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

Summary

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.

Abstract

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.

Introduction

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 life^1,2. However, their market share as ene....

Protocol

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.

1. Preparation of lead methanesulfonate (1 L, 1 M as an example)
   1. 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.
   2. Prepare 223.2 g of lead (II) oxide (9....

Results

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 "death" 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 li.......

Discussion

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 .......

Materials

List of materials used in this article

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