Polyolefin Separator with Inorganic Particles for Thermal Stability
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Solution Overview
Problem
Existing electrochemical battery separators face challenges in achieving high capacity, lightweight miniaturization, shape stability against heat, thermal shrinkage control, and electrolyte solution permeability while maintaining mechanical strength.
Innovation Solution
A polyolefin-based porous separator is developed, comprising multiple polyolefin-based porous films with inorganic particles, specifically designed to have a controlled thickness ratio and thermal shrinkage rate, enhanced tensile strength, and improved air permeability, manufactured through a process involving melt-kneading, extrusion, stretching, and heat-setting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polyolefin-based separator is used to ensure chemical inertness and electrochemical stability, then reliability is improved, but thermal shrinkage control and shape stability deteriorate
Solution Approach 1:
The patent applies composite materials by combining polyolefin resin with inorganic particles (such as alumina, silica, or boehmite) to create a separator that maintains the electrochemical stability of polyolefin while gaining improved thermal stability and controlled shrinkage characteristics. The inorganic particles act as a thermal skeleton that prevents excessive shrinkage at elevated temperatures.
Solution Approach 2:
The patent employs parameter changes by carefully controlling the particle size distribution (average 0.1-10 μm), inorganic particle content (1-50 wt%), and processing conditions (heating temperature, pressing pressure, cooling rate) to optimize the balance between electrochemical performance and thermal shrinkage behavior. The crystallinity of the polyolefin is also controlled through processing parameters to achieve desired thermal properties.
2Weight of stationary object
If the separator thickness is reduced to enable miniaturization and lightweight design, then weight and volume are improved, but mechanical strength deteriorates
Solution Approach 1:
The patent uses composite materials by incorporating inorganic particles into the polyolefin matrix, which provides reinforcement that maintains mechanical strength even at reduced thickness. The inorganic particles create a rigid framework that prevents deformation and rupture while allowing the separator to be thinner.
Solution Approach 2:
The patent applies local quality by creating a heterogeneous structure where inorganic particles are distributed throughout the polyolefin matrix, providing localized reinforcement. The inorganic particles concentrate mechanical strength at specific points, allowing the overall separator to be thinner while maintaining adequate strength through distributed reinforcement rather than uniform thickening.
3Stability of the object's composition
If inorganic particles are added to improve thermal stability, then thermal shrinkage control is improved, but manufacturing complexity increases
Solution Approach 1:
The patent merges the inorganic particles directly into the polyolefin resin composition before extrusion, combining two separate materials into a single homogeneous composite that is then processed as one unit. This integration eliminates the need for separate coating or lamination steps, reducing manufacturing complexity despite the addition of inorganic particles.
Solution Approach 2:
The patent controls manufacturing complexity through parameter optimization, specifically by selecting inorganic particle size ranges (0.1-10 μm average) that prevent aggregation and ensure uniform distribution, and by controlling inorganic particle content (1-50 wt%) to balance thermal stability with processability. These parameter controls simplify the extrusion and forming processes.
4Quantity of substance
If the separator structure is optimized for high electrolyte absorption, then electrolyte solution permeability is improved, but mechanical strength deteriorates
Solution Approach 1:
The patent uses composite materials where inorganic particles provide structural reinforcement that compensates for the mechanical strength loss associated with high porosity. The inorganic framework maintains integrity even when the polyolefin matrix is highly porous, enabling both high electrolyte absorption and adequate mechanical strength.
Solution Approach 2:
The patent applies local quality by concentrating inorganic particles in specific regions or at controlled densities within the separator structure. This localized reinforcement allows high porosity in the bulk material for electrolyte absorption while maintaining mechanical strength through strategically placed inorganic support structures.
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 provides a separator with improved thermal stability, high tensile strength, and excellent electrolyte solution absorption, enabling enhanced battery performance, including high power and cycle characteristics, while simplifying the manufacturing process and avoiding the need for additional coating layers.
Implementation Method 1
continuously maintaining ion conductivity to enable charge and discharge of the battery
Implementation Method 2
electrolyte solution absorption amount measured after dipping the polyolefin-based porous separator in an electrolyte solution
Implementation Method 3
thermal shrinkage rates of the separator in a machine direction and a transverse direction measured after standing at 120° C. for 1 hour each
Data Source
AI summary
A polyolefin-based porous separator, including a first polyolefin-based porous film on a first surface of a second polyolefin-based porous film, and a third polyolefin-based porous film on a second surface of the second polyolefin-based porous film, each of the first and third polyolefin-based porous films containing inorganic particles having an average particle size of 10 nm to 100 nm, a thickness ratio of the first polyolefin-based porous film, the second polyolefin-based porous film, and the third polyolefin-based porous film being 0.5 to 1.5:1 to 6:0.5 to 1.5, and thermal shrinkage rates of the separator in a machine direction and a transverse direction measured after standing at 120° C. for 1 hour each being 5% or less, and air permeability of the separator being 250 sec/100 cc or less.