Lithium Ion Battery Separator Slurry for Thermal Stability
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Solution Overview
Problem
Lithium ion secondary batteries face challenges in maintaining high temperature cycle properties and safety due to heat-induced shrinkage of organic separator layers, which can lead to short circuits.
Innovation Solution
A slurry for porous membranes in lithium ion secondary batteries is developed, comprising non-conductive particles with a specific BET surface area and particle size distribution, combined with a water-soluble polymer and particulate polymer, to enhance mechanical strength, heat resistance, and ion permeability, preventing short circuits and improving high temperature performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an organic separator layer formed of resin is used, then the separator provides basic separation function, but it causes shrinkage at temperatures of 150°C or lower leading to short circuit
Solution Approach 1:
The patent applies composite materials by combining organic separator layers with inorganic porous layers containing non-conductive particles (such as alumina, silica, or boehmite). This composite structure provides dimensional stability at elevated temperatures while maintaining the separation function, preventing the shrinkage-induced short circuits that occur with pure organic separators.
Solution Approach 2:
The patent utilizes porous materials by forming an inorganic porous layer with controlled porosity (30-70%) on the organic separator. This porous inorganic layer maintains structural integrity and dimensional stability at temperatures up to 150°C and above, preventing shrinkage while allowing ion transport through the separator.
2Reliability
If inorganic filler is added to prevent short circuit, then safety is improved, but high temperature cycle property remains insufficient
Solution Approach 1:
The patent applies parameter changes by optimizing the BET specific surface area of non-conductive particles (5-50 m²/g), controlling porosity (30-70%), and adjusting the thickness of the inorganic porous layer (1-20 μm). These parameter optimizations ensure both safety through short circuit prevention and improved high temperature cycle property by maintaining stable ion transport characteristics during repeated thermal cycling.
Solution Approach 2:
The patent applies local quality by creating an inorganic porous layer with specific local properties (controlled porosity, particle size distribution, and surface area) on the organic separator. This localized inorganic layer provides both safety functions and stable thermal cycling performance without affecting the bulk properties of the entire separator system.
3Reliability
If non-conductive particles with high BET surface area are used, then ion permeability and heat resistance are improved, but manufacturing precision becomes difficult to control
Solution Approach 1:
The patent applies parameter changes by defining specific ranges for BET specific surface area (5-50 m²/g), particle diameter (0.1-10 μm), and porosity (30-70%). These parameter specifications balance ion permeability and heat resistance while maintaining manufacturability, avoiding the difficulties associated with ultra-fine particles that would require excessive manufacturing precision.
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 effectively improves the high temperature cycle properties and safety of lithium ion secondary batteries by ensuring stable operation and preventing short circuits, while maintaining mechanical strength and heat resistance.
Implementation Method 1
a water-soluble polymer having an acidic group-containing monomer unit
Implementation Method 2
a porous membrane formed using a slurry that includes non-conductive particles, a water-soluble polymer having an acidic group-containing monomer unit, and a particulate polymer
Data Source
AI summary
A slurry for a lithium ion secondary battery porous membrane, including non-conductive particles, a water-soluble polymer containing an acidic group-containing monomer unit, and a particulate polymer, wherein: an amount of the water-soluble polymer is 0.05 parts by weight to 2 parts by weight relative to 100 parts by weight of the non-conductive particles; and a BET specific surface area of the non-conductive particles is 5 m2/g to 10 m2/g.