Core-Shell Polymer Porous Film for Li-Ion Battery Separator
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Solution Overview
Problem
Conventional lithium ion secondary batteries face issues with the binding property of porous membranes to separator substrates or electrode plates in electrolytic solutions, leading to decreased low-temperature output and safety concerns due to membrane separation during vibration.
Innovation Solution
A porous membrane composition featuring a core-shell structured particulate polymer with specific swelling properties in electrolytic solutions, where the core portion swells 5 to 30 times and the shell portion swells 1 to 4 times, providing enhanced binding and ion diffusivity while preventing membrane separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a porous membrane is provided on a separator substrate or electrode plate, then ion conductivity is improved, but binding property decreases leading to membrane separation during vibration
Solution Approach 1:
The patent uses a composite porous membrane consisting of a fluororesin base layer and a porous coating layer containing lithium ion conductive particles and binder. This composite structure provides both high ion conductivity through the porous layer and strong binding property through the fluororesin base layer that firmly adheres to the electrode plate or separator substrate, preventing membrane separation during vibration while maintaining excellent ion transport.
2Power
If a porous membrane with high swelling degree is used, then low-temperature output is improved, but binding property to separator substrate or electrode plate decreases
Solution Approach 1:
The patent applies local quality by creating a porous coating layer with specific swelling properties on top of a fluororesin base layer. The porous layer containing hydrophilic particles provides high swelling degree (1.5-5 times) for excellent low-temperature output, while the fluororesin base layer maintains dimensional stability and strong binding property to the substrate, thus achieving both high power at low temperature and reliable adhesion.
3Ease of manufacture
If conventional porous membrane materials are used, then manufacturing is simple, but binding property in electrolytic solution is insufficient
Solution Approach 1:
The patent employs a composite structure where a porous coating layer is formed on a fluororesin base layer. The porous layer contains lithium ion conductive particles and binder in a porous matrix, providing excellent binding property in electrolytic solution. This composite approach maintains relatively simple manufacturing processes while achieving superior binding performance that prevents membrane separation during battery operation and vibration.
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 solution achieves improved binding properties, low-temperature output, and safety by maintaining membrane integrity, reducing internal resistance, and extending battery life through controlled swelling and ion conductivity.
Implementation Method 1
the core portion is formed from a polymer having a swelling degree in an electrolytic solution of 5 times or more and 30 times or less
Implementation Method 2
the shell portion is formed from a polymer having a swelling degree in the electrolytic solution of 1 time or more and 4 times or less
Data Source
AI summary
A porous membrane composition for a lithium ion secondary battery, including a first particulate polymer, wherein the first particulate polymer has a core-shell structure including a core portion and a shell portion that partially covers an outer surface of the core portion, the core portion is formed from a polymer having a swelling degree in an electrolytic solution of 5 times or more and 30 times or less, and the shell portion is formed from a polymer having a swelling degree in the electrolytic solution of 1 time or more and 4 times or less.