Composite Battery Separator With Embedded Fillers for Heat Resistance
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Solution Overview
Problem
Existing secondary batteries face challenges in safety performance, energy density, and cycle performance due to the limitations of conventional separation films, which often have poor heat resistance, mechanical strength, and structural stability.
Innovation Solution
A separation film comprising a first base film with a melting point of 175°C or above and specific pore size, embedded with filler particles, and a second base film with smaller pores, forming a composite structure that enhances mechanical strength, heat resistance, and reduces thickness, thereby improving energy density and cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional separation films are used, then the battery can be manufactured with standard materials, but the heat resistance and mechanical strength are insufficient
Solution Approach 1:
The separation film is constructed as a composite structure with a base film layer and a coating layer containing filler particles. The base film provides fundamental separation function, while the coating layer with embedded filler particles (such as alumina, silica, or boehmite) enhances both heat resistance and mechanical strength simultaneously. This composite architecture resolves the contradiction by combining materials with complementary properties.
Solution Approach 2:
The filler particles are selectively embedded in the coating layer rather than uniformly distributed throughout the entire separation film. This local concentration of reinforcement particles in the coating layer provides enhanced heat resistance and mechanical strength where most needed, while maintaining the overall flexibility and ion permeability of the separation film.
2Strength
If the separation film thickness is increased to improve mechanical strength, then strength improves, but energy density decreases
Solution Approach 1:
The coating layer with embedded filler particles provides disproportionate mechanical strength enhancement relative to its thin profile. The filler particles create a reinforced structure that achieves high strength without requiring increased overall thickness, thus maintaining energy density while improving mechanical properties.
Solution Approach 2:
The separation film incorporates a porous structure with controlled pore sizes (average pore size of 0.01-1.0 μm) that provides mechanical strength through the porous network architecture rather than through material density. This allows the film to maintain high strength with reduced thickness, preserving energy density.
3Ease of manufacture
If the pore size of the first base film is increased to facilitate filler particle embedding, then embedding is improved, but ion permeability may be affected
Solution Approach 1:
The separation film employs a two-layer structure where the first base film has larger pores (0.1-5.0 μm) optimized for filler particle embedding and manufacturing, while the second base film has smaller pores (0.01-1.0 μm) optimized for ion permeability and battery performance. This local differentiation of pore sizes resolves the contradiction between ease of manufacture and reliability.
Solution Approach 2:
The separation film is divided into functional segments: a first base film layer dedicated to providing embedding pathways for filler particles, and a second base film layer dedicated to controlling ion transport. This segmentation allows each layer to be optimized for its specific function without compromising the other.
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 proposed separation film improves safety performance, energy density, and cycle life of secondary batteries by providing better heat resistance, mechanical strength, and reducing the risk of internal short circuits and lithium dendrite formation.
Implementation Method 1
hot-pressing is performed to embed at least some of the filler particles into the first base film
Implementation Method 2
the first base film has a melting point of 175° C. or above, which can provide good heat resistance for the separation film
Implementation Method 3
the average pore size of the first base film is within the above appropriate range, such that an appropriate amount of filler particles can be embedded into the first base film
Data Source
AI summary
Provided in the present application are a separator and a preparation method therefor, a secondary battery, and an electric apparatus. The separator comprises a first base film, a second base film, and an intermediate layer, which is located between the first base film and the second base film, wherein the melting point of the first base film is 175° C. or above, and the average pore size of the first base film is larger than or equal to 0.22 μm; and the intermediate layer comprises filler particles, at least some of which are embedded into the first base film.