This work was supported by the Ministry of Science and Technology, R.O.C., under the funding number of NSC 102-2221-E-002-146-, MOST 103-2221-E-002-233-, and MOST 104-2628-E-002-016-MY3.

1. Construction of a SLFB Beaker Cell with a Sodium Acetate Additive
NOTE: This section describes the procedure to construct a SLFB beaker cell with an additive for long-term cycling experiment. The protocol includes the electrolyte preparation with and without additive, electrode pretreatment, cell assembly, and efficiency calculations.
<ol>
	<li>Preparation of lead methanesulfonate (1 L, 1 M as an example)
	<ol>
		<li>In the fume hood, add 274.6 g of methanesulfonic acid (MSA, 70%) to a beaker stirring with a stir bar. Dissolve the MSA with 300 mL of deionized (DI) water.</li>
		<li>Prepare 223.2 g of lead (II) oxide (98%) and add in increments to the aforementioned beaker until the prepared lead oxide is completely dissolved.</li>
		<li>Filter through the B&#252;chner funnel with 70 mm cellulose filter paper to separate any undissolved lead oxide.</li>
		<li>Repeat this procedure for 3 times. Add DI water to reach 1 L in total volume.</li>
	</ol>
	</li>
	<li>Preparation of electrolyte without additive (300 mL)
	<ol>
		<li>Add 20.595 g of MSA (70%) to a beaker. Add 150 mL of prepared 1 M lead methanesulfonate to the same beaker.</li>
		<li>Add DI water to reach 300 mL in total volume and stir the electrolyte until uniformly mixed, which results in a solution of 0.5 M lead methanesulfonate mixed with 0.5 M MSA.</li>
	</ol>
	</li>
	<li>Preparation of electrolyte with sodium acetate (300 mL) 
	<ol>
		<li>Add 20.595 g of MSA (70%) to a beaker. Add 150 mL of prepared 1 M lead methanesulfonate to the same beaker.</li>
		<li>Add 1.23 g of NaOAc (98%) to the beaker as an additive agent.</li>
		<li>Add DI water to reach 300 mL in total volume and stir the electrolyte until uniformly mixed, which results in a solution of 0.5 M lead methanesulfonate, 0.5 M methanesulfonic acid, and 50 mM sodium acetate.</li>
	</ol>
	</li>
	<li>Pretreatment of the positive and negative electrodes
	<ol>
		<li>Repeatedly polish the positive (commercial carbon composite) and negative (nickel) electrodes with a sandpaper (aluminum oxide, P100) until no visible impurities are left and then rinse electrodes with DI water.</li>
		<li>Add 20.83 g of hydrogen chloride (35%) in 200 mL DI water and stir the solution until all of the hydrogen chloride is dissolved.</li>
		<li>Immerse the entire positive electrode in the prepared 1 M hydrogen chloride solution overnight to remove impurities at the electrode surface.</li>
		<li>Rinse the positive electrode thoroughly with DI water and dry the electrode with delicate task wipers. Tape one side of each electrode using polytetrafluoroethylene (PTFE) tape while exposing the other side of the electrodes.</li>
		<li>Prepare another solution with 3.03 g of potassium nitrate (99%) and 300 mL DI water, which results in a solution of 0.1 M potassium nitrate.</li>
		<li>Immerse the positive and negative electrodes in 0.1 M potassium nitrate with the exposed surface facing each electrode.</li>
		<li>Apply a potential of 1.80 V vs. Ag/AgCl to the positive electrode for 5 min. Subsequently, apply a potential of -1.0 V vs. Ag/AgCl to the positive electrode for 2 min.</li>
	</ol>
	</li>
	<li>Assemble the SLFB beaker cell
	<ol>
		<li>Attach the pretreated positive and negative electrodes to a home-made electrode positioning board for a fixed electrode distance. Place the positioning board together with electrodes in a beaker as schematically illustrated in Figure 1 and add electrolyte to the beaker until the designated level of immersion.</li>
		<li>Place a magnetic stirrer into the beaker, position the beaker on a hot plate and control the rotating rate of the stirrer. Connect the battery tester to the electrodes and cover the beaker cell with plastic wrap to prevent evaporation.</li>
	</ol>
	</li>
	<li>Calculate the battery efficiency
	<ol>
		<li>After galvanostatic charge and discharge, calculate the efficiency of the battery as the following: 
		Coulombic efficiency: <img alt="Equation 1" src="/files/ftp_upload/58484/58484eq1.jpg" /> 
		Voltage efficiency: <img alt="Equation 2" src="/files/ftp_upload/58484/58484eq2.jpg" /> 
		Energy efficiency: <img alt="Equation 3" src="/files/ftp_upload/58484/58484eq3.jpg" /> 
		Here, Q denotes coulombs of charged/discharged equivalent electrons, V the apply/output voltage, and E the total energy stored/consumed.</li>
	</ol>
	</li>
</ol>
2. Throwing Index Measurement
NOTE: This section describes the procedure to measure throwing index (TI) of the electrodeposit at positive electrodes in SLFB cells. Reversing the role of positive and negative electrodes delivers the other set of TI results. Here, TI is investigated by using a home-made Haring-Blum cell as schematically depicted in Figure 2.
<ol>
	<li>Measurement
	<ol>
		<li>Weigh and record two positive electrodes respectively before the experiments.</li>
		<li>Place the negative electrode at the center of a Haring-Blum cell and one positive electrode at a distance ratio of 1 from the negative electrode. Place the second positive electrode at another distance ratio from the negative electrode (take 6 as an example in Figure 2).</li>
		<li>Immerse the two positive electrodes and one negative electrode with the same immersed surface area (2 cm2 here) in the Haring-Blum cell with the electrolyte of interest.</li>
		<li>Apply a controlled current density (20 mA&#183;cm-2 here) at the electrodes by using a battery tester. Carry out the galvanostatic charge for a certain duration (30 min here).</li>
		<li>After plating, rinse the two positive electrodes with DI water and dry them at room temperature overnight.</li>
		<li>Weigh and record two positive electrodes again respectively and calculate the metal distribution ratio (MDR) according to the equation listed below.</li>
		<li>Repeat the aforementioned experiments by placing the second positive electrode at various linear distance ratios (LR) to acquire the TI diagram (varied from 6 to 1 here).</li>
	</ol>
	</li>
	<li>Calculation
	<ol>
		<li>As an example, consider the anode as the electrode of interest, and determine each data on the TI diagram by the measured MDR versus LR, which are calculated as the following: 
		<img alt="Equation 7" src="/files/ftp_upload/58484/58484eq7.jpg" /> 
		<img alt="Equation 8" src="/files/ftp_upload/58484/58484eq8.jpg" /></li>
	</ol>
	</li>
</ol>
3. SEM Sample Preparation
<ol>
	<li>Rinse the graphite electrode with DI water and dry at room temperature after electroplating.</li>
	<li>Slice graphite electrodes into the desired sample size by diamond saw with care. Cold mount the electrode sample and then mechanically polish it with 14, 8, and 3 &#956;m silicon carbide sand papers, subsequently.</li>
	<li>Further polish the samples with 1 &#956;m diamond suspension and 0.05 &#956;m Al2O3. Deposit the cold-mounted sample with platinum and attach it with copper tapes to ensure conductivity for SEM observation.</li>
</ol>

<ol>
	<li>Soloveichik, G. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Flow+batteries:+current+status+&amp;+trends.">Flow batteries: current status &amp; trends.</a> Chemical Reviews. 115 (20), 11533-11558 (2015).</li><li>Ravikumar, M. K., Rathod, S., Jaiswal, N., Patil, S., Shukla, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+renaissance+in+redox+flow+batteries.">The renaissance in redox flow batteries.</a> Journal of Solid State Electrochemistry. 21 (9), 2467-2488 (2017).</li><li>Hazza, A., Pletcher, D., Wills, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+flow+battery:+A+lead+acid+battery+based+on+an+electrolyte+with+soluble+lead+(II)+Part+I.+Preliminary+studies.">A novel flow battery: A lead acid battery based on an electrolyte with soluble lead (II) Part I. Preliminary studies.</a> Physical Chemistry Chemical Physics. 6 (8), 1773-1778 (2004).</li><li>Pletcher, D., Wills, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+flow+battery:+A+lead+acid+battery+based+on+an+electrolyte+with+soluble+lead+(II)+Part+II.+Flow+cell+studies.">A novel flow battery: A lead acid battery based on an electrolyte with soluble lead (II) Part II. Flow cell studies.</a> Physical Chemistry Chemical Physics. 6 (8), 1779-1785 (2004).</li><li>Pletcher, D., Wills, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+flow+battery-a+lead+acid+battery+based+on+an+electrolyte+with+soluble+lead+(II).+III.+The+influence+of+conditions+on+battery+performance.">A novel flow battery-a lead acid battery based on an electrolyte with soluble lead (II). III. The influence of conditions on battery performance.</a> Journal of Power Sources. 149, 96-102 (2005).</li><li>Hazza, A., Pletcher, D., Wills, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+flow+battery-a+lead+acid+battery+based+on+an+electrolyte+with+soluble+lead+(II).+IV.+The+influence+of+additives.">A novel flow battery-a lead acid battery based on an electrolyte with soluble lead (II). IV. The influence of additives.</a> Journal of Power Sources. 149, 103-111 (2005).</li><li>Pletcher, D., Zhou, H., Kear, G., Low, C. T. J., Walsh, F. C., Wills, R. G. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+flow+battery-A+lead-acid+battery+based+on+an+electrolyte+with+soluble+lead+(II).+V.+Studies+of+the+lead+negative+electrode.">A novel flow battery-A lead-acid battery based on an electrolyte with soluble lead (II). V. Studies of the lead negative electrode.</a> Journal of Power Sources. 180 (1), 621-629 (2008).</li><li>Pletcher, D., Zhou, H., Kear, G., Low, C. T. J., Walsh, F. C., Wills, R. G. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+flow+battery-A+lead-acid+battery+based+on+an+electrolyte+with+soluble+lead+(II).+Part+VI.+Studies+of+the+lead+dioxide+positive+electrode.">A novel flow battery-A lead-acid battery based on an electrolyte with soluble lead (II). Part VI. Studies of the lead dioxide positive electrode.</a> Journal of Power Sources. 180 (1), 630-634 (2008).</li><li>Li, X., Pletcher, D., Walsh, F. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+flow+battery:+a+lead+acid+battery+based+on+an+electrolyte+with+soluble+lead+(II).+Part+VII.+Further+studies+of+the+lead+dioxide+positive+electrode.">A novel flow battery: a lead acid battery based on an electrolyte with soluble lead (II). Part VII. Further studies of the lead dioxide positive electrode.</a> Electrochimica Acta. 54 (20), 4688-4695 (2009).</li><li>Krishna, M., Fraser, E. J., Wills, R. G. A., Walsh, F. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Developments+in+soluble+lead+flow+batteries+and+remaining+challenges:+An+illustrated+review.">Developments in soluble lead flow batteries and remaining challenges: An illustrated review.</a> Journal of Energy Storage. 15, 69-90 (2018).</li><li>Lin, Y. -. T., Tan, H. -. L., Lee, C. -. Y., Chen, H. -. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stabilizing+the+electrodeposit-electrolyte+interphase+in+soluble+lead+flow+batteries+with+ethanoate+additive.">Stabilizing the electrodeposit-electrolyte interphase in soluble lead flow batteries with ethanoate additive.</a> Electrochimica Acta. 263, 60-67 (2018).</li><li>Oury, A., Kirchev, A., Bultel, Y., Chainet, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=PbO2/Pb2++cycling+in+methanesulfonic+acid+and+mechanisms+associated+for+soluble+lead-acid+flow+battery+applications.">PbO2/Pb2+ cycling in methanesulfonic acid and mechanisms associated for soluble lead-acid flow battery applications.</a> Electrochimica Acta. 71, 140-149 (2012).</li><li>Oury, A., Kirchev, A., Bultel, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Potential+response+of+lead+dioxide/Lead+(II)+galvanostatic+cycling+in+methanesulfonic+acid:+a+morphologico-kinetics+interpretation.">Potential response of lead dioxide/Lead (II) galvanostatic cycling in methanesulfonic acid: a morphologico-kinetics interpretation.</a> Journal of The Electrochemical Society. 160 (1), A148-A154 (2013).</li></ol>

We have nothing to disclose.

This paper describes an economical method to extend the cycle life of SLFBs: by employing NaOAc agent as an electrolyte additive. A batch of fresh graphite electrodes and nickel plates are preprocessed as aforementioned in Step 1 before long-term cycling experiments. Because inconsistency among commercial carbon electrodes may cause performance deviation of the SLFBs, the physical/chemical pretreatment in Step 1.4 is critical to remove surface residues. The second part of Step 1.4 is employing electrochemical methods to remove impurities that may induce redox reactions between the potentials of 0 to 1.8 V vs. Ag/AgCl. As demonstrated in Figure 3, the cycle life of SLFBs is extended by approximately 50% when the NaOAc additive is supplied in 50 mM to the MSA based electrolyte, under a current density of 15 mA cm-2 and a charge/discharge duration of 40 min.
Since the focus of this study is on the electrolyte additive effects, we employed beaker cells rather than flow cells to minimize uncertainties derived from flow conditions. The beaker cell is magnetically stirred at a rotation rate of ~200 rpm to maintain a certain level of concentration uniformity of the electrolyte without severe agitation. The temperature of beaker cells is not controlled in the experiments, which leaves it close to the atmospheric temperature (25 &#177; 5 &#176;C). While temperature variation, if significant enough, may affect the deposition quality and battery performance, the two compared experiments are conducted in parallel to avoid the temperature perturbation interference. In addition, the long-term charge/discharge cycling of SLFBs can continue for several weeks during which the electrolyte in beaker cells will evaporate unignorably. It is thus also important to conceal the beaker cell to prevent excess evaporation. We find the aforementioned beaker cell experiment useful to simplify the analysis of electrolyte/electrode modification effects in single-flow RFBs.
Since the SLFB is a single-flow energy storage device operates through electroplating/stripping of PbO2 and Pb at the positive and the negative electrode, respectively, during charge/discharge, the quality of electrodeposits is pivotal to the battery efficiency. TI measurement has been historically utilized to investigate the quality of electrodeposit and thus is employed here to assess the additive effect. A pivotal consideration for accurate TI measurement in Step 2 is to choose the appropriate plating duration. Since the weight of electrodeposit is proportional to the amount of charges supplied and the current density is chosen to be representable of the battery operation condition, the plating duration should be chosen to accumulate appropriate amount of electrodeposit for later measurements.
Another prominent phenomenon observed in NaOAc-assisted SLFBs is the significant decrease of PbO2 shedding, which can be visually observed in the beaker cell. This reduced shedding in electrolyte with NaOAc additive is in accordance with the more congregated surface of the PbO2 electrodeposit observed in SEM images shown in Figure 5a. The extended cycle life of SLFBs is thus achieved by the plating of more integrated PbO2 deposits when NaOAc is added adequately to the electrolyte.
In this report, we present findings on a significant extension of SLFB lifespan by the NaOAc additive. Our work marks substantial improvement of SLFB technology and sheds lights on the failure mechanisms of SLFBs. In light of how high-quality electrodeposition can be assisted by NaOAc additive, our work opens up an exciting avenue to the advancement of batteries involving redox reactions associated with electrodeposition during cyclization.

Renewable energy sources including solar and wind have been developed for decades, but their intermittent nature poses great challenges. For a future power grid with renewable energy sources incorporated, grid stabilization and load leveling are critical and can be achieved by integrating energy storage. Redox flow batteries (RFBs) are one of the promising options for grid-scale energy storage. Traditional RFBs contain ion-selective membranes separating anolyte and catholyte; for example, the all-vanadium RFB has shown to operate with high efficiency and a long cycle life1,2. However, their market share as energy storage is very limited in part due to the expensive comprising materials and ineffective ion-selective membranes. On the other hand, a single-flow soluble lead flow battery (SLFB) is presented by Plectcher et al.1,2,3,4,5. The SLFB is membrane-less because it has only one active species, Pb(II) ions. Pb(II) ions are electroplated at the positive electrode as PbO2 and the negative electrode as Pb simultaneously during charging, and convert back to Pb(II) during discharging. A SLFB thus needs one circulation pump and one electrolyte storage tank only, which in turn can potentially lead to reduced capital and operational cost compared to conventional RFBs. The published cycle life of SLFBs, however, is so far limited to less than 200 cycles under normal flow conditions6,7,8,9,10.
Factors leading to a short SLFB cycle life is preliminarily associated with deposition/dissolution of PbO2 at the positive electrode. During charge/discharge processes, the electrolyte acidity is found to increase over deep or repeated cycles11, and protons are suggested to induce the generation of a passivation layer of non-stoichiometric PbOx12,13. The shedding of PbO2 is another phenomenon related to SLFB degradation. Shed PbO2 particles are irreversible and can no longer be utilized. The coulombic efficiency (CE) of SLFBs consequentially declines because of imbalanced electrochemical reactions as well as accumulated electrodeposits at both electrodes. To extend cycle life of SLFBs, stabilizing the pH fluctuation and electrodeposit structure are critical. A recent paper demonstrates an enhanced performance and extended cycle life of SLFBs with addition of sodium acetate (NaOAc) in methanesulfonic electrolyte11.
Here, a detailed protocol for employing NaOAc as an additive to the methanesulfonic electrolyte in SLFBs is described. The SLFB performance is shown to be enhanced and the lifespan can be extended by over 50% in comparison to SLFBs without NaOAc additives. In addition, procedures for throwing index (TI) measurement are illustrated for the purpose of quantitative comparison of additive effects on electrodeposition. Finally, a scanning electron microscopy (SEM) sample preparation method for electrodeposit on SLFB electrodes is described and the additive impact on electrodeposit is manifested in acquired images.

<table><tbody><tr><td>70 mm cellulose filter paper</td><td>Advance</td><td></td><td></td></tr><tr><td>Autolab</td><td>Metrohm</td><td>PGSTA302N</td><td></td></tr><tr><td>BT-Lab</td><td>BioLogic</td><td>BCS-810</td><td></td></tr><tr><td>commercial carbon composite electrode</td><td>Homy Tech,Taiwan</td><td></td><td>Density 1.75 g cm&lt;sup&gt;-3&lt;/sup&gt;, and electrical conductivity 330 S cm&lt;sup&gt;-1&lt;/sup&gt;</td></tr><tr><td>Diamond saw</td><td>Buehler</td><td></td><td></td></tr><tr><td>Hydrochloric Acid</td><td>SHOWA</td><td>0812-0150-000-69SW</td><td>35%</td></tr><tr><td>Lead (II) Oxide</td><td>SHOWA</td><td>1209-0250-000-23SW</td><td>98%</td></tr><tr><td>Lutropur MSA</td><td>BASF</td><td>50707525</td><td>70%</td></tr><tr><td>nickel plate</td><td>Lien Hung Alloy Trading Co., LTD., Taiwan,&amp;nbsp;</td><td></td><td>99%</td></tr><tr><td>Potassium Nitrate</td><td>Scharlab</td><td>28703-95</td><td>99%</td></tr><tr><td>Scanning electron microscopy</td><td>JEOL</td><td>JSM-7800F</td><td>at accelerating voltage of 15 kV</td></tr><tr><td>Sodium Acetate</td><td>SHOWA</td><td>1922-5250-000-23SW</td><td>98%</td></tr><tr><td>water purification system</td><td>Barnstead MicroPure</td><td></td><td>&amp;nbsp;18.2 M&amp;Omega;&amp;nbsp;&amp;bull; cm</td></tr></tbody></table>

extending the lifespan of soluble lead flow batteries with a sodium acetate additive

In this report, we present a method for the construction of a soluble lead flow battery (SLFB) with an extended cycle life. By supplying an adequate amount of sodium acetate (NaOAc) to the electrolyte, a cycle life extension of over 50% is demonstrated for SLFBs via long-term galvanostatic charge/discharge experiments. A higher quality of the PbO2 electrodeposit at the positive electrode is quantitatively validated for NaOAc-added electrolyte by throwing index (TI) measurements. Images acquired by scanning electron microscopy (SEM) also exhibit more integrated PbO2 surface morphology when the SLFB is operated with the NaOAc-added electrolyte. This work indicates that electrolyte modification can be a plausible route to economically enable SLFBs for large-scale energy storage.

To extend cycle life of SLFBs, NaOAc is supplied as an electrolyte additive. Cycling performance of SLFBs with and without NaOAc additive are examined in parallel, and results are shown in Figure 3. For easier quantitative comparison of cycle life, we define the &#34;death&#34; of a SLFB as when its CE is lower than 80% under continuous galvanostatic charge/discharge. Figure 3a and 3b show that approximately 50% cycle life extension of the SLFB is achieved when 50 mM NaOAc is added to the electrolyte of 0.5 M lead methanesulfonate and 0.5 M MSA, under 40-minute charge/discharge with a current density of 15 mA cm-2. The cycle number we hence accounted for is a representation of the battery life under full depth of discharge. The positive effect of NaOAc additive on SLFB performance is even more pronounced when the depth of charge/discharge is increased, and no additional redox reaction is observed in the SLFB operational potential range11.
Since SLFB is operated through electroplating/dissolution, TI experiments are conducted for the positive and negative electrodes of SLFBs, with and without NaOAc, to gain insight into the additive effect. TI measurements conducted for the positive electrodes employing an electrolyte with NaOAc demonstrate a shallower&#160;slope of the metal distribution ratio (MDR) to linear distance ratio (LR) than the one without additive in Figure 4a. The steeper slope of MDR to LR in TI measurement suggests that the electrodeposition is more affected by non-uniform current distribution, and a high-quality electrodeposit is harder to be plated. On the contrary, TI results for negative electrodes in Figure 4b show similar slopes of MDR to LR for both electrolytes. This result indicates that a better quality of PbO2 deposition is achieved with NaOAc-added electrolyte at the positive electrode, while the Pb plating at the negative electrode is nearly unaffected by NaOAc additive.
In addition, SEM images are acquired for the PbO2 electrodeposits as plated at the positive electrodes of SLFBs after 50-cycle galvanostatic charge/discharge experiments, under 60-minute charge/discharge with a current density of 15 mA cm-2. A smoother surface with less defects of the PbO2 electrodeposit is observed in Figure 5a in an electrolyte with the NaOAc additive, compared to the more fractured PbO2 surface plated without NaOAc as shown in Figure 5b. This morphological observation of PbO2 electrodeposit is in accordance with the TI measurement results, which indicates higher quality of electrodeposition with NaOAc additive.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/58484/58484fig1.jpg" /> 
Figure 1. A schematic diagram of the beaker cell employed for SLFB galvanostatic charge/discharge experiment. A home-made electrode positioning board is used to fix the electrode distance (18 mm), and the electrolyte mixing is achieved by controlling the rotation rate of the magnetic stirrer. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58484/58484fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/58484/58484fig2.jpg" /> 
Figure 2. A schematic diagram of the Haring-Blum cell employed for TI measurements. In this diagram, the far to near anode distance ratio is set at 6 to 1. The complete set of TI results is acquired by varying the far to near electrode distance ratios with fresh electrodes in each individual measurement. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58484/58484fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/58484/58484fig3.jpg" /> 
Figure 3. Galvanostatic charge/discharge cycle efficiencies of SLFBs with electrolyte (a) with; and (b) without 50 mM NaOAc additive; under 40-minute charge/discharge cycling and a current density of 15 mA&#183;cm-2. The cutoff potential is set at 1.05 V and the electrolyte volume is of 260 mL. This figure has been plotted based on data in Ref11 with permission. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58484/58484fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/58484/58484fig4.jpg" /> 
Figure 4. A comparison of the metal distribution ratio to linear distance ratio measured by throwing index experiments (a) PbO2 deposition at the positive electrodes; (b) Pb deposition at the negative electrodes. This figure has been modified from Ref11 with permission. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58484/58484fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/58484/58484fig5.jpg" /> 
Figure 5. SEM images of electroplated PbO2 at the positive electrode by electrolyte (a) with 50 mM NaOAc additive; (b) without additive. The magnification is of 20,000X. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58484/58484fig5large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Extending the Lifespan of Soluble Lead Flow Batteries with a Sodium Acetate Additive at JoVE.com

Extending the Lifespan of Soluble Lead Flow Batteries with a Sodium Acetate Additive

A protocol for the construction of a soluble lead flow battery with an extended lifespan, in which sodium acetate is supplied in the methanesulfonic electrolyte as an additive, is presented.

In this report, we present a method for the construction of a soluble lead flow battery (SLFB) with an extended cycle life. By supplying an adequate ...

extending-lifespan-soluble-lead-flow-batteries-with-sodium-acetate

Nanyang Technological University

Research

JoVE Journal

Chemistry

9.1K Views.  National Taiwan University. Deze methode verlengt de levensduur van oplosbare loodstroombatterijen door natriumacetaat in te zetten als elektrolytditief, wat een economische en effectieve aanpak is. Bovendien is het in deze methode gebruikte modelcelontwerp handig voor het bestuderen van de effecten van het elektrolytadditief op single flow redox flow batterijen. Het aantonen van de procedure zal Yong-Hong Lai, Ho-Wei Chan, en Kai-Rui Pan, twee grad studenten en een student van mijn laboratorium.Om te beginnen, i...

Video: Extending the Lifespan of Soluble Lead Flow Batteries with a Sodium Acetate Additive

Construction and Testing of Coin Cells of Lithium Ion Batteries

Rechargeable lithium ion batteries have wide applications in electronics, where customers always demand more capacity and longer lifetime. Lithium ion batteries have also been considered to be used in electric and hybrid vehicles1 or even electrical grid stabilization systems2. All these applications simulate a dramatic increase in the research and development of battery materials3-7, including new materials3,8, doping9, nanostructuring10-13, coatings or surface modifications14-17 and novel binders18. Consequently, an increasing number of physicists, chemists and materials scientists have recently ventured into this area. Coin cells are widely used in research laboratories to test new battery materials; even for the research and development that target large-scale and high-power applications, small coin cells are often used to test the capacities and rate capabilities of new materials in the initial stage. 
 In 2010, we started a National Science Foundation (NSF) sponsored research project to investigate the surface adsorption and disordering in battery materials (grant no. DMR-1006515). In the initial stage of this project, we have struggled to learn the techniques of assembling and testing coin cells, which cannot be achieved without numerous help of other researchers in other universities (through frequent calls, email exchanges and two site visits). Thus, we feel that it is beneficial to document, by both text and video, a protocol of assembling and testing a coin cell, which will help other new researchers in this field. This effort represents the "Broader Impact" activities of our NSF project, and it will also help to educate and inspire students.
In this video article, we document a protocol to assemble a CR2032 coin cell with a LiCoO2 working electrode, a Li counter electrode, and (the mostly commonly used) polyvinylidene fluoride (PVDF) binder. To ensure new learners to readily repeat the protocol, we keep the protocol as specific and explicit as we can. However, it is important to note that in specific research and development work, many parameters adopted here can be varied. First, one can make coin cells of different sizes and test the working electrode against a counter electrode other than Li. Second, the amounts of C black and binder added into the working electrodes are often varied to suit the particular purpose of research; for example, large amounts of C black or even inert powder were added to the working electrode to test the "intrinsic" performance of cathode materials14. Third, better binders (other than PVDF) have also developed and used18. Finally, other types of electrolytes (instead of LiPF6) can also be used; in fact, certain high-voltage electrode materials will require the uses of special electrolytes7.

A protocol to construct and test coin cells of lithium ion batteries is described. The specific procedures of making a working electrode, preparing a counter electrode, assembling a cell inside a glovebox and testing the cell are presented.

Rechargeable lithium ion batteries have wide applications in electronics, where customers always demand more capacity and longer lifetime.  Lithium ion ...

Engineering

Solid-state Graft Copolymer Electrolytes for Lithium Battery Applications

Battery safety has been a very important research area over the past decade. Commercially available lithium ion batteries employ low flash point (&lt;80 &deg;C), flammable, and volatile organic electrolytes. These organic based electrolyte systems are viable at ambient temperatures, but require a cooling system to ensure that temperatures do not exceed 80 &deg;C. These cooling systems tend to increase battery costs and can malfunction which can lead to battery malfunction and explosions, thus endangering human life. Increases in petroleum prices lead to a huge demand for safe, electric hybrid vehicles that are more economically viable to operate as oil prices continue to rise. Existing organic based electrolytes used in lithium ion batteries are not applicable to high temperature automotive applications. A safer alternative to organic electrolytes is solid polymer electrolytes. This work will highlight the synthesis for a graft copolymer electrolyte (GCE) poly(oxyethylene) methacrylate (POEM) to a block with a lower glass transition temperature (Tg) poly(oxyethylene) acrylate (POEA). The conduction mechanism has been discussed and it has been demonstrated the relationship between polymer segmental motion and ionic conductivity indeed has a Vogel-Tammann-Fulcher (VTF) dependence. Batteries containing commercially available LP30 organic (LiPF6 in ethylene carbonate (EC):dimethyl carbonate (DMC) at a 1:1 ratio) and GCE were cycled at ambient temperature. It was found that at ambient temperature, the batteries containing GCE showed a greater overpotential when compared to LP30 electrolyte. However at temperatures greater than 60 &deg;C, the GCE cell exhibited much lower overpotential due to fast polymer electrolyte conductivity and nearly the full theoretical specific capacity of 170 mAh/g was accessed.

Lithium ion batteries employ flammable and volatile organic electrolytes that are suitable for ambient temperature applications. A safer alternative to organic electrolytes are solid polymer batteries. Solid polymer batteries operate safely at high temperatures (&gt;120 &deg;C), thus making them applicable to high temperature applications such as deep oil drilling and hybrid electric vehicles. This paper will discuss (a) the polymer synthesis, (b) the polymer conduction mechanism, and (c) provide temperature cycling for both solid polymer and organic electrolytes.

Battery safety has been a very important research area over the past decade. Commercially available lithium ion batteries employ low flash point (&lt;80 ...

Characterization of Electrode Materials for Lithium Ion and Sodium Ion Batteries Using Synchrotron Radiation Techniques

Intercalation compounds such as transition metal oxides or phosphates are the most commonly used electrode materials in Li-ion and Na-ion batteries. During insertion or removal of alkali metal ions, the redox states of transition metals in the compounds change and structural transformations such as phase transitions and/or lattice parameter increases or decreases occur. These behaviors in turn determine important characteristics of the batteries such as the potential profiles, rate capabilities, and cycle lives. The extremely bright and tunable x-rays produced by synchrotron radiation allow rapid acquisition of high-resolution data that provide information about these processes. Transformations in the bulk materials, such as phase transitions, can be directly observed using X-ray diffraction (XRD), while X-ray absorption spectroscopy (XAS) gives information about the local electronic and geometric structures (e.g.&#160;changes in redox states and bond lengths). In situ experiments carried out on operating cells are particularly useful because they allow direct correlation between the electrochemical and structural properties of the materials. These experiments are time-consuming and can be challenging to design due to the reactivity and air-sensitivity of the alkali metal anodes used in the half-cell configurations, and/or the possibility of signal interference from other cell components and hardware. For these reasons, it is appropriate to carry out ex situ experiments (e.g.&#160;on electrodes harvested from partially charged or cycled cells) in some cases. Here, we present detailed protocols for the preparation of both ex situ and in situ samples for experiments involving synchrotron radiation and demonstrate how these experiments are done.

We describe the use of synchrotron X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) techniques to probe details of intercalation/deintercalation processes in electrode materials for Li-ion and Na-ion batteries. Both in situ and ex situ experiments are used to understand structural behavior relevant to the operation of devices

Intercalation compounds such as transition metal oxides or phosphates are the most commonly used electrode materials in Li-ion and Na-ion batteries. ...

In Situ Neutron Powder Diffraction Using Custom-made Lithium-ion Batteries

Li-ion batteries are widely used in portable electronic devices and are considered as promising candidates for higher-energy applications such as electric vehicles.1,2 However, many challenges, such as energy density and battery lifetimes, need to be overcome before this particular battery technology can be widely implemented in such applications.3 This research is challenging, and we outline a method to address these challenges using in situ NPD to probe the crystal structure of electrodes undergoing electrochemical cycling (charge/discharge) in a battery. NPD data help determine the underlying structural mechanism responsible for a range of electrode properties, and this information can direct the development of better electrodes and batteries.
We briefly review six types of battery designs custom-made for NPD experiments and detail the method to construct the &#8216;roll-over&#8217; cell that we have successfully used on the high-intensity NPD instrument, WOMBAT, at the Australian Nuclear Science and Technology Organisation (ANSTO). The design considerations and materials used for cell construction are discussed in conjunction with aspects of the actual in situ NPD experiment and initial directions are presented on how to analyze such complex in situ data.

In Situ Neutron Powder Diffraction Using Custom-made Lithium-ion Batteries

We describe the design and construction of an electrochemical cell for the examination of electrode materials using in situ neutron powder diffraction (NPD). We briefly comment on alternate in situ NPD cell designs and discuss methods for the analysis of the corresponding in situ NPD data produced using this cell.

Li-ion batteries are widely used in portable electronic devices and are considered as promising candidates for higher-energy applications such as electric ...

Ultrasound Velocity Measurement in a Liquid Metal Electrode

A growing number of electrochemical technologies depend on fluid flow, and often that fluid is opaque. Measuring the flow of an opaque fluid is inherently more difficult than measuring the flow of a transparent fluid, since optical methods are not applicable. Ultrasound can be used to measure the velocity of an opaque fluid, not only at isolated points, but at hundreds or thousands of points arrayed along lines, with good temporal resolution. When applied to a liquid metal electrode, ultrasound velocimetry involves additional challenges: high temperature, chemical activity, and electrical conductivity. Here we describe the experimental apparatus and methods that overcome these challenges and allow the measurement of flow in a liquid metal electrode, as it conducts current, at operating temperature. Temperature is regulated within &#177;2 &#176;C using a Proportional-Integral-Derivative (PID) controller that powers a custom-built furnace. Chemical activity is managed by choosing vessel materials carefully and enclosing the experimental setup in an argon-filled glovebox. Finally, unintended electrical paths are carefully prevented. An automated system logs control settings and experimental measurements, using hardware trigger signals to synchronize devices. This apparatus and these methods can produce measurements that are impossible with other techniques, and allow optimization and control of electrochemical technologies like liquid metal batteries.

Ultrasound velocimetry is used to study mixing by fluid flow in liquid metal electrodes. The focus of this manuscript is to illustrate the methods used for making precise, spatially-resolved ultrasound measurements while limiting oxidation and controlling and monitoring temperature, applied current, and the heater power being supplied.

A growing number of electrochemical technologies depend on fluid flow, and often that fluid is opaque. Measuring the flow of an opaque fluid is inherently ...

Non-aqueous Electrode Processing and Construction of Lithium-ion Coin Cells

Research into new and improved materials to be utilized in lithium-ion batteries (LIB) necessitates an experimental counterpart to any computational analysis. Testing of lithium-ion batteries in an academic setting has taken on several forms, but at the most basic level lies the coin cell construction. In traditional LIB electrode preparation, a multi-phase slurry composed of active material, binder, and conductive additive is cast out onto a substrate. An electrode disc can then be punched from the dried sheet and used in the construction of a coin cell for electrochemical evaluation. Utilization of the potential of the active material in a battery is critically dependent on the microstructure of the electrode, as an appropriate distribution of the primary components are crucial to ensuring optimal electrical conductivity, porosity, and tortuosity, such that electrochemical and transport interaction is optimized. Processing steps ranging from the combination of dry powder, wet mixing, and drying can all critically affect multi-phase interactions that influence the microstructure formation. Electrochemical probing necessitates the construction of electrodes and coin cells with the utmost care and precision. This paper aims at providing a step-by-step guide of non-aqueous electrode processing and coin cell construction for lithium-ion batteries within an academic setting and with emphasis on deciphering the influence of drying and calendaring.

Non-aqueous electrode processing is central to the construction of coin cells and the evaluation of new electrode chemistries for lithium-ion batteries. A step-by-step guide to the basic practices needed as an electrochemical engineer working with batteries in an academic experimental setting is furnished.

Research into new and improved materials to be utilized in lithium-ion batteries (LIB) necessitates an experimental counterpart to any computational ...

A Protocol for Electrochemical Evaluations and State of Charge Diagnostics of a Symmetric Organic Redox Flow Battery

Redox flow batteries have been considered as one of the most promising stationary energy storage solutions for improving the reliability of the power grid and deployment of renewable energy technologies. Among the many flow battery chemistries, non-aqueous flow batteries have the potential to achieve high energy density because of the broad voltage windows of non-aqueous electrolytes. However, significant technical hurdles exist currently limiting non-aqueous flow batteries to demonstrate their full potential, such as low redox concentrations, low operating currents, under-explored battery status monitoring, etc. In an attempt to address these limitations, we recently reported a non-aqueous flow battery based on a highly soluble, redox-active organic nitronyl nitroxide radical compound, 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO). This redox material exhibits an ambipolar electrochemical property, and therefore can serve as both anolyte and catholyte redox materials to form a symmetric flow battery chemistry. Moreover, we demonstrated that Fourier transform infrared (FTIR) spectroscopy could measure the PTIO concentrations during the PTIO flow battery cycling and offer reasonably accurate detection of the battery state of charge (SOC), as cross-validated by electron spin resonance (ESR) measurements. Herein we present a video protocol for the electrochemical evaluation and SOC diagnosis of the PTIO symmetric flow battery. With a detailed description, we experimentally demonstrated the route to achieve such purposes. This protocol aims to spark more interests and insights on the safety and reliability in the field of non-aqueous redox flow batteries.

We present the protocols for electrochemically evaluating a symmetric non-aqueous organic redox flow battery and for diagnosing its state of charge using FTIR.

Redox flow batteries have been considered as one of the most promising stationary energy storage solutions for improving the reliability of the power grid ...

Synthesis of Ionic Liquid Based Electrolytes, Assembly of Li-ion Batteries, and Measurements of Performance at High Temperature

The chemical instability of the traditional electrolyte remains a safety issue in widely used energy storage devices such as Li-ion batteries. Li-ion batteries for use in devices operating at elevated temperatures require thermally stable and non-flammable electrolytes. Ionic liquids (ILs), which are non-flammable, non-volatile, thermally stable molten salts, are an ideal replacement for flammable and low boiling point organic solvent electrolytes currently used today. We herein describe the procedures to: 1) synthesize mono- and di-phosphonium ionic liquids paired with chloride or bis(trifluoromethane)sulfonimide (TFSI) anions; 2) measure the thermal properties and stability of these ionic liquids by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA); 3) measure the electrochemical properties of the ionic liquids by cyclic voltammetry (CV); 4) prepare electrolytes containing lithium bis(trifluoromethane)sulfonamide; 5) measure the conductivity of the electrolytes as a function of temperature; 6) assemble a coin cell battery with two of the electrolytes along with a Li metal anode and LiCoO2 cathode; and 7) evaluate battery performance at 100 &#176;C. We additionally describe the challenges in execution as well as the insights gained from performing these experiments.

Here, we describe protocols to prepare phosphonium-based ionic liquid and lithium bis(trifluoromethane)sulfonimide salt electrolytes, and assemble a non-flammable and high temperature functioning lithium-ion coin cell battery.

The chemical instability of the traditional electrolyte remains a safety issue in widely used energy storage devices such as Li-ion batteries. Li-ion ...

The Effect of Charging and Discharging Lithium Iron Phosphate-graphite Cells at Different Temperatures on Degradation

The effect of charging and discharging lithium iron phosphate-graphite cells at different temperatures on their degradation is evaluated systematically. The degradation of the cells is assessed by using 10 charging and discharging temperature permutations ranging from -20 &#176;C to 30 &#176;C. This allows an analysis of the effect of charge and discharge temperatures on aging, and their associations. A total of 100 charge/discharge cycles were carried out. Every 25 cycles a reference cycle was performed to assess the reversible and irreversible capacity degradation. A multi-factor analysis of variance was used, and the experimental results were fitted showing: i) a quadratic relationship between the rate of degradation and the temperature of charge, ii) a linear relationship with the temperature of discharge, and iii) a correlation between the temperature of charge and discharge. It was found that the temperature combination for charging at +30 &#176;C and discharging at -5 &#176;C led to the highest rate of degradation. On the other hand, the cycling in a temperature range from -20 &#176;C to 15 &#176;C (with various combinations of temperatures of charge and discharge), led to a much lower degradation. Additionally, when the temperature of charge is 15 &#176;C, it was found that the degradation rate is nondependent on the temperature of discharge.

This article describes the effect of dissimilar charging/discharging temperatures on the degradation of lithium iron phosphate-graphite pouch cells, aiming at simulating close to real case scenarios. In total, 10 temperature combinations are investigated in the range -20 to 30 &#176;C in order to analyze the impact of temperature on degradation.

The effect of charging and discharging lithium iron phosphate-graphite cells at different temperatures on their degradation is evaluated systematically. ...

Zinc-Sponge Battery Electrodes that Suppress Dendrites

We report two methods to create zinc-sponge electrodes that suppress dendrite formation and shape change for rechargeable zinc batteries. Both methods are characterized by creating a paste made of zinc particles, organic porogen, and viscosity-enhancing agent that is heated under an inert gas and then air. During heating under the inert gas, the zinc particles anneal together, and the porogen decomposes; under air, the zinc fuses and residual organic burns out, yielding an open-cell metal foam or sponge. We tune the mechanical and electrochemical properties of the zinc sponges by varying zinc-to-porogen mass ratio, heating time under inert gas and air, and size and shape of the zinc and porogen particles. An advantage of the reported methods is their ability to finely tune zinc-sponge architecture. The selected size and shape of the zinc and porogen particles influence the morphology of the pore structure. A limitation is that resulting sponges have disordered pore structures that result in low mechanical strength at low volume fractions of zinc (&#60;30%). Applications for these zinc-sponge electrodes include batteries for grid-storage, personal electronics, electric vehicles, and electric aviation. Users can expect zinc-sponge electrodes to cycle up to 40% depth of discharge at technologically relevant rates and areal capacities without the formation of separator-piercing dendrites.

The goal of the reported protocols is to create rechargeable zinc-sponge electrodes that suppress dendrites and shape change in zinc batteries, such as nickel&#8211;zinc or zinc&#8211;air.

We report two methods to create zinc-sponge electrodes that suppress dendrite formation and shape change for rechargeable zinc batteries. Both methods are ...

Extending the Lifespan of Soluble Lead Flow Batteries with a Sodium Acetate Additive

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