Internal Electrolyte Rebalancing Reactor for Flow Battery Stacks
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Solution Overview
Problem
Existing redox flow battery systems face limitations in cycling capabilities due to side reactions at the plating electrode, particularly the coalescence of hydrogen gas bubbles in external rebalancing reactors, which reduces the available catalyst surface area and increases parasitic power draw, and the use of precious metals like platinum as catalysts raises costs.
Innovation Solution
Incorporating an internal rebalancing reactor positioned within the battery stack, where the negative electrolyte is introduced to the catalyst before hydrogen bubbles can coalesce, and directing the electrolyte radially inward to increase catalyst exposure, thereby avoiding the need for injectors and booster pumps and reducing the amount of precious metal required.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If an external jelly roll rebalancing reactor is used, then the rebalancing reaction can occur, but hydrogen gas bubbles coalesce into larger bubbles reducing catalyst surface area and reaction efficiency
Solution Approach 1:
The internal rebalancing reactor is positioned within the battery stack to perform rebalancing action before hydrogen bubbles have time to coalesce. This preliminary action maintains small bubble size and maximizes catalyst surface area utilization, resolving the contradiction between maintaining reaction rate and preserving catalyst surface area.
Solution Approach 2:
Instead of introducing electrolyte to the center of the jelly roll and having it flow outward (which limits catalyst exposure), the invention introduces electrolyte to the outer surface and forces it radially inward. This inverted flow direction maximizes the amount of catalyst exposed to the electrolyte, increasing effective reaction surface area.
2Area of stationary object
If an injector and booster pump are added to break down hydrogen bubbles, then bubble size is reduced, but parasitic power draw increases
Solution Approach 1:
The system uses the natural flow of electrolyte through the battery stack to drive the rebalancing reaction without requiring external pumps or injectors. The electrolyte flow itself serves the dual purpose of transporting ions and providing the medium for hydrogen bubble breakup at the catalyst surface, eliminating parasitic power draw while maintaining small bubble size.
Solution Approach 2:
The invention replaces the mechanical system of pumps and injectors with a chemically-driven approach where the electrolyte flow and catalyst surface work together to naturally break down and utilize hydrogen bubbles. This substitution eliminates the need for additional mechanical components and their associated energy consumption.
3Productivity
If more catalyst is added to increase rebalancing reaction rate, then reaction efficiency improves, but system cost increases due to precious metal usage
Solution Approach 1:
By performing rebalancing before hydrogen bubbles coalesce, the system maximizes the effectiveness of each unit of catalyst surface area. This preliminary action ensures that the limited catalyst available is fully utilized, achieving high reaction rates without requiring large amounts of precious metal catalyst.
Solution Approach 2:
The invention changes the flow dimension from radial outward (center to edge) to radial inward (edge to center), maximizing the path length and contact area between electrolyte and catalyst. This dimensional change increases the effective utilization of catalyst surface area, achieving higher reaction rates with less catalyst material.
4Device complexity
If electrolyte is introduced to the center of the jelly roll, then flow path is simplified, but catalyst exposure is limited to the center region
Solution Approach 1:
The invention inverts the conventional flow direction by introducing electrolyte to the outer surface and forcing it radially inward to the center, rather than the conventional center-to-outward flow. This inversion maximizes catalyst exposure area as the electrolyte contacts the entire outer surface and progresses through the full radial path, while the forced flow mechanism maintains relatively simple flow path control.
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 enhances the efficiency of the redox flow battery system by maintaining smaller hydrogen bubbles for increased reaction surface area, reducing parasitic power draw, and lowering overall costs by minimizing the use of expensive catalysts.
Implementation Method 1
a catalyst is immobilized on a flat sheet of substrate and is spirally wound. The jelly roll may be positioned within a housing configured to receive electrolyte and hydrogen from the redox flow battery cell and direct the electrolyte and hydrogen through a center of the jelly roll to flow radially outwards
Implementation Method 2
catalytic electrolyte rebalancing to address hydrogen (H2) gas generation from equations (1) and (2) and electrolyte charge imbalances (e.g., excess Fe3+) from equation (3) by ion crossover via equation (4)
Implementation Method 3
Redox flow batteries are suitable for grid-scale storage applications due to their capability for scaling power and capacity independently, as well as for charging and discharging over thousands of cycles with reduced performance losses in comparison to conventional battery technologies
Data Source
AI summary
Systems and methods are provided for rebalancing electrolytes of a redox flow battery system. The redox flow battery system includes a positive electrolyte, a negative electrolyte, and a battery stack configured to receive the positive and negative electrolytes. Additionally, the battery stack includes an internal rebalancing reactor positioned internal to the battery stack and in fluid contact with the negative electrolyte.