Polyolefin Microporous Membrane Separator for Li-Ion Batteries
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current microporous membranes for lithium ion secondary batteries lack sufficient puncture strength and long-term compression resistance, leading to potential short-circuits and reliability issues due to foreign objects and uneven pressure distribution.
Innovation Solution
A polyolefin microporous membrane with a high content of inorganic particles (20-60% by mass) and a particle size of 1-100 nm, produced through melt-kneading, uniaxial stretching, and plasticizer extraction, achieving a puncture strength of 3 N/20 µm or more and a membrane thickness retention ratio of 16% or more.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a polyolefin microporous membrane is used as a separator, then it provides basic separation function, but it lacks sufficient puncture strength and compression resistance leading to safety issues
Solution Approach 1:
The patent applies composite materials by combining polyolefin resin with inorganic particles (such as metal oxides or ceramic particles) to create a microporous membrane that maintains the base polymer's separation function while adding puncture strength and compression resistance through the inorganic reinforcement phase
Solution Approach 2:
The patent changes physical parameters including inorganic particle size (0.1-10 μm), inorganic particle content (10-50 wt%), and membrane thickness (10-100 μm) to optimize the balance between puncture strength, compression resistance, and ion permeability for enhanced safety and reliability
2Quantity of substance
If the separator membrane is made thinner to increase energy density, then energy density improves, but puncture strength and compression resistance decrease
Solution Approach 1:
The patent uses composite materials with inorganic particles dispersed in the polyolefin matrix to provide mechanical reinforcement that allows thin membrane design while maintaining sufficient puncture strength and compression resistance for safety
Solution Approach 2:
The patent applies local quality by strategically distributing inorganic particles within the membrane structure to provide localized reinforcement at critical points, enabling thin overall membrane design while maintaining strength where needed
3Reliability
If foreign objects or active material protrusions occur, then short-circuit risk increases, but increasing membrane thickness to prevent this reduces energy density
Solution Approach 1:
The patent employs composite materials with reinforced inorganic content to create a membrane that can withstand foreign objects and active material protrusions without short-circuiting, while maintaining thin profile to preserve energy density
4Reliability
If uneven pressure distribution causes local high pressure on separator, then short-circuit risk increases, but enhancing compression resistance increases manufacturing complexity
Solution Approach 1:
The patent uses composite materials with inorganic particles to inherently enhance compression resistance at the material level, simplifying manufacturing compared to complex structural designs or additional protective layers
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 membrane exhibits enhanced puncture strength and compression resistance, preventing short-circuits and ensuring long-term reliability as a separator for lithium ion batteries, particularly in electric and hybrid vehicles.
Implementation Method 1
a porous membrane keeping an electrolyte therein, called a separator having functions of preventing contact between a cathode and an anode and allowing ion to permeate
Implementation Method 2
having functions of preventing contact between a cathode and an anode and allowing ion to permeate
Data Source
AI summary
The present invention provides a polyolefin microporous membrane made of a polyolefin resin and an inorganic particle, and the puncture strength of the microporous membrane is 3 N/20 µm or more and the membrane thickness retention ratio in penetration creep is 16% or more, thereby being excellent in safety and long-term reliability, and a separator for a nonaqueous electrolyte battery, and the like can be provided.