Battery Separator Filler Layer for Shutdown and Low Resistance
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries face challenges in maintaining low battery resistance during normal operation while effectively suppressing temperature increases during abnormal conditions, such as internal short-circuiting or excessive heating, due to the trade-off between ion permeability and shutdown function of the separator.
Innovation Solution
A non-aqueous electrolyte secondary battery design featuring a separator with a porous base member and a filler layer containing phosphate particles and polyvinylidene fluoride-based resin in a mesh form, where the phosphate particles have specific size and surface area ranges to enhance shutdown functionality and ion permeability, and the polyvinylidene fluoride-based resin improves adhesion to electrodes, eliminating the need for additional adhesion layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a functional layer is provided over a porous base member to improve shutdown function, then the shutdown function is enhanced, but ion permeability is reduced and battery resistance is increased
Solution Approach 1:
The patent employs a porous base member as the core structure of the separator, which provides inherent ion permeability pathways. The porous structure allows lithium ions to pass through efficiently during normal operation, while the base member itself provides the shutdown function when temperature rises. This principle resolves the contradiction by using the porous structure to maintain ion permeability even with the addition of functional layers.
Solution Approach 2:
The patent creates a composite separator structure combining a porous base member with a functional layer containing phosphate particles and polyvinylidene fluoride-based resin. The composite material approach allows the separator to simultaneously achieve enhanced shutdown function (through the functional layer) and maintain ion permeability (through the porous base member structure). The synergistic combination of materials resolves the contradiction between improved reliability and reduced harmful resistance.
2Stability of the object's composition
If the separator and electrodes are adhered to each other to suppress position deviation, then position stability is improved, but ion permeability may be reduced
Solution Approach 1:
The porous base member structure maintains open pathways for ion transport even when adhesion is achieved. The porous nature ensures that the adhesion process does not completely seal the separator, allowing ions to pass through while the adhered structure provides position stability. This resolves the contradiction between stability and resistance.
Solution Approach 2:
The patent applies adhesion locally at the interfaces between the separator and electrodes, rather than creating a complete seal. The functional layer with specific composition (phosphate particles and polyvinylidene fluoride-based resin) provides localized adhesion strength where needed, while maintaining porosity and ion permeability in the bulk separator structure. This local quality approach resolves the contradiction between position stability and ion permeability.
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
This configuration achieves superior battery resistance during normal operation and effectively suppresses temperature increases during abnormal conditions by quickly blocking lithium ion movement and filling pores, while maintaining high ion permeability and improved adhesion for enhanced performance.
Implementation Method 1
the separator has a shutdown function in which the separator is melted by heat and pores of the separator are thus filled
Implementation Method 2
the electrode and the separator are adhered to each other using a separator having a porous base member, and an adhesive porous layer formed over the porous base member and including a polyvinylidene fluoride-based resin
Implementation Method 3
a separator in which a functional layer is provided over a porous base member tends to have reduced ion permeability
Data Source
AI summary
A separator for use in a non-aqueous electrolyte secondary battery according to the present invention comprises a porous substrate and a filler layer disposed upon the substrate. The filler layer includes phosphate particles and a reticulated polyvinylidene fluoride resin. The filler layer has a polyvinylidene fluoride resin content of 15 mass % to 40 mass %, inclusive. The D10 particle size (D10) of the phosphate particles on a volume basis is 0.02 μm to 0.5 μm, inclusive, and is smaller than the average pore size of the pores in the substrate. The BET specific surface area of the phosphate particles 30 is 5 m2/g to 100 m2/g, inclusive.