A high performance redox-flow battery for grid-scale energy storage

As our reliance on renewable energy sources grows, so too does our need to store this energy to mitigate against troughs in supply. Energy storage in batteries or by conversion to chemical fuels are the two most flexible and scalable options, but are normally considered mutually exclusive. Energy storage solutions that can act as both batteries and fuel generation devices (depending on the requirements of the user) could therefore find great utility. In this talk, we shall investigate new device architectures for water splitting and energy storage that use Electron-Coupled-Proton Buffers (ECPBs) as redox mediators (see, for example: Nature Chem. 2013, 5, 403-409; Science, 2014, 345, 1326-1330; Joule, 2018, 2, 1390-1395) allowing high energy-density redox flow batteries and devices for the on-demand generation of hydrogen to be realised based on a common underlying chemistry (Nature Chem. 2018, 10, 1042-1047). Figure 1

SPEEK scaling UP

Harnessing Interfacial Electron Transfer in Redox Flow Batteries

An analytical method for identifying synergies between behind-the-meter battery and thermal energy storage

Molten Lithium-Brass/Zinc Chloride System as High-Performance and Low-Cost Battery

Chapter 9 - Stationary applications. III. Lead-acid batteries for solar and wind energy storage

Conventional redox flow batteries (RFB) use electrolyte solutions as energy storage media. For this reason the energy density is mainly limited by the solubility of the redox couples in the solutions. The kinetics of the reactions is mostly moderate so that cycling power densities can only reach max. 100 mW/cm². Depending on the energy / performance ratio the cost of the energy converter of RFBs clearly dominates the total investment costs. For longer storage periods the influence of the cost of the energy storage medium increases. For these reasons RFBs with redox pairs with high kinetics and thus a high power density are desirable. Hydrogen and bromine-based energy storage fulfill both requirements because the kinetics of the reactions are very fast and both elements are inexpensive and very abundant. In addition potentially high energy densities and efficiencies can be achieved. Anode: H2 -> 2 H+ +2 e- E0 = 0.00 V Cathode: Br2 +2 e- -> 2 Br- E0 = + 1.06 V Cell: H2 + Br2 -> 2 HBr E = 1.06 V Although the first studies were made in the 80s of the last century [1], the research intensified due to these positive characteristics in the last years [2, 3]. For a viable use, hydrogen storage, bromine diffusion, bromine complexation and system behavior are the biggest challenges. In this work we want to present the results of the development and the construction of an H/Br-RFB with an active area of 40 cm² and its behavior at different electrolyte compositions, temperatures and current densities. For better identification of the properties the half-cell potentials and impedances were also measured and evaluated. This research forms the basis for our future studies involving the use of advanced bromine complexation agents (BCAs) and their impact on H/Br-RFB. [1] Yeo, R. S.; Chin, D. ‐T. (1980): A Hydrogen‐Bromine Cell for Energy Storage Applications. In: Journal of The Electrochemical Society 127 (3), S. 549–555. DOI: 10.1149/1.2129710. [2] Cho, Kyu Taek; Albertus, Paul; Battaglia, Vincent; Kojic, Aleksandar; Srinivasan, Venkat; Weber, Adam Z. (2013): Optimization and Analysis of High-Power Hydrogen/Bromine-Flow Batteries for Grid-Scale Energy Storage. In: Energy Technology 1 (10), S. 596–608. DOI: 10.1002/ente.201300108. [3] Cho, Kyu Taek; Tucker, Michael C.; Ding, Markus; Ridgway, Paul; Battaglia, Vincent S.; Srinivasan, Venkat; Weber, Adam Z. (2014): Cyclic Performance Analysis of Hydrogen/Bromine Flow Batteries for Grid-Scale Energy Storage. In: ChemPlusChem, S. n/a. DOI: 10.1002/cplu.201402043. Figure 1

Rechargeable battery is the leading energy storage option for renewable power sources such as solar, wind and tidal (Park, et al., 2019, Tarascon, 2010). Furthermore, everyone owns a device powered by a rechargeable battery. Most of these devices are powered by lithium ion batteries (LIBs) owing to their rechargeability and high-energy density (Shin, et al., 2019). However, the rechargeable battery will lose its ability to retain a charge over time, forcing the consumer to discard the battery or product, which ends up in landfills. Owing to the high chemical activity of Li and the toxicity and flammability of organic solvent-based electrolytes, LIBs cause alarming safety and environmental issues (Yang, et al., 2018). Although Na+/K+ batteries are possible alternatives, these technologies also utilize organic electrolytes. Hence, there is a huge motivation to explore a battery chemistry that is long lasting, environmentally friendly, and cost-efficient. Rechargeable batteries based on water-based electrolytes are a revolutionary alternative and hold a prominent place in the energy storage research community. Along with other advantages, water also has a higher ionic conductivity (1 S cm-1) than organic electrolytes (~10-2 – 10-3 S cm-1) which is ideal for high rate cycling of batteries (Fang, et al., 2018, Winter, et al., 2004).The development of rechargeable aqueous batteries is ongoing, and there are systems based on monovalent ions (e.g. K+) and multivalent ions (e.g. Al3+, Zn2+ and Mg2+) (Liu, et al., 2014, Zhang, et al., 2017). Multivalent systems are more desirable given that their multiple redox states promise high specific capacity and energy density. Among multivalent systems, the rechargeable zinc ion battery (ZIB) has a huge potential, owing to its large overpotential for hydrogen evolution reaction (HER) (Fang, et al., 2018, Xu, et al., 2012, Glatz, et al., 2020, Zeng, et al., 2019). Apart from that, Zn holds a number of advantages over others, namely: high Earth abundance (low cost), high theoretical capacity (820 mAh g-1), low redox potential (-0.762 V vs SHE) and nontoxicity (Blanc, et al., 2020). Clearly, the electrochemical stability of Zn in aqueous solutions enlightens an opportunity to develop a “green” rechargeable battery.The aqueous ZIB consists of three main components, the Zn anode, electrolyte (e.g. Zn salts, such as ZnSO4, ZnNO3 or Zn(CF3SO3) in water) (Zhang, et al., 2016) and the cathode material (layered transition metal oxides, metal sulphides, polyaniline compounds, Prussian blue analogues etc.) (Fang, et al., 2018). Most scientific contributions on ZIB are devoted to the development of high-capacity and stable cathode materials. Owing to the cost effectiveness, environmental friendliness, and high theoretical capacity, Mn and V-based layered oxides are popular as cathode materials (Xu, et al., 2012, Alfaruqi, et al., 2015, Zhang, et al., 2019, Wei, et al., 2019). However, due to the +2 charge of Zn, it can suffer severe electrostatic interactions with the layered host material resulting in sluggish charge transfer kinetics (Yang, et al., 2018). Incorporation of metal ions (Zn2+, Mg2+, Ca2+, Li+, Na+) or structural water molecules between layers can mitigate these interactions and improve structuralstability (Zeng, et al., 2019, Lewis, et al., 2022). Dissolution of cathode material in aqueous electrolytesis another issue, which is typically addressed by electrolyte optimization (Zhao, et al., 2019).When considering the anode, growth of Zn dendrites on the anode surface is a major bottleneckfor the expansion of ZIB (Zhao, et al., 2019), i.e. localized nucleation of Zn, further aggravated by thedeposition of new Zn at preformed crystals. These Zn dendrites lead to an internal short circuit of thebattery. Furthermore, as deposited highly active Zn surface can undergo side reactions (corrosion,HER), leading to by-products and low coulombic efficiency (Zhao, et al., 2018). There have been fourmain strategies to tackle these problems: (i) electrolyte optimization, (ii) Zn anode surfacemodification, (iii) 3D Zn host design, and (iv) electrochemical protocol development (Blanc, et al.,2020). Among these, the surface passivation of Zn anode with inorganic (ZnO, TiO2, CaCO3) (Kang,et al., 2018, Kim, et al., 2020, Zhao, et al., 2020, Xie, et al., 2020) and organic (polyamide, polyvinylbutyl) (Zhao, et al., 2019, Hao, et al., 2020) coatings is a promising new approach.Although there has been some progress, effective and practically viable approaches to retardZn dendrite growth are yet insufficient. The final fate of the electrodeposited Zn critically relies on theinitial nucleation pattern and nanoscale surface kinetics (Zhao, et al., 2019, White, et al., 2012).Researchers have recognized the importance of this and have analyzed the dendrite formation viatechniques such as ex-situ atomic force microscopy (AFM), scanning electron microscopy (SEM) andtransmission electron microscopy (TEM) (Song, et al., 2016), yet these “stop-and-go” methods restrictsthe study of dynamic processes in real-time. Operando techniques are necessary to observe theevolution of micro/nanostructure of Zn deposits as it happens, which would help to establish thedeposition kinetics and transfer dynamics at the Zn anode. Hence, advanced operando characterizationtools are expected to guide the development of safe, cost-effective, and environmentally friendlyaqueous batteries and supercapacitors for future grid scale energy storage.

Solar cells hold a function of photovoltaic conversion, while rechargeable metal batteries have an advantage of high energy storage. The conventional charge mode of batteries is made based on complete utilization of electric energy. The combination of solar cells and rechargeable metal batteries brings a new opportunity for the development of photo‐assisted rechargeable batteries, in which the solar energy can be utilized to partially achieve photo‐charging with or without external electrical bias. This review highlights the working mechanism and structure design of photo‐assisted rechargeable metal batteries according to the characteristics of rechargeable metal batteries and advantage of the photovoltaic technology. In particular, the recent advances are introduced for photo‐assisted rechargeable batteries based on light‐weight metal anodes, including metal lithium, metal sodium, and metal zinc. The working features of the integrated devices are also discussed for energy saving under photo‐assisted charging mode. Finally, a future outlook is provided for further improving the performance of photo‐assisted rechargeable metal batteries.

Investigation of gas diffusion behavior and detection of 86 Ah LiFePO4 batteries in energy storage systems during thermal runaway

The Energy and Evaluation Special Committee of the China Price Association proposed two types of bill for battery energy storage (BES) subsidies in 2017: the first was that energy storage should be subsidised based on the initial installation capacity of BES system, while the second was that it should be subsidised based on the energy discharged by the BES system during the operational period. The economic benefits of a distributed photovoltaic (PV) system or a distributed system with PV and BES in the overall life cycle are discussed in the context of an industrial zone in Shanghai. The results suggest that the net present value (NPV) of a PV-BES system with an optimised configuration is higher than the NPV of a PV system alone. The NPV of a distributed PV system with four different BESs is found to decrease in the order Li-ion > NaS > VFB > Pb-C because of the characteristics of their batteries. The NPVs of PV-BES systems increase in equal proportion to the increase in the BES subsidy based on installation capacity for these four BES systems, while they show an inequable growth rate of earnings for the same BES subsidy based on the energy discharged over the operational period. The second bill for BES subsidy is more beneficial to the BES industry than the first, as it encourages higher pay for more work.

Due to unreliability of power supply from national grid, high cost of diesel and maintenance of generators being an alternate for national grid, there is need to adopt a renewable energy source for efficient and reliable power supply. Savings associated with conversion of a stand-alone diesel generator powered system to a reliable PV/Diesel hybrid power system with energy storage in batteries for Bayero University Kano Library using HOMER software was presented in this study. The economic parameter of merit used in selecting an optimum energy system from set of configurations was total Net Present Cost (NPC) in billions of naira. Generator + PV + Battery system has a total NPC of (₦ 1.17B) and saves (₦ 0.9B), Generator + PV system has a total NPC of (₦ 1.68B) and saves (₦0.4B), Generator + Battery system has a total NPC of (₦ 2.05B) and saves (₦ 0.03B), PV + Battery system has a total NPC of (₦ 2.28B) and saves (₦ - 0.2B) when all compared with Generator-only system (₦ 2.08B). It can be seen that the best case is the PV + Gen + Battery system. Even though it has the highest capital cost, but it resulted to the least net present cost (NPC); as such, PV + Gen + Battery system is the optimized model to fulfill the load demands. Therefore, this research work shows that the integration of PV with battery storage into the existing diesel stand-alone system in the University library is more reliable at the lowest lifecycle cost.

The integration of electrical energy generated from renewable sources such as solar and wind power into the electricity grid faces the challenge of intermittent electricity output from these renewable sources. Storing the electricity during times of excess production and releasing the electrical energy to the grid during times of peak demand is an obvious solution. Rechargeable batteries are very attractive for energy storage because of their high energy efficiency and scalability. [1-3] Since grid-scale electrical energy storage at a global scale requires hundreds of gigawatt-hours to be stored, the batteries for this application must be inexpensive, robust, safe and sustainable. None of today’s mature battery technologies meet all of these requirements. In this presentation, we will summarize the recent research advancements in three aqueous battery systems that have the potential to meet the demanding requirements of grid-scale energy storage: (1) alkaline iron-air battery, (2) the iron-chloride redox flow battery and (3) a new aqueous organic redox flow battery. These three battery systems satisfy the primary criterion of using of inexpensive or abundantly-available and sustainable materials for energy storage. The use of toxic heavy metals is completely avoided. By careful selection of additives, the iron electrode of the alkaline iron-air battery can now be charged at high as C-rate with no more than 5% loss in faradaic efficiency to parasitic hydrogen evolution. The iron electrode also has a utilization 0.3 Ah/g and can be discharged continuously at rates as high as 3C. Such a high-performance iron electrode has also been cycled over 500 times without the loss of capacity or change in faradaic efficiency. Separated air electrodes based on carbon and spinel oxides can be charged and discharged with a significant reduction with overpotential losses not exceeding 250 mV at 10 mA/cm2. [4,5] The electro-deposition efficiency of the iron-chloride flow battery has been improved to as high as 95% with use of additives for complexing the iron (II) in solution and by controlling the pH to be higher than 2. An iron-chloride flow cell that uses an anion-exchange membrane for the transport of chloride ions has been operated successfully over multiple charge discharge cycles.We have advanced a new type of Organic Redox Flow Battery (ORBAT) that employs two different water-soluble organic redox couples on the positive and negative side of a flow battery. Compounds such as quinones are particularly suitable as redox couples. No precious metal catalyst is needed because of the fast proton-coupled electron transfer processes. The ORBAT cell uses a membrane-electrode assembly configuration similar to that used in polymer electrolyte fuel cells and can be charged and discharged multiple times at high faradaic efficiency without any noticeable degradation of performance. The ORBAT configuration presents a unique opportunity for developing an inexpensive and sustainable metal-free rechargeable battery for large-scale electrical energy storage. AcknowledgementsThe authors thank ARPA-E, US Army RDECOM, the University of Southern California, and the Loker Hydrocarbon Research Institute for funding the research.

Electrical energy storage in batteries and electrochemical capacitors (ECs) will be vital for any future success in the global effort to shift energy usage away from fossil fuels. A marked improvement in the performance of these power sources is critical for this effort, yet both are mature technologies with over two centuries worth of chemical energy storage in batteries, while the physical principles underlying storing charge at electrochemical interfaces date to Helmholtz.

Nitrogen-doped mesoporous carbon for energy storage in vanadium redox flow batteries