Materials challenges and technical approaches for realizing inexpensive and robust iron–air batteries for large-scale energy storage

Hoober-Burkhardt

Krishnamoorthy

et al. 2016

Self Cite

210

265

We have demonstrated the repeated cycling of a redox flow cell based on water-soluble organic redox couples (ORBAT) at high voltage efficiency, coulombic efficiency and power density. These cells were successfully operated with 4,5-dihydroxybenzene-1,3-disulfonic acid (BQDS) at the positive electrode and anthraquinone-2,6-disulfonic acid (AQDS) at the negative electrode. Reduction of the voltage losses arising from mass transport limitations, and understanding of the chemical transformations of BQDS during charging have led to these improvements in performance. The specific advances reported here include the use of organic redox couples in the free-acid form, improvements to the flow field configuration, and novel high-surface-area graphite-felt electrode structures. We have identified various steps in the chemical and electrochemical transformations of BQDS during the first few cycles. We have also confirmed that the crossover of the reactants through the membrane was not significant. The performance improvements and new understanding presented here will hasten the development of ORBAT as an inexpensive and sustainable solution for large-scale electrical energy storage. With the increasing penetration of solar photovoltaic and windbased electricity generation, the variable and intermittent output of these energy generation systems is a grave concern for stable operation of the electricity grid. To buffer the inevitable surges in electricity supply and demand, large-scale energy storage systems are needed. Such energy storage systems must be capable of storing thousands of giga-watt hours of electricity per day. Rechargeable batteries are particularly attractive for electrical energy storage because of their high energy efficiency and scalability.1-3 However, for such a largescale application, these batteries must be inexpensive, robust, safe, and sustainable. None of today's commercially-available batteries can meet all the performance and cost targets at this scale of deployment of energy storage. This situation has led to a global search for a transformational solution.In 2013, we described an organic redox flow battery -also known as ORBAT -that uses water-soluble organic redox couples as a safe, scalable, and efficient energy storage system with the potential to meet the United States Department of Energy (DoE) cost target of $100/kWh for large-scale energy storage. 4 In such a battery, aqueous solutions of two different water-soluble organic redox couples -quinones and anthraquinones or their derivatives -were circulated past carbon electrodes in an electrochemical cell. In our current system, the positive electrode is supplied with a solution of 4,5-dihydroxybenzene-1,3-disulfonic acid (BQDS) and the negative electrode uses a solution of anthraquinone-2,6-disulfonic acid (AQDS). The positive and negative electrode compartments are separated by a proton-conducting polymer electrolyte membrane (Figure 1). During charge and discharge, the redox couples undergo rapid proton-coupled electron transfer to store ...

mentioning

confidence: 99%

High-Performance Aqueous Organic Flow Battery with Quinone-Based Redox Couples at Both Electrodes

Hoober-Burkhardt

Krishnamoorthy

et al. 2016

Self Cite

210

265

“…7,8,33,34 Consequently, at high rates of discharge, the active material in the iron electrode is poorly utilized. In commercial electrodes, complete passivation of the iron electrode occurs even at rates of C/5, and almost no capacity is obtainable at higher discharge rates.…”

mentioning

confidence: 99%

The Role of Sulfide Additives in Achieving Long Cycle Life Rechargeable Iron Electrodes in Alkaline Batteries

Manohar

Narayanan

2015

Iron-based alkaline rechargeable batteries such as nickel-iron and iron-air batteries are promising candidates for large-scale energy storage applications because of their relatively low cost, inherent robustness to cycling, and eco-friendliness. In the present study, we demonstrate iron electrodes containing iron (II) sulfide and bismuth oxide additives that do not exhibit any noticeable capacity loss even after 1200 cycles at 100% depth of discharge in each cycle. In iron electrodes prepared with bismuth sulfide additive, capacity loss occurred during cycling, accompanied by a decrease in discharge rate capability and rapid passivation. The recovery of capacity by adding sulfide ions to the electrolyte confirmed that the electrode that suffered capacity fade did not have an adequate supply of sulfide ions. We also found that the loss of cycleability was accompanied by the steady accumulation of magnetite and loss of iron sulfides at the iron electrode. The use of sparingly soluble iron (II) sulfide as an electrode additive ensured a sustained and steady supply of sulfide preventing the accumulation of magnetite during cycling. Thus, we have gained understanding of the critical role of sulfide additives in achieving long cycle life in rechargeable alkaline iron electrodes. Inexpensive and efficient methods of storing electrical energy are essential for the successful integration of solar and wind-based electricity generation into the grid. Among the various means to store electrical energy at a large scale, batteries are particularly promising because of their advantages of high energy efficiency, modularity and flexibility to siting.1-4 The state-of-art commercially-available lithium-ion, lead-acid, nickel-metal hydride and vanadium redox flow batteries may be rated by the levelized cost of energy delivered (LCOE). LCOE is calculated as the ratio of the cost (including capital and operating costs) to the total amount of energy delivered by the battery over its useful lifetime. The LCOE for commercially-available batteries is at least five to ten times higher than the DoE targets of $0.10 to $0.20/kWh. 5,6 Also, since energy storage will be required at the scale of thousands of gigawatt-hours, we are faced with the challenge of providing a sustainable solution, as the global material reserves are quite limited for these state-of-art batteries.7 Therefore, the development of inexpensive, efficient, robust and sustainable battery systems for grid-scale energy storage is a topic of intense research.3-6 Under an effort funded by ARPA-E, we have been focusing on developing such batteries. 7,[8][9][10][11][12] Iron-based battery systems such as nickel-iron and iron-air batteries are based on raw materials that are relatively inexpensive, globally-abundant, and eco-friendly. The promise of iron-based batteries for large-scale energy storage has spurred renewed interest in their development. 11,[13][14][15][16] The development of iron-based alkaline batteries began several decades ago. [17][18][19][20][21][22] In the U...

“…The concentration of sulfide ions in the electrolyte was determined from the electrode potentials of the sulfide selective reference electrode according to Equation 6, where E S 2− is the potential of the sulfide reference electrode and C S 2− is the concentration of sulfide ions in the electrolyte. 47 E S 2− = −610.8 mV − 28.1 log C S 2− [6] The concentration of sulfide in the electrolyte at the beginning of formation was 6.4×10 −2 mole/L. After the capacity decrease at around the 200 th cycle, the sulfide concentration in the electrolyte had decreased to a very low value of 10 −17 mole/L.…”

Section: Resultsmentioning

confidence: 98%

A High-Performance Sintered Iron Electrode for Rechargeable Alkaline Batteries to Enable Large-Scale Energy Storage

Manohar

Narayanan

2017

Iron-based alkaline rechargeable batteries such as iron-air and nickel-iron batteries are particularly attractive for large-scale energy storage because these batteries can be relatively inexpensive, environment-friendly, and also safe. Therefore, our study has focused on achieving the essential electrical performance and cycling properties needed for the widespread use of iron-based alkaline batteries in stationary and distributed energy storage applications. We have demonstrated for the first time, an advanced sintered iron electrode capable of 3500 cycles of repeated charge and discharge at the 1-hour rate and 100% depth of discharge in each cycle, and an average Coulombic efficiency of over 97%. Such a robust and efficient rechargeable iron electrode is also capable of continuous discharge at rates as high as 3C with no noticeable loss in utilization. We have shown that the porosity, pore size and thickness of the sintered electrode can be selected rationally to optimize specific capacity, rate capability and robustness. These advances in the electrical performance and durability of the iron electrode enables iron-based alkaline batteries to be a viable technology solution for meeting the dire need for large-scale electrical energy storage. Electrical energy storage systems will enable the seamless integration of the electricity generated from wind turbines and solar photovoltaics into the electricity grid. Rechargeable batteries are particularly good candidates for such large-scale energy storage because of their high round-trip efficiency, inherent scalability, and flexibility for being located almost anywhere.1-6 Batteries such as vanadiumredox, lead-acid and lithium-ion are under consideration for this application because of their commercial availability. Yet, the widespread deployment of these battery systems is limited by their materials cost, lifetime, safety concerns, and the high cost of delivered energy. 7,8Rechargeable iron-based alkaline batteries such as nickel-iron and iron-air have unique advantages that make them particularly attractive for meeting the emerging demands of grid-scale electrical energy storage systems.6,9-12 Iron, the primary raw material for these battery systems, is globally abundant, relatively inexpensive, eco-friendly and is recycled readily. Thus, iron is particularly attractive as a raw material for batteries required at such a large scale.6 Iron-based batteries such as the nickel-iron battery are historically well known for their extraordinary robustness to thousands of cycles of charge and discharge, and tolerance to overcharge and over-discharge. [13][14][15][16] Such robustness is generally uncommon among rechargeable batteries; other types of batteries in use today degrade in about 1000 cycles.17 For example, lead-acid batteries typically offer 500-800 cycles, and lithium-ion batteries usually last no more than 1000 cycles especially when subjected to deep discharge.18 Despite these striking attributes of iron-based batteries, the large-scale use of these batteries ...