Nonwoven Battery Separator Structure for Heat-Resistant Electrode Insulation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium secondary battery separators made from porous polyolefin films face issues with thermal shrinkage and ignition risks due to their material properties, leading to internal short circuits and increased fire hazards during thermal runaway.
Innovation Solution
A separator with a non-woven fabric base composed of fibers with different diameters and inorganic particles filled in the pores, where the first fiber has a melting point of 150°C or less and the second fiber has a melting point of 200°C or more, providing improved adhesion and insulation, and the inorganic particles have a D50 of 400 nm or less, enhancing heat resistance and preventing direct contact between electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a porous polyolefin film is used as the separator base, then porosity and ionic conductivity are improved, but thermal shrinkage and ignition risk increase at high temperatures
Solution Approach 1:
The patent uses a composite structure combining organic polyolefin fibers with inorganic particles (such as metal oxides or ceramic particles). The inorganic particles are dispersed within the polyolefin matrix and positioned in the pores, creating a hybrid material that leverages the porosity and ionic conductivity of the organic component while the inorganic component provides thermal stability and prevents shrinkage at high temperatures.
Solution Approach 2:
The inorganic particles are specifically positioned in the pores of the non-woven fabric base, creating localized regions of enhanced thermal stability where they are most needed. This local reinforcement allows the separator to maintain its porous structure and prevent thermal shrinkage at critical heat-generating interfaces between electrodes.
2Ease of manufacture
If the separator uses a single fiber type, then manufacturing is simplified, but adhesion to electrodes and insulation performance are insufficient
Solution Approach 1:
The patent employs a mixed fiber system combining at least two different fiber types with distinct properties. One fiber type provides structural integrity and thermal stability, while the other enhances adhesion to electrodes and ionic conductivity. This composite fiber approach allows each fiber type to contribute its specialized function, achieving superior overall performance without significantly complicating the non-woven fabric manufacturing process.
Solution Approach 2:
Different fiber types are distributed throughout the separator structure to provide localized functions. For example, fibers with higher surface energy or specific chemical groups are positioned near electrode interfaces to enhance adhesion, while fibers with higher thermal stability are distributed throughout to prevent overall structural collapse during thermal events.
3Temperature
If inorganic particles with large size are used, then heat resistance is improved, but pore filling efficiency and insulation performance decrease
Solution Approach 1:
The patent specifies controlling the particle size of inorganic particles to fall within a particular range (typically sub-micron to low micron dimensions). This parameter optimization ensures particles are small enough to effectively fill and stabilize the porous structure without completely blocking ion transport pathways, while still providing sufficient thermal stability. The particle size is tuned to match the pore dimensions of the non-woven fabric for optimal packing and reinforcement.
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 ensures strong adhesion to electrodes, maintaining battery cell integrity and preventing distortion, while the inorganic particles improve insulation and prevent ignition by preventing direct contact between electrodes during thermal events.
Implementation Method 1
the separators may thermally shrink at high temperatures, causing internal short circuits and melting of the polymeric separator base during thermal runaway
Implementation Method 2
the first fiber has a melting point of approximately 150° C. or less
Implementation Method 3
the inorganic particles have D50 of approximately 400 nm or less, enhancing heat resistance and preventing direct contact between electrodes
Data Source
AI summary
A separator for an electrode assembly of a battery includes a non-woven fabric base formed by mixing a first fiber with an average diameter of approximately 10 μm or more and a second fiber with an average diameter of approximately 1 μm or less; and inorganic particles positioned in pores formed between the first and second fibers of the non-woven fabric base. The first fiber has a melting point of about 150° C. or less, and the inorganic particles have D50 of about 400 nm or less.