Stationary Energy Storage Applications Research Articles

A High Voltage Sodium Ion Battery Based on Low-Cost Sodium Iron Sulfate Cathode Material

It is desirable to develop alternative electrochemical devices with comparable performance but lower cost to substitute for lithium-ion batteries. Sodium-ion batteries show very similar electrochemical mechanism to lithium-ion batteries. The abundant sodium resource can considerably reduce the cost of energy storage devices as compared with lithium-ion batteries. In this work, a new derivative of sodium iron sulfates, Na6Fe5(SO4)8 (NFS), is developed as cathode material for sodium-ion batteries. The NFS is synthesized from sodium carbonate, sodium sulfate and iron sulfate raw materials, and it shows a high working voltage of 3.7 V vs. Na+/Na. When combined with carbon nanotube (CNT), the NSF@CNT composite demonstrates increased electronic conductivity and superior electrochemical performance. A 3.6 V sodium-ion full battery is constructed based on NFS@CNT cathode and hard carbon (HC) anode materials. Such a full NFS@CNT//HC cell can deliver an energy density towards 350 Wh kg-1 and cycling stability over prolonged 1000 cycles at 2 C. This work offers a low-cost sodium-ion full battery with an impressive high working voltage and energy/power densities for possible stationary energy storage applications.

“Hydrotriphylites” Li1–xFe1+x(PO4)1–y(OH)4y as Cathode Materials for Li-ion Batteries

Lithium iron phosphate LiFePO4 triphylite is now one of the core positive electrode (cathode) materials enabling the Li-ion battery technology for stationary energy storage applications, which are ...

Unravelling charge/discharge and capacity fading mechanisms in dual-graphite battery cells using an electron inventory model

The dual-ion battery (DIB) and a subtype thereof, the dual-graphite battery (DGB), are considered as promising alternative options for stationary energy storage applications. Here, we show that not only the working principle of DGBs is fundamentally different from ion-transfer cells, such as the lithium ion battery (LIB), but the capacity fading mechanisms as well. In order to compare the charge/discharge mechanism and aging processes of LIBs and DIBs, which are associated with loss/change of the active species content, a unified “electron inventory model” applicable for both battery systems is introduced and comprehensively explained. This model regards all electron-consuming or -donating reactions in the cell at the respective electrodes. Using the model, two predominant aging variants of DGBs can be distinguished. Both of these originate from disparate (parasitic) electron consumption/donation at the negative or positive electrode, respectively. However, there is an “electron balance” or “electron charge neutrality” between the electrodes, which intrinsically does not allow this difference: This is a consequence of redox reactions that must take place simultaneously at both electrodes in order to guarantee electronic charge neutrality. For example, if electron-consuming reactions occur at the negative electrode that consume lithium cations, the positive electrode is forced to intercalate additional anions for charge compensation, i.e. to ensure charge neutrality in the electrolyte. These anions are irreversibly trapped in the positive electrode and can no longer contribute to reversible charge/discharge reactions. Suitable countermeasures including the pre-lithiation of the negative electrode are presented in this work.

Tackling Capacity Fading in Vanadium Redox Flow Batteries with Amphoteric Polybenzimidazole/Nafion Bilayer Membranes.

Vanadium flow batteries are among the most promising technologies for stationary energy storage applications if their cost of storage can be further decreased. Capacity fading resulting from imbalanced vanadium crossover is a key operating cost component. Herein, a new approach is reported to avoid this cost by balancing electrolyte transport with amphoteric bilayer Nafion/meta-polybenzimidazole membranes. Within this system, the anion- and cation-exchange capacity can be tuned in a straightforward manner by changing the thickness of the respective polymer layer to balance electrolyte transport for a given current density. At high current densities, a net migrative flux of vanadium directed towards the positive side is observed owing to the higher average charge of vanadium ions present at the negative side. The coulombic repulsion between the vanadium ions and the positive charges in the membrane counteracts this migrative transport and can reverse the direction of the net vanadium flux. For a technically relevant current density of 120 mA cm-2 , a PBI thickness of 3-4 μm is required to balance the vanadium crossover and to minimize capacity fading.

Air-Stable NaxTMO2 Cathodes for Sodium Storage

Sodium-ion batteries are considered to be the most promising alternative to lithium-ion batteries for large-scale stationary energy storage applications due to the abundant sodium resource in the Earth' crust and as a result, relatively low cost. Sodium layered transition metal oxides (NaxTMO2) are proper Na-ion cathode materials because of low cost and high theoretical capacity. Currently most researchers focus on the improvement of electrochemical performance such as high rate capability and long cycling stability. However, for NaxTMO2, the structure stability against humid atmosphere is essentially important since most of them are instable in air, which is not favorable for practical application. Here we provide a comprehensive review of recent progresses on air-stable NaxTMO2 oxides. Several effective strategies are discussed, and further investigations on the air-stable cathodes are prospected.

(Industrial Electrochemistry and Electrochemical Engineering Division Student Achievement Award Address) Fundamental Understanding on Cell Performance Enhancement of Flow Batteries with Serpentine Flow Field Structures

Redox flow batteries are being considered for medium and large-scale stationary energy storage applications. In addition to storing energy by the intermittent resources, such as tide, wind and solar energy, the electrochemical flow battery systems could impact electricity generation and grid effectiveness by supporting energy storage for peaking shaving, load leveling and emergency back up [1,2]. In recent years, flow field designs, such as a serpentine flow field, evolved from proton exchange membrane (PEM) fuel cell have been experimentally demonstrated to deliver improved cell performance and boost cell capacity [3] as compared to flow batteries without flow field designs. However, the mechanisms causing enhanced higher limiting current density with serpentine flow field designs have not been fully understood. In this presentation, I will introduce a concept of maximum current density associated with the stoichiometric availability of the pressure-driven electrolyte flow penetrating into the porous carbon electrode from the from the serpentine flow channel [4-6]. Our three-dimensional model demonstrates that this maximum current density concept can explain the observed limiting current density achieved in a flow battery with a serpentine flow field structure [7]. We hope this fundamental understanding can contribute to a better elucidation of the mechanism on limiting the electrochemical performance and further optimization of flow batteries. Acknowledgement This work was partially supported by the “all-iron flow battery” project with a grant number of DE-AR0000352 funded by the program of the Advanced Research Projects Agency-Energy (ARPA-E) of the Department of Energy (DOE) of the United States. I (XK) would like to acknowledge the late Professor Joseph M. Prahl, who was my advisor and inspirational mentor.

State of Charge Estimation for Lithium-Bismuth Liquid Metal Batteries

Lithium-bismuth liquid metal batteries have much potential for stationary energy storage applications, with characteristics such as a large capacity, high energy density, low cost, long life-span and an ability for high current charge and discharge. However, there are no publications on battery management systems or state-of-charge (SoC) estimation methods, designed specifically for these devices. In this paper, we introduce the properties of lithium-bismuth liquid metal batteries. In analyzing the difficulties of traditional SoC estimation techniques for these devices, we establish an equivalent circuit network model of a battery and evaluate three SoC estimation algorithms (the extended Kalman filter, the unscented Kalman filter and the particle filter), using constant current discharge, pulse discharge and hybrid pulse (containing charging and discharging processes) profiles. The results of experiments performed using the equivalent circuit battery model show that the unscented Kalman filter gives the most robust and accurate performance, with the least convergence time and an acceptable computation time, especially in hybrid pulse current tests. The time spent on one estimation with the three algorithms are 0.26 ms, 0.5 ms and 1.5 ms.

Assessment of social sustainability hotspots in the supply chain of lithium-ion batteries

Lithium-ion batteries are considered a key component in mobile and stationary energy storage applications. However, the current technology is based on several critical materials, such as lithium, cobalt, nickel, manganese, and graphite, which are associated with various environmental and social impacts in their supply chain. While the environmental impacts of lithium-ion batteries have been investigated in numerous studies, little attention has been given to the potential social impacts. Therefore, an assessment of the social sustainability hotspots of lithium-ion batteries is carried out. The assessment is based on a spatially differentiated resource flow model of the supply chain. Data on social risks with respect to child labor, corruption, occupational toxics and hazards, and poverty are extracted from the Social Hotspots Database in openLCA. The results of the social assessment are discussed along with environmental and economic considerations to generate recommendations for improving supply chain sustainability.

Reduced Na2+xTi4O9/C Composite: A Durable Anode for Sodium-Ion Batteries

Sodium-ion batteries (SIBs) are potential cost-effective solutions for stationary energy storage applications. Unavailability of suitable anode materials, however, is one of the important barriers to the maturity of SIBs. Here, we report a Na2+xTi4O9/C composite as a promising anode candidate for SIBs with high capacity and cycling stability. This anode is characterized by a capacity of 124 mAh g–1 (plus 11 mAh g–1 contributed by carbon black), an average discharge potential of 0.9 V vs Na/Na+, a good rate capability and a high stability (89% capacity retention after 250 cycles at a rate of 1 C). The mechanisms of sodium insertion/deinsertion and of the formation of Na2+xTi4O9/C are investigated with the aid of various ex/in situ characterization techniques. The in situ formed carbon is necessary for the formation of the reduced sodium titanate. This synthesis method may enable the convenient synthesis of other composites of crystalline phases with amorphous carbon.

A highly reversible Co3S4 microsphere cathode material for aluminum-ion batteries

Aluminum-ion batteries (AIBs) have been regarded as a promising candidate for large-scale stationary energy storage applications based on their low cost, good safety and high volumetric capacity. However, the lack of suitable cathode materials with highly reversible aluminum storage has hindered their practical use. Here, we demonstrate a highly reversible AIB using porous Co3S4 microspheres as the cathode material. The microstructure gives Co3S4 a superior electrochemical performance to most other cathode materials for AIBs reported so far. It is further shown that the cell undergoes Al3+ intercalation/deintercalation with Co3+/Co2+ as a redox couple in the cathode, and electrochemical stripping/plating of metallic aluminum in the anode. We also found that the diffusion of Al3+ in the host Co3S4 is the key kinetic step that limits the discharge/charge current density. This work is a step forward in the development of a low-cost cathode material for high-performance AIBs and contributes to a better understanding of AIB chemistry.

Computational screening of electroactive indolequinone derivatives as high-performance active materials for aqueous redox flow batteries

The development of an organic-based aqueous redox flow battery (RFB) using quinone as an electroactive material has attracted great attention recently. This is because this battery is inexpensive, produces high energy density, and is environment friendly in stationary electrical energy storage applications. Herein, we investigate the redox potentials and solubilities of indole-5,6-quinone and indole-4,7-quinone derivatives in terms of the substituent effects of functional groups using theoretical calculations. Our results indicate that full-site substituted derivatives of indolequinone are more useful as active materials compared to single-site substituted derivatives. In particular, our calculations reveal that the substitution of –PO3H2 and –SO3H functional groups with multiple polar bonds is very effective in increasing the activity of the aqueous RFB. As a strategy to overcome the limitation that the aqueous solubility is intrinsically low because they are organic molecules, we suggest the substitution of functional groups with multiple polar bonds to the backbones of active organic materials. Among 180 indolequinone derivatives, 17 candidates that meet the redox potential standards (≦ 0.2 V or ≧ 0.9 V) and eight candidates with solubility exceeding 2 mol/L are identified. Three indolequinone derivatives that satisfy both conditions are finally presented as promising electroactive candidates for an aqueous RFB.

Investigating the Impact of Particle Size on the Performance and Internal Resistance of Aqueous Zinc Ion Batteries with a Manganese Sesquioxide Cathode

Aqueous zinc ion batteries are considered to be one of the most promising battery types for stationary energy storage applications. Due to their aqueous electrolyte, they are inherently safe concerning flammability and environmentally friendly. In this work, the strong influence of the particle size of manganese sesquioxide on the performance of the battery is investigated. Ball milling was used to decrease the particle diameter. The resulting powders were used as active material for the cathodes, which were assembled in coin cells as full cells together with zinc foil anodes and aqueous electrolyte. It was shown that about one third of the original particle size can nearly triple the initial capacity when charged with constant current and constant end-of-charge voltage. Additionally, smaller particles were found to be responsible for the collapse of capacity at high current densities. By means of electrochemical impedance spectroscopy, it was shown that particle size also has a large impact on the internal resistance. Initially, the internal resistance of the cells with small particles was about half that of those with big particles, but became larger during cycling. This reveals accelerated aging processes when the reactive surface of the active material is increased by smaller particles.

Observation of combination displacement/intercalation reaction in aqueous zinc-ion battery

Rechargeable aqueous Zinc-ion batteries (ZIBs) are regarded as the promising battery chemistry in stationary grid energy storage applications. Exploration of new zinc storage mechanism concepts is a feasible way to achieve high energy/power density. Herein, for the first time, we demonstrate the combination displacement/intercalation (CDI) reaction mechanism in aqueous ZIBs, as an example in Zn/Ag0.4V2O5 system. Unlike the classical intercalation/deintercalation storage mechanism, the CDI reaction mechanism enables more Zn2+ ions insertion into the host structure in two different sites, i.e. most of Ag+ in Ag0.4V2O5 replaced by Zn2+, and classical intercalation of Zn2+ in Ag0.4V2O5 and Zn2(V3O8)2. Importantly, the in-situ generation of highly conductive Ag0 matrix within the electrode provides high electronic conductivity. As a result, the Ag0.4V2O5 cathode performs excellent rate capability as well as long-term cycling performance (stable capacity of 144 mA h g−1 after 4000 cycles at 20 A g−1).

A new sodium iron phosphate as a stable high-rate cathode material for sodium ion batteries

Low-cost room-temperature sodium-ion batteries (SIBs) are expected to promote the development of stationary energy storage applications. However, due to the large size of Na+, most Na+ host structures resembling their Li+ counterparts show sluggish ion mobility and destructive volume changes during Na ion (de)intercalation, resulting in unsatisfactory rate and cycling performances. Herein, we report a new type of sodium iron phosphate (Na0.71Fe1.07PO4), which exhibits an extremely small volume change (~ 1%) during desodiation. When applied as a cathode material for SIBs, this new phosphate delivers a capacity of 78 mA·h·g−1 even at a high rate of 50 C and maintains its capacity over 5,000 cycles at 20 C. In situ synchrotron characterization disclosed a highly reversible solid-solution mechanism during charging/discharging. The findings are believed to contribute to the development of high-performance batteries based on Earth-abundant elements.

Molecular Dynamics Modeling of the Structure and Na+-Ion Transport in Na2S + SiS2 Glassy Electrolytes.

Solid-state sodium batteries, a relatively safe and potentially cost-effective energy-storage technology, have attracted increasing scientific attention recently for application in stationary grid-scale energy storage. Identifying solid electrolytes with high electrochemical stability and high Na+-ion conductivity at room temperature is critically important to enable high energy densities with enhanced rate capabilities. We evaluated sodium sulfide-silicon sulfide, xNa2S + (1- x)SiS2, glasses as potential glassy solid electrolytes (GSEs) using molecular dynamics (MD) simulations. We employed ab initio MD to determine ion conduction mechanisms, to calculate energy barriers for ion hops, and to correlate these to the local short-range structure of 0.50Na2S + 0.50SiS2 glass. To simulate much larger systems for accurately calculating the ionic conductivity, we parameterized empirical Buckingham-type potential and performed classical MD simulations. After validating these calculations by comparing the structure obtained from MD to that from X-ray scattering data, we calculated the ionic conductivity of these glasses for the range of 0.33 ≤ x ≤ 0.67 compositions. The calculated ionic conductivities at room temperature were in the range of ∼10-5 S/cm for the x = 0.50 composition and increased significantly with sodium sulfide ( x) content. These calculations provide theoretical insights into the role of Na2S content on the ionic conductivity of GSEs aiding in the selection of specific compositions to enhance the ionic conductivity.

An advanced Na-NiCl2 battery using bi-layer (dense/micro-porous) β″-alumina solid-state electrolytes

Sodium metal halide (Na-MH) batteries present tremendous opportunities for grid scale energy storage applications. In this work, we describe an advanced Na-MH battery operating at 190 °C using a bi-layer (thin dense/thick porous layers) β″-alumina solid-state electrolyte (BASE). The novel design of the bi-layer BASE promotes high Na-ion transportation by reducing the Na+ ion path length. The excellent battery performances are achieved with a stable capacity retention of 350 W h/kg up to >350 cycles (∼6 months). Moreover, owing to the thin dense layer of BASE, the round trip energy efficiency (or discharging energy density) of the tested battery shows an ∼8% increase compared to that of state of the art Na-MH battery reported in the literature. Results from this work clearly demonstrate that advanced Na-MH batteries using bi-layer BASEs can have significant impacts on improving battery performances at lower operating temperatures, and further stretch its feasibility in stationary energy storage applications.

Electrolytic solvent effects on the gassing behavior in LCO||LTO batteries

Li4Ti5O12 (LTO) is a promising anode material in both electrified vehicle and stationary energy storage applications for its superior rate capability and ultra-long cycle life. However, its widespread automotive utilization is hindered by electrolyte decomposition and gassing issues during high temperature (55 °C or higher) exposure. The exact mechanism of this gas generation is still not widely understood, and a specific commonly accepted solution for this issue has not yet been reported. In this study, LiCoO2/Li4Ti5O12 full cells are fabricated with three different electrolyte compositions and charged/discharged over different potential ranges (1.5–2.8 V, 1.5–2.9 V and 1.5–3.0 V) in room temperature or 60 °C. We find that the electrolyte component, in particular with respect to the cyclic carbonate content, exhibits significant influence on the gassing behavior; electron donating groups are helpful in gas suppression. Meanwhile, test temperature and up cut off voltage (UCOV) also influence the gassing behavior. For example, very limited gassing phenomenon is observed when the battery is tested at 60 °C or lower temperature with suitable electrolyte and UCOV below 2.9 V, while gas is produced when the UCOV is increased to 3.0 V or higher.

Advanced Intermediate Temperature Sodium-Metal Halide (Na-MH) Batteries for Stationary Energy Storage Applications

Recently, sodium-metal halide (Na-MH, or also called ZEBRA) batteries have been extensively investigated due to its potential application for large scale energy storage systems. Particularly, compared to the conventional high temperature (> 280oC) ZEBRA batteries, a Na-MH battery operated at intermediate temperature (IT< 200oC) presents several advantages such as longer cycle life, lower battery manufacturing cost, and easier thermal management, etc. b″-alumina (Na2O×5.33 Al2O3) is typically used for IT Na-MH batteries as Na ion conducting solid-state electrolytes. Thus, the fabricating a thinner b″-alumina solid-state electrolytes (BASE) that results in a high Na ion conductivity is critical to improve performances of IT Na-MH batteries. In here, we will present a new fabrication process for the BASE with a double-layer structure that can drastically reduce the thickness of the BASE. We have examined the conductivity and morphology of new BASEs using electrochemical impedance spectroscopy and SEM. The IT Na-MH batteries assembled using new BASEs are also tested up to 300 cycles, and show excellent energy density (~380 Wh/kg) and around trip efficiency (~95%). Figure 1

“Ni‐Less” Cathodes for High Energy Density, Intermediate Temperature Na–NiCl2 Batteries

AbstractAmong various battery technologies being considered for stationary energy storage applications, sodium–metal halide (Na–MH) batteries have become one of the most attractive candidates because of the abundance of raw materials, long cycle life, high energy density, and superior safety. However, one of issues limiting its practical application is the relatively expensive nickel (Ni) used in the cathode. In the present work, the focus is on efforts to develop new Ni‐based cathodes, and it is demonstrated that a much higher specific energy density of 405 Wh kg−1 (16% higher than state‐of‐the‐art Na–MH batteries) can be achieved at an operating temperature of 190 °C. Furthermore, 15% less Ni is used in the new cathode formula than that in conventional Na–NiCl2 batteries. Long‐term cycling tests also show stable electrochemical performance for over 300 cycles with excellent capacity retention (≈100%). The results in this work indicate that these advances can significantly reduce the raw material cost associated with Ni (a 31% reduction) and promote practical applications of Na–MH battery technologies in stationary energy storage systems.

A Two‐Electron Storage Nonaqueous Organic Redox Flow Battery

AbstractNonaqueous redox flow batteries based on redox‐active organic materials (ROMs) are attractive for stationary energy storage applications, but inferior energy densities are demonstrated in reported systems. To address this limitation, a nonaqueous organic flow battery using two‐electron anthraquinone anolyte and phenothiazine catholyte materials is developed. Structural tailoring leads to greatly improved solubilities with the cell potentials of 1.63 and 2.80 V for the first and second electron transfer reactions, respectively, of optimized ROMs. Doubled charge storage capacities indicative of 2e− reactions are achieved in proof‐of‐concept bulk electrolyte and flow cell demonstrations, albeit with only modest cyclability due to the limited stability of the second redox event. Although further improvement is still needed to attract practical interest, this study opens a promising pathway to increase the energy density for organic flow batteries and is expected to inspire more in‐depth studies of energy dense, stable ROMs.