One-Step Molded Lithium Ion Battery Separator with Ceramic Coating
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Solution Overview
Problem
Lithium ion battery separators face challenges with thermal stability, as existing materials like polyolefin and non-woven fabric separators suffer from limited temperature resistance, mechanical weakness, and issues with filler particle adhesion, leading to potential thermal runaway and safety concerns.
Innovation Solution
A one-step molded lithium ion battery separator is developed, comprising a support layer and a filler layer with superfine main fibers, thermoplastic bonded fibers, and inorganic fillers, which are uniformly structured and compact, with a thickness of up to 30 μm, maintaining strength and porosity even at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polyolefin stretched film is used as separator, then mechanical properties and chemical stability are improved, but temperature resistance deteriorates (suitable working temperature lower than 150°C)
Solution Approach 1:
The patent uses a composite structure consisting of a polyolefin base layer combined with a ceramic coating layer. The ceramic layer contains inorganic particles (such as alumina, silica, or boehmite) dispersed in a binder polymer, creating a composite material that combines the mechanical advantages of polyolefin with the thermal stability of ceramics, enabling the separator to withstand temperatures above 150°C while maintaining structural integrity
2Temperature
If ceramic coating is applied on polyolefin separator, then thermal stability is improved, but strength is completely lost at 300°C
Solution Approach 1:
The patent creates a composite coating system where inorganic ceramic particles are dispersed in a binder polymer matrix. The binder polymer (such as polyacrylic acid, carboxymethyl cellulose, or styrene-butadiene rubber) acts as a binding agent that holds the ceramic particles together and adheres them to the polyolefin substrate, preventing particle detachment and maintaining coating integrity at high temperatures up to 300°C
Solution Approach 2:
The binder polymer serves as an intermediary material between the polyolefin substrate and the inorganic ceramic particles. It provides adhesion between the substrate and ceramic layer, and also acts as a flexible matrix that prevents the rigid ceramic structure from becoming brittle and losing strength at elevated temperatures
3Temperature
If non-woven fabric separator is used, then high temperature resistance is improved, but strength and pore structure deteriorate (low strength and large pores causing micro-short circuit)
Solution Approach 1:
The patent employs a porous ceramic coating layer with controlled pore structure. The inorganic particles are arranged to create interconnected pores that allow lithium ion transport while maintaining mechanical strength. The pore size is controlled to be small enough to prevent micro-short circuits between electrodes, yet large enough to ensure efficient ion conductivity, achieving both strength and high-temperature resistance
4Temperature
If inorganic fillers are coated on substrate, then thermal stability is improved, but filler particles drop-off and preparation process complexity increases
Solution Approach 1:
The patent combines the coating of inorganic fillers with the formation of a binder polymer matrix in a single integrated process. The binder polymer not only adheres the ceramic particles to the substrate but also binds the particles together, creating a cohesive coating layer that prevents particle drop-off during battery assembly and operation, simplifying the overall preparation process while maintaining 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
The separator achieves a heat shrinkage rate of zero at 110°C and less than 3% at 300°C, ensuring excellent thermal stability and strength retention, thereby enhancing battery safety and performance.
Implementation Method 1
a support layer and a filler layer, wherein the support layer comprises or consists of at least two of superfine main fiber, thermoplastic bonded fiber and first nanofiber
Implementation Method 2
the heat shrinkage rate at 110° C. is zero, a good strength retention after treatment at 300° C. for 1 h, and the heat shrinkage rate at 300° C. being less than 3%
Data Source
AI summary
A one-step molded lithium ion battery separator and preparation method and application thereof are provided. The battery separator comprises a support layer and a filler layer. The support layer comprises at least two of superfine main fiber, thermoplastic bonded fiber and first nanofiber, and the filler layer comprises at least one of inorganic fillers and third nanofiber. The lithium ion battery separator has a thickness of 19-31 μm, a maximum pore diameter of no more than 1 μm, and a heat shrinkage rate of less than 3% after treatment at 300° C. for 1 hour, and the separator still has a certain strength at a high temperature, ensuring stability and isolation of the rigid structure of the filler layer at a high temperature, satisfying requirements of the separator in terms of heat resistance, pore size and strength, having excellent comprehensive performance.