Battery Separator Coating With Node-Filament Porosity and Low Resistance
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Solution Overview
Problem
Conventional separators for electrochemical devices, particularly in soft pack batteries, face challenges with adhesion between electrodes and separators, leading to degradation of cycle life due to gaps formed during charge/discharge, and require improvements in resistance, porosity, and electrolyte retention.
Innovation Solution
A separator with a low-resistance coating layer formed on a porous substrate using a PVdF-based binder resin and inorganic particles, applied through a method involving slurry preparation, coating, and solidification in a controlled non-solvent solution, achieving a node-filament structure for enhanced adhesion and ion permeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a conventional separator is used in soft pack batteries, then the battery can be manufactured with flexible casing, but gaps form between electrodes and separator during charge/discharge leading to degradation of cycle life
Solution Approach 1:
The patent applies composite materials by combining a polyolefin microporous membrane with a porous layer containing polyvinylidene fluoride resin and inorganic particles. This composite structure provides both the mechanical properties of the base separator and the adhesive properties of the porous layer, ensuring stable adhesion between electrodes and separator during charge/discharge cycles while maintaining flexibility for soft pack battery application.
Solution Approach 2:
The patent utilizes porous materials by forming a porous layer with controlled porosity (30-80%) on the separator surface. The porous structure allows electrolyte penetration while providing sufficient adhesion strength, preventing gap formation between electrodes and separator during battery operation, thus improving cycle life without compromising reliability.
2Reliability
If a porous layer including polyvinylidene fluoride resin is formed on the separator to improve adhesion, then electrode adhesion is enhanced, but resistance increases and porosity decreases
Solution Approach 1:
The patent applies local quality by creating a porous layer with specific local properties (porosity of 30-80%, controlled thickness of 1-10 μm) on the separator surface. This localized modification provides high adhesion where needed while maintaining low resistance through the porous structure, and the inorganic particles further enhance adhesion without significantly increasing resistance.
3Reliability
If the porous layer thickness is increased to improve adhesion, then electrode adhesion is enhanced, but ion permeability and electrolyte retention are degraded
Solution Approach 1:
The patent applies parameter changes by optimizing the porous layer thickness to 1-10 μm and controlling porosity at 30-80%. This precise parameter control ensures sufficient adhesion strength while maintaining adequate ion permeability and electrolyte retention. The inorganic particles content (20-80 wt%) is also optimized to balance adhesion and ion transport properties.
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 provides a separator with improved air permeation time, reduced resistance, and effective electrolyte retention, ensuring heat resistance and enhanced cycle life while maintaining adhesion with electrodes.
Implementation Method 1
dipping the product of step (S2) in a solidifying solution containing a non-solvent... wherein the binder resin... has a molecular weight (Mw) of 600,000 or less and a melting point (Tm) of 140° C. or less
Implementation Method 2
applying the slurry for an inorganic coating layer to at least one surface of a porous substrate... preparing slurry for an inorganic coating layer including a solvent, inorganic particles and a binder resin
Implementation Method 3
step (S3) is carried out once, or twice or more, and the initial solidifying solution is controlled to a temperature equal to or higher than 5° C. and less than 20° C.
Data Source
AI summary
A separator having low resistance, suitable porosity and electrolyte retention while ensuring heat resistance is provided. The separator includes a porous substrate and a low-resistance coating layer formed on at least one surface of the porous substrate, wherein the low-resistance coating layer includes node(s) containing inorganic particles and a polymer resin covering at least a part of the surfaces of inorganic particles, and filament(s) formed from the polymer resin of the node in a thread-like shape, at least one filament extended from one node is formed, and the filaments are arranged in such a manner that they connect one node with another node.