as a backing that prevents filler particles from dropping, thus protecting the cut section quality without complicating the manufacturing process
2Device complexity
If the separator uses only a porous base material layer, then the structure is simple, but thermal shrinkage causes shape instability at high temperature
Solution Approach 1:
The patent employs composite materials by combining the porous base material layer with both a filler layer and a resin layer. The filler layer provides heat resistance and prevents thermal shrinkage, while the resin layer contributes to shape stability. This composite structure maintains relatively simple manufacturing processes while significantly improving shape stability at high temperatures
Solution Approach 2:
Different layers are assigned specific functional qualities: the filler layer is positioned to provide heat resistance and prevent shrinkage, while the resin layer provides structural support and shape stability. This local differentiation of qualities allows each layer to perform its specific function optimally without requiring complex overall restructuring
3Reliability
If the resin layer melting point is lowered to trigger shutdown before thermal shrinkage, then shutdown function is improved, but the resin layer becomes more prone to powder dropping during cutting
Solution Approach 1:
The patent resolves this contradiction by inverting the cutting approach. Even though the resin layer has a low melting point (100-130°C) for effective shutdown function, cutting from the filler layer side allows the resin layer to act as a supporting backing, preventing powder dropping. This inversion enables both low melting point and good cut quality to coexist
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
Prevents powder dropping during the cutting process, ensuring the separator's shutdown function is maintained and preventing contamination, thus enhancing the safety and performance of nonaqueous electrolyte secondary batteries.
Implementation Method 1
the resin particles having a melting point of 100° C. to 130° C.
Implementation Method 2
a filler layer, provided on one surface of the porous base material layer, which contains an inorganic filler as a main component
Data Source
AI summary
A method is provided for producing a separator by cutting a laminated porous film. The laminated porous film includes a porous base material layer containing polyolefin as a main component and a filler layer containing inorganic particles as a main component. The filler layer is provided on one surface of the porous base material layer; and a resin layer containing resin particles as a main component is provided on the other surface of the porous base material layer. The method includes a step of cutting, using a slit blade, the laminated porous film from the one surface on which the filler layer is provided.