Battery Separator Filler Layer to Resist Plastic Deformation
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries suffer from plastic deformation of the separator due to changes in electrode thickness during charge and discharge cycles, leading to decreased battery capacity and safety concerns.
Innovation Solution
Incorporating a separator with a filler layer containing first and second inorganic particles, where the second particles form projections, with a specific number and size distribution, to inhibit plastic deformation and maintain electrode distance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional separator is used, then the battery structure is simple, but the separator undergoes plastic deformation and thinning due to electrode thickness changes during charge and discharge
Solution Approach 1:
The separator is constructed as a composite material consisting of a porous substrate layer and a heat-resistant filler layer containing inorganic particles. This composite structure provides both the necessary porosity for ion transport and the thermal stability to resist plastic deformation during battery operation, directly resolving the contradiction between reliability and structural simplicity.
Solution Approach 2:
The filler layer is applied locally on the substrate layer to provide targeted heat resistance and dimensional stability at the separator surface that contacts the electrodes. This local reinforcement prevents plastic deformation without requiring the entire separator structure to be complex, balancing reliability improvements with structural simplicity.
2Quantity of substance
If the separator thickness decreases due to plastic deformation, then the battery capacity increases temporarily, but the distance between electrodes decreases leading to safety issues
Solution Approach 1:
The heat-resistant filler layer is applied in advance to the separator surface before battery assembly. This preliminary action prevents plastic deformation from occurring during subsequent charge and discharge cycles, maintaining consistent electrode distance and preventing safety issues while allowing normal capacity development.
Solution Approach 2:
The rigid inorganic particles in the filler layer act as a cushioning structure that resists compressive forces from electrode expansion. This beforehand cushioning prevents excessive thinning of the separator and maintains safe electrode spacing throughout the battery lifecycle, eliminating the trade-off between capacity and safety.
3Use of energy by moving object
If a filler layer with large particles is used, then the projections can hold electrolyte, but the plastic deformation of separator is not sufficiently inhibited
Solution Approach 1:
The filler layer is segmented into two distinct particle size populations: first inorganic particles (0.3-2.0 μm) providing fine surface coverage and electrolyte retention, and second inorganic particles (3-10 μm) forming rigid projections for deformation resistance. This segmentation allows each particle size to perform its specialized function, simultaneously achieving electrolyte holding and plastic deformation inhibition.
Solution Approach 2:
The invention changes the particle size parameter distribution in the filler layer, using a bimodal distribution with specific size ranges for first and second inorganic particles. This parameter optimization ensures that smaller particles fill gaps for electrolyte retention while larger particles form the structural framework for deformation resistance, resolving the contradiction between electrolyte holding and deformation prevention.
Data Source
AI summary
Provided is a non-aqueous electrolyte secondary battery in which plastic deformation of a separator is suppressed. A non-aqueous electrolyte secondary battery comprises an electrode body formed by winding a positive electrode and a negative electrode with a separator therebetween; a non-aqueous electrolyte; and an outer can for accommodating therein the electrode body and the non-aqueous electrolyte. The separator has a base material layer and a filler layer formed at least on one surface of the base material layer. The filler layer contains first inorganic particles and second inorganic particles having a larger average particle diameter than the first inorganic particles, and has protruding parts formed from the second inorganic particles. When the surface of the filler layer is observed by a scanning electron microscope, 10-35 particles of the second inorganic particles forming the protruding parts are detected in a range of 100 μm×100 μm.