Inorganic Oxide Powder for Battery Separator Membranes
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Solution Overview
Problem
Existing inorganic oxide porous membranes for lithium ion secondary batteries have insufficient ion permeability and porosity, leading to inadequate load characteristics and safety concerns due to high heat resistance and dimension stability issues.
Innovation Solution
An inorganic oxide powder with specific properties, including high oxide purity, small average particle diameter, high three-dimensional particle unevenness, and a specific BET specific surface area, is used to form a porous membrane on the electrodes and separator, enhancing ion permeability and heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If an inorganic oxide porous membrane is formed using conventional inorganic oxide powder with high heat resistance and dimension stability, then the separator contraction is suppressed, but the average pore radius and porosity are insufficient leading to inadequate ion permeability
Solution Approach 1:
The invention changes the particle size parameter of the inorganic oxide powder to an average particle diameter of 0.5 μm or less (significantly smaller than conventional powder), and controls the particle size distribution so that 90 mass% or more of particles are 0.5 μm or less. This parameter change enables formation of a porous membrane with sufficient average pore radius and porosity while maintaining heat resistance, thereby resolving the contradiction between heat resistance and ion permeability.
2Object-affected harmful factors
If the separator is made of microporous sheet, then electrical insulation between electrodes is provided, but when battery temperature exceeds 150°C the separator contracts drastically causing short circuit expansion
Solution Approach 1:
The invention forms a composite porous membrane by combining inorganic oxide particles (α-alumina, γ-alumina, or amorphous alumina) with a binder resin. This composite structure provides both the electrical insulation function of the separator and high dimension stability at elevated temperatures, preventing the drastic contraction that occurs with conventional microporous sheets above 150°C.
3Reliability
If inorganic oxide powder with sufficient ion permeability is used, then load characteristic is improved, but heat resistance and insulation performance may be compromised
Solution Approach 1:
The invention achieves both sufficient ion permeability and heat resistance by changing the particle size parameter to 0.5 μm or less and controlling the particle size distribution so that 90 mass% or more of particles fall within this range. This fine particle size enables formation of a porous structure with adequate pore radius for ion transport while the inorganic oxide material itself maintains high heat resistance and insulation performance.
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 resulting membrane provides superior lithium ion conductivity and load characteristics, ensuring improved safety and performance of lithium ion secondary batteries even at elevated temperatures.
Implementation Method 1
an inorganic oxide porous membrane having insulation performance on at least one surface of a positive electrode, a negative electrode and a separator
Implementation Method 2
average pore radius and porosity which can provide at least one surface of a positive electrode, a negative electrode and a separator which constitute a lithium ion secondary battery with sufficient ion permeability
Data Source
Figure 1
AI summary
An object of the present invention is to provide an inorganic oxide powder suitable for forming an inorganic oxide porous membrane, which is superior in lithium ion conductivity and has insulation performance, on at least one surface of a positive electrode, a negative electrode and a separator which constitute a lithium ion secondary battery. The present invention relates to an inorganic oxide powder for use in forming an inorganic oxide porous membrane having insulation performance on at least one surface of a positive electrode, a negative electrode and a separator which constitute a lithium ion secondary battery, wherein the powder has 1) an oxide purity of 90% by weight or higher, 2) an average particle diameter of 1 µm or less, and 3) an average three-dimensional particle unevenness of 3.0 or higher.