Composite Separator Coating to Limit Electrode Sheet Wrinkling
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Solution Overview
Problem
Conventional lithium-ion battery separators exhibit poor cooperation stability with electrode sheets, leading to mechanical weakness, electrode sheet wrinkling, and decreased cycle performance due to inadequate adhesion and expansion during charging/discharging.
Innovation Solution
A composite separator with a porous base film coated by a base layer containing inorganic particles and a non-adhesive polymer with larger particles than the base layer thickness, combined with an adhesive polymer, enhances adhesion through physical and chemical interactions, forming gaps for electrolyte infiltration and improving mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional separator with adhesive polymer and inorganic particles coated on polyolefin base film is used, then the separator structure is simple and manufacturing is easy, but the adhesion between separator and electrode sheet is poor leading to reduced mechanical strength
Solution Approach 1:
The patent uses a composite coating layer comprising inorganic particles, adhesive polymer, and non-adhesive polymer on the base film. This composite structure combines the mechanical strength from inorganic particles, the adhesion from adhesive polymer, and the expansion buffer from non-adhesive polymer, resolving the contradiction between strength and complexity by creating a multi-functional composite material system.
Solution Approach 2:
The coating layer is designed with spatially differentiated functions: inorganic particles provide localized mechanical reinforcement, adhesive polymer creates localized bonding zones with electrode sheets, and non-adhesive polymer provides localized expansion space. This local quality differentiation allows the separator to achieve high mechanical strength without requiring complex overall structural changes.
2Quantity of substance
If the electrode sheet area and cell size are increased, then the battery capacity is improved, but the cooperation stability between separator and electrode sheet deteriorates leading to increased looseness
Solution Approach 1:
The coating layer is segmented into distinct functional components (inorganic particles, adhesive polymer, non-adhesive polymer) that work independently yet cooperatively. The adhesive polymer segments create multiple bonding points across the separator-electrode interface, while non-adhesive polymer segments provide distributed expansion buffer zones, maintaining stability even as electrode area increases.
Solution Approach 2:
The patent changes the chemical and physical parameters of the coating layer by introducing non-adhesive polymer with specific glass transition temperature and molecular weight, creating a material that dynamically adjusts its adhesion properties in response to electrode expansion, thereby maintaining cooperation stability across different battery sizes.
3Reliability
If adhesive polymer is used to fix inorganic particles, then the particle fixation is improved, but the adhesion to electrode sheet is reduced due to non-adhesive properties
Solution Approach 1:
The patent merges adhesive polymer and non-adhesive polymer in the same coating layer, creating a synergistic system where adhesive polymer provides bonding to electrode sheets while non-adhesive polymer provides expansion buffer. This merging allows the system to simultaneously achieve particle fixation and adhesion strength without compromise.
Solution Approach 2:
The non-adhesive polymer acts as an intermediary between the adhesive polymer and the electrode sheet, mediating the interaction by providing expansion buffer while allowing adhesive polymer to maintain bonding. This intermediary function resolves the contradiction by decoupling the adhesion function from the expansion buffer function.
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 composite separator stabilizes the electrode sheet adhesion, reduces electrode sheet expansion, and enhances lithium-ion battery cycling performance by maintaining mechanical strength and electrolyte wetting, thereby improving cycle capacity retention and reducing lithium precipitation.
Implementation Method 1
the inorganic particles in the porous active layer are fixed to each other by the adhesive polymer
Implementation Method 2
the non-adhesive polymer C is capable of generating physical adhesion between the electrode sheet and the electrode sheet under a certain temperature and pressure condition
Implementation Method 3
the coating includes a base layer and a non-adhesive polymer C provided on the base layer... forming gaps for electrolyte infiltration
Data Source
AI summary
Disclosed in the present disclosure is a composite separator and a preparation method and application thereof. A composite separator includes a porous base film and a coating. The coating is provided on a surface of the porous base film, the coating includes a base layer and a non-adhesive polymer C provided on the base layer, and the base layer includes inorganic particles A and an adhesive polymer B. A maximum particle size of the non-adhesive polymer C is greater than a thickness of the base layer and a particle size of the non-adhesive polymer C is in a range of 0.3 μm to 30 μm. The adhesive polymer B includes a first component and a second component. The first component includes at least one of a vinyl polymer, a propylene-based polymer, an amide-based polymer, and an epoxy-based polymer. The second component includes a cellulose-based polymer.