Porous Layer Separator for Non-Aqueous Battery Cycle Stability
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries with existing separators fail to retain initial discharge capacity after repeated charge-discharge cycles, lacking sufficient cycle characteristics.
Innovation Solution
A porous layer with controlled voidage variability, laminated onto polyolefin-based porous films, utilizing a resin layer with fibrillar or granular structure and specific filler distribution to enhance ion permeability and structural stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a porous film made of polyolefin is used as a separator, then electrical insulating property and ion permeability are improved, but cycle characteristic deteriorates
Solution Approach 1:
The invention uses a composite porous layer comprising a polyolefin base layer combined with a heat-resistant resin layer containing inorganic filler particles. This composite structure maintains the excellent ion permeability and electrical insulating properties of polyolefin while adding thermal stability and structural integrity that prevents capacity degradation during cycling. The heat-resistant resin layer acts as a protective barrier that maintains separator performance under repeated thermal and mechanical stress of charge-discharge cycles.
Solution Approach 2:
The invention applies different material properties to different regions of the separator structure. The base layer uses polyolefin for optimal ion permeability, while the surface layer uses heat-resistant resin with inorganic filler for thermal stability and mechanical strength. This local differentiation of material properties allows each layer to perform its specific function optimally, resolving the contradiction between ion permeability and cycle stability.
2Ease of manufacture
If existing separator structures are used, then manufacturing simplicity is maintained, but discharge capacity retention deteriorates
Solution Approach 1:
The invention incorporates a heat-resistant resin layer with inorganic filler particles on the separator surface before battery assembly. This preliminary protective layer prevents electrode material adhesion and maintains pore structure integrity during initial battery cycling, thereby preserving discharge capacity retention without complicating the manufacturing process. The heat-resistant layer acts as a pre-established protective barrier against capacity degradation.
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 enables non-aqueous electrolyte secondary batteries to maintain initial discharge capacity and exhibit improved cycle characteristics by ensuring uniform voidage distribution and ion flow across the separator.
Implementation Method 1
a porous film made of polyolefin is excellent in electrical insulating property and exhibits good ion permeability
Implementation Method 2
a porous film made of polyolefin is excellent in electrical insulating property
Data Source
AI summary
In a porous layer of the present invention, in a case where the porous layer is divided into 32 sections, a degree of variability in voidage that is measured in the 32 sections is 16.0% or lower. Each of the 32 sections is a rectangular parallelepiped whose longitudinal length is 2.3 μm, transverse length is 2.3 μm, and thickness is identical with that of the porous layer. The porous layer of the present invention and a separator formed by laminating the porous layer are suitable as a member for a non-aqueous electrolyte secondary battery that has an excellent cycle characteristic.