Flow Battery Membrane with Varying Selectivity Zones
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Solution Overview
Problem
Flow batteries face inefficiencies due to cross-over of redox ions through ion exchange membranes, leading to unbalanced electrolytes and reduced coulombic efficiency, with existing solutions either increasing ohmic losses or increasing system costs.
Innovation Solution
A flow battery design incorporating a porous barrier material layer with varying selectivity towards redox ions, placed between the electrodes, to modulate ion blockage and reduce cross-over, allowing necessary exchange ions to pass while blocking detrimental ions, thereby reducing ohmic losses and maintaining high coulombic efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the ion exchange membrane is increased to reduce cross-over of redox ions, then the selectivity towards redox ions is improved, but the ohmic losses increase
Solution Approach 1:
The membrane system is divided into two distinct layers: a thin ion exchange membrane layer (50-200 μm) that maintains low ohmic resistance, and an additional porous barrier layer (10-500 μm) that provides enhanced selectivity. This segmentation allows each layer to perform its specialized function without compromising the other, resolving the contradiction between thickness/selectivity and ohmic losses.
Solution Approach 2:
The invention uses a composite membrane structure combining an ion exchange membrane (such as perfluorosulfonic membrane) with an additional porous barrier layer. This composite material integrates the proton conductivity and oxidizing environment resistance of the ion exchange membrane with the size-based selectivity of the porous layer, achieving both low ohmic losses and high redox ion selectivity simultaneously.
2Reliability
If a porous membrane with small pore size (≤100 nm) is added to block redox ions, then the cross-over is reduced, but the hydronium passage is partially inhibited, increasing ohmic losses
Solution Approach 1:
The porous barrier layer is designed with specific local properties: pore sizes of 10-100 nm that are small enough to block redox ions (0.5-2 nm) but large enough to allow hydronium ion passage. This localized quality control in the barrier layer structure enables selective ion transport, reducing cross-over while maintaining low ohmic losses by not overly restricting hydronium flow.
3Reliability
If an additional porous membrane is applied to reduce ion passage, then the selectivity is improved, but the device complexity increases
Solution Approach 1:
The ion exchange membrane and porous barrier layer are combined into a single integrated membrane assembly that functions as one unit in the flow battery. This merging approach, while adding a layer, simplifies the overall system architecture by maintaining a single membrane component rather than requiring separate selective barriers, and enables manufacturing as a unified structure.
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 effectively blocks detrimental redox ions while minimizing ohmic losses, enhancing coulombic efficiency and reducing system costs by allowing selective ion passage, potentially replacing traditional ion exchange membranes with lower-cost alternatives.
Implementation Method 1
the pores thereof have a size not greater than 100 nm. Such additional porous membrane has the object of reducing the redox ions passage through the membrane, by exploiting the dimension of the pores, comparable to the size of the redox ions to be blocked, and greater than the size of the exchange ion
Implementation Method 2
The two semi-cells are separated by an ion exchange membrane, among this type of membranes, the most used are the proton-exchange membranes... one ion required for the charge transport in the electrolyte, which is typically hydronium H3O+
Implementation Method 3
A flow battery is an electrochemical cell wherein the charge and discharge processes are performed by ion oxidation and reduction reactions
Implementation Method 4
a complex water transporting mechanism controlled by the diffusion and electroosmosis is added
Implementation Method 5
a complex water transporting mechanism controlled by the diffusion and electroosmosis is added
Data Source
Figure 1
AI summary
The flow battery comprises a first semi-cell (2), wherein a first electrolyte is fed through a first electrode (21); a second semi-cell (3), wherein a second electrolyte is fed through a second electrode (31); a partition membrane (4) disposed between the first electrode (21) and second electrode (31) in order to prevent them from reciprocally contacting with each other, and suitable to enable ions to permeate; and at least one porous barrier material layer (5) disposed between the first electrode (21) and second electrode (31), and suitable to block an undesired flow of ions of one or both the electrolytes through the partition membrane (4), the barrier material layer (5) having zones with different selectivities towards the ions whose flow is undesired.