Redox Flow Battery Electrolyte Volume Bias for Cycle Stability
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Solution Overview
Problem
Conventional redox flow batteries experience a reduction in total discharge capacity and average energy efficiency due to imbalances in active material concentration and electrolyte volume between compartments, caused by the permeation of active materials and solvents through the ion exchange membrane during charge/discharge cycles.
Innovation Solution
The redox flow battery is designed with an initial volume of the negative electrolyte greater than the positive electrolyte, and an initial vanadium ion concentration in the negative electrolyte greater than or equal to the positive electrolyte, which helps to balance the electrolyte volumes and concentrations over multiple cycles, reducing the impact of permeation rates and enhancing discharge capacity and energy efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an ion exchange membrane is used to separate negative and positive compartments, then hydrogen ions can pass through during charging and discharging, but active materials and solvents will still permeate through the membrane causing concentration imbalance
Solution Approach 1:
The patent applies preliminary action by pre-adjusting the initial electrolyte volumes in the negative and positive compartments before operation begins. The negative compartment is filled with a greater volume of electrolyte than the positive compartment, which anticipates and compensates for the expected permeation imbalance that will occur during charge/discharge cycles. This preliminary volume adjustment ensures that concentration balance is maintained throughout battery operation.
2Productivity
If multiple charge/discharge cycles are performed, then the battery provides energy storage and release functions, but active material permeation through the membrane destroys the balance of active material concentration and solution volume
Solution Approach 1:
The patent applies parameter changes by modifying the initial volume parameter of the electrolyte in the negative compartment. Specifically, the negative compartment is designed to contain a greater volume of electrolyte than the positive compartment at the start of operation. This parameter adjustment compensates for the volume loss that occurs in the negative compartment during charge/discharge cycles due to active material permeation, thereby maintaining overall volume balance and enabling sustained cycling performance.
3Power
If V2+ and V3+ ions permeate through the ion exchange membrane at a higher rate than V5+ and V4+ ions, then the membrane allows ion transport, but vanadium ion concentration becomes unbalanced between compartments
Solution Approach 1:
The patent applies parameter changes by adjusting the initial concentration parameter of vanadium ions in the negative electrolyte. The negative compartment is prepared with a higher concentration of vanadium ions compared to the positive compartment. This concentration differential compensates for the preferential permeation of V2+ and V3+ ions through the membrane, ensuring that vanadium ion concentration remains balanced between compartments during charge/discharge cycles.
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 improves the total discharge capacity and average energy efficiency of the redox flow battery by slowing down electrolyte volume imbalances and active material permeation, leading to increased performance over multiple charge/discharge cycles.
Implementation Method 1
an ion exchange membrane is provided between a negative compartment and a positive compartment, which is used to separate a negative active material and a negative solvent located in the negative compartment from a positive active material and a positive solvent located in the positive compartment, and allow hydrogen ions (protons) to pass through during charging and/or discharging
Implementation Method 2
there will still be a small amount of active materials and/or solvents passing through the ion exchange membrane
Data Source
AI summary
An electrolyte of a redox flow battery, including a negative electrolyte and a positive electrolyte, is provided. The negative electrolyte includes a negative active material and a negative solvent, and the positive electrolyte includes a positive active material and a positive solvent. An initial volume of the negative electrolyte is greater than an initial volume of the positive electrolyte. A redox flow battery including the electrolyte is also provided.