Composite Battery Separator Structure for Thermal Shrinkage Resistance
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Solution Overview
Problem
Secondary battery separators, particularly those used in vehicles, face challenges with heat resistance and mechanical properties due to thermal shrinkage, leading to potential battery explosions.
Innovation Solution
The introduction of cellulose nano fibers with low thermal expansion coefficients and inorganic additives into a polyolefin-based polymer matrix, treated with organic additives, enhances the heat resistance and mechanical properties of the separator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polyolefin separator fabric is used in secondary batteries, then the battery can operate with standard materials and manufacturing processes, but the fabric undergoes heat shrinkage at high temperatures causing thermal instability and potential battery explosion
Solution Approach 1:
The patent applies composite materials by combining polyolefin-based polymer matrix with inorganic additives (such as alumina, silica, or boehmite) to create a separator fabric that maintains dimensional stability at high temperatures. The inorganic additives prevent the heat shrinkage that occurs with pure polyolefin fabrics, thereby resolving the contradiction between using standard materials and achieving thermal stability.
2Power
If the operating temperature range is increased to meet vehicle battery requirements, then high capacity and high output can be achieved, but the separator fabric experiences greater thermal shrinkage and mechanical property degradation
Solution Approach 1:
The patent changes the physical and chemical parameters of the separator fabric by incorporating inorganic additives with high thermal stability. These additives modify the thermal expansion characteristics and mechanical strength parameters of the fabric, enabling it to maintain integrity at elevated temperatures required for high-power vehicle batteries.
Solution Approach 2:
By creating a composite structure of polyolefin polymer and inorganic particles, the fabric achieves enhanced mechanical properties and thermal resistance that allow it to withstand the stresses of high-capacity, high-output battery operation without degradation.
3Reliability
If inorganic additives are added to improve heat resistance, then thermal stability is enhanced, but the dispersibility and workability of the matrix may be compromised
Solution Approach 1:
The patent uses surface treatment agents or coupling agents as intermediaries between the inorganic additives and the polyolefin matrix. These intermediaries improve the interfacial adhesion and dispersibility of inorganic particles within the polymer matrix, preventing aggregation and ensuring uniform distribution while maintaining the heat resistance benefits.
Solution Approach 2:
The patent modifies the surface parameters of inorganic additives through chemical treatment or coating processes. By changing surface properties such as hydrophobicity, surface charge, or reactivity, the inorganic particles achieve better compatibility with the polyolefin matrix, improving dispersibility and ease of manufacturing while preserving thermal stability.
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 solution significantly reduces thermal shrinkage, improves dispersibility, workability, and binding properties, thereby enhancing the stability and performance of secondary batteries.
Implementation Method 1
the cellulose nano fibers having a low thermal expansion coefficient
Implementation Method 2
surface-treatment using the organic additive may generate electrostatic repulsion and allow large particles to be formed to increase a spacing between the fibers
Implementation Method 3
the polyolefin-based polymer matrix and the inorganic additive may constitute a composite to improve a binding force therebetween
Data Source
AI summary
Disclosed are a separator for a lithium ion secondary battery, a method for producing the same, and a secondary battery using the same. A separator structure includes a support disposed inside a secondary battery. The support includes a porous polymer matrix, cellulose nano fibers dispersed in the matrix, and inorganic additives dispersed in the matrix, wherein at least some of the inorganic additives are attached to the cellulose nano fibers and are distributed in the matrix.