Battery Separator Coating with Mg(OH)2 for Heat-Shrink Resistance
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Solution Overview
Problem
Lithium secondary batteries face safety issues due to mechanical shrinkage or damage of the separator at high temperatures, leading to potential short circuits and explosions.
Innovation Solution
A separator for lithium secondary batteries is developed, featuring a porous substrate with a coating layer containing polyethylene particles, a mixture of first and second inorganic particles, and a binding binder. The second inorganic particles are plate-shaped Mg(OH)2, and the mixing ratio of polyethylene particles to inorganic particles is optimized to enhance safety and air permeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separator is used in lithium secondary batteries, then ion transfer between electrodes is enabled, but the separator may mechanically shrink or be damaged at high temperatures causing short circuits
Solution Approach 1:
The separator comprises a porous substrate combined with a coating layer containing polyethylene particles, inorganic particles (including plate-shaped Mg(OH)2), and a binding binder. This composite structure provides both ion transfer capability and high-temperature mechanical stability, preventing shrinkage and damage that would cause short circuits.
Solution Approach 2:
The coating layer uses a specific mixing ratio of polyethylene particles to inorganic particles (5:5 to 8:2 by weight ratio) and controls the amount of plate-shaped Mg(OH)2 to be greater than other inorganic particles. These parameter optimizations enhance the separator's thermal stability and mechanical strength at elevated temperatures while maintaining ion permeability.
2Temperature
If a coating layer with inorganic particles is applied to the separator, then high temperature resistance is improved, but air permeability may be reduced
Solution Approach 1:
The separator uses a porous substrate as its base structure, which inherently provides ion and air permeability. The coating layer is applied on this porous structure, allowing the coating to provide heat resistance while the underlying porous architecture maintains the necessary permeability for ion transport.
Solution Approach 2:
The coating layer is positioned on at least one surface of the porous substrate rather than throughout the entire separator structure. This localized application allows the heat-resistant coating to provide thermal protection where needed while preserving the bulk porous structure's permeability characteristics for ion transport.
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 exhibits excellent safety and air permeability characteristics, effectively preventing short circuits and ensuring the battery's safety even under high temperature conditions.
Implementation Method 1
the second inorganic particles are plate-shaped Mg(OH)2
Implementation Method 2
The separator may be a porous material that may transfer ions or electrolytes
Data Source
AI summary
Provided are a separator for a lithium secondary battery and a lithium secondary battery comprising same. The separator for a lithium secondary battery includes a porous substrate and a coating layer positioned on at least one surface of the porous substrate and including polyethylene particles, inorganic particles, and a binding binder, wherein the inorganic particles are a mixture of first inorganic particles and second inorganic particles, the second inorganic particles are plate-shaped Mg(OH)2, the mixing ratio of the polyethylene particles and the inorganic particles is 5:5 to 8:2 by weight, and the mixing ratio of the first inorganic particles and the second inorganic particles is 1:9 to 3:7 by weight.