Porous Separator with ALD Inorganic Oxide Coating
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Solution Overview
Problem
Existing battery separators face challenges in achieving a balance between heat stability, gas permeability, and thickness, often resulting in reduced battery performance due to increased thickness, low permeability, and deteriorated impregnability.
Innovation Solution
A porous separator with an inorganic oxide layer formed on a porous substrate using atomic layer deposition, where the thickness of the oxide layer is controlled by adjusting the injection times of a metal precursor and oxidant, and the number of deposition process repetitions, ensuring a specific thickness ratio between the surface and internal layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a multilayer separator or coating layer is used to improve separator properties, then heat stability and mechanical strength are improved, but thickness increases and battery performance deteriorates
Solution Approach 1:
The patent employs a porous inorganic oxide coating layer with controlled porosity (30-70%) that allows ion transport while providing heat stability. The porous structure maintains battery performance by preventing excessive thickness increase, as the void spaces enable electrolyte penetration and ion mobility without requiring a thick dense barrier layer.
Solution Approach 2:
The separator comprises a composite structure combining an organic porous polymer substrate with an inorganic oxide coating layer. This composite approach integrates the mechanical strength and porosity of the polymer substrate with the thermal stability of the inorganic coating, achieving both heat resistance and thin profile without sacrificing battery performance.
2Temperature
If a coating layer is added to improve separator properties, then heat resistance is improved, but gas permeability and electrolyte impregnability deteriorate
Solution Approach 1:
The inorganic oxide coating layer is designed with controlled porosity (30-70%) and specific surface area (5-20 m²/g) to maintain gas permeability while providing heat resistance. The porous structure allows electrolyte and gas penetration necessary for battery operation, preventing the coating from becoming an impermeable barrier.
Solution Approach 2:
The coating layer exhibits localized properties with different porosity and thickness distributions throughout the separator structure. This local quality variation enables regions with higher permeability for ion transport while maintaining sufficient heat resistance in critical areas, resolving the contradiction between protection and permeability.
3Reliability
If the inorganic oxide layer thickness is increased to improve heat stability, then heat shrinkage resistance is improved, but ion mobility is hindered
Solution Approach 1:
The patent specifies a controlled thickness range (0.1-10 μm) for the inorganic oxide layer, optimized to provide sufficient heat shrinkage resistance (≤5% at 150°C) while maintaining ion mobility. The porous structure within this thickness range creates ion transport pathways that prevent the layer from becoming a diffusion barrier.
Solution Approach 2:
The patent optimizes multiple parameters including layer thickness, porosity, and surface area to achieve the desired balance. By controlling these parameters within specific ranges, the coating provides adequate thermal protection while maintaining sufficient ion transport capability for high-performance battery operation.
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
This approach results in a separator with enhanced heat stability, gas permeability, and electrolyte impregnability, suitable for lithium secondary batteries, while maintaining a thin profile and preventing excessive gas permeation that could hinder ion mobility.
Implementation Method 1
an inorganic oxide layer formed on a porous substrate by an atomic layer deposition process
Implementation Method 2
by an atomic layer deposition process, wherein a thickness of the inorganic oxide layer is decreased in a direction from a surface of the porous substrate to a center thereof
Data Source
AI summary
Provided is a porous separator for a secondary battery including an inorganic oxide layer formed on a porous substrate by an atomic layer deposition process, such that a thin separator having excellent heat stability, permeability and electrolyte impregnability may be provided by controlling specific conditions in the process and thicknesses of the inorganic oxide layers on a surface and inside of the porous separator.