Molten Salt Systems Research Articles

Boiling sodium and melting salt: Evaluation and optimisation of a novel solar–thermal system concept

The phase-change phenomenon facilitates efficient heat transfer and the storage of a large amount of heat close to an upper-bound temperature limit. In this paper, a novel solar-thermal system configuration is evaluated and optimised, where liquid sodium is boiled in a receiver and energy is stored through the melting and freezing of NaCl salt. Polar and surround field configurations of a 1 MWe sodium-boiler plant were investigated where co-optimisation of solar multiple, field parameters, receiver geometry and storage parameters was performed to obtain lowest possible levelised cost of electricity (LCOE); this compared to a 100 MWe two-tank molten salt plant optimised via the same method. The LCOE values obtained for the 1 MWe sodium-boiler plant was 128.3 USD/MWh for a polar field configuration and 144.9 USD/MWh for a surround field configuration, compared to 107.1 USD/MWh for the 100 MWe two-tank molten salt system. Whilst promising for smaller-scale systems, the analysis identifies limitations and challenges associated with high operating temperatures and low receiver flux limits, which opens the possibilities for the investigation of lower-temperature phase change materials (PCMs) and alternative PCM geometries. • Phase change thermal energy storage is coupled with a boiling sodium solar receiver. • A detailed physical model is used to optimise the design for lowest energy cost. • The system achieves 128 USD/MWhe at 1 MWe scale with 14 h of storage.

Molecular Dynamics Simulation of the Effect of Zr and b on Cryolite Molten Salt System 78%Na<sub>3</sub>AlF<sub>6</sub>-9.5%AlF<sub>3</sub>-5.0%CaF<sub>2</sub>-7.5%Al<sub>2</sub>O<sub>3</sub>

The analysis of high temperature physical and chemical properties of molten salt system of aluminum electrolysis has guiding significance for practical production In this paper, the molecular dynamics calculation method was used to simulate the physical and chemical properties of 78%Na3AlF6-9.5%AlF3-5.0%CaF2-7.5%Al2O3 molten salt electrolyte system with Zr and B as additives at 1200K and standard atmospheric pressure. The effects of Zr and B elements on the radial distribution function, coordination number, diffusion coefficient, viscosity, and conductivity of electrolyte system were discussed in detail. The simulation results showed that Zr4+ weakened the connection between Al3+, while the addition of B3+ enhanced the interaction between Al3+, Na+, and F-. In the electrolyte system without impurities, the order of self-diffusion coefficient is Na+ > O2- > F- > Ca2+ > Al3+. And the addition of Zr4+ is conducive to the diffusion of ions in the system, while the addition of B3+ is not conducive to the diffusion of ions in the system. What’s more, the addition of Zr improves the conductivity of the system, while the addition of B reduces the conductivity of the system.

Nanoparticle-based anticorrosion coatings for molten salts applications

High-temperature molten salt systems are employed in a wide variety of industrial applications, linked to energy production and storage, such as concentrated solar power, waste heat recovery, storage plants, fuel cells nuclear, etc. The reactivity of these salts is one of the main issues to address for the employment of affordable steels as constructive materials. In this work, the performance of a polymeric anticorrosion coating based on nanoparticles is analyzed for carbon and stainless steel subjected to solar salt, at 390 and 565 °C, respectively.The application of the protective coating produced a more homogeneous corrosion layer in both steels compared to uncoated samples. For carbon steel, the spallation of the corrosion layer was mitigated. For stainless steel, the corrosion was significantly reduced. The was confirmed by SEM-EDX confirmed the inclusion of alumina nanoparticles into the corrosion scale and their reaction with stainless steel to form mixed oxides was corroborated by XRD. Molten salts were analyzed by ICP. The obtained results pave the way for anticorrosion coatings based on nanoparticles for high temperature molten salts applications.

Techno-economic analysis of a concrete storage concept for parabolic trough solar power plants

In an energy transition towards 100 % renewable electricity, concentrating solar power (CSP) with thermal energy storage (TES) should be deployed on a wide scale due to the dispatchability capacity of this technology. To achieve this, a decrease of its levelized cost of electricity (LCOE) is essential. This paper evaluates the techno-economic potential of a CSP plant with high temperature concrete as TES system compared to the standard commercial molten salts system. The general plant design includes creating a bank of metal tubes enclosed by concrete in a modular configuration, aiming to maximize the performance of the plant (e.g., reducing parasitics). Nevertheless, the results proved that the selected configuration underperforms during the discharge phase in nominal conditions. Despite existing expectations, this study shows the prevalence of the current molten salt TES system as a better solution over the high temperature optimized concrete configuration studied.

Assessing the interfacial corrosion mechanism of Inconel 617 in chloride molten salt corrosion using multi-modal advanced characterization techniques

The United States Department of Energy (DOE) has committed to expanding the domestic clean energy portfolio in response to the rising challenges of energy security in the wake of climate change. Accordingly, the construction of a series of Generation IV reactor technologies are being demonstrated, including sodium-cooled, small modular, and molten chloride fast reactors (MCFRs). To date, there are no fully qualified structural materials for constructing MCFRs. A number of commercial structural alloys have been considered for the construction of MCFRs, including alloys from the Inconel and Hastelloy series. Informed qualification of structural materials for the construction of MCFRs in the future can only be ensured by expanding the current fundamental knowledgebase of information pertaining to material performance under environmental stressors relevant to operation of the reactor, including corrosion susceptibility. The purpose of this investigation is to illustrate how a correlative multi-modal electron microscopy characterization approach, including the novel application of focused-ion beam 3D reconstruction capabilities, can elucidate the corrosion mechanism of a candidate structural material Inconel 617 for MCFR in NaCl-MgCl2 eutectic salt at 700°C for 1,000 h. Evidence of intergranular corrosion, Ni and Fe dealloying, and Cr-O enrichment along the grain boundary, which most likely corresponds to Cr2O3, is a phenomenon that has been documented in other Ni-based superalloys exposed to chloride molten salt systems. Additional corrosion products, including the formation of insoluble MgAl2O4, within the porous network produced by the salt attack is a novel observation. In addition, Mo3Si5 and τ2 precipitates are detected in the alloy bulk and are dissolved by the salt. Furthermore, the lack of detection of design γ′ precipitates in Inconel 617 after 1,000 h could indicate that the molten salt corrosion mechanism has indirectly induced a phase transformation of Al2TiNi (τ2) and Ni3(Al,Ti) (γ’) phase. This investigation provides a comprehensive understanding of molten salt corrosion mechanisms in a complex material system such as a commercial structural alloy for applications in MCFRs.

Thermodynamic measurements and assessments for LiCl-NaCl-KCl-UCl3 systems

Thermodynamic descriptions of higher-order molten salt systems are essential for the effective application of molten salt technologies. However, for pyroprocessing and molten salt reactor development, a complete description of the key Li-Na-K-U(III) chloride system has yet to be provided. To remedy this, we applied the CALculation of PHAse Diagrams (CALPHAD) approach to all available phase equilibria and related thermodynamic measurements that include new differential scanning calorimetry (DSC) observations for pseudo-binary and pseudo-ternary systems to obtain consistent and accurate sets of thermodynamic properties. An outcome of that effort was the apparent discovery of a previously unreported intermediate compound in the NaCl-UCl3 system. In this effort, we adopted a unique approach to the quantification of uncertainty in phase equilibria obtained from DSC measurements, which can provide distinct advantages in phase diagram analysis. The methodology indicates that reported values of uncertainty are often underestimated. The assessed systems of the current effort were incorporated in the publicly available Molten Salt Thermal Properties Database - Thermochemical.

Optimization of pulse bi-directional electrolysis in-situ synthesis of tungsten carbide by response surface methodology

The response surface methodology was used to optimize the parameters of pulse bi-directional electrolysis (PBE) in-situ synthesis of tungsten carbide (WC) in NaF-KF molten salt system. The process of PBE synthesis of WC is a short process method of in-situ synthesis of WC powders in molten salt electrolyte. WC were used both as cathode and anode. A symmetrical bi-directional pulse is applied between the two electrodes. Tungsten ions dissolved by forward pulse, and WC were produced in situ with carbon near the electrode during reverse pulse. During the research, it was found that the factors affecting the phase of the experimental product were Current intensity, Pulse period and Electrolysis duration. In this paper, the cathode and anodic dissolved mass and the Proportion of WC in the product were used as the response values. The Box-Behnken center combined test and response surface analysis are used to optimize the factors that affect significantly, and the optimal process parameters were determined. Finally, the model was experimentally verified. Under the optimized experimental conditions, high-performance tungsten carbide nanopowders were prepared with short-process and high-efficiency.

Investigation into cathodic reduction process of Yb(III) ion in (LiF-YbF3)eut.-Yb2O3 molten salt system

• The electrochemical behavior of Yb (III) and Yb (Ⅱ) was determined by using different electrodes (W or Ni) in (LiF-YbF 3 ) eut. and (LiF-YbF 3 ) eut. -Yb 2 O 3 system. • The Ni 2 Yb alloy can be prepared by using the molten salt electrolysis in (LiF-YbF 3 ) eut. -Yb 2 O 3 system on the Ni electrode. • The crystallization process on the surface of W and Ni electrode were determined by chronoamperometry analysis of (LiF-YbF 3 ) eut. -Yb 2 O 3 system. The electrochemical behavior of Yb 3+ ions is investigated through cyclic voltammetry and chronoamperometry/potentiometric methods on the surface of a W/Ni working electrode in a (LiF-YbF 3 ) eut -Yb 2 O 3 molten salt system. The results show that the reduction of Yb 3+ ions is completed by two-step quasi-reversible processes of Yb 3+ /Yb 2+ and Yb 2+ /Yb on the W and Ni cathodes in LiF-YbF 3 and (LiF-YbF 3 ) eut -Yb 2 O 3 molten salt systems at 1223K; and the diffusion coefficients of Yb 3+ are 5.45×10 -4 cm 2 ·s -1 and 3.75×10 -3 cm 2 ·s -1 , respectively. The addition of Yb 2 O 3 can improve the electrochemical activity of Yb 3+ in the LiF-YbF 3 system. The crystallization of Yb 3+ ions are through three-dimensional instantaneous and continuous nucleation on the W and Ni electrodes in the (LiF-YbF 3 ) eut -Yb 2 O 3 molten salt system, respectively. The reduction activity of Yb 2+ ions on the Ni cathode is stronger than on the W cathode, which is beneficial to alloying. The Ni 2 Yb alloy can be prepared by constant voltage electrolysis with Ni as a consumable cathode in the (LiF-YbF 3 ) eut -Yb 2 O 3 molten salt system.

Molecular dynamic study of the local structure and transport properties of LiF-NaF molten salt

LiF-NaF molten salts have received extensive attention due to their excellent heat transfer performance in molten salt reactors. However, their structural and thermodynamic properties have not been systematically studied. In this study, molecular dynamic simulations were performed using polarized force fields to investigate the local structures of cations and thermodynamic properties of mixed salts in a temperature range of 873 K to 1273 K and at all concentration components. Furthermore, a linear relationship between density and LiF concentration at different temperatures was fitted. Regarding local structure, an increase in LiF concentration gradually increased the coordination numbers of Li and Na ions, but the strength of Li–F and Na–F ionic bonds gradually weakened. Regarding the thermodynamic properties, an increase in the LiF concentration linearly increased the self-diffusion coefficients of all ionic species, while the viscosity of the system approximately decreases exponentially. The ionic conductivities were calculated using the Green–Kubo and Nernst–Einstein relationships, and the results reflect that the Nernst–Einstein approximation is not suitable for describing molten salt systems.

V2(Al1−xGax)C microrods synthesized through molten-salt show efficient microwave absorption capability

In this study, a series of V2(Al1−xGax)C microrods are synthesized for the first time in a molten salt system using short carbon fibers as carbon source and sacrificial template. The phase components, structural characteristics, and microwave absorption performance of as-prepared V2(Al1−xGax)C microrods are systematically investigated. The calculated lattice distortion degree results confirm that the phase structure, grain boundary density, and internal stress of V2(Al1−xGax)C microrods can be effectively modulated by controlling the doping amount of gallium element. The synergistic effects of dielectric loss, magnetic loss, multiple reflection and scattering afford the V2(Al1−xGax)C microrods with enhanced microwave absorption intensity and bandwidth. Specifically, V2(Al0.5Ga0.5)C microrod displays a minimum RL value of − 55.62 dB at 12.00 GHz, and the broadest EAB could reach 4.16 GHz with a thickness of 1.75 mm. Compared with the M sites doped MAX phases, A sites doped V2(Al1−xGax)C exhibit more excellent electromagnetic energy attenuation capacities.

Fundamental Issues Identified for Thermodynamic Description of Molten Salt Systems

Thermodynamic modeling of the molten salt systems is critical in the design of advanced nuclear power plants, materials recycling, and many other important clean energy applications. As one of the most capable computational thermodynamic approaches, the CALPHAD (Calculation of Phase Diagrams) method has been widely used for multicomponent thermodynamic database development and further support more physics-based modeling. Although considerable CALPHAD modeling efforts for molten salt systems have been made, we found that no evaluation has been performed regarding the unary thermodynamic models for the molten salt systems despite the fact that more than one pure substance database is available for the CALPHAD modeling. Therefore, the thermodynamic descriptions of the pure salts should be critically evaluated to ensure a high-fidelity molten salt thermodynamic database. In this work, we comprehensively analyzed some selected molten salts using different available thermodynamic descriptions from two databases as an example. One is the SSUB database released by the SGTE (Scientific Group Thermodata Europe), and the other is the FactPS database from the FactSage. The significant discrepancies observed in the thermodynamic description between the existing CALPHAD pure substance databases and experiments call for an urgent effort to improve.

Electrochemical extraction mechanism of Nd on Ga-Al alloy electrode

In order to reveal the extraction mechanism of Nd on Ga-Al alloy electrode, the electrode reactions and alloy formation between Nd(III), Ga(III) and Al(III) ions in different molten salt systems were studied by multiple electrochemical methods. The cyclic voltammetry curves measured in melts with different concentrations confirmed that only three intermetallic compounds were formed in both Ga-Nd and Al-Nd systems. The preferential interaction of Nd with Ga in Ga-Al-Nd ternary system was further verified by cyclic voltammetry curves with varying potential window. In particular, the co-reduction process of three ions was gradually determined by the comparison of electrochemical behaviour in different melts. In addition, the interfacial reaction of Nd(III) ion on liquid Ga-Al alloy cathode was investigated, and the corresponding exchange current densities were measured through galvanostatic pulse (0.0049, 0.0047, 0.0056 and 0.0055 A cm−2) and Tafel method (0.0029 A cm−2).

Molten salt guided synthesis of carbon Microfiber/FeS dielectric/magnetic composite for microwave absorption application

In this work, a series of carbon microfiber (CMF)/FeS composites are synthesized by a molten-salt-guided synthetic strategy. The microstructures, electromagnetic (EM) response behaviors, and microwave absorption (MA) properties of these CMF/FeS composites have been systematically investigated. The results indicate that the prepared CMF/FeS exhibits effective MA performance, where its effective absorbing bandwidth (EAB) is 6.64 GHz (11.36–18 GHz). The check test shows that different molten salt (MS) systems influence the morphology, crystal planes and magnetic properties, and thus influence the MA performance of the composites. This research expands the application of molten salt strategy (MSS) in the MA field and explores the effects of different types of MS on the EM properties and MA performance, which supplies a reference for the application of MSS in the MA field.

Micromorphology and texture of niobium coating electrodeposited in NaCl—KCl—CsCl molten salt system

A low-toxicity and environment-friendly NaCl—KCl—CsCl—K2NbF7 system was used to prepare Nb coatings on Mo substrates. The effects of temperature, current density and electrodeposition time on the micromorphologies and textures of the electrodeposited Nb coatings were studied. The results showed that Nb coatings obtained at 30—70 mA/cm2 in the temperature range of 700—750 °C were continuous and compact, with a hardness range of 2.16—2.45 GPa. As the columnar crystals grew with time, the preferential growth orientations of the Nb coatings changed from 〈200〉 to 〈211〉 and then became disordered. With increasing polarization, the morphologies of the Nb coatings changed from hexagonal star-like surface to conical or pyramid-like surface.

Effect of Cathode Physical Properties on the Preparation of Fe3Si0.7Al0.3 Intermetallic Compounds by Molten Salt Electrode Deoxidation.

As a new process, molten salt electrolysis is widely used in the preparation of metal materials by in situ reduction in solid cathodes. Therefore, it is meaningful to study the influence of the physical properties of solid cathodes on electrolysis products. In this paper, mixed oxides of Fe2O3-Al2O3-SiO2 were selected as raw materials, and their particle size distribution, pore size distribution, specific surface area, and other physical properties were investigated by mechanical ball milling at different times. The CaCl2-NaCl molten salt system was selected to electrolyze the sintered cathode solid at 800 °C and a voltage of 3.2 V. The experimental results show that with the prolongation of ball-milling time, the particle size of mixed oxide raw materials gradually decreases, the specific surface area gradually increases, the distribution of micropores increases, and the distribution of mesopores decreases. After sintering at 800 °C for 4 h, the volume and particle size of the solid cathode increased, the impedance value gradually decreased, and the pores first increased and then decreased. The electrolysis results showed that the prolongation of the ball-milling time hindered the electrolysis process.

Atomwise force fields for molten alkali chlorides (LiCl and KCl) and their mixtures: efficient parameterization via genetic algorithms

Over the last few decades, molten salts have gained significant attention in the field of green energy production. One useful method that can accelerate the discovery and optimization of desirable molten salts from a vast range of materials is classical molecular dynamics (CMD). However, because of the absence of CMD force fields that can reasonably reproduce experimental physical properties, the use of CMD to study molten salts remains a significant challenge. Hence, in this study, we report non-polarizable rigid ion models (RIMs) for the widely used LiCl, KCl, and LiCl–KCl molten salts, obtained via genetic algorithms (GAs). Based on the results presented in this study, GAs proved to be very effective in simultaneously optimizing a large number of force field parameters. With GAs, the force field generation process is automated and no manual intervention is required. The RIM force fields developed herein can reasonably reproduce experimental physical properties at different temperatures and various salt compositions, provides microstructural characteristics similar to those obtained using highly accurate and reliable first-principles MD, and an improved overall performance in contrast to previously reported polarizable force fields, all at a lower computational cost. In contrast to previous studies, we developed atomwise RIM force fields that employ mixing rules for interactions between ions of different types. This reduced the total number of optimizable terms, and thus resulted in RIM parameters that are transferrable between different molten salt systems.

Behavior of Thermodynamic Reference Electrode for Molten Flibe Environment

Designing and fabricating a stable thermodynamic reference electrode (TRE) for use in molten fluoride salts has proven challenging for several reasons. An ideal TRE will not allow mass diffusion of molten salt across its system boundary while it will allow ionic contact across the system boundary. Appropriate material candidates for the fabrication of a TRE need to remain inert in molten salt environments and be electrically insulating, all while remaining stable at temperatures greater than 700C. UC Berkeley has been working with Ultramet on the Department of Energy SBIR DE-FOA-0002359 to develop such a TRE for 2LiF-Be2F (FLiBe) which is resilient to degradation after long term FLiBe exposure, produces repeatable electrochemical data, and can be incorporated into molten salt systems modularly.This first testing campaign consisted of two main experimental thrusts which characterized the materials degradation and the electrochemical response of the TRE. The first experimental thrust concerns the degradation of a boron-nitride (BN) coating on a porous graphite substrate under long term exposure to FLiBe at high temperatures. Six (6) unique BN coated graphite foam coupons were exposed to FLiBe held at 700C for 96 hours. The cross sections of each coupon were imaged by macro lens photography for initial qualitative results which help determine the presence and efficacy of the BN coating after the FLiBe exposure. The next phase of research in this thrust requires SEM/EDS imaging of the coupons for quantitative results that will determine the approximate BN thickness remaining on the coupons and indicate if any materials migrated into the graphite foam pores during the exposure. The second experimental thrust characterizes the electrochemical response of the novel TRE in FLiBe. The Ni/NiF2 redox couple was used as a reference reaction for this study since it has been previously studied in FLiBe. Ultramet provided UC Berkeley with open-ended cylinder TRE bodies for electrochemical characterization. Each TRE body consists of graphite foam coated in BN and contained lanthanum-fluoride (LaF3) coated on the inside diameter which acts as an ionic membrane and a mass barrier. Ultramet’s TRE was loaded with NiF2 and assembled with a Ni wire electrode. Open circuit potential (OCP) and polarizability of the TRE were measured using a Gamry Ref 600 potentiostat, where the novel TRE was connected to the working lead, a second Ni wire was connected to the counter lead, and a third Ni wire was connected to the reference lead. Initial polarizability testing confirmed there was ionic contact between the interior TRE body and the exterior bulk salt. Next steps include characterizing the degradation to the LaF3 membrane to ensure it still functions as a mass barrier. Long term OCP drift can be studied after confirmation the LaF3 membrane still functions. These results indicate the novel TRE shows promise for accurately monitoring salt chemistry under high temperature environments for timescales up to 96 hours and beyond.

Kinetic and Thermodynamic Properties of Ytterbium Chloride and Fluoride Complexes in Chloride Melts

An important problem concerning rare earth metals and molten salts is the reprocessing of nuclear fuel, since lanthanides are always present in spent nuclear fuel. According to the technology being developed for pyroelectrochemical processing of nuclear waste spent fuel is converted into molten salts by anodic dissolution, followed by electrochemical extraction of actinides from lanthanides.Thus a knowledge of the electrochemistry and thermodynamics of lanthanide compounds in molten salt systems is very useful for the understanding the recycling of spent nuclear fuel.The electroreduction of YbCl3 in alkali chloride melts (NaCl-KCl, KCl, CsCl) was studied in the temperature range 973-1173 K by different electrochemical methods. The diffusion coefficients (D) for Yb(III) and Yb(II) were determined by linear sweep voltammetry, chronopotentiometry and chronoamperometry methods. Decreasing values of D were obtained when the cation in the second coordination sphere changed from Na to Cs. It was shown that such changes are due to the decreasing of counter polarizing effect of cations with increasing cationic radius.The standard rate constants of charge transfer (k s) for the Yb(III)/Yb(II) redox couple were calculated on the basis of cyclic voltammetry data using Nicholson’s approach. The following row of the standard rate constants of charge transfer has been experimentally determined: k s (KCl) < k s (CsCl) < k s (NaCl-KCl).The formal redox potentials E* Yb(III)/Yb(II were obtained in alkali chlorides melts from the linear sweep voltammetry data. From the values of the formal redox potentials were calculated the Gibbs energies and equilibrium constants for the reaction:YbCl2(sol.) +1/2 Cl2(g.) « YbCl3(sol.) (1)It was determined the increasing of the formal entropy for the reaction (1) in transition from NaCl-KCl to CsCl melt that associated with a greater degree of ordering of the reaction products due to the complex formation.Influence of fluoride ions (NaF) on the electrochemical behavior of the Yb(III)/Yb(II) redox couple in an equimolar NaCl-KCl melt was studied. It was determined а decrease of diffusion coefficients and standard rate constants, as well as a shift of the formal redox potentials to the negative region.

Analysis of Electrochemical Behavior of (LiF–CaF2)eut.–Yb2O3 System with (Ni2+/Ni) Internal Reference Electrode

The transient electrochemical behavior of the Yb (III) ion (Yb3+) on the surface of a Ni working electrode in a (LiF–CaF2)eut.–Yb2O3 molten salt system was analyzed using a three-electrode system with a reversible (Ni2+/Ni) internal reference electrode and Pt external reference electrode. The (Ni2+/Ni) internal reference electrode exhibited good stability and reliability, and provided results that were consistent with those of the Pt external reference electrode. The (Ni2+/Ni) electrode also had a wider measurement window for analysis of the electrochemical process than that of the Ni working electrode. Cyclic voltammetry, square wave voltammetry, chronopotentiometry, and chronoamperometry were used to analyze the Yb3+ ion in the (LiF–CaF2)eut.–Yb2O3 (0.03 mol%) system. It was confirmed that the Yb3+ ion was reduced according to Yb3+ + e → Yb2+ and Yb2+ + 2e → Yb, and the electrode reaction process was quasi-reversible and controlled by diffusion. Moreover, the Yb3+ ion alloyed with the Ni electrode to form a Ni–Yb alloy.

Toward high stability single crystal material by structural regulation with high and low temperature mixing sinter

Single-crystal cathode materials are a potential research focus for high-nickel ternary cathode materials owing to their high compaction density and good electrochemical stability. However, in the traditional sintering process, lithium is lost because of the long-time and higher-temperature sintering, which reduces the migration energy barrier of Ni2+ and increases the degree of mixing of Li+ and Ni2+. Herein, for the first time, a method for short-time high-temperature sintering combined with low-temperature heat preservation is proposed to prepare LiNi0.6Co0.6Mn0.2O2 (NCM622) single crystal materials in a mixed molten salt system of LiOH and Li2CO3. In analyses of morphology, structure and electrochemical properties, the prepared NCM622 exhibits excellent cycling stability owing to an ordered layered structure and low cation mixing degree. The single-crystal material shows an excellent capacity retention of 93.19% (150.49–140.24mAh·g−1) after 100 cycles at 1 C in the voltage range of 2.8–4.3 V. The single crystal particles exhibit reliable stability after long cycling without microcracks in the cycled particles. Furthermore, the preparation cost could be significantly reduced with a closed loop of the flux salt. The short-time high-temperature combined with the low-temperature holding sintering method may provide an effective strategy for the synthesis of other single-crystal materials with excellent electrochemical properties.