ZEBRA Batteries Research Articles

Hollow nickel sources for improving nickel utilization in Zebra batteries

The Zebra (Na-NiCl2) batteries are regarded as a promising option for large-scale electrical energy storage due to their plentiful electrode material resources, high energy density, and safety features. In the cathode of Zebra battery, the nickel powders serve as both an active material and a conductive agent. In practice, its amount is significantly greater than its theoretical usage, often exceeding three times the theoretical amount. Hence, the presence of ultra-excessive nickel results in high material costs, posing obstacles to the wider implementation of Zebra batteries. To address this problem, we introduce hollow nickel source as active material to improve the nickel utilization in Zebra battery. In this work, we assemble Zebra batteries using nickel hollow spheres (NHS) with sizes of ∼200 nm, ∼500 nm, ∼1 μm and ∼ 5 μm as nickel source. The battery using NHSs with a size of 1 μm exhibits the best cycling performance and the lowest polarization voltage. By reducing the Ni(NHS, ∼1 μm)/NaCl mass ratio to 1.0, 60% theoretical capacity can be achieved after 170 cycles at 260 °C, which surpasses the traditional batteries using solid nickel source at the same Ni/NaCl ratio. This performance is comparable to that of traditional solid nickel sources with a mass ratio of 1.5 to NaCl. Therefore, using NHS as the nickel source in Zebra batteries reduces nickel usage by 33% without compromising performance.

Electrical Conductivity Measurements of the Binary NaCl-CaCl2, the Ternary NaCl-CaCl2-BaCl2 and the Quaternary NaCl-CaCl2-BaCl2-ZnCl2 Molten Salts

An emerging set of batteries, called the molten salts or all liquid battery, are designed for cheap energy storage and electrical grid buffering purposes (1). Some molten salt batteries are commercial or close to commercial like the ZEBRA, NaS and Ambri batteries, however, most of these battery technologies are still on an experimental, lower TRL level but can become increasingly important in the future as the shift towards more intermittent energy sources emerge and as the development of these batteries become more mature. One suggested battery technology is the Na-Zn battery (2). This battery technology is currently further investigated in the EU funded SOLSTICE project (Grant Agreement No 963599). The Na-Zn battery will have Na and Zn electrodes and the electrolyte – the molten salt – will be a NaCl-CaCl2 based electrolyte, with additions of BaCl2 or perhaps even BaCl2 and SrCl2. The NaCl content of the electrolyte gives the charge of the battery, CaCl2 lowers the operating temperature and BaCl2 and SrCl2 increases the density of the electrolyte. The operating temperature of the battery is approximately 600 °C and joule heat generated inside battery during charging and discharging due to resistance of the electrolyte allows to maintain this operating temperature. The composition of electrolyte changes with the battery state of charge hence the internal resistance of battery is not constant during normal operation. Therefore, precise data of electrical conductivity of the electrolyte is required for modelling its performance thermal balance.A method for measuring electrical conductivity has been built in the SINTEF laboratory. The setup used for the measurements is presented in Figure 1a. It consists of two tungsten electrodes immersed in molten electrolyte – one electrode is stationary and the other is moving inside a capillary. Position of the moving electrode inside the capillary is precisely controlled by a height gauge. Shielded thermocouple is used for measuring temperature. To avoid polarization of electrodes during measurement, electrical impedance spectroscopy (EIS) at open circuit potential is used. The principle of the method is that resistance between the electrodes is measured at different positions of the moving electrode inside the capillary. Measured resistance can be expressed by the following formula: R=R0+ρ·(l/A) Where R0 is the offset resistance of electrolyte outside capillary including resistance of electrodes and leads,ρ is the resistivity of electrolyte, l is the length between end of capillary and tip of the moving electrode, A is the area of the capillary. The measurement of resistance is repeated at different positions of the moving electrode relative to the chosen reference position. Since R0 and A are constant, resistivity can be calculated knowing only the tangent of function R = f(l) (Figure 1b) divided by A. The presented approach is characterized by high precision and robustness due to no requirement of cell constant values, which is problematic to estimate at high temperature. It is only based on relative movement of one electrode which is easy to control. In addition, a higher number of positions of the moving electrode at which the measurement is performed effectively helps to eliminate errors. Conductivity is the inverse resistivity. Electrical conductivity measurements were done at a range of temperatures, from 600 °C to 800 °C with 50 °C steps and the results are presented in the form of linear formulas intended for use in User Defined Functions in modelling.Conductivity of various chloride salt compositions containing NaCl, CaCl2, BaCl2 and ZnCl2 have been investigated using the presented technique. It is generally found that the electrical conductivity is almost linear with temperature increase in the range of liquidus temperature up to approximately 800 °C for the investigated electrolyte compositions. Above that region the relationship is not linear anymore. This region is not presented in this presentation. It is also found that the conductivity increases with increasing NaCl content and that larger cations like Ca and Ba reduce the conductivity of the molten salt. The method has proven very powerful to measure electrical conductivity on molten salts and the results are comparable to experimental results found in literature (3).

AlCl3-NaCl-ZnCl2 Secondary Electrolyte in Next-Generation ZEBRA (Na-ZnCl2) Battery

Increasing demand to store intermittent renewable electricity from, e.g., photovoltaic and wind energy, has led to much research and development in large-scale stationary energy storage, for example, ZEBRA batteries (Na-NiCl2 solid electrolyte batteries). Replacing Ni with abundant and low-cost Zn makes the ZEBRA battery more cost-effective. However, few studies were performed on this next-generation ZEBRA (Na-ZnCl2) battery system, particularly on its AlCl3-NaCl-ZnCl2 secondary electrolyte. Its properties such as phase diagrams and vapor pressures are vital for the cell design and optimization. In our previous work, a simulation-assisted method for molten salt electrolyte selection has shown its successful application in development of molten salt batteries. The same method is used here to in-depth study the AlCl3-NaCl-ZnCl2 salt electrolyte in terms of its phase diagrams and vapor pressures via FactSageTM and thermo-analytical techniques (Differential Scanning Calorimetry (DSC) and OptiMeltTM), and their effects on battery performance such as operation safety and charging/discharging reaction mechanism. The DSC and OptiMelt results show that the experimental data such as melting temperatures and phase changes agree well with the simulated phase diagrams. Moreover, the FactSageTM simulation shows that the salt vapor pressure increases significantly with increasing temperature and molar fraction of AlCl3. The obtained phase diagrams and vapor pressures will be used in the secondary electrolyte selection, cell design and battery operation.

Pore-Scale Micro-Structural Analysis of Electrode Conductance in Metal Displacement Batteries

Metal displacement batteries (MDBs), or liquid metal batteries, are an emerging technology with significant potential in providing high capacity, low-cost energy storage solutions, capable of addressing many of the challenges associated with storing energy from renewable sources. The key characteristic of metal displacement batteries is that at least one of the electrodes is in liquid state and a molten salt is used as an electrolyte. Since its original proposal in the 1960’s liquid metal batteries have re-emerged in recent years and different battery chemistries and designs have been explored, including Ca-Bi, Na-Sb, and many others [2,10]. Recently, Na-Zn liquid metal batteries have been studied as an alternative to other configurations, showing significant potential in achieving good performance for large-scale energy storage, while avoiding the high cost associated with some electrode materials such as Nickel or Lithium [7,8]. In past years, alternatives to all-liquid cells have emerged in the form of designs where the cell materials are a mixture of solids and liquids. Examples of this include the commercially available Zebra battery, where a Na-NiCl electrode pair is used [1,6]. These designs offer some of the advantages of all-liquid cells, while simultaneously mitigating many of the disadvantages of handling and operating a very high temperature system. Na-Zn have also been proposed for solid cathode designs, taking advantage of the lower cost of Zn over Ni [4,3].The cathode in these designs is composed of a porous structure, within which multiple chemical species can co-exist. Electrolyte components share the space with metal deposits,salt crystals, and other electrochemical reaction products. As a result, the micro-porous structure of this composite system is an important factor in determining the performance of the cell, as the spatial distribution of different materials can have an impact on the effective conductivity of the electrode [5,9]. The porous structure hosts complex multi-component mass transfer phenomena as well, potentially having an impact on the mass-transfer overpotential of the cell.This work aims to study the impact of the microstructural properties of the solid electrode in a liquid displacement battery, and their importance to the effective conductivity of the system. We have developed a computational tool that enables us to create randomized microstructures in 3D, representing the electrode-electrolyte assembly. We are able to preserve the desired physical characteristics by using target pore-size distributions and volume fraction input as seed parameters. We use this tool to generate representative structures and analyze their effective bulk conductivity by solving Laplace’s equation over the resulting domain, accounting for the different local conductivity of each material.This methodology is applied to a novel Na-Zn cell in order to assess the importance of the pore-scale properties of the cathode, as well as its material components, including solid Zn metal, solid NaCl deposits, and molten salt components. It is expected that different material arrangement configurations will induce heterogeneous current distributions in this system. Furthermore, the ionic composition of the electrolyte would be different at different charge levels, leading to additional variation through its charge/discharge cycle.Using this methodology, the range of different electrode phase configurations produced during operation can be studied in the absence of microstructure imaging data. A representative elementary volume for the Zn electrode assembly is analyzed to determine the best approach for up-scaled performance predictions of the Na-Zn cell. With this method, it is possible to acquire data to elucidate desirable or undesirable electrode structure properties of this system, providing insight which can be used for improving manufacture and operation of the cell. [1] Dustmann. “Advances in ZEBRA batteries”. J. Power Sources (2004).[2] Kim et al. “Liquid metal batteries: Past, present, and future”. ChemicalReviews (2013).[3] Lu et al. “An Intermediate-Temperature High-Performance Na-ZnCl2 Bat-tery”. ACS Omega (2018).[4] Lu et al. “Liquid-metal electrode to enable ultra-low temperature sodium-beta alumina batteries for renewable energy storage”. Nature Communications(2014).[5] Qiu et al. “Pore-scale analysis of effects of electrode morphology and electrolyteflow conditions on performance of vanadium redox flow batteries”. J. PowerSources (2012).[6] Sudworth. “The sodium / nickel chloride ( ZEBRA ) battery”. J. Power Sources (2001).[7] Xu et al. “Electrode Behaviors of Na-Zn Liquid Metal Battery”. Journal ofThe Electrochemical Society (2017).[8] Xu et al. “Na-Zn liquid metal battery”. Journal of Power Sources (2016).[9] Zhang et al. “Progress in 3D electrode microstructure modelling for fuel cellsand batteries: transport and electrochemical performance”. Progress in Energy(2019).[10] Zhang et al. “Liquid Metal Batteries for Future Energy Storage”. EnergyEnvironmental Science (2021). Figure 1

Stabilizing Metallic Na Anodes via Sodiophilicity Regulation: A Review.

This review focuses on the Na wetting challenges and relevant strategies regarding stabilizing sodium-metal anodes in sodium-metal batteries (SMBs). The Na anode is the essential component of three key energy storage systems, including molten SMBs (i.e., intermediate-temperature Na-S and ZEBRA batteries), all-solid-state SMBs, and conventional SMBs using liquid electrolytes. We begin with a general description of issues encountered by different SMB systems and point out the common challenge in Na wetting. We detail the emerging strategies of improving Na wettability and stabilizing Na metal anodes for the three types of batteries, with the emphasis on discussing various types of tactics developed for SMBs using liquid electrolytes. We conclude with a discussion of the overlooked yet critical aspects (Na metal utilization, N/P ratio, critical current density, etc.) in the existing strategies for an individual battery system and propose promising areas (anolyte incorporation and catholyte modifications for lower-temperature molten SMBs, cell evaluation under practically relevant current density and areal capacity, etc.) that we believe to be the most urgent for further pursuit. Comprehensive investigations combining complementary post-mortem, in situ, and operando analyses to elucidate cell-level structure-performance relations are advocated.

An advanced Ni–Graphite molten salt battery with 95 °C operating temperature for energy storage application

Based on the high safety and low costs, molten salt batteries (Na-S battery, liquid metal battery, ZEBRA battery, etc.) have received more and more attention as large-scale electrical storage technology. However, the high operating temperature of molten salt batteries is still one of the roadblocks that impeded their practical application. Here we present the novel Ni-graphite molten salt battery based on outstanding electrochemical reversibility of the Ni/NiCl2 redox and intercalation/de-intercalation chemistry of chloroaluminate anions in graphite. By using the low-cost, quaternary inorganic molten salt AlCl3/KCl/NaCl/LiCl as electrolyte, the as-designed Ni-graphite battery possesses low operating temperature of 95 °C, and average voltage about 1.7 V. The Ni-graphite battery delivers stable specific capacity of 174 mAh/g at 500 mA/g after 120 cycles, with the capacity retention rate of 98%. In addition, the Ni-graphite battery also shows low material costs about 113.6 $/kWh and high electrode energy density of 289 Wh/kg. This work develops an advanced molten salt battery with low operating temperature and high energy density, as well as provides an alternative means of developing future large-scale power storage equipment based on molten salt batteries.

Overview of Canada's energy storage related research activities: A perspective

Overview of Canada's energy storage related research activities: A perspective

Evaluating ZEBRA Battery Module under the Peak-Shaving Duty Cycles.

With the recent rapid increase in demand for reliable, long-cycle life, and safe battery technologies for large-scale energy-storage applications, a battery module based on ZEBRA battery chemistry is extensively evaluated for its application in peak shaving duty cycles. First, this module is tested with a full capacity cycle consisting of a charging process (factory default) and a discharging process with a current of 40 A. The battery energy efficiency (discharge vs. charge) is about 90%, and the overall energy efficiency is 80.9%, which includes the auxiliary power used to run the battery management system electronics and self-heating to maintain the module operating temperature (265 °C). Generally, because of the increased self-heating during the holding times that exist for the peak shaving duty cycles, the overall module efficiency decreases slightly for the peak-shaving duty cycles (70.7–71.8%) compared to the full-capacity duty cycle. With a 6 h, peak-shaving duty cycle, the overall energy efficiency increases from 71.8% for 7.5 kWh energy utilization to 74.1% for 8.5 kWh. We conducted long-term cycling tests of the module at a 6 h, peak-shaving duty cycle with 7.5 kWh energy utilization, and the module exhibited a capacity degradation rate of 0.0046%/cycle over 150 cycles (>150 days).

Life Cycle Assessment of an NMC Battery for Application to Electric Light-Duty Commercial Vehicles and Comparison with a Sodium-Nickel-Chloride Battery

This paper presents the results of an environmental assessment of a Nickel-Manganese-Cobalt (NMC) Lithium-ion traction battery for Battery Electric Light-Duty Commercial Vehicles (BEV-LDCV) used for urban and regional freight haulage. A cradle-to-grave Life Cycle Inventory (LCI) of NMC111 is provided, operation and end-of-life stages are included, and insight is also given into a Life Cycle Assessment of different NMC chemistries. The environmental impacts of the manufacturing stages of the NMC111 battery are then compared with those of a Sodium-Nickel-Chloride (ZEBRA) battery. In the second part of the work, two electric-battery LDCVs (powered with NMC111 and ZEBRA batteries, respectively) and a diesel urban LDCV are analysed, considering a wide set of environmental impact categories. The results show that the NMC111 battery has the highest impacts from production in most of the impact categories. Active cathode material, Aluminium, Copper, and energy use for battery production are the main contributors to the environmental impact. However, when vehicle application is investigated, NMC111-BEV shows lower environmental impacts, in all the impact categories, than ZEBRA-BEV. This is mainly due to the greater efficiency of the NMC111 battery during vehicle operation. Finally, when comparing BEVs to a diesel LDCV, the electric powertrains show advantages over the diesel one as far as global warming, abiotic depletion potential-fossil fuels, photochemical oxidation, and ozone layer depletion are concerned. However, the diesel LDCV performs better in almost all the other investigated impact categories.

Understanding the influencing factors of porous cathode contributions to the impedance of a sodium-nickel chloride (ZEBRA) battery

Molten-sodium beta-alumina batteries including sodium–sulfur (NAS) and sodium-metal chloride (ZEBRA) batteries have been considered as promising candidates for reliable low-cost stationary energy storage devices. The structural parameters of the porous cathode wetted by NaAlCl4 have been proved to be one of the important reasons for the degradation of ZEBRA batteries. Herein, the influencing factors of porous cathode on the impedance of Na–NiCl2 battery are investigated in detail. The interface between the NaAlCl4 catholyte and Ni/NaCl cathode material and the ratio of the conductive components in the cathode are discussed in this paper. Based on the wettability results of each component of the cathode material at different porosities and temperatures, the wetting behavior between NaAlCl4 and the porous cathode is summarized. Both the porosity and metal ratio of the cathode need to be considered in order to achieve the optimal catholyte/cathode material interface and minimum operating impedance. The proposed cathode parameters are porosity greater than 24% and conductive component ratio of 1.5 at NaAlCl4 ratio of 1.75. This work provides a quantitative guidance and deep understanding for the material design of ZEBRA battery cathodes.

(Invited) Advanced Intermediate Temperature Na-Metal Halide Batteries for Grid Applications

Developing battery systems that are inexpensive, enduring, and safe is essential for integrating renewable energy sources such as solar and wind power into the electricity grid and providing valuable grid services such as frequency regulation, peak shaving, and arbitrage. In this regard, Na-based batteries are promising candidates because they use naturally abundant sodium (Na) as the charge carrier, which can potentially reduce the materials cost and support multiple energy storage applications. Among various Na-based batteries developed to date, thorough investigations have been done on high-temperature (~300°C) Na-metal halide (Na-MH) batteries, which offer long cycle life and superior safety. In particular, the tubular sodium-nickel chloride (Na-NiCl2 or Zebra) battery has been commercialized and found wide application in the telecom and oil/gas industries. However, the high operating temperature and cost of the Zebra battery has hindered its further market penetration. Recently, the research of Na-MH battery has been focusing on the development of battery technologies operated at intermediate temperature (< 200oC), which has several advantages including simple cell architectures, improved thermal management, lower operating temperature, and lower manufacturing cost over high temperature Na based batteries. Here, we will introduce the mechanism of battery degradation, the development of advanced low-cost cathode materials, long-term cycle results, and the current status and prospects of scale up this promising battery technology.

(Invited) Low-Cost and High Rate Na-FeCl2 Batteries for Large Scale Energy Storage Applications

Developing battery systems that are inexpensive, enduring, and safe is essential for integrating renewable energy sources such as solar and wind power into the electricity grid and providing valuable grid services such as frequency regulation, peak shaving, and arbitrage. In this regard, Na-based batteries are promising candidates because they use naturally abundant sodium (Na) as the charge carrier, which can potentially reduce the materials cost and support multiple energy storage applications. Among various Na-based batteries developed to date, thorough investigations have been done on high-temperature (~300°C) Na-metal halide (Na-MH) batteries, which offer long cycle life and superior safety. In particular, the tubular sodium-nickel chloride (Na-NiCl2 or Zebra) battery has been commercialized and found wide application in the telecom and oil/gas industries. However, the high operating temperature and cost of the Zebra battery has hindered its further market penetration. Considering constraints of the Ni-based cell chemistry, it is highly desirable to develop an alternate cathode for Na-MH batteries towards next-generation energy storage applications. This pursuit, unsurprisingly, led us to the Fe/NaCl cathode. In this study, we present an advanced Na-FeCl2 battery with unprecedented high-rate performance and low cost for stationary energy storage applications. Operated at an extremely high current density of 33.3 mA/cm2 at 190°C, the cell can output 74% of its total capacity—a capacity retention double that of IT Na-NiCl2 cells. The origin of the high rate capability of Na-FeCl2 batteries was elucidated by means of comprehensive phase/structure analysis and electrochemical/electroanalytical characterizations. Moreover, Fe particle pulverization originating from liquid-phase reactions was determined to be the major source of capacity fading during long-term cycling. Accordingly, we designed a unique cathode with Ni additive, which delivered a high discharge specific energy density of over 295 Wh/kg for 200 cycles at C/5 with almost no capacity fading.

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

Summary Batteries with high safety, low cost, and reasonable energy density are essential for grid-scale energy storage and still remain elusive. Here, we report a solid electrolyte-based liquid lithium-brass/zinc chloride (SELL-brass/ZnCl2) battery using garnet-type lithium-ion solid electrolyte, lithium anode, and brass/ZnCl2 cathode. The chemistry of the cell reaction and the ability of being assembled in discharged state ensures a high safety. The use of low-cost ZnCl2 cathode can realize a low cell material cost of $16 kWh−1. The adoption of lithium anode guarantees a high theoretical energy density of 750 Wh kg−1 and 2,250 Wh L−1. Moreover, by using brass powder as a Zn source in the cathode, the Zn particle growth issue is successfully solved, and a good cycling stability of the battery can be obtained. As full cell performance and scalability are also verified, our SELL-brass/ZnCl2 battery shows a high potential for practical use in grid energy storage.

A Garnet-Type Solid-Electrolyte-Based Molten Lithium-Molybdenum-Iron(II) Chloride Battery with Advanced Reaction Mechanism.

Solid-electrolyte-based molten-metal batteries have attracted considerable attention for grid-scale energy storage. Although ZEBRA batteries are considered one of the promising candidates, they still have the potential concern of metal particle growth and ion exchange with the β"-Al2 O3 electrolyte. Herein, a Li6.4 La3 Zr1.4 Ta0.6 O12 solid-electrolyte-based molten lithium-molybdenum-iron(II) chloride battery (denoted as Li-Mo-FeCl2 ) operated at temperature of 250 °C, comprising a mixture of Fe and LiCl cathode materials, a Li anode, a garnet-type Li-ion ceramic electrolyte, and Mo additive, is designed to overcome these obstacles. Different from conventional battery reaction mechanisms, this battery revolutionarily synchronizes the reversible Fe-Mo alloying-dealloying reactions with the delithiation-lithiation processes, meaning that the porous Mo framework derived from Fe-Mo alloy simultaneously suppresses the growth of pure Fe particles. By adopting a Li anode and a Li-ion ceramic electrolyte, the corrosion problem between the cathode and the solid electrolyte is overcome. With similar battery cost ($12 kWh-1 ), the theoretical energy density of Li-Mo-FeCl2 battery surpasses that of a Na-FeCl2 ZEBRA battery over 25%, to 576 Wh kg-1 and 2216 Wh L-1 , respectively. Experimental results further prove this cell has excellent cycling performance (472 mAh gLiCl -1 after 300 cycles, 50 mg active material) and strong tolerance against the overcharge-overdischarge (3-1.6 V) and freezing-thawing (25-250 °C) incidents.

Low-Cost and High Rate Na-FeCl2 Batteries for Large Scale Energy Storage Applications

Developing battery systems that are inexpensive, enduring, and safe is essential for integrating renewable energy sources such as solar and wind power into the electricity grid and providing valuable grid services such as frequency regulation, peak shaving, and arbitrage. In this regard, Na-based batteries are promising candidates because they use naturally abundant sodium (Na) as the charge carrier, which can potentially reduce the materials cost and support multiple energy storage applications. Among various Na-based batteries developed to date, thorough investigations have been done on high-temperature (~300°C) Na-metal halide (Na-MH) batteries, which offer long cycle life and superior safety. In particular, the tubular sodium-nickel chloride (Na-NiCl2 or Zebra) battery has been commercialized and found wide application in the telecom and oil/gas industries. However, the high operating temperature and cost of the Zebra battery has hindered its further market penetration. Considering constraints of the Ni-based cell chemistry, it is highly desirable to develop an alternate cathode for Na-MH batteries towards next-generation energy storage applications. This pursuit, unsurprisingly, led us to the Fe/NaCl cathode. In this study, we present an advanced Na-FeCl2 battery with unprecedented high-rate performance and low cost for stationary energy storage applications. Operated at an extremely high current density of 33.3 mA/cm2 at 190°C, the cell can output 74% of its total capacity—a capacity retention double that of IT Na-NiCl2 cells. The origin of the high rate capability of Na-FeCl2 batteries was elucidated by means of comprehensive phase/structure analysis and electrochemical/electroanalytical characterizations. Moreover, Fe particle pulverization originating from liquid-phase reactions was determined to be the major source of capacity fading during long-term cycling. Accordingly, we designed a unique cathode with Ni additive, which delivered a high discharge specific energy density of over 295 Wh/kg for 200 cycles at C/5 with almost no capacity fading.

ICE/HPM generator range extender for a series hybrid EV powertrain

This study discusses an optimised auxiliary power unit for applications in series hybrid electric vehicles (SHEVs). The auxiliary power source consists of an internal combustion engine (ICE) and a hybrid permanent magnet (HPM) generator. The ICE acts as a prime mover to the HPM generator the electrical output of which is connected to the vehicle DC-link via a passive rectifier. The vehicle primary energy is supplied by a ZEBRA battery system while the ICE/HPM generator provides a range extension. The SHEV performance is evaluated over some driving cycles using performance indicators such as driving range, fuel consumption, emissions and, battery utilisation. A dynamic model of the ICE/HPM generator system is developed and a vehicle range, with consideration of the battery dynamics, is numerically evaluated via a simulation platform. The predicted results are compared with measurements from a laboratory prototype HPM generator system, which shows a good agreement hence validating the models and simulation platform.

Understanding and Engineering Interfacial Transport in K-β′′-Alumina at Room Temperature

Aided by Prof. Huggins’s contributions1, the research and development of sodium beta-alumina solid electrolytes led to the commercialization of the molten sodium-sulfur battery, used today for grid-scale energy storage. Sodium-sulfur and ZEBRA batteries typically operate above 300 °C, and recent efforts have explored lowering the operating temperature to 100-200 °C2–4. The melting point of sodium is 98 °C, but its alloy with potassium (Na-K) has a eutectic melting point of -13 °C and is a liquid metal at room temperature with a capacity in the liquid region of 580 mAh/g (using K). Na-K has seen recent attention for batteries with organic electrolytes5 as well as for flow batteries using K-β′′-alumina 6, since polycrystalline sodium beta-alumina is not compatible with Na-K. A key challenge in using beta-alumina at low temperatures is transport through the interfaces. We discuss transport through the interfaces in a Na-K — K-β′′-alumina — aqueous potassium ferrocyanide (model posolyte) battery. On the Na-K — K-β′′-alumina interface, although Na-K does not wet K-β′′-alumina at room temperature, we find a form of reactive wetting, given certain conditions, that nearly eliminates the interfacial resistance between Na-K and K-β′′-alumina. On the aqueous posolyte — K-β′′-alumina interface, we find that ion exchange of hydrogen/hydronium species and K+ increases the interfacial resistance substantially over time, but this can be greatly decreased through modifying the solution chemistry.7 Understanding and engineering the interfaces of beta-alumina may enable novel applications of this amazing fast ionic conductor at low temperatures. References Whittingham, M. S. & Huggins, R. A. J. Chem. Phys. 54, 414 (1971).Lu, X. et al. Energy Environ. Sci. 6, 299–306 (2013).Lu, X. et al. Nat. Commun. 5, 4578 (2014).Li, G. et al. Nat. Commun. 7, 10683 (2016).Xue, L. et al. Adv. Mater. 28, 9608–9612 (2016).Baclig, A. C. et al. Joule 2, 1287–1296 (2018).McConohy, G. et al. Solid State Ionics 337, 82–90 (2019).

A molten battery consisting of Li metal anode, AlCl3-LiCl cathode and solid electrolyte

High performance rechargeable batteries are urgently needed to address the demands of grid-scale stationary energy storage. High temperature battery systems, such as Na-S battery, Na-NiCl2 battery (ZEBRA battery) and liquid metal electrode (LME) battery, exhibit advantages like high power density and high cyclic stability, but also suffer from the high operating temperature. We recently invented new concept of molten lithium metal batteries, consisting of liquid lithium anodes, alloy (Sn, Bi, Pb) liquid cathodes and lithium ion conductor as solid electrolytes. Here we demonstrate a molten metal chloride battery that operates at a relatively low temperature of 210 °C. The battery has been designed to include molten (AlCl3-LiCl) cathode, solid electrolyte (garnet-type Li6.4La3Ta0.6Zr1.4O12 (LLZTO) ceramic tube) and molten lithium anode. The assembled AlCl3-LiCl||LLZTO||Li full cell has an average discharge voltage of 1.55 V and energy efficiency of 83% and has been successfully cycled for 100 cycles (800 h) without capacity fade. The theoretical specific energy of cell is 350 Wh/kg and the estimated cost is $11.6/kWh based on the weight of electrode materials. Considering the high performance, high safety, low operating temperature and low cost of raw materials, our new type of molten-electrode battery system opens up new opportunities for stationary energy storage.

Performance Improvement of Zebra Batteries By Using a Simple and Functional Planar Architecture

ZEBRA batteries (Zero Emission Battery Research Activities) for their high energy and power density are one of the possible solutions to electrical storage for stationary applications. These systems are based on nickel chloride-sodium cells operating at high temperatures (about 270°–350 °C), and rely on a ceramic β”-alumina tube or planar membrane as solid electrolyte. In this work, recent results generated from 3 cm2 button cells, including base line cell performance, cell design and chemistry will be presented. The activity was directed to the realization of two new planar configuration of a beta sodium battery, that means the study of a planar sealing between the metal and the ceramic components. This battery, as many other electrochemical storage technologies, may play an important role for the transmission and distribution of electricity, because it can satisfy, in a very flexible way, many different needs (voltage and frequency control, self consumption of stochastic renewable energy, peak shaving etc.). For this purpose the storage system has to be characterized not only by a suitable energy capacity, but by quick response and high power performance too. A planar configuration could optimize the battery in terms not only of energy density (already satisfactory for this kind of batteries), but also of power density (still to be improved). The planar configuration could also provide a better stack design and thermal regulation. This battery utilizes a ceramic material as the ionic membrane between the anodic and cathodic semi cells and so it has to operate at 300°C. The current form of the β”-alumina membrane is “glass shaped” in order to contain the reagents, so the possible planar shape has to include a sealing system able to contain the reagents, which are in liquid status at the high temperature of the battery and they are also highly chemical reactive, especially the liquid sodium. In particular the research activity was previously directed to the study of the components of the seal between the metal bodies of the semi cells and the ceramic beta alumina and afterwards to a new configuration of the sealing system. The studied materials were insulating paints, ceramic pastes and glass seals and they were tested in order to assess their chemical stability in presence of sodium and their mechanical stability during thermal cycling. The research activity was addressed to define the right geometry of the ceramic support of the β”-alumina. Another purpose was to define a mechanical seals between the ceramics support and metallic body of the two, anodic and cathodic, electrodic compartments. A new activity was started to realize a new configuration in which also the body of battery was realized in ceramic material (α-Alumina), which allows a greater wettability in the anodic compartment. The mono cell was realized with a new sealing system, composed by a new geometry of a ceramic ring to contain the beta alumina membrane and to guarantee the mechanical stability. In both planar configurations of the cell made, it has been noticed that this type of design reduces the volume of the cathodic and anodic semi cell; in this way, not only the energy density is increased but also the power density is improved. Furthermore, the planar design would improve the stack geometry and its thermal distribution. The problems faced in this work were the material resistance to the chemical attack of liquid sodium at high temperature, the mechanical resistance and the compensation of the different thermal expansion coefficient between the solid electrolyte (β-alumina) and the metallic body. The first button cell consisted of two battery cases (stainless steel) for cathode and anode sides, a Nichel network cathode current collector, a stainless steel anode current collector, an α-alumina (99.5% purity) fixture and a planar composite yttria-stabilized zirconia (YSZ)/ BASE (3 cm2 active area) disc. The second buttom cell consisted of battery cases (α-Alumina) for cathode and anode sides, a steel plate held by a spring as a current collector both at the anode and at the cathode (the use of springs makes it possible to better exploit cathodic and anodic active materials), an α-alumina (99.5% purity) fixture and a planar composite yttria-stabilized zirconia (YSZ)/ BASE (3 cm2 active area) disc. It is using an inexpensive stacked design to improve performance at lower temperatures, leading to a less expensive overall storage technology. The new design greatly simplifies the manufacturing process, providing a subsequent pathway to the production of scalable, modular batteries at half the cost of the existing tubular designs.

Effect of Halide Doping on the Structure and Properties of Na3SbS4 Solid Electrolyte

Compared to Li-ion batteries, rechargeable sodium (Na) batteries hold much promise for medium and large-scale energy storage systems due to the decreased price, natural abundance and suitable electrochemical window of Na metal. In addition to Na-S and ZEBRA batteries, solid-state Na batteries that operate at room temperature are highly desirable. To realize this target, solid electrolytes with highly ionic conductivities are necessitated. Na3SbS4 is a newly discovered Na-ion conductor [1] and exhibits an excellent ionic conductivity of 1 mS cm-1. To further improve its performance in solid-state Na batteries, faster Na-ion transportation through Na3SbS4 is expected. In this report, we introduced halide ions into Na3SbS4 solid electrolyte and studied doping effect on the crystal structure and conductive properties of Na3SbS4. It was found that the iodide (I-) doping expanded the lattice structure of Na3SbS4 without generating a new phase. Tuning the dopant concentration led to an overall higher ionic conductivity in doped Na3SbS4. The enhancement of ionic conductivity is explained by the creation of vacancies due to alivolent anion substitution. Reference [1] Wang, H., Chen, Y., Hood, Z.D., Sahu, G., Pandian, A.S., Keum, J.K., An, K. and Liang, C., An Air‐Stable Na3SbS4 Superionic Conductor Prepared by a Rapid and Economic Synthetic Procedure. Angewandte Chemie International Edition, 2016, 55(30), pp.8551-8555.