Substrate-Free Porous Separator for Heat-Stable Battery Insulation
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Solution Overview
Problem
Conventional lithium secondary battery separators with polyolefin substrates suffer from insufficient adhesion to electrodes, thermal instability, low electrical insulation, and vulnerability to short circuits due to low tensile strength and elongation, which are exacerbated in high-temperature environments.
Innovation Solution
A porous separator composed of inorganic particles, a polymer binder, and a crosslinking agent, without a polyolefin substrate, is developed to enhance electrical insulation, ion transfer ability, and mechanical strength through a crosslinking process, forming a three-dimensional net-shaped structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a polyolefin separator substrate is used, then the separator exhibits good adhesion to electrodes and sufficient mechanical strength, but the separator shows poor thermal stability as polyolefin melts at high temperature
Solution Approach 1:
The patent changes the material composition parameters by replacing polyolefin with inorganic particles (alumina, silica, boehmite) and polymer binders (PVdF, CMC, SBR) in specific ratios. This compositional parameter change enables the separator to maintain mechanical strength while achieving high thermal stability, as inorganic particles do not melt at elevated temperatures unlike polyolefin
Solution Approach 2:
The patent creates a composite separator structure combining inorganic particles with polymer binders, and further composite coatings of inorganic particles with ceramic materials. This composite approach allows the separator to simultaneously achieve the mechanical properties of polymers and the thermal stability of inorganic materials, resolving the contradiction between strength and thermal stability
2Stability of the object's composition
If an inorganic coating layer alone without polyolefin substrate is used, then the separator shows improved thermal stability, but the separator exhibits very low electrical insulation and is vulnerable to short circuits
Solution Approach 1:
The patent develops a composite separator consisting of inorganic particles combined with specific polymer binders (PVdF, CMC, or SBR) in optimized ratios. This composite structure maintains the thermal stability of inorganic materials while the polymer binder provides the necessary electrical insulation properties, preventing short circuits between electrodes
Solution Approach 2:
The patent adjusts the compositional parameters by controlling the ratio of inorganic particles to polymer binders and selecting specific binder types. This parameter optimization ensures that the separator achieves both high thermal stability from inorganic components and sufficient electrical insulation from the polymer matrix, eliminating the short circuit vulnerability
3Stability of the object's composition
If an inorganic coating layer alone without polyolefin substrate is used, then the separator shows improved thermal stability, but the separator is easily torn due to low tensile force and low elongation
Solution Approach 1:
The patent creates a composite structure where inorganic particles are embedded in a polymer binder matrix. The polymer binder (PVdF, CMC, or SBR) provides flexibility, tensile strength, and elongation properties, while the inorganic particles provide thermal stability. This composite architecture allows the separator to resist tearing and mechanical failure
Solution Approach 2:
The patent optimizes the compositional parameters by adjusting the proportion of inorganic particles to polymer binder and selecting binders with appropriate mechanical properties. This parameter control ensures the separator achieves the desired balance between thermal stability from inorganic materials and tensile strength/elongation from the polymer matrix, preventing easy tearing
4Strength
If a separator substrate is used, then the separator provides good mechanical support, but the adhesion force between the separator and electrode is insufficient causing local separation or wrinkles
Solution Approach 1:
The patent eliminates the heterogeneous structure of substrate plus coating and creates a homogeneous composite material where inorganic particles and polymer binders are uniformly distributed. This homogeneous composite structure ensures consistent adhesion properties throughout the separator, preventing local separation and wrinkles while maintaining mechanical support
Solution Approach 2:
The patent develops a composite separator material that integrates the functions of mechanical support and adhesion into a single homogeneous structure. The combination of inorganic particles and polymer binders in optimized ratios provides both the mechanical strength needed for support and the surface properties needed for strong electrode adhesion, eliminating the adhesion problems of layered structures
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 high stability in high-temperature environments, maintains electrical insulation, and prevents short circuits by increasing tensile strength and elongation, ensuring reliable battery performance.
Implementation Method 1
a crosslinking agent, wherein a content of the crosslinking agent in the composition is greater than 0 wt% and equal to or less than 5 wt% of a total weight of the composition
Implementation Method 2
exhibit ion permeability and mechanical strength such that an electrolytic solution can pass smoothly through the separator
Implementation Method 3
maintains electrical insulation, and prevents short circuits by increasing tensile strength and elongation
Data Source
AI summary
Disclosed herein is a porous separator for electrochemical devices, configured to guarantee electrical insulation between a positive electrode and a negative electrode, wherein the separator includes no polyolefin substrate, and includes inorganic particles, a binder for coupling between the inorganic particles, and a crosslinking agent.