A low-cost amperometric sensor for the combined state-of-charge, capacity, and state-of-health monitoring of redox flow battery electrolytes

Stolze, Christian; Rohland, Philip; Zub, Karina; Nolte, Oliver; Hager, Martin D.; Schubert, Ulrich S.

doi:10.1016/j.ecmx.2022.100188

Cited by 8 publications

(18 citation statements)

References 35 publications

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“…Taking the standard deviations of the measurement during the first day into account, however, it is evident that the values are nearly equal within their statistical variation. Considering the error in the absolute capacity measurements with the OCV cells (0.7−1.6%), which we obtained in a recent study of our group, 19 it remains questionable if the obtained value is quantitatively distinguishable from zero with this measurement technique. In any case, the assessed NCLS capacity fade allows the following conclusion: even if MV was transferred from the CLS to the NCLS during the first day in the observed order of magnitude, this would have facilitated the decrease of the CLS capacity and led to an apparent increase of the capacity fade.…”

Section: Impact Of Electrolyte Leakages And/or Solventmentioning

confidence: 70%

“…In the experiment (Figure b), the NCLS electrolyte SOC was assessed during symmetric cell cycling based on the calibration data. Using the SOC data and the amount of charge transferred during RFB (dis)charge (example in Figure a), the NCLS capacity was estimated using a recently reported combination of SOC measurement and coulomb counting (Figure b) q normalN normalC normalL normalS = normalΔ q · normalΔ normalS normalO normalC normalN normalC normalL normalS − 1 where q NCLS is the NCLS capacity, and Δ q and ΔSOC NCLS are the changes in the absolute charge and the NCLS electrolyte SOC over the chosen time range, respectively. These parameters were estimated separately for each half cycle during symmetric cycling (excluding calibration cycles).…”

Section: Resultsmentioning

confidence: 99%

“…The determination of the diffusion coefficient ratio was performed according to our previous study. 19 The measurement was performed in a 5 mL analytical cell (VC-4, BioLogic) with a two-electrode setup in a grounded Faraday cage using a 33 μm diameter disk carbon fiber microelectrode as the WE and 3 mm disk glassy carbon electrode as the CE. The measurement was performed according to the following steps: (1) rinsing the WE with deoxygenated water inside the glovebox and polishing on a dry polishing pad, (2) performing a chronoamperometric measurement with a potential step at −0.2 V versus the CE for 1 min, (3) performing a chronoamperometric measurement with a potential step at +0.2 V versus the CE for 1 min, and (4) changing the sample and starting at step (1) again.…”

Section: Stability Assessment Viamentioning

confidence: 99%

“…In contrast to that, ex situ stability assessment techniques overcome these issues by investigating the flow battery electrolyte itself under isolated conditions. So far, in the literature, ex situ stability measurement techniques are mostly represented by spectroscopic ,, and electrochemical methods. − Spectroscopy is capable of providing high accuracy; however, it requires special equipment, preliminary calibration, temperature control, or corrections, and it can often struggle with interference of other electrolyte components with the signal of the redox-active substance under investigation. Recently, electrochemical methods based on steady-state amperometry have gained increased interest for the measurement of the electrolyte state of charge (SOC) and state of health (SOH) due to their accuracy, experimental simplicity, cost efficiency, and fair accuracy. ,,− In particular, Brushett and co-workers proposed that redox species concentrations can be monitored both in situ and ex situ using the mass-transfer-limited current at microelectrodes. , …”

Section: Introductionmentioning

confidence: 99%

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State and Prospects of Unbalanced, Compositionally Symmetric Flow Battery Cycling and Steady-State Amperometry Techniques for Electrolyte Stability Assessment: The Case of Methyl Viologen

Volodin

Stolze

Nolte

et al. 2022

ACS Appl. Energy Mater.

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An increasing number of redox-active substances with improved electrochemical stability is currently being reported in the literature for potential applications in redox flow batteries (RFBs). Consequently, the demand for methods capable of estimating the long-term stability of redox couples is increasing as well. It seems to be of particular importance to understand the limitations of existing stability assessment techniques. In this work, two recently established and highly promising stability assessment techniques are directly compared for the first time to measure the capacity fade rate of a N,N′-dimethyl-4,4′-bipyridinium dichloride (methyl viologen or MV) molecule as a benchmark anolyte substance. These two methods are the unbalanced, compositionally symmetric flow cell cycling (symmetric cycling or UCSFCC) and the steady-state amperometric state of health (ASOH) measurement. The results of the symmetric cycling indicate a 3-fold higher stability for MV compared to a previous literature report as well as a high standard deviation for the measured capacity fade rate. More comprehensive investigations of the technique revealed that the influence of the MV purity, electrolyte leakage, and membrane cross-over could not cause the difference between the measured and earlier reported capacity fades and, thus, indicated insufficiency of the technique’s accuracy for the measurement of highly stable redox species. ASOH as the second technique exhibited similar capacity fade rates like the symmetric cycling as well as comparably high standard deviations. Furthermore, it is prone to temperature fluctuations and variations of the electrode radius. Thus, we demonstrate an approach for a temperature correction in this method, which enables significantly higher accuracy and reliability. Despite this, the variation of the electrode radius remains the main concern for this technique. Based on the obtained results for the MV anolyte, the state and prospects of both techniques for the stability assessment in RFB research are discussed in detail.

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Section: Impact Of Electrolyte Leakages And/or Solventmentioning

confidence: 70%

Section: Resultsmentioning

confidence: 99%

Section: Stability Assessment Viamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

State and Prospects of Unbalanced, Compositionally Symmetric Flow Battery Cycling and Steady-State Amperometry Techniques for Electrolyte Stability Assessment: The Case of Methyl Viologen

Volodin

Stolze

Nolte

et al. 2022

ACS Appl. Energy Mater.

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“…As for the Coulomb Counting method and open-circuit voltage calculations which can provide accurate real-time estimates of SOC. The algorithm is one method that depends on the application of the battery system and the requirements of the battery management system [26], [27]. Coulomb Counting and OCV battery parameters were obtained using the recursive least square (RLS) algorithm and were able to anticipate the nonlinear nature of the battery [28], [29].…”

Section: Introductionmentioning

confidence: 99%

Direct Comparison using Coulomb Counting and Open Circuit Voltage Method for the State of Health Li-Po Battery

Amifia¹

2022

Journal of Robotics and Control

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Electric cars have undergone many developments in the current digital era. This is to avoid the use of increasingly scarce fuel. Recent studies on electric cars show that battery estimation is an interesting topic to be implemented directly. The battery estimation strategy is carried out by the Battery Management System (BMS). BMS is an indispensable part of electric vehicles or hybrid vehicles to ensure optimal and reliable operation of regulating, monitoring, and protecting batteries. A reliable BMS can extend battery life by setting voltage, temperature, and charging and discharging current limits. The main estimation strategy used by BMS is battery fault, SOH, and battery life. Battery State of Health (SOH) is part of the information provided by the BMS to avoid battery damage and failure. SOC is the proportion of battery capacity SOH is a measure of battery health. This study aims to develop a method for estimating SOH simultaneously using Coulomb Counting and Open Circuit Voltage (OCV) algorithms. The battery is modeled to obtain battery parameters and components of internal resistance, capacitance polarization and OCV voltage source. Several tests were implemented in this research by applying the constant current (CC)-charge CC-discharge test. The state-space system is then formed to apply the Coulomb Counting and OCV algorithms so that SOH can be estimated simultaneously. The OCV-SOC function is obtained in the form of a tenth order polynomial and the battery model parameters say that these parameters change with the health of the battery. The results of the model validation are able to accurately model the battery with an average relative error of 0.027%. Coulomb Counting resulted in an accurate SOH estimation with an error of 3.4%.

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A Review of Capacity Decay Studies of All‐vanadium Redox Flow Batteries: Mechanism and State Estimation

Wang,

Mu,

Wang

et al. 2024

ChemSusChem

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As a promising large‐scale energy storage technology, all‐vanadium redox flow battery has garnered considerable attention. However, the issue of capacity decay significantly hinders its further development, and thus the problem remains to be systematically sorted out and further explored. This review provides comprehensive insights into the multiple factors contributing to capacity decay, encompassing vanadium cross‐over, self‐discharge reactions, water molecules migration, gas evolution reactions, and vanadium precipitation. Subsequently, it analyzes the impact of various battery parameters on capacity. Based on this foundation, the article expounds upon the significance of battery internal state estimation technology. Additionally, the review also summarizes domestic and international mathematical models utilized for simulating capacity decay, serving as a valuable reference for future research endeavors. Finally, through the comparison of traditional experimental methods and mathematical modeling methods, this article offers effective guidance for the future development direction of battery state monitoring. This review generally overview the problems related to the capacity attenuation of all‐vanadium flow batteries, which is of great significance for understanding the mechanism behind capacity decay and state monitoring technology of all‐vanadium redox flow battery.

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A low-cost amperometric sensor for the combined state-of-charge, capacity, and state-of-health monitoring of redox flow battery electrolytes

Cited by 8 publications

References 35 publications

State and Prospects of Unbalanced, Compositionally Symmetric Flow Battery Cycling and Steady-State Amperometry Techniques for Electrolyte Stability Assessment: The Case of Methyl Viologen

State and Prospects of Unbalanced, Compositionally Symmetric Flow Battery Cycling and Steady-State Amperometry Techniques for Electrolyte Stability Assessment: The Case of Methyl Viologen

Direct Comparison using Coulomb Counting and Open Circuit Voltage Method for the State of Health Li-Po Battery

A Review of Capacity Decay Studies of All‐vanadium Redox Flow Batteries: Mechanism and State Estimation

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