Semi-Solid Redox Flow Cell for Higher Energy Density
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Solution Overview
Problem
Redox flow batteries have a relatively low energy density due to the solubility limitations of metal ion redox couples in liquid solvents, which restricts their application in high-energy-demand devices like electric vehicles and stationary energy storage systems.
Innovation Solution
The development of a swappable fuel tank system for redox flow batteries, where the cathode and anode slurries are semi-solid and can be easily replaced or refilled, allowing for increased energy density and versatility in power generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal ion redox couples are used in liquid solvents, then the battery can operate with reversible redox reactions, but the energy density is limited by solubility constraints
Solution Approach 1:
The patent changes the physical state parameter of the electrolyte from liquid to semi-solid slurry, allowing much higher concentrations of redox-active materials (up to 30-40 wt%) while maintaining flowability and reversible electrochemical reactions. This parameter change directly resolves the contradiction by enabling high energy density without sacrificing reaction reversibility
Solution Approach 2:
The patent uses composite electrolyte systems combining semi-solid slurries with specific viscosity modifiers and dispersants to maintain stable suspension of redox-active particles while ensuring adequate flow properties. This composite approach enables both high concentration (energy density) and operational reliability
2Quantity of substance
If the cathode and anode slurries are made semi-solid, then the energy density increases, but the system complexity increases due to swappable fuel tank requirements
Solution Approach 1:
The patent segments the battery system into modular components: a stationary electrochemical cell stack and replaceable fuel tank cartridges containing pre-filled semi-solid slurries. This segmentation allows the complex slurry handling to be contained in self-contained cartridges while keeping the main battery system simple and reusable
Solution Approach 2:
The fuel tanks are pre-filled with optimized semi-solid slurries at the factory before deployment. This preliminary action eliminates the need for complex on-site slurry preparation, mixing, and viscosity control systems, reducing operational complexity while maintaining high energy density
3Reliability
If metal particle suspensions are used in aqueous electrolytes, then dendrite formation is prevented, but the energy density remains relatively low
Solution Approach 1:
The patent changes the electrolyte from low-viscosity liquid to higher-viscosity semi-solid slurry, which suppresses dendrite formation through increased resistance to metal ion deposition while simultaneously enabling much higher concentrations of redox-active materials, thus achieving both reliability and high energy density
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 solution significantly enhances the energy density of redox flow batteries by overcoming solubility limitations, enabling their use in high-energy applications such as electric vehicles and improving their performance in stationary energy storage systems.
Implementation Method 1
an ion-permeable membrane separating the positive and negative current collectors
Implementation Method 2
the positive and negative electrode reactants are soluble metal ions in liquid solution that are oxidized or reduced during the operation of the cell
Data Source
Figure 1~2
Figure 3~4
Figure 5~6B
AI summary
The invention provides a bipolar electrochemical cell, comprising: an end anode current collector; a first ion-permeable membrane spaced from the end anode current collector and at least partially defining a first anode; a bipolar electrode including an anode current collector and a cathode current collector, the bipolar electrode spaced from the first ion-permeable membrane and at least partially defining a first cathode between the first ion-permeable membrane and the cathode current collector of the bipolar electrode; a second ion-permeable membrane spaced from the bipolar electrode and at least partially defining a second anode between the second ion-permeable membrane and the anode current collector of the bipolar electrode; and an end cathode current collector spaced from the second ion-permeable membrane and at least partially defining a second cathode between the end cathode current collector and the second ion-permeable membrane, wherein at least one of the first anode, the second anode, the first cathode, and the second cathode includes a semi-solid or condensed liquid ion-storing redox composition and wherein the semi-solid or condensed liquid ion-storing redox composition is capable of taking up or releasing ions, and remains substantially insoluble during operation of the cell.