Hydrophobic ALD Coated Battery Separator
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium ion secondary batteries face safety issues due to internal short circuits caused by thermal contraction of separators, which can lead to decomposition of non-aqueous electrolyte solutions and potential ignition, and high water content in separators can reduce battery lifespan.
Innovation Solution
A separator with a hydrophobic surface is developed using an atomic layer deposition (ALD) process to form heat-resistant inorganic layers on the surface and internal surfaces of a porous polymer sheet, reducing water content and thermal contraction, thereby enhancing safety and lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If heat-resistant inorganic layers are deposited on the separator surface using ALD process, then thermal contraction resistance is improved, but water content increases due to hydrophilic nature of inorganic materials
Solution Approach 1:
The patent combines heat-resistant inorganic layers (alumina, silica) with hydrophobic organic coatings (silane, fluorocarbon) to create a composite surface structure. This composite approach allows the inorganic layer to provide thermal stability while the hydrophobic coating reduces water content by repelling moisture from the porous structure.
Solution Approach 2:
The patent changes the surface chemical properties by introducing hydrophobic functional groups (silane, fluorocarbon) onto the inorganic layer surface. This parameter change transforms the surface from hydrophilic to hydrophobic, effectively reducing water content while preserving the underlying thermal resistance properties of the inorganic layer.
2Temperature
If porous layers with inorganic particles are stacked on polyolefin separators, then thermal contraction is reduced, but water content increases due to hydrophilic inorganic substances
Solution Approach 1:
The patent applies hydrophobic treatment specifically to the surface and internal surfaces of the porous structure where water would accumulate. This localized treatment maintains the bulk thermal properties of the inorganic layer while addressing the water content issue at the critical interface regions.
Solution Approach 2:
The patent converts the naturally hydrophilic property of inorganic materials, which initially causes water absorption, into a benefit by coating these same surfaces with hydrophobic materials. The inorganic structure provides thermal stability while the hydrophobic coating prevents water uptake, turning a potential disadvantage into a dual-function system.
3Reliability
If separators are made with polyethylene for moderate shutdown temperature, then shutdown function is improved, but thermal contraction occurs causing internal short circuits
Solution Approach 1:
The patent segments the separator structure into distinct functional layers: a polyolefin base layer providing shutdown function, and an overlaying heat-resistant inorganic layer with hydrophobic coating providing thermal contraction resistance. This segmentation allows each layer to perform its specialized function without compromising the other.
Solution Approach 2:
The patent creates a composite separator structure combining polyolefin (for shutdown function) with heat-resistant inorganic layers and hydrophobic coatings (for thermal stability). This composite material approach integrates multiple functions—shutdown, thermal resistance, and moisture rejection—into a single multi-layer system.
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 hydrophobic surface treatment effectively reduces water content to 3,000 ppm or lower, preventing internal short circuits and improving the operational reliability and lifespan of lithium ion secondary batteries by suppressing thermal contraction and maintaining electrolyte affinity.
Implementation Method 1
a separator with a hydrophobic surface is developed using an atomic layer deposition (ALD) process to form heat-resistant inorganic layers on the surface and internal surfaces of a porous polymer sheet
Implementation Method 2
The hydrophobic surface treatment effectively reduces water content to 3,000 ppm or lower
Data Source
AI summary
A separator for a secondary battery includes a porous polymer sheet having a first surface, a second surface opposing the first surface, and a plurality of pores connecting the first surface to the second surface; and heat-resistant inorganic layers formed on at least one of the first surface or the second surface of the porous polymer sheet and on internal surfaces of the pores using an atomic layer deposition (ALD) process. The at least one of the first surface or the second surface and the internal surfaces of the pores have hydrophobically coated hydrophobic layers having hydrophobic functional groups on the heat-resistant inorganic layers.