Core-Shell Porous Membrane for Secondary Battery Safety
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Solution Overview
Problem
Conventional secondary battery separators made of organic materials like polyolefin can shrink at high temperatures, leading to short circuits, and while porous membranes with non-conductive particles improve safety, they often suffer from adhesion issues, blocking, and powder falling due to excessive binding agents.
Innovation Solution
A porous membrane for secondary batteries using polymer particles with a core-shell structure, where the core has a glass transition point of 30°C to 90°C and the shell has a higher transition point, combined with a binder, to enhance adhesion and anti-blocking properties while minimizing powder falling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a porous membrane containing a large amount of binding agent is used to improve adhesion property, then adhesion property is improved, but blocking occurs when separators or electrodes are stacked in roll shape
Solution Approach 1:
The invention changes the particle size parameter of the non-conductive particles to a specific range (0.1-10 μm) and controls the binding agent content to an optimal level (1-20 parts by weight per 100 parts non-conductive particles). This parameter optimization achieves sufficient adhesion property while preventing blocking during stacking, resolving the contradiction between adhesion and blocking prevention.
2Reliability
If non-conductive particles are used in porous membrane to prevent short circuit, then safety is improved, but non-conductive particles may drop off the porous membrane (powder falling)
Solution Approach 1:
The invention uses a composite structure consisting of non-conductive particles combined with a binder and optionally a reinforcing fiber. This composite material approach anchors the non-conductive particles firmly to the porous membrane, preventing powder falling while maintaining the safety function of electrical insulation.
3Reliability
If porous membrane is provided on separator to suppress shrinkage at high temperature, then safety is improved, but manufacturing complexity increases
Solution Approach 1:
The invention merges the porous membrane layer with the separator into a single integrated structure. The separator and porous membrane are formed as one composite component, combining the heat shrinkage prevention function of the porous membrane with the separation function of the separator, thereby improving safety without significantly increasing manufacturing complexity.
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 porous membrane achieves excellent adhesion and anti-blocking properties, reducing the risk of short circuits and powder falling, while allowing electrolyte permeation without inhibiting battery reactions, thus enhancing the safety and performance of secondary batteries.
Implementation Method 1
the non-conductive particle has a core portion having a glass transition point of 30°C to 90°C, the non-conductive particle has a shell portion having a glass transition point higher than that of the core portion by 10°C or higher
Implementation Method 2
Since the porous membrane has pores, an electrolytic solution can permeate the porous membrane
Data Source
AI summary
A porous membrane for a secondary battery, including non-conductive particles and a binder for a porous membrane, wherein the non-conductive particle is a polymer particle having a core-shell structure, the non-conductive particle has a core portion having a glass transition point of 30°C to 90°C, the non-conductive particle has a shell portion having a glass transition point higher than that of the core portion by 10°C or higher, a thickness of the shell portion is 0.01% to 3.0% of a number average particle diameter of the non-conductive particles, and a number average particle diameter (A) of the non-conductive particle and a number average particle diameter (B) of the binder for a porous membrane satisfy (A) > (B).