Dual-Base-Film Battery Separator for Heat-Resistant Cycling
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Solution Overview
Problem
Secondary batteries face safety hazards due to poor heat resistance, which can lead to potential issues during high-temperature cycling.
Innovation Solution
A separator is designed with a first base film and a second base film, where the melting point of the second film is higher than the first, and their thickness ratio and total thickness are optimized to improve heat resistance and high-temperature cycling performance. The separator may include a binding layer to enhance stability and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a single base film is used for the separator, then the structure is simple and manufacturing is easy, but the heat resistance is insufficient
Solution Approach 1:
The separator is divided into multiple base films with different melting points (first base film with lower melting point and second base film with higher melting point). This segmentation allows each layer to contribute differently to heat resistance, with the higher melting point film providing enhanced thermal stability while the lower melting point film maintains shutdown functionality, thereby resolving the contradiction between heat resistance and structural simplicity.
Solution Approach 2:
The separator uses a composite structure combining different polymer materials with distinct melting characteristics. The first base film (e.g., polyethylene) and second base film (e.g., polypropylene or polyether block amide) form a multi-layer composite that leverages the complementary properties of each material to achieve superior heat resistance while maintaining the necessary safety shutdown function.
2Temperature
If the separator thickness is increased to improve heat resistance, then thermal stability improves, but the battery energy density decreases
Solution Approach 1:
Different regions of the separator have different thicknesses and material compositions optimized for their specific functions. The first base film region provides shutdown functionality with thinner coverage, while the second base film region provides heat resistance with enhanced thickness and material properties in critical areas, achieving local optimization that balances heat resistance and energy density.
Solution Approach 2:
The invention optimizes specific parameters including the thickness ratio between first and second base films (T1/T2 ≥ 1.02), the proportion of each layer (0.3 ≤ T1/T ≤ 0.7), and the melting point ratio (1.05-2.50). These parameter changes enable precise control over heat resistance performance while minimizing the overall thickness impact on energy density.
3Temperature
If the thickness ratio between first and second base films is optimized, then heat resistance improves, but manufacturing precision requirements increase
Solution Approach 1:
The invention establishes specific parameter ranges for manufacturing: T1/T2 ≥ 1.02, 0.3 ≤ T1/T ≤ 0.7, and melting point ratio between 1.05-2.50. These parameter specifications provide clear manufacturing targets that balance heat resistance performance with achievable production tolerances, making the complex multi-layer structure manufacturable with standard precision equipment.
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 optimized thickness and melting point ratio of the base films, along with a binding layer, significantly enhance the heat resistance and high-temperature cycling performance of the secondary battery, ensuring improved safety and reliability.
Implementation Method 1
A melting point of the second base film is higher than a melting point of the first base film
Data Source
AI summary
This application provides a separator, including a first base film and a second base film. A melting point of the second base film is higher than a melting point of the first base film. A thickness of the first base film is denoted as T1, a thickness of the second base film is denoted as T2, and a total thickness of the separator is denoted as T, where T1/T2≥1.02, and 0.3≤T1/T≤0.7. The setting of a thickness relationship between the first base film and the second base film as well as a melting point relationship between the first base film and the second base film can improve the heat resistance of batteries and also effectively improves the high-temperature cycling performance of the batteries.