Large-scale Electrical Energy Storage Research Articles

High performance phenothiazine-based battery materials achieved by synergistic steric blocking and extended conjugation

Phenothiazine derivatives, as sustainable cathode materials for batteries, show significant promise for large-scale electrical energy storage applications. However, the irreversibility of the sulfur redox active center severely limits their energy density and discharge voltage in rechargeable organic batteries. This study concentrates on identifying the potential side reactions that contribute to the irreversibility of phenothiazine-based materials. We propose a molecular design strategy that synergistically blocks the active site and extends the conjugation, markedly improving the electrochemical reversibility of these materials. Our findings reveal that phenothiazine derivatives can undergo two successive, one-electron redox reactions without interference from chemical bond rearrangement and reactive radicals. The assembled cells, utilizing lithium (Li) and sodium (Na) as anodes, display two distinct discharge plateaus at 3.3/3.9 V vs. Li+/Li and 3.1/3.7 V vs. Na+/Na, respectively, with nearly identical contributions from the nitrogen (N) and sulfur (S) redox centers. The phenothiazine derivatives designed via this strategy rank among the few phenothiazine-based organic electrode materials capable of achieving highly reversible, two-electron transfer redox reactions in organic batteries.

Comparison of Fluid Dynamics of Different Flow Geometries in an Iron Flow Battery Prototype

Introduction: Renewable energy sources demand is increasing in the world due to their less environmental effect. Solar and wind energy, which requires largescale electrical energy storage, are major contributors to this growth. The iron flow battery is one of the Redox flow battery technologies, which is encouraging for electrical energy storage because of their long lifetime, flexibility to increase storage, and minimum chemical hazard compared to conventional batteries Method: In this research, the engineering design and fabrication of a locally made Iron flow battery prototype is described. Then, electrolyte flow simulation was carried out through COMSOL Multiphysics to compare the fluid velocity and pressure profiles in three different flow geometries such as plain, parallel, and serpentine, to select the most compatible flow pattern for the Iron flow battery. Result: The resulting velocity profiles indicated that plain flow had stagnated points, the parallel flow had uneven velocity distribution, and serpentine flow had a uniform and high-velocity profile. The simulation results of pressure profiles showed the serpentine, parallel, and plain flows had inlet pressures of 34.38 Pa, 10.01 Pa, and 0.254 Pa, respectively. Conclusion: Given that pumping power is directly proportional to the pressure gradient, the power requirement of electrolyte pumps from highest to lowest is as serpentine flow, parallel flow, and plain flow.

The Critical Analysis of Membranes Towards Sustainable and Efficient Vanadium Redox Flow Batteries.

Vanadium redox flow batteries (VRFB) are a promising technology for large-scale storage of electrical energy, combining safety, high capacity, ease of scalability, and prolonged durability; features which have triggered their early commercial implementation. Furthering the deployment of VRFB technologies requires addressing challenges associated to a pivotal component: the membrane. Examples include vanadium crossover, insufficient conductivity, escalated costs, and sustainability concerns related to the widespread adoption of perfluoroalkyl-based membranes, e.g., perfluorosulfonic acid (PFSA). Herein, we review recent advances in high-performance and sustainable membranes for VRFB, offering insights into prospective research directions to overcome these challenges. Our analysis reveals the disparities and trade-offs between performance advances enabled by PFSA membranes and composites, and the lack of sustainability in their final applications. We discuss the potential of PFSA-free membranes and present strategies to enhance their performance. Our study delves into vital membrane parameters to enhance battery performance, suggesting protocols and design strategies to achieve high-performance and sustainable VRFB membranes. This article is protected by copyright. All rights reserved.

Thermodynamic performance investigation of environmentally friendly working fluids in a geothermal integrated pumped thermal energy storage system

Abstract Among the available energy storage technologies, pumped thermal energy storage (PTES) is emerging as a potential solution for large-scale electrical energy storage with no geographical limitations and high roundtrip efficiencies. However, PTES requires a low-cost, high-temperature heat source to achieve reasonable roundtrip efficiencies. Moreover, organic Rankine cycle-based PTES systems require high-performance and environmentally friendly working fluids. In this study, the thermodynamic performance of a geothermal integrated PTES system using environmentally friendly working fluids is investigated. The mathematical model of the geothermal integrated PTES system is developed using the first and second laws of thermodynamics and implemented in Engineering Equation Solver (EES). With the developed model, the thermodynamic performance of the PTES system for different working fluids, including Butene, cyclopentane, iso-butane, R1233zd(E), R1234ze(Z), R1224yd(Z), HFO1336-mzz(Z), R365mfc, n-hexane, and n-pentane was investigated. For geothermal fluid outlet temperatures between 60°C and 120°C and geothermal fluid inlet and outlet temperature differences across the evaporator between 20°C and 60°C, the net power ratio i.e., the ratio of the electrical energy discharged to the electrical energy used to run the charging cycle, is between 0.25 and 1.40. This shows that the system has the potential to give back more than 100% of the electrical energy used during charging under certain conditions. High net power ratios are obtained for a combination of high source temperatures and low geothermal fluid inlet and outlet temperature differences.

Vanadium redox flow battery: Characteristics and application

Renewable energy such as solar energy and wind energy will enter a new period of development. However, the output power of photovoltaic power generation has great randomness. In order to ensure the normal operation of the whole photovoltaic power generation system, it is particularly important to introduce smooth power dynamics of energy storage system (ESS) to ensure electrical stability. As an energy storage device, flow batteries will develop in the direction of large-scale and modularization in the future. The flow battery system can easily realize computer automatic control and is an ideal smart battery. In addition, the combination of flow batteries with photovoltaic cells, wind power stations, tidal power stations, biogas power stations and other renewable energy systems is an important category and content in developing the application fields of flow batteries. As a new type of green battery, Vanadium Redox Flow Battery (VRFB) has the advantages of flexible scale, good charge and discharge performance and long life. It is suitable for large-scale electric energy storage and has attracted wide attention in recent years. In this paper, the characteristics and applications of liquid flow battery and VRFB are summarized. This paper starts from introducing ESS, analyzing several types of flow batteries, and finally focusing on VRFB to analyze its technical characteristics and application market.

Electrospun Na3MnTi(PO4)3/C film: A multielectron-reaction and free-standing cathode for sodium-ion batteries

With the continuous advancement of renewable energy sources, sodium-ion batteries are currently regarded as highly promising technologies for large-scale electric energy storage. The compound Na3MnTi(PO4)3 has garnered significant attention owing to its exceptional theoretical capacity, robust structural stability, and abundant availability of resources. Herein, hierarchical carbon-decorated Na3MnTi(PO4)3 nanofibers are synthesized via a feasible electrospinning technique followed by pyrolysis, effectively addressing the issue of poor electronic conductivity in phosphate cathodes. The free-standing Na3MnTi(PO4)3/C electrode serves as a cathode for sodium-ion batteries, exhibiting exceptional electronic conductivity and superior Na+ transport capability. Moreover, it demonstrates an impressive reversible capacity of 171.4 mA h g−1 at 0.2C and exhibits outstanding cyclic stability with a capacity retention of 63.7 % after 6300 cycles at 1C. The full cell, assembled with independent Na3MnTi(PO4)3/C cathode and hard carbon anode, exhibits a reversible capacity of 153.7 mA h g−1 at a current density of 10 mA g−1. The in-situ synthesis of nanomaterial particles within interconnected porous nanocarbon fibers can effectively enhance the materials' poor electronic conductivity, thereby further improving their cyclic stability and Na+ transport kinetics.

Probing Degradation in Lithium Ion Batteries with On-Chip Electrochemistry Mass Spectrometry.

The rapid uptake of lithium ion batteries (LIBs) for large scale electric vehicle and energy storage applications requires a deeper understanding of the degradation mechanisms. Capacity fade is due to the complex interplay between phase transitions, electrolyte decomposition and transition metal dissolution; many of these poorly understood parasitic reactions evolve gases as a side product. Here we present an on-chip electrochemistry mass spectrometry method that enables ultra-sensitive, fully quantified and time resolved detection of volatile species evolving from an operating LIB. The technique's electrochemical performance and mass transport is described by a finite element model and then experimentally used to demonstrate the variety of new insights into LIB performance. We show the versatility of the technique, including (a) observation of oxygen evolving from a LiNiMnCoO2 cathode and (b) the solid electrolyte interphase formation reaction on graphite in a variety of electrolytes, enabling the deconvolution of lithium inventory loss (c) the first direct evidence, by virtue of the improved time resolution of our technique, that carbon dioxide reduction to ethylene takes place in a lithium ion battery. The emerging insight will guide and validate battery lifetime models, as well as inform the design of longer lasting batteries.

Probing Degradation in Lithium Ion Batteries with On‐Chip Electrochemistry Mass Spectrometry**

AbstractThe rapid uptake of lithium ion batteries (LIBs) for large scale electric vehicle and energy storage applications requires a deeper understanding of the degradation mechanisms. Capacity fade is due to the complex interplay between phase transitions, electrolyte decomposition and transition metal dissolution; many of these poorly understood parasitic reactions evolve gases as a side product. Here we present an on‐chip electrochemistry mass spectrometry method that enables ultra‐sensitive, fully quantified and time resolved detection of volatile species evolving from an operating LIB. The technique's electrochemical performance and mass transport is described by a finite element model and then experimentally used to demonstrate the variety of new insights into LIB performance. We show the versatility of the technique, including (a) observation of oxygen evolving from a LiNiMnCoO2 cathode and (b) the solid electrolyte interphase formation reaction on graphite in a variety of electrolytes, enabling the deconvolution of lithium inventory loss (c) the first direct evidence, by virtue of the improved time resolution of our technique, that carbon dioxide reduction to ethylene takes place in a lithium ion battery. The emerging insight will guide and validate battery lifetime models, as well as inform the design of longer lasting batteries.

The Nanostructured Future of Electrolytes

Lithium-ion and lithium-metal batteries with cobalt-free high-energy cathodes, as well as the newly emerging batteries employing post-lithium ions as charge carriers, are a few topics tackled in recent years for the development of batteries with higher energy density, lower cost, and improved sustainability. While all of them could (and will) be improved over time, electrolytes are prominent because of their ease of adapting to current technologies. Conventional organic electrolytes are usually flammable, toxic, and harmful to humans and the environment. For these reasons, over the years, several alternatives have been proposed. Ionic Liquids1 are promising from a safety point of view, being non-volatile and non-flammable, but they are usually fluorinated to meet specific performance standards. Another sustainable and cost-efficient approach is represented by the Water-in-salt electrolytes (WiSEs)2,3, given that the used salt is sustainable itself. Finally, the newest approach is to tackle the solubility properties of salts to obtain locally concentrated electrolytes using non-solvating solvents4. For all of the proposed new technologies, their impressive properties seem to emerge from the peculiar structural organizations of the species in the system. Therefore, employing experimental (SAXS and Raman) and computational (MD and DFT) techniques to comprehensively understand how the chemical species interact in such systems, is mandatory to further progress in the research.Figure 1: a) Snapshot of the simulation box of a Locally Concentrated electrolyte. The ionic liquid comprise the worm-like structures, the solvent is only depicted on the left side as a transparent medium. b) coordination numbers as a function of salt concentration in a Water-in-salt electrolyte. c) X-ray scattering patterns for ionic liquid electrolytes and locally concentrated ionic liquid electrolytes at two different temperatures (20 °C top, and -20 °C bottom).References1 J. S. Wilkes, A short history of ionic liquids—from molten salts to neoteric solvents, Green Chemistry, 2002, 4, 73–80.2 L. Suo, F. Han, X. Fan, H. Liu, K. Xu and C. Wang, ‘water-in-Salt’ electrolytes enable green and safe Li-ion batteries for large scale electric energy storage applications, J Mater Chem A Mater, 2016, 4, 6639–6644.3 J. Han, A. Mariani, S. Passerini and A. Varzi, Energy Environ Sci, 2023, https://doi.org/10.1039/D2EE03682G4 X. Liu, A. Mariani, H. Adenusi and S. Passerini, Angewandte Chemie - International Edition, 2023,https://doi.org/10.1002/ange.202219318. Figure 1

Insights into P-Type Iron- and Manganese-Based Layered Sodium Cathodes

Sodium-ion batteries are a low-cost alternative to lithium-ion batteries in large-scale electric energy storage applications due to the natural-abundant sodium resources and similar working principle to LIBs during cycling [1]. Until now, many different cathodes for SIBs have been studied, including layered transition metal oxides (NaxTMO2, x<1), Prussian blue-type compounds, polyanionic and organic compounds [2]. Among them, NaxTMO2 has been extensively reported, due to its layered structure, easy synthesis, promising electrochemical properties, and feasibility for commercial production [3]. According to the occupation of Na ions and oxygen stacking, NaxTMO2 can be classified into P2 and O3 types, where P2 structure contasins trigonal prismatic sites of sodium ions and ABBA oxygen stacking sequence and O3 structure represents octahedral sites of sodium ions and ABCABC oxygen stacking sequence [4]. At low potentials (<2.0V), there is a phase transition P2-P2’ connected with the manganese redox activity and the Jahn-Teller distortion [5]. Compared with O3-type structure, P2-type NaxTMO2 provides higher specific capacity and better structural stability due to the lower diffusion barriers through Na-ion prismatic sites [6].Iron- and manganese-based layered oxides for sodium-ion batteries have attracted renewed interest due to their low cost and environmental friendliness. However, the phase change at high voltage and the Jahn-Teller effect lead to shortening cycle life and poor rate capability. We design a structure optimization of the Na2/3Mn1/2Fe1/2O2 cathode through a partial substitution of Fe3+ to explore the mechanism of redox activity of P2-type Mn/Fe-based layered cathodes. We present the investigation of the effect of simultaneous cationic substitution on the electrochemical performance and structural stability of P2-Na2/3Mn1/2Fe1/2O2. The obtained material exhibits a solid solution mechanism during desodiation/resodiation process and delivers an initial discharge capacity of 168 mA h g-1 at 0.1C and a capacity retention of 80% after 50 cycles. The modified P2 composition has stable cycle performance in the potential window from 1.5V to 4.5V. The main focus here is to understand the fundamental electrochemical mechanism of this layered cathode material by exploring the redox processes of transition metal cations and oxygen anions upon cycling. In situ X-ray synchrotron radiation diffraction is used to explore the structural changes during cycling. In situ X-ray Absorption Near Edge Spectroscopy is used to elucidate the local electronic structure of Fe and Mn atoms as it evolves throughout this electrochemical process. 23Na solid-state nuclear magnetic resonance spectroscopy is used to investigate Na coordination environments during desodiation/resodiation. Ex situ soft X-ray absorption spectroscopy results reveal the participation of oxygen anions in the electrochemical reactions. Thus, we explore the redox reactions of transition metals and oxygen to explain the mechanism and the electrochemical performance for the P2-type Mn/Fe-based layered cathodes.

Shunt Current Analysis of Vanadium Redox Flow Battery System with Multi-Stack Connections

Vanadium redox flow battery (VRFB) systems with multiple stacks due to long lifetime, low self-discharge, and flexible design, are commonly used in large-scale electrical energy storage applications In a VRFB system, pumps deliver positive and negative electrolytes to each stack through a piping system including channels and manifolds. However, the electrolyte flowing between cells through channels and manifolds and the electrolyte flowing between stacks through pipes are electrically conductive. Shunt currents are generated due to the voltage difference between the cells and between the stacks, which reduce the energy efficiency of the battery system. In particular, under different load connections, the shunt currents of a multi-stack VRFB system have different distributions and cause different impairments to the system efficiency. Therefore, it is important to predict the shunt currents of the multi-stack system under different load connections before the actual construction of the system. In this paper, a multi-stack VRFB system with 120 cells was explored by circuit-based modeling to evaluate the shunt currents according to the stack configuration such as serial, parallel, and mixed connections.Then, the Coulomb efficiencies (CEs) were investigated with operating currents at 36 and 54A. The results show that shunt currents are generally more significant at the center cell of a stack than at other cells under these stack configurations and exhibit a positive correlation with the battery state of charge (SOC), i.e., larger shunt currents increase with SOC. In addition, the CEs of the system are higher at 54A compared to those at 36A due to smaller shunt current losses regardless of the stack configurations. Furthermore, regardless of the operating current levels, the multi-stack system connected by parallel loads achieves the highest CEs compared to the series and mixed connected systems due to the absence of shunt current losses in the piping system. Figure 1

High-Resolution Electron Microscopic Characterization of Surfaces and Interfaces of Calcium in Calcium-Sulfur Batteries

As we globally realize large-scale electrical energy storage coupled with the rapid increase in global electromobility, the challenge of securing a consistent supply of critical raw materials utilized in lithium-ion batteries (LIB) continues to grow. Consequently, the search for alternative systems delivering comparable energy densities has become an important topic. Multivalent metals, renowned for their long-term stability, emerge as promising candidates in this regard.The combination of calcium and sulfur represents a potent alternative, attributed to their abundant availability and recent research delineating the appreciable stability of their electrolyte system 1. Nevertheless, to enhance fabrication efficiency, performance, and stability, a deeper understanding of the electrochemical dynamics at the anode surface, where the electrolyte interfaces with calcium, is essential. The work in the Casino project aims for an understanding and optimization of key aspects towards its application.Outer surfaces, shared with the electrolyte system are central to battery health, dictating its longevity and efficiency, making their degradation a critical aspect affecting the overall battery degradation. Therefore, investigating all galvanic surfaces stands paramount to this study. Drawing parallels with LIB systems, the application of artificial or potential optimization of natural Solid-Electrolyte Interphases (SEI) presents itself as a viable strategy to further stability within the full cells of Ca-S batteries. Envisioning the manufacturing, galvanic processes may offer significant merits for battery production, regarding its ability to build natural SEI layers.This work leans on a detailed exploration of battery systems sharing similar electrochemical foundations with galvanic systems, asserting that an investigation into galvano systems can furnish vital insights not only into the fabrication process but also unravel the undercurrent processes active during battery charging. A focal point of this research is the internal surfaces, which potentially delivers data to the understanding the electrochemical reactions, which produces the particle-like structures.In our pursuit to further unravel the intricacies of the internal particle surfaces, we used Focused Ion Beam (FIB) as preparation method to craft lamellas (see Fig.) from galvanic plating samples generated using both pulsed and constant currents. Despite the soft nature of the material posing challenges in FIB preparation, refined techniques were utilized to mitigate these issues. The analysis extended to Scanning Transmission Electron Microscopy (STEM) observations, intending to offer spectroscopic insights. Energy-Dispersive X-ray Spectroscopy (EDX) coupled with Electron Energy Loss Spectroscopy (EELS) for a detailed chemical characterization. This approach aimed to unravel bonding configurations and potential electronic transitions during the battery's operational life and to identify the potential variations in material phases or the presence of different chemical components. This approach afforded a closer look at the atomic arrangements potentially influencing the electrochemical properties.The project was financially supported by the Bundesministerium für Bildung und Forschung (BMBF), under project CaSino, Grant number (Förderkennzeichen) 03XP0487D.[1] Li, Z., Fuhr, O., Fichtner, M. & Zhao-Karger, Z. Towards stable and efficient electrolytes for room-temperature rechargeable calcium batteries. Energy Environ. Sci. 12, 3496–3501 (2019). Figure 1

Experimental studies on dynamic performance of 250-kW alkaline electrolytic system

Alkaline water electrolysis is a mature hydrogen production technology and an important means for future large-scale green hydrogen production and electrical energy storage, while enhancing and optimizing its dynamic characteristic speed is the urgent problem to achieve this goal. In this study, the dynamic response characteristics of the system current, voltage, temperature, hydrogen to oxygen (HTO) and pressure parameters are experimentally investigated at two levels (start-stop and variable load processes) and three-time scales (hours, minutes and seconds) based on the 250-kW industrial alkaline water electrolysis system. The experimental study of cold start (25 °C)→full load (90 °C)→hot shutdown (75 °C)→hot start (70 °C)→full load (90 °C)→cold shutdown (30 °C) revealed that the response time of start-stop process is hourly and temperature is the main limiting factor. The response time of HTO is on the order of minutes based on the variable load test: full load (3500 A, 1.7 MPa)→minimum load (1400 A, 1.7 MPa)→full load (3500 A, 1.7 MPa)→minimum load (800 A, 0.6 MPa). The response of HTO to parameter changes has severe time delay and inertia links, and the latter with significantly longer response time. The response time for different current step is in the order of seconds. This experimental study points out the dynamic performance level of industrial-scale alkaline water electrolysis system at the present stage and provides directions for the optimization of dynamic performance indexes, which is an important guideline for designing control strategies that integrate with renewable energy sources.

Comprehensive Review of Liquid Air Energy Storage (LAES) Technologies

In recent years, liquid air energy storage (LAES) has gained prominence as an alternative to existing large-scale electrical energy storage solutions such as compressed air (CAES) and pumped hydro energy storage (PHES), especially in the context of medium-to-long-term storage. LAES offers a high volumetric energy density, surpassing the geographical constraints that hinder current mature energy storage technologies. The basic principle of LAES involves liquefying and storing air to be utilized later for electricity generation. Although the liquefaction of air has been studied for many years, the concept of using LAES “cryogenics” as an energy storage method was initially proposed in 1977 and has recently gained renewed attention. With the growing need for alternative energy storage methods, researchers have increasingly explored the potential of cryogenic media, leading to the development of the first LAES pilot plant and a growing body of research on LAES systems. However, one notable drawback of LAES is its relatively low round-trip efficiency, estimated to be around 50–60% for large-scale systems. However, due to its thermo-mechanical nature, LAES offers versatility and can be easily integrated with other thermal energy systems or energy sources across a wide range of applications. Most of the existing literature on LAES focuses on thermodynamic and economic analyses, examining various LAES configurations, and there is a clear lack of experimental studies in this field. This paper aims to conduct a comprehensive review of LAES technology, with a focus on the performance enhancement of these systems. Future perspectives indicate that hybrid LAES solutions, incorporating efficient waste energy recovery sections, hold the most promise for enhancing the tech-no-economic performance of standalone LAES systems.

Thermodynamic and Economic Analysis of a Liquid Air Energy Storage System with Carbon Capture and Storage for Gas Power Plants

Liquid air energy storage (LAES) technology is helpful for large-scale electrical energy storage (EES), but faces the challenge of insufficient peak power output. To address this issue, this study proposed an efficient and green system integrating LAES, a natural gas power plant (NGPP), and carbon capture. The research explores whether the integration design is theoretically feasible for future adoption in operating the LAES system and NGPP. The effect of the charging pressure, the number of air expansion stages, and electricity prices on the overall thermodynamic and economic characteristics are investigated. The round-trip efficiency and the exergy round-trip efficiency of the proposed system are 47.72% and 69.74%, respectively. The calculations show that the minimum dynamic payback period for such a project is 3.72 years, and the lowest levelized cost of electricity is 0.0802 USD·kWh−1. This work provides a reference for peak-shaving power stations with energy storage and carbon capture.

Ultra-Long Cycle of Prussian Blue Analogs Achieved by Equilibrium Electrolyte for Aqueous Sodium-Ion Batteries.

Aqueous sodium-ion batteries have promising prospects in large-scale electrical energy storage, which lack of suitable cathode with high specific capacity and long cycle lifespan, unfortunately. Manganese-based Prussian blue analogs (PBAs) (KMnHCF/NaMnHCF) are ideal candidates for low-cost and high theoretical specific capacity merits. But the rapid decline hinders their application, due to side reactions caused by water imbalance. Here, an equilibrium strategy, which can balance the interstitial water supplement and water attack, is proposed. As proof of the concept, xCS (x: proportion, CS: co-solvent, such as polyethylene glycol and trimethyl phosphate) equilibrium electrolytes areintroduced to solve the rapid decline. Assisting with the electrolyte, KMnHCF realizes excellent performance (10 000 cycles), which is beyond most cathode materials of sodium-ion batteries. The full batteries composed of KMnHCF cathode and NaTi2 (PO4 )3 anode also display outstanding performance (7000 cycles) and promising application prospects at low-temperature and engineering scenes. And then, the equilibrium electrolyte concept isverified by NaMn0.8 Fe0.2 HCF and NaMnHCF, proving its universality for low-cost and long-life manganese based PBAs.

Thermal runaway propagation behavior of the Cell-to-Pack battery system

Structurally compact battery packs significantly improve the driving range of electric vehicles. Technologies like Cell-to-Pack increase energy density by 15%–20%. However, the safety implications of multiple tightly-packed battery cells still require in-depth research. This paper studies thermal runaway propagation behavior in a Cell-to-Pack system and assesses propagation speed relative to other systems. The investigation includes temperature response, extent of battery damage, pack structure deformation, chemical analysis of debris, and other considerations. Results suggest three typical patterns for the thermal runaway propagation process: ordered, disordered, and synchronous. The synchronous propagation pattern displayed the most severe damage, indicating energy release is the largest under the synchronous pattern. This study identifies battery deformation patterns, chemical characteristics of debris, and other observed factors that can both be applied to identify the cause of thermal runaway during accident investigations and help promote safer designs of large battery packs used in large-scale electric energy storage systems.

A Flexible Six-in-One Microsensor Embedded in a Vanadium Redox Flow Battery for Long-Term Monitoring.

The vanadium redox flow battery (VRFB) can be used as a supporting technology for energy storage corresponding to wind and solar power generation. An aqueous vanadium compound solution can be used repeatedly. As the monomer is large, the flow uniformity of electrolytes in the battery is better, the service life is long, and the safety is better. Hence, large-scale electrical energy storage can be achieved. The instability and discontinuity of renewable energy can then be solved. If the VRFB precipitates in the channel, there will be a strong impact on the flow of vanadium electrolyte, and the channel could even be blocked as a result. The factors which influence its performance and life include electrical conductivity, voltage, current, temperature, electrolyte flow, and channel pressure. This study used micro-electro-mechanical systems (MEMS) technology to develop a flexible six-in-one microsensor which can be embedded in the VRFB for microscopic monitoring. The microsensor can perform real-time and simultaneous long-term monitoring of the physical parameters of VRFB, such as electrical conductivity, temperature, voltage, current, flow, and pressure to keep the VRFB system in the best operating condition.

Engineering of Sodium-Ion Batteries: Opportunities and Challenges

The recent proliferation of sustainable and eco-friendly renewable energy engineering is a hot topic of worldwide significance with regard to combatting the global environmental crisis. To curb renewable energy intermittency and integrate renewables into the grid with stable electricity generation, secondary battery-based electrical energy storage (EES) technologies are regarded as the most promising solution, due to their prominent capability to store and harvest green energy in a safe and cost-effective way. Due to the wide availability and low cost of sodium resources, sodium-ion batteries (SIBs) are regarded as a promising alternative for next-generation large-scale EES systems. This review discusses in detail the key differences between lithium-ion batteries (LIBs) and SIBs for different application requirements and describes the current understanding of SIBs. By comparing technological evolutions among LIBs, lead-acid batteries (LABs), and SIBs, the advantages of SIBs are unraveled. This review also offers highlights on commercial achievements that have been realized based on current SIB technology, focusing on an introduction of five major SIB companies, each with SIB chemistry and technology, as well as commercialized SIB products. Last but not least, it discusses outlooks and key challenges for the commercialization of next-generation SIBs.

Thermodynamic analysis of a hybrid system combining compressed air energy storage and pressurized water thermal energy storage

Large-scale electrical energy storage is an urgent requirement currently. This paper presents a hybrid system integrating compressed air energy storage (CAES) with pressurized water thermal energy storage (PWTES). The open type isothermal compressed air energy storage (OI-CAES) device is applied to the CAES subsystem to achieve near-isothermal compression of air. Meanwhile, the heat storage capacity of liquid water is improved by pressurization in the PWTES subsystem. Electricity is converted directly to heat through joule-resistive heating to improve the temperature of pressurized water. Moreover, the thermodynamic model of the hybrid system and the transient mathematical model of the OI-CAES in the four stages of intake, compression, exhaust and expansion are developed in this paper. The effects of design parameters on the working process of OI-CAES with and without spraying are the focus of the study. Furthermore, three different cases of the hybrid system are analyzed. The results show that the increase in tank height or tank volume is beneficial to restrain the variation of air temperature in the operation of OI-CAES when there is spraying, and the fluctuation range of the air temperature with spraying can be controlled within 25.7 K. When the tank volume is 5 m3 and the flow rate of the pump unit is 10 m3/h, the maximum temperature rise of the air in the compression process of OI-CAES can be managed within 30.5 K and 11.5 K respectively when there is no spraying and spraying. When the water in the PWTES subsystem supplies thermal energy, the efficiency of the CAES subsystem of the hybrid system can achieve 91.9 % with the energy storage density being 2.28 kWh/m3. When the hybrid system provides thermal energy through heat transfer, the energy efficiency of the hybrid system is expected to reach 65.6 %. With the supply of thermal energy, the flow rate of heating water can be flexibly adjusted and the heating water supply temperature is able to meet 363.16 K. Without the supply of thermal energy, the electrical efficiency of the hybrid system can reach 53.7 %.