Separator Coating Composition for Heat-Resistant Lithium-Ion Cells
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Solution Overview
Problem
Lithium ion cells require improved mechanical strength and thermal resistance in their separators to enhance safety and performance, while maintaining electrical properties.
Innovation Solution
A coating liquid containing inorganic particles and alkali silicate is applied to a porous film, forming a coating film with a content of at least 0.05 weight % inorganic particles, which enhances the mechanical strength and thermal resistance of the separator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a porous film is used as a separator in lithium ion cells, then the cell can be downsized and lightweight with high energy density, but the mechanical strength and thermal resistance of the separator are insufficient
Solution Approach 1:
The patent applies composite materials by combining organic binder resin with inorganic particles (such as alumina, silica, or boehmite) to form a coating layer on the porous film. This composite structure enhances the mechanical strength and thermal resistance of the separator while maintaining its porous architecture and electrochemical performance.
Solution Approach 2:
The patent utilizes porous materials by forming a coating layer with controlled porosity on the porous film separator. The coating layer contains pores that allow lithium ion transport while the inorganic particles provide structural reinforcement, thus improving mechanical strength without blocking ion transport pathways.
2Temperature
If the separator structure is simplified for manufacturing, then production cost decreases, but thermal resistance and safety performance deteriorate
Solution Approach 1:
The patent applies preliminary action by pre-forming the coating layer with inorganic particles and binder resin on the porous film before the separator is assembled into the lithium ion cell. This pre-coating process enhances thermal resistance early in manufacturing, allowing subsequent assembly steps to remain simple and cost-effective.
Solution Approach 2:
The patent utilizes parameter changes by controlling the composition ratios, particle size distribution, and coating thickness of the inorganic particle layer. By optimizing these parameters, the separator achieves high thermal resistance while maintaining manufacturing feasibility through standard coating processes.
3Strength
If inorganic particles are added to enhance mechanical strength, then separator strength improves, but the content of inorganic particles increases manufacturing complexity
Solution Approach 1:
The patent applies local quality by concentrating inorganic particles specifically in the coating layer on the separator surface, rather than uniformly distributing them throughout the entire separator structure. This localized approach enhances mechanical strength where needed (at the surface and interface regions) while minimizing the total quantity of inorganic particles required.
Solution Approach 2:
The patent uses composite materials to create a synergistic effect where inorganic particles provide mechanical reinforcement and thermal stability, while the organic binder resin provides cohesion and flexibility. This composite approach allows achieving high strength with optimized inorganic particle content rather than excessive amounts.
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 improves the mechanical strength and thermal resistance of the porous film and lithium ion cell, maintaining or improving electrical properties such as air permeability and cycle performance.
Implementation Method 1
a coating film formed on a surface of the porous base substance, and the coating film contains inorganic particles and alkali silicate
Implementation Method 2
improve the mechanical strength and the thermal resistance of the separator
Data Source
AI summary
Properties of a porous film used as a separator of a lithium ion cell are improved. A porous film (separator) of the present invention is a porous film including: a porous base substance S; and a coating film CF arranged on a surface of the porous base substance, the coating film includes: alkali silicate; and a first filler, the first filler is made of inorganic particles, and a content of the alkali silicate is equal to or more than 0.05 weight % with respect to the inorganic particles. The inorganic particle includes a material selected from nano silica, micro silica, carbon nanotube, talc, alumina, boehmite, aluminum hydroxide and glass fiber, and the porous film includes a second filler (a hydrophilic group of a cellulose is substituted with a hydrophobic group), a content of which is equal to or more than 0.05 weight % with respect to the inorganic particles. By usage of the porous film, the cell properties such as the thermal resistance and the cycle property can be improved.