Microcapsule Separator Coating for Battery Thermal Stability
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Solution Overview
Problem
Conventional separators for electrochemical devices, such as lithium secondary batteries, exhibit heat shrinking at high temperatures, leading to potential short-circuits, and metal hydroxide particles used for improved flame resistance show high moisture adsorbability, causing battery performance degradation due to moisture reaction with electrolyte salts.
Innovation Solution
Microcapsules with a core-shell structure comprising metal hydroxide particles coated with a flame-resistant resin, specifically aluminum hydroxide and melamine resin, are used to reduce moisture adsorption and enhance flame resistance, thereby improving battery safety and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a polyolefin-based porous substrate is used as a separator, then it provides good porosity and ion conductivity, but it shows severe heat shrinking behavior at temperatures of 100°C or higher, causing short-circuit between electrodes
Solution Approach 1:
The patent applies composite materials by forming an organic-inorganic coating layer on the polyolefin-based porous substrate. This coating layer comprises inorganic particles (such as alumina, silica, or boehmite) dispersed in a binder polymer, creating a composite structure that combines the porosity and ion conductivity of the polyolefin substrate with the thermal stability of inorganic materials, thereby preventing heat shrinking at high temperatures while maintaining separator functionality
Solution Approach 2:
The patent changes the physical and chemical parameters of the separator by applying a coating layer that modifies the thermal properties of the substrate. The coating layer changes the dimensional stability parameter of the separator, enabling it to maintain its structure at temperatures of 100°C or higher without the severe heat shrinking behavior characteristic of pure polyolefin substrates
2Reliability
If metal hydroxide particles are added to improve flame resistance, then flame resistance is enhanced, but moisture adsorbability increases, causing battery performance degradation
Solution Approach 1:
The patent applies local quality by selectively coating metal hydroxide particles with hydrophobic materials or applying hydrophobic treatments to specific regions of the coating layer. This creates local hydrophobic zones on the particle surfaces that maintain the flame resistance provided by metal hydroxide while reducing the harmful moisture adsorption property, allowing different regions of the coating layer to have different functional characteristics
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 microcapsules effectively reduce moisture absorption and enhance flame resistance, leading to improved cycle characteristics and safety of electrochemical devices by preventing moisture-induced degradation and heat-related issues.
Implementation Method 1
metal hydroxide particles used for improved flame resistance show high moisture adsorbability
Implementation Method 2
capsule coating layer including a flame resistant resin
Data Source
AI summary
A separator for an electrochemical device, including: a porous polymer substrate; and a porous coating layer formed on at least one surface of the porous polymer substrate and containing a plurality of microcapsules and a binder polymer positioned on the whole or a part of the surface of the microcapsules to connect and fix the microcapsules with one another, wherein the microcapsules include metal hydroxide particles, and capsule coating layer surrounding each surface of the metal hydroxide particles. An electrochemical device including the separator, and the microcapsules are also provided. The microcapsules and separator show excellent flame resistance and can reduce degradation of battery performance caused by water adsorbability of the plurality of a metal hydroxide particle.