Crosslinked Battery Separator Coating for Heat Shrinkage Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing lithium secondary batteries face safety issues due to heat shrinkage of polyolefin-based separators, leading to potential short-circuits and thermal runaway, and existing crosslinked polymer separators lack sufficient thermal stability and adhesion.
Innovation Solution
A separator with a porous coating layer containing a crosslinkable binder resin, non-crosslinkable binder resin, inorganic particles, and an acid with OH groups to enhance crosslinking, improving heat resistance and adhesion by increasing crosslinking sites and binding forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a general-purpose separation membrane is used in both alkaline and non-alkaline electrolytes, then device versatility is improved, but membrane durability deteriorates due to chemical attack and mechanical degradation
Solution Approach 1:
The separation membrane is divided into multiple layers with different functions: a first separation membrane layer for ion separation and a second separation membrane layer for enhanced durability. This segmentation allows each layer to be optimized for its specific function, resolving the contradiction between versatility and durability.
Solution Approach 2:
The invention uses composite materials consisting of different polymer types (e.g., polyolefin and polyaromatic polyamide) with complementary properties. The first layer provides ion selectivity while the second layer provides chemical and mechanical stability across different electrolyte conditions, enabling both versatility and durability.
2Reliability
If the membrane thickness is increased to improve durability, then reliability is improved, but mass transport efficiency deteriorates due to longer diffusion paths
Solution Approach 1:
The membrane thickness function is segmented between two layers: the first layer provides the necessary ion transport pathways with optimal thickness for efficiency, while the second layer adds durability without significantly impeding mass transport. This segmentation resolves the trade-off between thickness-related durability and transport efficiency.
Solution Approach 2:
Different regions of the membrane have different thicknesses and material properties optimized for their local functions. The ion-conducting regions maintain thin pathways for efficient transport, while protective regions provide additional thickness for durability, achieving both goals simultaneously.
3Reliability
If the membrane thickness is increased to prevent pinhole defects, then reliability is improved, but manufacturing complexity increases due to tighter thickness control requirements
Solution Approach 1:
The defect prevention function is segmented to the second membrane layer, which acts as a protective barrier. This allows the first layer to be manufactured with standard thickness tolerances, while the second layer compensates for any pinhole defects, thereby reducing overall manufacturing complexity while maintaining reliability.
Solution Approach 2:
The second separation membrane layer serves as a pre-established protective barrier against pinhole defects. By incorporating this protective layer in advance, the system compensates for potential manufacturing defects without requiring extremely tight thickness control during production, thus reducing manufacturing complexity.
4Reliability
If conventional membrane materials are used to maintain chemical stability, then reliability is improved, but adaptability deteriorates due to incompatibility with different electrolyte compositions
Solution Approach 1:
The invention employs composite materials where the first separation membrane layer uses materials optimized for specific electrolyte compositions (providing adaptability), while the second layer uses chemically inert materials like polyolefin that provide universal chemical stability across different electrolyte types. This composite structure resolves the contradiction between stability and adaptability.
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 enhanced crosslinking and binding forces increase thermal stability and prevent separation of inorganic particles, ensuring improved safety and durability of the separator.
Implementation Method 1
the first splicing part joining the first separation membrane layer and the second separation membrane layer to each other
Implementation Method 2
a first separation membrane layer and a second separation membrane layer that are different from each other in material composition or porous structure
Data Source
AI summary
Provided is a separator for an electrochemical device. The separator includes a porous coating layer formed from an acid which participates in crosslinking upon the crosslinking of a crosslinkable polymer. As a result, the separator has increased heat resistance, safety and physical strength, shows improved peel strength between the porous substrate and the porous coating layer, and prevents separation of the inorganic particles from the porous coating layer. In addition, the separator shows an improved crosslinking degree so that the added amount of a crosslinkable binder resin may be reduced. Thus, it is possible to increase the added amount of a non-crosslinkable resin, inorganic particles, or both. In other words, even when using a small amount of a crosslinkable binder resin, it is possible to provide both an effect of improving heat resistance and an effect of improving adhesion.