Redox Flow Battery Separation Membrane with Ion-Exchange Layer
Solution Overview
Problem
The existing separation membranes for redox flow secondary batteries experience an increase in electrical resistance and a decrease in current efficiency after a cycle test, which affects their performance over time.
Innovation Solution
A separation membrane comprising a microporous membrane with a polyolefin or vinylidene fluoride resin and an inorganic filler, combined with an ion-exchange resin layer, specifically a fluorine-based polyelectrolyte polymer, to maintain low electrical resistance and high current efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separation membrane with high ion-exchange resin content is used, then current efficiency is improved, but mechanical properties deteriorate
Solution Approach 1:
The invention creates a composite structure where a microporous membrane (providing mechanical strength) is combined with a cation-exchange membrane layer (providing high ion-exchange capacity). The microporous membrane serves as a robust substrate that maintains mechanical integrity, while the cation-exchange layer on its surface provides the necessary ion-selective properties for high current efficiency, resolving the contradiction between mechanical strength and ion-exchange performance.
Solution Approach 2:
The invention applies ion-exchange resin locally on the surface of the microporous membrane rather than throughout the entire membrane structure. This localized application ensures high ion-exchange capacity at the critical interface where ion separation occurs, while the bulk microporous membrane structure maintains its mechanical properties, resolving the contradiction between current efficiency and mechanical strength.
2Productivity
If microporous membrane with high porosity is used, then ion transport is improved, but mechanical strength decreases
Solution Approach 1:
The invention combines a microporous membrane with high porosity (30-80%) for excellent ion transport with a cation-exchange membrane layer that provides additional structural support. The high-porosity microporous membrane enables efficient ion diffusion, while the cation-exchange layer on its surface adds mechanical reinforcement, resolving the contradiction between ion transport efficiency and mechanical strength.
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 proposed membrane configuration ensures sufficient mechanical properties, low electrical resistance, and high current efficiency over a long period, enhancing the performance and durability of redox flow secondary batteries.
Implementation Method 1
an ion-exchange resin layer contacting the microporous membrane
Implementation Method 2
a microporous membrane having a specific structure
Implementation Method 3
a microporous membrane comprising a polyolefin resin or a vinylidene fluoride resin and an inorganic filler
Data Source
Figure 1
Figure 2
AI summary
The redox flow secondary battery includes an electrolytic cell including a positive electrode cell, a negative electrode cell, and a separation membrane that separates the positive electrode cell and the negative electrode cell. Moreover, the above described redox flow secondary battery is configured as follows. That is, the separation membrane has a microporous membrane and an ion-exchange resin layer contacting the microporous membrane, and the air resistance of the separation membrane per thickness of 200 µm is 10000 sec/100 cc or more. Furthermore, the microporous membrane includes a polyolefin resin or a vinylidene fluoride resin and an inorganic filler. Further, the smoothness of at least a surface of the microporous membrane contacting the ion-exchange resin layer is 16000 seconds or less.