Battery Electrode Coating Layer for High-Temperature Insulation
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Solution Overview
Problem
Lithium secondary batteries face safety issues due to short circuits and ignition risks in high-temperature environments, primarily caused by the shrinkage of polyolefin-based separators leading to electrical insulation failure between the positive and negative electrodes.
Innovation Solution
A coating layer is formed on the electrode active material layer, comprising polymer particles with a zeta potential of 25 mV or more, a dispersant, and a binder, which includes specific materials like PVDF and PVA, to enhance electrical insulation and prevent shrinkage, thereby replacing or assisting the separator function.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polyolefin-based separator is used to ensure electrical insulation between electrodes, then electrical insulation is achieved at normal temperatures, but the separator shrinks in high-temperature environments causing short circuits and ignition
Solution Approach 1:
The patent changes the material parameters of the separator by using a copolymer composition (ethylene-propylene-diene polymer) with specific glass transition temperatures and melting points, along with controlling crystallinity (30-70%) and adding inorganic particles, to maintain dimensional stability at high temperatures while preserving electrical insulation properties
Solution Approach 2:
The patent creates a composite separator structure by combining organic copolymer materials with inorganic particles (such as alumina, silica, or boehmite) to achieve both thermal stability and electrical insulation. The composite structure prevents shrinkage at high temperatures while maintaining the separator's insulating function
2Quantity of substance
If the separator structure is made thinner to increase energy density, then battery capacity increases, but the separator becomes more prone to shrinkage and failure at high temperatures
Solution Approach 1:
The patent optimizes the thickness and physical parameters of the thin separator by controlling the copolymer composition ratios (ethylene content 30-70%, propylene content 20-60%), glass transition temperature (-50 to 0°C), and melting point (100-150°C), enabling the separator to maintain mechanical integrity and prevent shrinkage even at reduced thickness for higher energy density
Solution Approach 2:
The patent incorporates inorganic particles (alumina, silica, boehmite) into the thin separator structure to provide thermal stability and dimensional control. These inorganic reinforcements prevent shrinkage and maintain electrical insulation in thin separators, enabling high energy density without sacrificing high-temperature safety
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 coating layer improves high-temperature safety by preventing short circuits and ignition, while maintaining lithium ion mobility, thus enhancing the battery's life characteristics and electrochemical performance.
Implementation Method 1
a thin film made of polyolefin is generally used. However, a polyolefin-based separator can easily shrink in high temperature environments
Implementation Method 2
A separator is used to ensure electrical insulation between a positive electrode and a negative electrode
Implementation Method 3
the coating layer includes polymer particles having an absolute value of zeta potential of 25 mV or more
Data Source
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AI summary
An electrode according to the present invention includes: an electrode active material layer and a coating layer formed on the electrode active material layer, wherein: the coating layer includes predetermined polymer particles, a dispersant, and a binder, and the binder includes at least one selected from the group consisting of polyvinylidenefluoride (PVDF), polyvinyl alcohol (PVA), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone (PVP), polyethylene (PE), polypropylene, ethylene-propylene-diene polymer, and a sulfonated ethylene-propylene-diene polymer.