Composite Battery Separator Coating Against Swelling and Distortion
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Solution Overview
Problem
Secondary batteries face issues such as lifting and distortion during assembly, leading to reduced efficiency and cycle life due to swelling or decomposition of acryl-based and fluorine-based resins in electrolyte solutions, and gaps forming between electrodes and separators during charge and discharge.
Innovation Solution
A composite separator with a polyolefin-based latex electrode adhesive layer, incorporating organic and inorganic particles, is used to maintain adhesion and prevent swelling, ensuring heat resistance and improved assemblability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If acryl-based resins or modified fluorine-based resins are coated on the separator surface to improve adhesion, then adhesion between electrode and separator is improved, but the resins are easily swollen or decomposed in electrolyte solution, resulting in decreased battery cycle life
Solution Approach 1:
The invention changes the chemical composition parameters of the coating layer by using polyolefin-based latex with specific glass transition temperature (-50°C to 0°C) and melting point (80°C to 180°C), along with controlled amounts of carboxylic acid groups (0.1-5 mmol/g) and inorganic particles (5-50 wt%), to achieve both adhesion and resistance to electrolyte-induced swelling
Solution Approach 2:
The invention creates a composite coating layer combining polyolefin-based organic particles with inorganic particles (such as alumina, silica, or boehmite) and controlled carboxylic acid content, where the inorganic particles provide structural stability and resistance to swelling while the polyolefin matrix provides adhesion
2Strength
If heat and pressure are applied during electrode-separator assembly to improve bonding, then adhesion is improved, but lifting phenomenon or distortion occurs, resulting in decreased efficiency and capacity
Solution Approach 1:
The invention optimizes the thermal parameters of the coating layer by controlling the glass transition temperature (-50°C to 0°C) and melting point (80°C to 180°C) of the polyolefin-based latex, allowing effective bonding at lower temperatures (60°C to 80°C) that prevent distortion while maintaining strong adhesion
3Strength
If the separator is coated to improve adhesion, then bonding between electrode and separator is improved, but gaps still form during charge and discharge, deteriorating cycle life
Solution Approach 1:
The invention adjusts the thermal expansion characteristics and mechanical flexibility of the coating layer by selecting polyolefin-based latex with specific glass transition temperature and melting point, along with controlled inorganic particle content (5-50 wt%), to maintain uniform adhesion during volume changes in charge and discharge cycles
Solution Approach 2:
The composite structure of polyolefin-based latex with inorganic particles provides both adhesion and dimensional stability, where the inorganic particles reinforce the coating to prevent gap formation during electrochemical cycling
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 composite separator prevents lifting and distortion, maintains battery capacity, and enhances cycle life by minimizing permeability changes and electrolyte-induced swelling, while providing excellent heat resistance and slip properties.
Implementation Method 1
a heat-resistant electrode adhesive layer formed on the porous substrate, wherein the heat-resistant electrode adhesive layer includes polyolefin-based organic particles and inorganic particles
Implementation Method 2
capable of maintaining a battery cycle life for a long time without easy swelling or decomposing in the electrolyte solution
Implementation Method 3
Gurley permeability satisfies the following Equation 1, and a change amount in a Gurley permeability satisfies the following Equation 2
Data Source
AI summary
Provided are a separator for an aqueous secondary battery and an electrochemical device using the same. More specifically, provided is a composite separator having a more excellent cycle life and including a coating layer which is not easily swollen in an electrolyte solution. In the composite separator for a secondary battery according to an aspect of the present invention, distortion or lifting phenomenon is suppressed even when the heat and pressure are applied without significant decrease in permeability of the separator.