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The operation of a liquid metal battery involves multiple physical fields, such as electrochemical reaction, mass transfer, heat transfer, fluid flow, magnetic field, etc. It is of great significance to closely couple these physical phenomena. Flow is an important phenomenon in liquid metal batteries, and its generation mechanism is also diverse. Flow can be triggered by temperature fields, electromagnetic fields, or concentration fields. In this work, we firstly established a multi-field coupled model for Li‖Bi liquid metal battery. Through this model, we compared and analyzed the various flow types in the molten salt and the positive electrode, and further discussed the effects of flow on mass transfer and electrochemical performance.

Sodium-based liquid metal batteries are well suited for stationary energy storage due to their long life, intrinsic safety, and ease of scale-up. However, the irreversible alloying reaction between the positive current collector (PCC) and the cathodes at high temperatures leads to severe capacity degradation of the battery, severely limiting its scale-up application. In this work, a Bi-Sb-Sn alloy cathode based on a synergistic stabilization mechanism was designed for the first time. Due to the density difference of Bi, Sb, and Sn and the compatibility difference of Bi and Sn with the PCC, a part of Bi and Sn is spontaneously distributed in the region close to the PCC. The protection of Sb is realized by blocking the contact of Sb with the PCC as well as removing the PCC material dissolved in the cathode to prevent the loss of active material. Based on such protection, the Na||Bi 36 Sb 24 Sn 40 cell maintained 99% Coulombic efficiency for 450 cycles at a rate of 0.75 C, with a capacity retention of 99.56% and a capacity decay rate of 0.001% per cycle. In addition, the interaction of Bi, Sb, and Sn during discharge also promotes capacity release and energy efficiency. At 0.3 C, the Na||Bi 36 Sb 24 Sn 40 cell achieved 89% capacity utilization and 82% energy efficiency. These results provide an idea for the design of other batteries based on liquid metal electrodes.

Because of their low cost, excellent safety, and simple structure, liquid metal batteries have drawn a lot of interest in the field of large-scale electrochemical energy storage. The application of this energy storage technology is inseparable from the efficient thermal management system for battery temperature management and control. The thermal management system can consume less electrical energy and hence enhance the efficiency of the liquid metal battery by leveraging the inherent thermal power of the fully employed battery. This paper profiles the self-generated thermal power characteristics based on an electrochemical–thermal model that fully accounts for the multiple physical environments.

Liquid metal batteries (LMBs) are a promising grid-scale storage device however, the scalability of this technology and its electrochemical performance is limited by mass transport overpotentials. In this work, an alternative design concept for the battery aimed at reducing mass transport overpotentials, increasing cell capacity, and improving electrochemical cell performance was implemented and evaluated. The design consisted of a coil implanted in the cathode, which induced mixing in the layer. Four cases were compared: three in a 241 Ah LMB at 0.3, 0.5 and 1 A/cm2, and one in a larger 481 Ah LMB at 0.5 A/cm2. LMB performance was determined by comparison against baseline diffusion cases and a change in molar fraction of 0.1. The modified LMB exhibited dramatic performance increases with a 78% and 85% reduction in mass-transport overpotentials at 0.3 A/cm2 and 0.5 A/cm2, respectively. The improved performance of the battery was directly attributed to the flow generated in the cathode. It was found that the coil substantially increased the poloidal volumetric average velocity. Periodically, vortices formed that removed concentration gradients from the cathode–electrolyte interface, minimising concentration polarisation. The viability of the design was tested in a lab-scale prototype using Galinstan as the working fluid. The velocity of the induced flow was determined using particle image velocimetry (PIV), and the results compared to the numerical model. There was a close match between the experimental and numerical results, validating the numerical model and the viability of the design. Implementation of this design concept in future LMBs could lead to the realisation of extended discharge capacities and improved voltages. Future work is planned to test the coil in a working battery. [Display omitted] • Design concept for mass transfer enhancement. • A small coil is used to generate a mixing electro-vortex flow. • The coil minimally increases ohmic overpotentials. • Large areal capacities with minimal mass transport overpotentials are achieved. • PIV results of the liquid metal flow in a prototype validate the numerical model. [ABSTRACT FROM AUTHOR]

Long-cycle-life, high-safety liquid metal batteries (LMBs) are considered competitive alternatives for large-scale energy storage applications. LMBs typically operate at high temperatures, and reducing their operating temperature has been a focus of research. In this study, we adopt a multi-cation molten salt LiCl-KCl-CsCl as the electrolyte for LMBs and achieve the stable operation of Li|LiCl-KCl-CsCl|Bi battery at 300 °C for the first time. However, the lower operating temperature significantly deteriorates the kinetic performance, resulting in a capacity utilization of only about 30 %. To address this issue, we apply a certain intensity of magnetic field to the battery using Helmholtz coils, which increases the capacity utilization to 100 %. This study combines the strategy of low-temperature LMBs with external magnetic field regulation, not only achieving a low operating temperature but also ensuring complete capacity release. Furthermore, this approach paves the way for the potential use of permanent magnets within battery modules to provide the magnetic field environment, without the risk of demagnetization. • Adopted multi cation LiCl-KCl-CsCl salt as the electrolyte for liquid metal batteries. • Achieved stable operation of Li.||Bi liquid metal batteries at 300 °C • Enhanced battery capacity utilization through the application of external magnetic fields. • Lower working temperatures facilitate easier self-heating of battery modules. [ABSTRACT FROM AUTHOR]

This study is a continuation of the combined experimental and numerical investigation [1] of the flow of the eutectic GaInSn alloy inside a cylindrical vessel exposed to a constant electrical current. The emerging electrovortex flow driven by the interaction of the current, which is applied through a tapered electrode, with its own magnetic field might have both detrimental and advantageous effects in liquid metal batteries. While the former work [1] was mainly concerned with time-averaged results, this paper focuses on the transient behaviour of the electrovortex flow which becomes most relevant under the influence of an external axial field. The additional Lorentz force generated by the interaction of the imposed current with the vertical component of the geomagnetic field bz drives the ordinary electrovortex jet flow into a swirling motion. Velocity distributions and motion characteristics, such as spiral streamlines and shortened and irregularly swinging jet regions, are investigated. The mechanism is analysed in detail for bz =--25.5 µT. The maximum angular velocity of the rotating jet is basically linearly dependent on bz, at least for the values studied here. A good agreement between the transient simulation and the experimental result is shown. [ABSTRACT FROM AUTHOR]

The implementation of Li-based liquid metal batteries (LMBs) for grid-scale energy storage has been limited by the high cost of materials, especially for fabrication of Li-halide based molten salt electrolytes (e.g., LiCl, LiBr, LiF, LiI). This study aims to determine the impact of incorporating lower cost alkali/alkaline earth halide salts with foreign cations (e.g., Sr2+, K+) into a Li-based molten salt electrolyte to build a foundation for continued LMB electrolyte design and development. The widely reported LiF–LiCl–LiBr (22-31-47 mol%, T m = 430–443 °C) electrolyte is used within the Li || Sb–Sn LMB system as a baseline from which to compare the performance of similar systems with eutectic salts of LiCl–SrCl 2 (64.3–35.7 mol%, T m = 489 °C) and LiCl–KCl (59.2–40.8 mol%, T m = 352 °C) with a specific focus on the positive Sb–Sn electrode in a 3-electrode cell. While good chemical reversibility was maintained for the Li || Sb–Sn systems with mixed-cation molten salts, a shift in the electroactive species from Li + to Sr2+ limited the capacity of the LMB system with a LiCl–SrCl 2 electrolyte and reduced rate capability was observed for the LiCl–KCl containing system. • Studied the impact of mixed-cation electrolytes on Sb–Sn electrode performance. • Performance maintained for LiCl–KCl system at low current density. • Limited rate capability observed for LiCl–KCl system at high current density. • LiCl–SrCl 2 electrolyte resulted in Sr as the dominant electroactive species. [ABSTRACT FROM AUTHOR]

• Novel array current collector configuration is designed for LMBs. • The system achieves ultra-high energy efficiency. • In-situ observation reveals the nucleation and growth process of discharge products. • More efficient contact modes and mass transfer interfaces. Liquid metal battery (LMB) is one of the most competitive large-scale energy storage technologies due to its low-cost, long-lifespan, and high-safety. However, the low energy efficiency of the battery is currently one of the major challenges hindering its application process. The problem of poor wettability of the cathode liquid alloy is exacerbated by the design of the conventional planar structure of the positive collector. And the resulting interfacial mass transfer modes are inefficient. These lead to slow electrode reaction kinetics and large internal polarization. To address this issue, a novel array current collector suitable for LMB was designed here for the first time. The unique structure of the collector greatly increases the effective reaction area at the electrolyte/cathode and the contact area of the cathode/collector, providing more efficient nucleation and growth modes of the products as well as richer ionic mass-transfer channels, thus accelerating the electrode reaction kinetics. Benefiting from the application of the array current collector, the voltage efficiency of Li||Sb-Sn LMBs with a capacity of 20 Ah at 0.5C rate is increased by 4.8 %. Meanwhile, an average voltage efficiency of ∼ 94.7 % and an average energy efficiency of ∼ 92.2 % are achieved at 0.1C, which is the highest efficiency among the most promising LMB systems known to date. These encouraging results provide new directions for the design of high-performance LMBs and further promote the practical process of LMBs. [ABSTRACT FROM AUTHOR]

[Display omitted] • The displacement reaction between Na and molten LiCl-NaCl-KCl in LMBs was revealed. • The effect of pressure on the interactions between Na and molten LiCl-NaCl-KCl was revealed. • The designed Na+-free electrolyte significantly suppressed the self-discharge of Na-based LMBs. • The designed Na-based LMB ran over 2500 cycles with a capacity retention near 100%. Sodium liquid metal battery has attracted attention for large-scale energy storage applications due to its low-cost, long-lifespan and high-safety. However, the self-discharging caused by sodium dissolving in the molten salt electrolyte reduces the efficiency of the battery and restricts the practical development of this chemistry. In this work, a low-melting point multi-cationic electrolyte (LiCl-NaCl-KCl) was designed to inhibit the dissolution of sodium in the electrolyte. The displacement reaction of Na and molten LiCl at high temperature were revealed for the first time, and the mechanism of improving battery performance was demonstrated in the Na| LiCl-NaCl-KCl |Sb-Bi batteries. Based on the displacement reaction mechanisms, the Na||Bi 9 Sb cell based on LiCl-KCl (54:46 mol%) electrolyte, without NaCl at the initial state, was constructed, which exhibited high coulombic efficiency of over 98 % and excellent cyclic performance (∼100 % capacity retention after 2500 cycles) at 450 °C. This work provides a unique idea of electrolyte design that can both inhibit the dissolution of metals in molten salts and ensure long-term stable battery operation by using electrolyte–electrode interactions, and provides a new way for the practical development of low-cost and long-lifespan liquid metal battery energy storage technology. [ABSTRACT FROM AUTHOR]

Mass transfer is of paramount importance for an efficient operation of liquid metal batteries. We show for the first time that electrodynamically driven flow can indeed improve mixing of liquid electrodes, and reduces concentration polarisation substantially. Simulating the discharge of a realistic Li||Bi cell at 1 A/cm2, the corresponding overpotential reduces by up to 62%. Moreover, the formation of intermetallic phases is delayed, which improves capacity usage. Finally, we demonstrate that vertical magnetic fields – which are originating from external sources – change the flow structure entirely, and will homogenise the positive electrode even better.

• Power networks can use inexpensive liquid metal batteries for large-scale energy storage. • Liquid metal batteries' special structure can prevent dendritic development and minimize safety risks. • The study of liquid metal electrolytes is less than that of liquid electrodes, hence the focus must be shifted to electrolyte research. • Liquid metal batteries' electrolyte issue must be resolved for them to function in low-temperature conditions. Liquid metal batteries possess stable safety performance, high rate performance, and thermal stability. The liquid metal battery stores a large amount of electrical energy producing from wind energy or solar energy. The remarkable performance of the liquid metal batteries is partly attributed to electrolyte, which is an important component of the battery. In this paper, the important research progress of liquid metal batteries electrolyte are reviewed and the electrolyte types which have an influence on energy efficiency are discussed in detail. Then, the limitations and challenges of existing electrolytes are also pointed out. On this basis, the key development directions of liquid metal electrolytes are discussed and clarified. [Display omitted] [ABSTRACT FROM AUTHOR]

The advanced electrolyte of liquid metal battery should have low melting point, low ionic solubility, low viscosity, high electric and thermal conductivities, and a suitable density between anode and cathode for declining the operating temperature and realizing the goal of saving-energy. In this study, an excellent quaternary LiF-LiCl-LiBr-LiI (9.1 : 30.0 : 21.7 : 39.2) electrolyte is refined by using thermodynamic models to balance various properties of LiX (X=F, Cl, Br, I) and meet the requirement of advanced electrolyte of liquid metal battery. The refined properties of electrolyte correspond to 2.398 g/cm 3 for density, 0.286 mol% for solubility, 4.486 Ohm -1  cm -1 for ionic conductivity, and 0.609 W m -1 for thermal conductivity. The measured melting point is 609.1 K, which is lower than the current operating temperature of 723 K for the lithium-based liquid metal battery. The refined electrolyte consisted by quaternary halide molten-salt provides important references for preparing the advanced liquid metal battery., (© 2023 Wiley-VCH GmbH.)

The electrical potential in a battery jumps at each electrode-electrolyte interface. We present a model for computing three-dimensional current and potential distributions, which accounts for such internal voltage jumps. Within the framework of the finite volume method we discretize the Laplace and gradient operators such that they account for internal jump boundary conditions. After implementing a simple battery model in OpenFOAM we validate it using an analytical test case, and show its capabilities by simulating the current distribution and discharge curve of a Li‖Bi liquid metal battery. [ABSTRACT FROM AUTHOR]

• A Thevenin model is used to simulate the dynamic behaviors of liquid metal batteries. • A co-estimator is developed to concurrently estimate the state and model parameters. • The AUKF is employed to estimate the state of charge for liquid metal batteries. • The accuracy and robustness of the co-estimator are verified through experiments. Liquid metal battery (LMB) is a novel battery technology that shows great application potential in the electric energy storage system. For the utilization of battery systems, an accurate estimate of the state of charge (SOC) for LMBs is of great significance. However, there are still many challenges need to be addressed due to the relatively low voltage and flat open-circuit-voltage versus SOC curve of LMBs. In this work, a novel state and parameter co-estimator is developed to concurrently estimate the state and model parameters of a Thevenin model for LMBs. The adaptive unscented Kalman filter is employed for state estimation including the battery SOC, and the forgetting factor recursive least squares is applied for online parameter estimation, which increase the model fidelity and further enhance the accuracy and robustness of the SOC estimation. A comparison with other algorithms is made based on the experimental data from laboratory-made LMBs. The evaluation results show that the proposed co-estimator exhibits the smallest root mean square error of 0.21% and is robust to external disturbances. [ABSTRACT FROM AUTHOR]

Abstract Liquid metal battery (LMB) is a newly developing energy storage technology with promising prospect for electric energy storage applications. However, few research efforts have been put into estimating the state of charge (SOC) of LMBs yet, which is of great significance for the battery utilization. In this paper, an adaptive unscented Kalman filter is developed for online estimating the state of a battery model for LMBs, including the SOC and the model parameters. Simultaneously estimated parameters ensure high fidelity of the model and hence facilitate a trustworthy SOC estimation. The algorithm is robust to external disturbances on account of the adaptive estimation of the process and measurement noise covariances. Experimental results show that the proposed algorithm has a satisfactory performance in the estimation of both the SOC and the model parameters. [ABSTRACT FROM AUTHOR]

Abstract The battery is one of the most important components in electrochemical energy storage systems (EESSs). Battery Management System (BMS) is developed to monitor the state of batteries to ensure the safety and reliability of battery module operation. However, the efficiency of the BMS largely depends on the accuracy of the established battery model. Recently, liquid metal battery (LMB) has attracted much attention due to its superiority in stationary energy storage. This paper presents a fractional-order model (FOM) for liquid metal batteries and its parameter identification using electrochemical impedance spectroscopy (EIS). Simulations and experiments both exhibit good performance. [ABSTRACT FROM AUTHOR]

• A multi-physics field model is proposed to evaluate the LMB electro-thermal behavior during the CC cycle and ESC. • The thermal characteristics of LMB are quite different from those of lithium-ion batteries. • Reversible heat accounts for a large proportion of the total heat generation in LMB. • The electro-thermal behavior of LMB in ESC failure is closely related to ESC resistance and battery SOC. As one of the most potent battery technology, liquid metal battery (LMB) plays an important role in addressing the requirement of grid energy storage. However, up to now, few attention has been paid to the heat generation characteristics and thermal safety of LMB, including the conventional and abusive conditions. In this paper, a 2D axisymmetric multi-physics field model coupling electrochemistry, heat transfer, and laminar flow is proposed to evaluate the electro-thermal behavior of 200 Ah Li||Bi LMBs under the states of constant current (CC) cycle and external short circuit (ESC). Verified by the experimental data, the maximum fitting errors of the voltage and temperature are 4.61% and 0.42%, respectively. The reversible and irreversible electrochemical heat generation rates are calculated to assess the total heat power (9.14 W during 0.2 C discharge and −5.06 W during 0.2 C charge). The reversible heat rate is found to occupy a large proportion in the total heat generation, while the percentage of irreversible heat is shown to increase with the increasing current rate. Based on the analysis of CC cycle, the model is applied to investigate the battery electro-thermal performance in ESC failure. The results show that the ESC current and surface temperature vary with the short-circuit resistance and initial state of charge (SOC). The lower ESC resistance and initial SOC may lead to a severer temperature rise due to the unique entropic heat behavior. The maximum current and temperature reach 455.8 A and 549.3 °C in 5 min (100% SOC, 0.1 mΩ). This work provides an important opportunity to advance the understanding of heat generation and abuse phenomena induced by ESC in LMB. [ABSTRACT FROM AUTHOR]

Abstract A Li/LiF-LiCl-LiBr/Sn battery cell is prepared for the first time to investigate the feasibility of pure tin metal as an environmentally friendly cathode material in the liquid metal battery. The Li-Sn cell can achieve the mean voltages of 0.820 and 0.607 V during charge and discharge at 100 mA cm−2, respectively. Increasing the discharge current density from 100 to 700 mA cm−2 results in 1.3% capacity loss, and the capacity loss is 12.4% when the charge current density increased from 100 to 1000 mA cm−2. This high rate capability of the cell is due to ultrafast charge-transfer kinetics at the interface of liquid electrode and liquid electrolyte. The Li-Sn cell exhibits a capacity retention of 94.0% after 220 cycles. The capacity loss originates from the loss of active Sn by forming SnFe and CrSn 2 intermetallics in side reaction between the Sn and stainless steel case, and these intermetallics are inert to lithium within the voltage window of 0.5–1.2 V. [ABSTRACT FROM AUTHOR]

Liquid metal battery (LMB), with three-liquid-layer structure and high operating temperature (300–700 °C), is a newly emerging technology for large scale energy storage applications. A thermal management system is critical to achieve satisfied LMB performance and extend the life of batteries. In this work, an improved coupling model composing of a 3D heat-transfer model and a 1D electrochemical model is developed for the thermal analysis of a Li||Sb–Sn LMBs module (5.5 kWh). Key results including transient values, the contribution ratio of heat sources, temperature homogeneity and distribution, as well as the energy efficiency of the battery module, are presented. Based on the coupling model, the changeable-power-heating mode, sand filling material and vacuum insulation are further proposed to achieve the high energy efficiency and optimal performance of the LMBs module. Moreover, the LMBs module can achieve “self-heating” when operated at 0.2 C charge/discharge, under the vacuum insulation (0.01 W m −1 K −1 thermal conductivity, 100 mm thickness), requiring no external heating to keep the batteries at operating temperature. [ABSTRACT FROM AUTHOR]

Magnetohydrodynamically induced interface instability in liquid metal batteries is analyzed. The batteries are represented by a simplified system in the form of a rectangular cell, in which strong vertical electric current flows through three horizontal layers: the layer of a heavy metal at the bottom, the layer of a light metal at the top, and the layer of electrolyte in the middle. A new two-dimensional nonlinear model based on the conservative shallow water approximation is derived and utilized in a numerical study. It is found that in the case of small density difference between the electrolyte and one of the metals, the instability closely resembles the rolling pad instability observed earlier in the aluminum reduction cells. When the two electrolyte-metal density differences are comparable, the dynamics of unstable systems is more complex and characterized by interaction between two nearly synchronized or nearly anti-synchronized interfacial waves. [ABSTRACT FROM AUTHOR]

Li-Bi based liquid metal batteries (LMBs) have attracted interest due to their potential for solving grid scale energy storage problems. In this study, the feasibility of replacing the bismuth cathode with a bismuth-antimony alloy cathode in lithium based LMBs is investigated. The influence of the Bi:Sb ratio on voltage characteristics is evaluated via the constant current discharge method and electrochemical titration. On observing the cross section of the electrode at various stages of discharge, it is determined that both Sb and Bi form solid intermetallics with Li on the cathode. Additionally, the addition of Bi not only reduces the melting temperature of the Bi:Sb intermetallic but also actively contributes to the electrode capacity. Thereafter, a Li|LiCl-LiF|Sb-Bi liquid metal battery with 3 A h nameplate capacity, assembled and cycled at 1 C rate, is found to possess a stable capacity for over 160 cycles. The overall performance of this battery is discussed in the context of cost effectiveness, energy and coulombic efficiencies. [ABSTRACT FROM AUTHOR]

Liquid metal batteries are proposed for low-cost grid scale energy storage. During their operation, solid intermetallic phases often form in the cathode and are known to limit the capacity of the cell. Fluid flow in the liquid electrodes can enhance mass transfer and reduce the formation of localized intermetallics, and fluid flow can be promoted by careful choice of the locations and topology of a battery's electrical connections. In this context we study four phenomena that drive flow: Rayleigh-Bénard convection, internally heated convection, electro-vortex flow, and swirl flow, in both experiment and simulation. In experiments, we use ultrasound Doppler velocimetry (UDV) to measure the flow in a eutectic PbBi electrode at 160 °C and subject to all four phenomena. In numerical simulations, we isolate the phenomena and simulate each separately using OpenFOAM. Comparing simulated velocities to experiments via a UDV beam model, we find that all four phenomena can enhance mass transfer in LMBs. We explain the flow direction, describe how the phenomena interact, and propose dimensionless numbers for estimating their mutual relevance. A brief discussion of electrical connections summarizes the engineering implications of our work. [ABSTRACT FROM AUTHOR]

The high-temperature corrosion behavior of an AlN/Mo functionally graded material (FGM) under the Li/LiF-LiCl-LiBr vapor has been investigated. It is suggested that the Li vapor diffuses along the AlN and AlN/Mo grain boundaries and enters the interior of adjacent AlN grains, leading to the disintegration of AlN grains and subsequent failures. The 3D Mo networks are barely corroded, thus preventing cracking that may occur due to the inconsistent deformation inside the FGM. This work unravels the high-temperature corrosion mechanisms for the AlN/Mo FGM. Meanwhile, the operating temperature threshold for the liquid metal batteries employing Mo/AlN/Mo seals is determined to be ∼ 600 °C. • The corrosion failure of AlN/Mo FGMs caused by Li/LiF-LiCl-LiBr Vapor vapor occurs at 650 ℃ and above. • Li vapor diffuses along the AlN and AlN/Mo grain boundaries and enters the interior of adjacent AlN grains. • AlN gradually disintegrates from the surface until it is severely distorted under the high-temperature Li/LiF-LiCl-LiBr vapor. • 3D networks of Mo in AlN/Mo FGMs significantly inhibit high-temperature corrosion. [ABSTRACT FROM AUTHOR]

Corrosion in grid-scale energy storage devices adversely affects service lifetime and thus has a significant economic impact on their deployment. In this work, we investigate the corrosion of steel and stainless steels (SSs) as positive current collectors in the Li||Sb-Pb liquid metal battery. The erosion and formation of new phases on low-carbon steel, SS301, and SS430 were evaluated both in static conditions and under cell operating conditions. The cell performance is not adversely affected by the dissolution of iron or chromium but rather nickel. Furthermore, the in situ formation of a Fe-Cr-Sb layer helps mitigate the recession of SS430. [ABSTRACT FROM AUTHOR]

Liquid metal battery (LMB) is considered a potential contender for grid-scale energy storage systems. However, high operating temperatures (>400 °C) leading to higher operational costs limit its commercial application. Therefore, the current work focuses on reducing the melting temperature of electrodes and electrolytes below 300 °C by compositional engineering. Moreover, this study utilizes earth-abundant elements like Zn (with less reliance on Li), in Zn–Sn||Bi–Pb LMB system. The composition of LiCl in the electrolyte is varied to optimize the battery performance, especially the energy efficiency and overpotential while maintaining an operating temperature of <275 °C. It is found that as the LiCl content in the electrolyte salt increases (5–30 Mol%), the overpotential of the battery decreases (0.9–0.3 V), and the energy efficiency of the charge-discharge process improves (14.5%–80.9%) owing to the better ionic conductivity of LiCl. For the optimized LiCl concentration of 30 Mol% LiCl in the electrolyte, the fabricated LMB exhibit good cyclability (no degradation till 100 cycles), a high discharging voltage plateau of 0.92 V, 24.6 mAh charge storage capacity, and a low operating temperature of 275 °C, which is the lowest operating temperature reported so far in a Zn-based LMB system. [Display omitted] • Operating temperature reduced to 275 °C while retaining the performance. • Utilized earth-abundant elements like Zn for electrodes in Zn–Sn.||Bi–Pb LMB system • Composition of LiCl in the electrolyte was varied to optimize battery performance. • Electrolyte with 30% LiCl concentration exhibited no degradation till 100 cycles. • Demonstrated storage capacity of 24.6 mAh, and energy efficiency as high as 80%. [ABSTRACT FROM AUTHOR]

After being fabricated successfully by spark plasma sintering technology, corrosion performance of aluminum nitride-molybdenum gradient material was investigated using X-ray diffraction, scanning electron microscope, XPS techniques, etc. in a simulated liquid metal battery environment with LiF–LiBr–LiCl eutectic salt as electrolyte. The research results indicated that low temperature corrosion at 550 °C occurs mainly in pure aluminum nitride region with the corrosion products grown on the grain boundaries including alumina, nitrogen-lithium, aluminum-lithium intermediate phase or their complex compounds. Moreover, the formed corrosion product morphology is influenced significantly by aluminum nitride distribution. As the gradient compositions developed towards the pure molybdenum zone, the product morphologies tended to evolve in a sequence of sphere, flake and octahedron. At temperatures higher than 600 °C, alumina tends to be dissolved in molten salt vapor and molybdenum starts to be corroded simultaneously resulting in a substitute of the formed lithium aluminum molybdenum oxide phases for alumina in the final corrosion products. Mass change study on the samples suggested both the holding time and temperature have significant influences on the corrosion behavior of aluminum nitride-molybdenum gradient material. At temperatures higher than 700 °C, sudden change in sample mass accompanied by interface cracking would happen within the holding time of 100 h. Therefore, under long-term isothermal conditions, the serviced temperature of aluminum nitride-molybdenum functional gradient materials is suggested to be lower than 600 °C. • A gradient AlN/Mo material was used as sealing material for liquid metal battery. • The corrosion behavior of the gradient material in liquid metal battery was investigated. [ABSTRACT FROM AUTHOR]

Gallium-based liquid alloys that exhibit high capacity and self-healing properties have been demonstrated to be promising cathodes for room temperature liquid metal batteries (RTLMBs). However, the electrochemical performances of these alloys are poor due to severe volume expansion and an unstable solid electrolyte interface layer during the lithiation process. Here, a sol-gel strategy was performed to construct yolk-shell structure nanodroplets (eGaSn@Void@SiO 2) that contain sufficient void space by amorphous silicon oxide, which generated a liquid metal electrode with a high performance. The amorphous SiO 2 shells not only play an important role in building stable SEI films, providing efficient electron/ion conduction channels and preventing agglomeration of active substances, but exhibit good elastic behavior during charging/discharging. Due to the appropriate voids in the yolk-shell structure, the eGaSn nanodroplets can expand freely without breaking or disrupting the electrode structure; thus, the resulting eGaSn@Void@SiO 2 NDs exhibited high capacities of 538, 454, and 338 mA h g−1 at current rates of 0.2, 1 and 5 C, respectively. No obvious decay was observed with more than 500 cycles and a capacity of 377 mA h g−1 at 2 C. Interestingly, the density functional theory (DFT) calculations revealed that the effective chemisorption between the discharge products and SiO 2 provides sufficient electrical contact sites with a significant drop in electrochemical impedance during cycling. The causes of the superior electrodes performance were investigated in depth using in situ X-ray diffraction and theoretical calculations. Our rational design may shed unprecedented light on the development of liquid alloy-based cathodes for high-performance RTLMBs. [ABSTRACT FROM AUTHOR]

In this work a 1D finite volume based model using coupled meshes is introduced to capture potential and species distribution throughout the discharge process in a lithium–bismuth liquid metal battery while neglecting hydrodynamic effects, focusing on the electrochemical properties of the cell and the mass transport in electrolyte and cathode. Interface reactions in the electrical double layer are considered through the introduction of a discrete jump of the potential modelled as periodic boundary condition to resolve interfacial discontinuities in the cell potential. A balanced-force like approach is implemented to ensure consistent calculation at the interface level. It is found that mass transport and concentration gradients have a significant effect on the cell overpotentials and thus on cell performance and cell voltage. By quantifying overvoltages in the Li | | Bi cell with a mixed cation electrolyte, it is possible to show that diffusion and migration current density could have counteractive effects on the cell voltage. Furthermore, the simulated limiting current density is observed to be much lower than experimentally measured, which can be attributed to convective effects in the electrolyte that need to be addressed in future simulations. The solver is based on the open source library OpenFOAM and thoroughly verified against the equivalent system COMSOL multiphysics and further validated with experimental results. • A charge and species transport model for liquid metal batteries (LMBs) is developed. • The OpenFOAM model is capable to simulate the full battery and thoroughly verified. • Ohmic and concentration overpotentials in LMBs are investigated and quantified. • Determined cell currents indicate the presence of fluid flow in the electrolyte. [ABSTRACT FROM AUTHOR]

• FFRLS is utilized to identify model parameters and reconstruct battery OCV. • An intelligent noise estimator is designed based on fuzzy inference system. • DFAEKF is proposed for battery SOC and parameter estimation. • Online estimated ohmic resistance is used to indicate battery SOH. • The DFAEKF is verified through different experiments. Liquid metal batteries (LMBs) are alternatives to conventional lithium-ion batteries due to their specific benefits including high current density and long cycle life. Accurate state of charge (SOC) estimation is an important evaluation index for the battery management system (BMS), which is of great significance to ensure the safe operation of batteries. However, the estimation accuracy of SOC is influenced by many factors, including self-aging and external operating environment changes. Therefore, an online battery model with real-time parameter updates is necessary for accurate SOC estimation. In this paper, a novel dual fuzzy-based adaptive extended Kalman filter (DFAEKF) method is proposed for the SOC estimation of LMBs. Firstly, a second-order RC equivalent circuit model is established to describe the battery's behavior. The forgetting factor recursive least squares (FFRLS) is utilized to identify the model parameters and reconstruct the battery open circuit voltage (OCV). Secondly, the dual adaptive extended Kalman filter (DAEKF) is derived from the battery model. And an intelligent noise estimator is designed based on a fuzzy inference system, which adaptively adjusts the length of the residual innovation sequence (RIS), to update the noise covariance. Finally, the DFAEKF algorithm is proposed for the battery SOC and parameter co-estimation. The online estimated ohmic resistance is employed to calculate the state of health (SOH) of the battery. The proposed DFAEKF is verified through different experiments and compared to conventional algorithms. Experimental results show that the DFAEKF has higher accuracy (error < 1 %) and stronger robustness. The proposed method can also be applied to other model-based state estimation areas. [ABSTRACT FROM AUTHOR]

A new kind of membrane free liquid metal battery was developed. The battery employs liquid sodium and zinc as electrodes both in liquid state, and NaCl-CaCl 2 molten salts as electrolyte. The discharge flat voltage is in the range of about 1.4 V–1.8 V, and the cycle efficiency achieved is about 90% at low discharge current densities (below 40 mA cm −2 ). Moreover, this battery can also be charged and discharged at high current density with good performance. The discharge flat voltage is above 1.1 V when it is discharged at 100 mA cm −2 , while it is about 0.8 V with 100% cycle efficiency when it is discharged at 200 mA cm −2 . Compared to other reported liquid metal battery, this battery has lower cost, which suggests broad application prospect in energy storage systems for power grid. [ABSTRACT FROM AUTHOR]

Generation of thermal convection flow in the liquid metal battery, a device recently proposed as a promising solution for the problem of the short-term energy storage, is analyzed using a numerical model. It is found that convection caused by Joule heating of electrolyte during charging or discharging is virtually unavoidable. It exists in laboratory prototypes larger than a few centimeters in size and should become much stronger in larger-scale batteries. The phenomenon needs further investigation in view of its positive (enhanced mixing of reactants) and negative (loss of efficiency and possible disruption of operation due to the flow-induced deformation of the electrolyte layer) effects. [ABSTRACT FROM AUTHOR]

While liquid metal batteries are attractive options for grid-scale energy storage applications as they have flexible siting capacities and small footprints, the compatibility between structural materials such as current collectors and negative electrode such as sodium is one of major issues for liquid metal batteries. Non-metallic elements such as carbon, oxygen, and nitrogen in the liquid sodium influence the material behaviors of the cell construction materials in the battery system. In this study, the compatibility of structural materials with sodium is investigated in high temperature liquid sodium, and electrochemical impedance spectroscopy (EIS) is used to monitor in-situ the corrosion behavior at the surface of materials in sodium. Chemical vapor deposition (CVD) coatings of SiC and Si 3 N 4 are applied as protective barriers against dissolution and corrosion on the steel surface. The results show that CVD coating of Si compounds can delay corrosion of steel in high temperature liquid sodium comparing to the result of as-received specimens, while SiC coating is more durable than Si 3 N 4 coating in high temperature liquid sodium. [ABSTRACT FROM AUTHOR]