Polymer Separator Composition for Lamination Pressure Resistance
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Solution Overview
Problem
Existing separators for electrochemical devices face deformation and pore damage during lamination due to high pressure, leading to reduced insulation breakdown voltage and potential failures like Hi-Pot and low-voltage failures.
Innovation Solution
A separator comprising a porous polymer substrate with a non-crystalline and crystalline polymer resin blend, optimized through temperature rising elution fractionation (TREF) to achieve a weight-average molecular weight of 100,000 or more, with specific resin content and ratio adjustments to enhance compression resistance and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high pressure is applied during lamination to bond the separator and electrodes, then bonding strength is improved, but the separator deforms and pores are damaged leading to reduced insulation breakdown voltage
Solution Approach 1:
The patent changes the molecular weight parameter of the crystalline polymer resin to a specific range (weight-average molecular weight of 100,000 or more) to optimize the balance between bonding strength and insulation performance. This parameter change allows the separator to withstand lamination pressure while maintaining pore structure and insulation breakdown voltage.
Solution Approach 2:
The patent uses a composite material system consisting of both crystalline polymer resin and non-crystalline polymer resin in specific proportions (crystalline: 60-100 wt%, non-crystalline: 0-40 wt%). This composite structure combines the mechanical strength of crystalline regions with the flexibility and bonding capability of non-crystalline regions, resolving the contradiction between bonding strength and insulation performance.
2Shape
If the crystalline polymer resin content is increased to improve compression resistance, then deformation during lamination is reduced, but the bonding ability may be compromised
Solution Approach 1:
The patent optimizes the molecular weight parameter of the crystalline polymer resin (weight-average molecular weight ≥100,000) to achieve both high compression resistance and adequate bonding ability. The specific molecular weight range ensures that the crystalline regions provide structural stability while maintaining appropriate chain mobility for bonding.
Solution Approach 2:
The patent employs a composite material system where crystalline polymer resin (60-100 wt%) provides compression resistance and structural stability, while non-crystalline polymer resin (0-40 wt%) contributes to bonding ability and flexibility. This composition balance resolves the contradiction between maintaining shape and achieving strong bonding.
3Shape
If the molecular weight of the crystalline polymer resin is increased to prevent deformation, then compression resistance is improved, but the processing difficulty increases
Solution Approach 1:
The patent specifies an optimal molecular weight range for the crystalline polymer resin (weight-average molecular weight of 100,000 or more) that balances deformation resistance with processability. This parameter optimization ensures that the high molecular weight provides sufficient mechanical strength while maintaining adequate chain mobility for processing operations like extrusion and forming.
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 solution minimizes deformation and maintains insulation breakdown voltage, preventing Hi-Pot and low-voltage failures, thereby enhancing battery performance and safety.
Implementation Method 1
allowing the passage of electrolyte and ions through its pores
Implementation Method 2
an eluate eluted from the porous polymer substrate through a temperature rising elution fractionation (TREF) method
Data Source
AI summary
A separator and an electrochemical device including the separator are provided. The separator comprises a porous polymer substrate including a polymer resin, and the polymer resin having specific polymer polydispersity index, weight-average molecular weight, content of a fraction eluted at a specific temperature, and indentation depth, thereby having improved compression resistance and insulation breakdown voltage.