Zinc-Bromine Flow Battery State-of-Charge Estimation via In Situ OCV
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Solution Overview
Problem
Zinc-bromine flow batteries face challenges in accurately estimating state-of-charge due to varying bromine ion concentrations and the corrosion of metal zinc electrodes used for analysis, which affects zinc ion concentration.
Innovation Solution
An apparatus with measuring electrodes comprising a working electrode, reference electrode, and counter electrode is installed in the cathode and anode electrolyte tanks, applying a constant current to electro-deposit zinc on the working electrode, allowing for state-of-charge estimation through open-circuit voltage (OCV) measurement and calculation of zinc ion concentration using the Nernst equation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a metal zinc electrode is used to measure zinc ion concentration, then electrochemical equilibrium with zinc ions is achieved, but the electrode is corroded and dissolved by the electrolyte causing changes in zinc ion concentration
Solution Approach 1:
A non-corroding working electrode (carbon, gold, platinum, or iridium) serves as an intermediary to measure zinc ion concentration without directly interacting with zinc ions through electrochemical equilibrium. The mediator applies constant current to electro-deposit zinc from the electrolyte onto the working electrode surface, enabling OCV measurement without the measurement electrode itself participating in the electrochemical equilibrium
Solution Approach 2:
The patent replaces the traditional metal zinc electrode (which relies on direct electrochemical equilibrium) with a non-corroding electrode system that uses controlled electro-deposition followed by open-circuit voltage measurement. This substitution eliminates the corrosion problem while maintaining the ability to estimate zinc ion concentration through OCV
2Productivity
If quaternary ammonium compounds are used to capture bromine molecules, then bromine capture efficiency is improved, but the anode electrolyte configuration becomes complicated with water-soluble and water-insoluble phases
Solution Approach 1:
The patent extracts and measures zinc ion concentration independently from the complicated multi-phase electrolyte system. By using a non-corroding working electrode to electro-deposit zinc and measure OCV, the measurement process is separated from the complex bromine capture chemistry involving quaternary ammonium compounds, water-soluble zinc bromide phase, and water-insoluble polybromide phase
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
Effectively estimates the state-of-charge of zinc flow batteries while preventing metal corrosion, ensuring accurate concentration measurement and stable operation by using non-reactive electrode materials like carbon, gold, or iridium and applying a controlled current for zinc deposition.
Implementation Method 1
the estimator supplies a constant current to the measuring electrodes for a predetermined time before measurement so that zinc is electro-deposited on the working electrode through the zinc ions contained in the cathode electrolyte or the anode electrolyte
Implementation Method 2
the estimator estimates the state-of-charge by measuring an open-circuit voltage (OCV) of the working electrode with respect to the reference electrode
Data Source
AI summary
Disclosed are an apparatus and method for estimating a state-of-charge of a zinc flow battery by measuring a concentration of zinc ions contained in an electrolyte through an open-circuit voltage (OCV). The apparatus according to embodiments of the present invention can estimate effectively the state-of-charge of the zinc flow battery from the concentration of zinc ions measured through the OCV of the working electrode with respect to the reference electrode when the measuring electrodes are installed in the cathode electrolyte tank or the anode electrolyte tank.