Electrolyte System Research Articles

Electrolyte Engineering with TFA- Anion-Rich Solvation Structure to Construct Highly Stable Zn2+/Na+ Dual-Salt Batteries.

Electrolyte engineering is recognized as an effective technique for high-performance aqueous zinc-ion rechargeable batteries, addressing difficulties such as free water decomposition, zinc anode corrosion, and zinc dendrite growth. Different from traditional strategies in aqueous electrolyte systems, this work focuses on organic electrolytes involving zinc trifluoroacetate hydrate (Zn(TFA)2·xH2O), sodium trifluoroacetate (NaTFA) dual-salt and acetonitrile (AN) solvent, in which trifluoroacetate anions (TFA- anions) have strong affinity toward zinc ions to form anion-rich solvates, thus inducing an inorganic-rich solid electrolyte interphase (SEI) to protect Zn from dendrite growth and side reactions. The Zn anode manifests long-term cycling over 2400h at a current density of 0.5mAcm-2 with a high Coulombic efficiency (CE) of 99.75%, showing an areal capacity as high as 5mAhcm-2. Owing to the high reversibility of the sodium ions intercalation/deintercalation process in Na2MnFe(CN)6, the Zn//Na2MnFe(CN)6 full cells with the dual-salt electrolyte perform much better in terms of capacity retention than a device with Zn(TFA)2/AN electrolyte. This approach may open a new avenue for efficient zinc-ion rechargeable batteries via developing organic electrolytes.

Sustainable Fabrication of Graphene Oxide Cathodes from Graphite of Failed Commercial Li-Ion Batteries for High-Performance Aqueous Zn-Ion Batteries.

The need for revamping spent graphite (SG) from battery waste of commercial lithium-ion batteries and employing it as a source for the synthesis of graphene oxide (GO) is focused. Thus, this work emphasizes the study of GO sheets, synthesized via modified Hummer's method from spent graphite (SG-GO) as cathodes for an aqueous zinc ion battery (AZIB) system, for the first time in literature. For comparison, graphene oxide is also synthesized using commercial graphite powder, its structural and morphological properties are analyzed with SG-GO. The coin cell AZIB device is fabricated for both the GOs and the electrochemical performances revealed that SG-GO portrayed an enhanced charge capacity of 270 mAh g-1 at 0.1 A g-1 in 3m ZnSO4 in comparison to GO which delivered ≈198 mAh g-1 at the same current density of 0.1 A g-1. The long-run cycling analysis of SG-GO elucidated the capacity retention of 77.3% at 1 A g-1 even after 1000 cycles. Moreover, the performance of SG-GO is inspected in different electrolyte systems and the suitable electrolyte underwent concentration variation studies to figure out the capability of the system in storing Zn2+ ions which is found to be more in 3M ZnSO4 electrolyte.

Self-grown carbon nanotubes supported fluorine-free Mo2CTx conductive layers for efficient potassium storage

Mo2CTx is relatively less studied among MXenes family, especially for rechargeable alkali metal ion batteries. Herein, a systematic investigation has been conducted to unlock its potential as electrode materials in potassium-ion battery (PIBs), including innovative fluorine-free synthesis strategy, construction of heterostructure, and exploration of suitable electrolyte systems. Firstly, Cetyltriethylammnonium bromide (CTAB)-assisted etching route was provided to fabricate high-quality multilayer Mo2CTx with expanded interlayer space (C-Mo2CTx). The as-obtained C-Mo2CTx demonstrates a large specific capacity of 200 mAh g−1over 300 cycles in potassium-ion battery, surpassing the HF etched counterparts (F-Mo2CTx) by about 300 %. Afterwards, Zeolitic Imidazolate Frameworks (ZIF-67) derived Co, N-codoped carbon nanotubes (Co@NCNTs) were homogenously grown on the surface of Mo2CTx, working as embedding spacer to open the stacked Mo2CTx conductive layers (Mo2CTx-Co@NCNTs). Mo2CTx-Co@NCNTs electrode represents stable reversible capacity of 280 mA h g−1 over 300 cycles. The highly conductive matrix constructed by the strong bond between CNTs arrays and Mo2CTx conductive layer could provide numerous K-ion-diffusion pathways, and buffer volume strain and facilitate electron transfer. The present work proves the potential of Mo2CTx in PIBs and gives the systematic research methodologies on Mo2CTx-based materials in alkali metal ion storage.

Enhanced Long-Term Cycling Life of Ni-Rich NMC Cathodes in High-Voltage Lithium-Metal Batteries.

Li metal batteries (LMBs) have revived people's interest due to their high energy density. This work compares the cycling stability, structure stability, and thermal stability of Li||0.7Nb-NMC 9055 (0.7% Nb-modified LiNi0.9Co0.05Mn0.05O2) system in commercial carbonate electrolyte (1.0 M LiPF6 in EC/DMC) and designed carbonate electrolyte (1.0 M LiPF6-0.125 M LiNO3-0.025 M Mg(TFSI)2 in FEC-EMC). Li||0.7Nb-NMC 9055 battery with designed carbonate electrolyte exhibited superior capacity retention, 80% after ∼500 cycles. This can be explained by the improved mechanical integrity of the secondary particles and large reduced charge transfer resistance. Further, the real-time thermal monitoring of full cell via a high-precision, multimode calorimeter TAM IV Micro XL shows that the designed carbonate electrolyte with multisalt additive and FEC cosolvent has less heat release during the charging and discharge process, allowing these high-nickel (Ni) cathodes to reach closer to their full potential.

Aluminum Corrosion Chemistry in High-Voltage Lithium Metal Batteries with LiFSI-Based Ether Electrolytes.

High-voltage Li metal batteries (LMBs) based on ether electrolytes hold potential for achieving high energy densities exceeding 500 Wh kg-1, but face challenges with electrolyte oxidative stability, particularly concerning aluminum (Al) current collector corrosion. However, the specific chemistry behind Al corrosion and its effect on electrolyte components remains unexplored. Here, our study delves into Al corrosion in the representative LiFSI-DME electrolyte system, revealing that low-concentration electrolytes exacerbate Al current collector corrosion and solvent decomposition. In contrast, high-concentration electrolytes mitigate these issues, enhancing long-term stability. Remarkably, LiFSI-0.7DME electrolyte demonstrates exceptional stability with up to 1000 cycles at high voltage without significant capacity decay. These findings offer crucial insights into Al corrosion mechanisms in ether-based electrolytes, advancing our comprehension of high-voltage LMBs and facilitating their development for practical applications.

Ion Transport at Polymer-Argyrodite Interfaces.

Solid-state electrolytes, particularly polymer/ceramic composite electrolytes, are emerging as promising candidates for lithium-ion batteries due to their high ionic conductivity and mechanical flexibility. The interfaces that arise between the inorganic and organic materials in these composites play a crucial role in ion transport mechanisms. While lithium ions are proposed to diffuse across or parallel to the interface, few studies have directly examined the quantitative impact of these pathways on ion transport and little is known about how they affect the overall conductivity. Here, we present an atomistic study of lithium-ion (Li+) transport across well-defined polymer-argyrodite interfaces. We present a force field for polymer-argyrodite interfacial systems, and we carry out molecular dynamics and enhanced sampling simulations of several composite systems, including poly(ethylene oxide) (PEO)/Li6PS5Cl, hydrogenated nitrile butadiene rubber (HNBR)/Li6PS5Cl, and poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)/Li6PS5Cl. For the materials considered here, Li-ion exhibits a preference for the ceramic material, as revealed by free energy differences for Li-ion between the inorganic and the organic polymer phase in excess of 13 kBT. The relative free energy profiles of Li-ion for different polymeric materials exhibit similar shapes, but their magnitude depends on the strength of interaction between the polymers and Li-ion: the greater the interaction between the polymer and Li-ions, the smaller the free energy difference between the inorganic and organic materials. The influence of the interface is felt over a range of approximately 1.5 nm, after which the behavior of Li-ion in the polymer is comparable to that in the bulk. Near the interface, Li-ion transport primarily occurs parallel to the interfacial plane, and ion mobility is considerably slower near the interface itself, consistent with the reduced segmental mobility of the polymer in the vicinity of the ceramic material. These findings provide insights into ionic complexation and transport mechanisms in composite systems, and will help improve design of improved solid electrolyte systems.

Entropy-Driven 60mol% Li Electrolyte for Li Metal-Free Batteries.

Highly Li-concentrated electrolytes are acknowledged for their compatibility with Li metal negative electrodes and high voltage positive electrodes to achieve high-energy Li metal batteries, showcasing stable and facile interfaces for Li deposition/dissolution and high anodic stability. This study aims to explore a highly concentrated electrolyte by adopting entropy-driven chemistry for Li metal-free (so-called anode-free) batteries. The combination of lithium bis(fluorosulfonyl)amide (LiFSA) and lithium trifluoromethanesulfonate (LiOTf)salts in a pyrrolidinium-based ionic liquid is found to significantly modify the coordination structure, resulting in an unprecedented 60mol% Li concentration and a low solvent-to-salt ratio of 0.67:1 in the electrolyte system. This novel 60mol% Li electrolyte demonstrates unique coordination stricture, featuring a high ratio of monodentate-anion structures and aggregates, which facilitates an enhanced Li+ transference number and improved anodic stability. Moreover, the developed electrolyte provides a facile de-coordination process and leads to the formation of an anion-based solid electrolyte interface, which enables stable Li deposition/dissolution properties and demonstrates excellent cycling stability in the Li metal-free full cell with a Li[Ni0.8Co0.1Mn0.1]O2 (NCM811) positive electrode.

Hydrated molten salt electrolytes effectively promote electrocatalytic NH3 synthesis at low temperatures

In the field of electrocatalytic nitrogen reduction reaction (NRR), molten salt is used as a unique electrolyte due to its advantages of high N2 solubility and wide electrochemical window. However, it has failed to be widely used due to its high reaction temperature (mostly > 200 °C) and low yield. Herein, a novel low-temperature (<100 °C) electrolysis system with hydrated molten salt hybrid electrolyte is designed. This system exhibits an ammonia yield of 1.003 × 10−8 mol s−1 cm−2 (−0.7 V vs. SCE) at 60 °C. Faradaic efficiency (FE) reaches 80.45 % (−0.65 V vs. SCE). The NH3 yield and FE are increased by 18.6 and 2 times compared to the previously reported low-temperature system, respectively. Linear sweep voltammetry (LSV), in situ Raman and in situ Fourier Transform-Infrared (FT-IR) experiments show that solid crystalline water can be used as a hydrogen source to effectively promote NRR while inhibiting the hydrogen evolution reaction (HER). Molecular dynamics (MD) experiments confirm that the electrolyte system maintains a high N2 solubility and mass transfer rate.

Emerging Two-Dimensional Materials for Proton-Based Energy Storage.

The rapid diffusion kinetics and smallest ion radius make protons the ideal cations toward the ultimate energy storage technology combining the ultrafast charging capabilities of supercapacitors and the high energy densities of batteries. Despite the concept existing for centuries, the lack of satisfactory electrode materials hinders its practical development. Recently, the rapid advancement of the emerging two-dimensional (2D) materials, characterized by their ultrathin morphology, interlayer van der Waals gaps, and distinctive electrochemical properties, injects promises into future proton-based energy storage systems. In this perspective, we comprehensively summarize the current advances in proton-based energy storage based on 2D materials. We begin by providing an overview of proton-based energy storage systems, including proton batteries, pseudocapacitors and electrical double layer capacitors. We then elucidate the fundamental knowledge about proton transport characteristics, including in electrolytes, at electrolyte/electrode interfaces, and within electrode materials, particularly in 2D material systems. We comprehensively summarize specific cases of 2D materials as proton electrodes, detailing their design concepts, proton transport mechanism and electrochemical performance. Finally, we provide insights into the prospects of proton-based energy storage systems, emphasizing the importance of rational design of 2D electrode materials and matching electrolyte systems.

Designing electrolytes for enhancing stability and performance of lithium-ion capacitors at large-scale cylindrical cells

This study investigates the impact of fluorinated ethylene carbonate (FEC) as a co-solvent in the electrolytes of large-scale lithium-ion capacitors (LICs), an area previously unexplored. Our comprehensive analysis integrates electrochemical analysis, gas detection, and surface chemical examination to assess the performance and stability of a 1.2 M LiPF6 electrolyte system. We explored various formulations, including a standard EC/EMC/DEC mixed solvent and newly designed electrolytes with FEC additions, such as EC/EMC/DEC/FEC and DMC/FEC blends. Our findings demonstrate that the DMC/FEC blend matches and even surpasses the capacity retention of traditional electrolytes, suggesting enhanced long-term stability. FEC's presence significantly reduces electrolyte decomposition, as confirmed by in situ Differential Electrochemical Mass Spectrometry and ex-situ gas chromatography. Further, surface chemical analysis highlighted the formation of a stable, LiF-rich solid electrolyte interface (SEI) when FEC is included, thereby improving the chemical stability of the system. These results underline FEC's crucial role in optimizing electrolyte compositions, thus advancing the development of more efficient and durable LIC systems. FEC's integration into LIC electrolytes represents a significant breakthrough, enhancing overall performance and longevity, with broad implications for the application of LICs in various technologies.

Understanding the Effect of Lithium Nitrate as Additive in Carbonate-Based Electrolytes for Silicon Anodes

Due to its high specific capacity, silicon is one of the most promising anode materials for next-generation lithium-ion batteries. However, its large volumetric changes upon (de)lithiation of ∼300% lead to a rupture/re-formation of the solid-electrolyte interphase (SEI) upon cycling, resulting in continuous electrolyte consumption and irreversible loss of lithium. Therefore, it is crucial to use electrolyte systems that form a more stable SEI that can withstand large volume changes. Here, we investigate lithium nitrate (LiNO3) and lithium nitrite (LiNO2) as electrolyte additives. Linear scan voltammetry on carbon black working electrodes in a half-cell configuration with LiNO3-containing 1 M LiPF6 in EC/DEC (1/2 v/v) revealed a two-step reduction mechanism, whereby the first reduction peak could be attributed to the conversion of LiNO3 to LiNO2, while X-ray photoelectron spectroscopy on harvested electrodes suggests the formation of Li3N during the second reduction peak. On-line electrochemical mass spectrometry (OEMS) on carbon black electrodes showed that N2O gas is evolved upon the reduction of LiNO3- and LiNO2-containing electrolytes but that the gassing associated with EC reduction is significantly reduced. Furthermore, OEMS and voltammetry were used to examine the redox chemistry of LiNO2 additive. Finally, LiNO3 and LiNO2 additives significantly improved the cycle-life of Si||NCM622 full-cells.

Density and coefficients of Jones–Dole equation for viscosity measurement of l-isoleucine, l-proline, and l-glutamine in aqueous KCl solution at 298.15–323.15 K

The present studies reported the experimental data on thermophysical properties such as density and viscosity of aqueous solutions of different amino acids namely l-isoleucine, l-proline, and l-glutamine in 1.5 mol/L KCl solution at different temperatures ranging from 298.15 to 323.15 K. Hence, the aim of this study is to investigate interactions between amino acids and KCl solution at dilute concentrations. For understanding amino acid and KCl solution interactions, we will investigate ion–ion and ion–solvent interactions. It has been observed that the density and viscosity rise with amino acid concentration and decrease with temperature. Using the Jones–Dole equation, the viscosity A and B coefficients have been determined. The viscosity B-coefficient values for all the three amino acids in aqueous electrolyte system are depicted as positive. The positive values of B-coefficient indicate a strong alignment of the solvent molecules with solute molecules. The amino acid l-glutamine acts as a structure breaker solute. This structure breaking effect of l-glutamine on solvent may be attributed to the domination of hydrophilic nature of amide group. l-isoleucine and l-proline act as structure maker in electrolyte system.

Conduction in heterogeneous systems in the low-frequency regime: variational principles and boundary integral equations.

The response of a homogeneous material to the presence of an external low-frequency oscillating electric field can be described by means of an effective complex conductivity. Low frequencies are characterized by negligible magnetic and radiative effects. The properties of heterogeneous systems, composed of multiple homogeneous regions, can be determined from those of the individual components and their geometric arrangement. Examples of such heterogeneous systems include soft materials such as colloidal suspensions, electrolyte systems, and biological tissues. The difference in the intrinsic conductivities between the homogeneous regions leads to the creation of an oscillating charge density localized at the interfaces between these regions. We show how to express key properties of these systems using this dynamic charge as a fundamental variable. We derive a boundary integral equation for the charges and reconstruct potentials and fields from its solution. We present a variational principle that recovers the fundamental equations for the system in terms of the oscillating charge and show that, in some formulations, the associated functional can be interpreted in terms of the power dissipated in the system. The boundary integral equations are numerically solved using a finite element method for a few illustrative cases.

Flexible magnesium-ion-conducting solid poly-blend electrolyte films for magnesium-ion batteries

Solid biodegradable polymer electrolyte systems are considered the optimal choice for energy storage devices because they are both cost-effective and energy-efficient. A solid blend polymer electrolyte (SBPE) membrane capable of transporting magnesium ions was prepared using a mixture of 70 wt% methylcellulose, 30 wt% chitosan, and varying wt% magnesium perchlorate salt. X-ray diffraction analysis revealed an increase in the amorphous nature caused by the inclusion of Mg(ClO4)2 salt in the polymer blend matrix. A Fourier transform infrared spectroscopy study of samples containing varying salt concentrations revealed secondary interactions between polymer segments and salt, which provides the basis for energy density. Moreover, through impedance analysis, it was determined that the bulk resistance decreased with increasing salt concentration. The SBPE containing 30 wt% magnesium perchlorate exhibited the highest ionic conductivity, with a value of 2.49 × 10–6 S cm−1. A comprehensive evaluation of the ion transport parameters, including mobility, carrier density, and diffusion, was conducted for the prepared electrolyte samples. Notably, an ionic transference number (tion) of approximately 0.83 was observed for the SBPE sample with 30 wt% magnesium salt, indicating ions’ prevalence as the system’s primary charge carriers. Electrochemical analyses demonstrated that the SBPE with the highest ion conductivity possessed an electrochemical stability window (ESW) of 1.92 V. Additionally, the thermal characteristics of the samples were evaluated using thermogravimetric analysis (TGA) to assess the thermal stability of the electrolyte. Finally, the highest conducting polymer electrolyte was employed to construct a primary magnesium battery, and its discharge profile with different cathode materials was studied. Based on these findings, the current study suggests an environmentally friendly, biodegradable, and economically viable electrolyte option suitable for separator cum electrolytes in magnesium-ion batteries.

Impact of functional groups on lithium salt dispersion and mobility in polymer electrolytes

AbstractSolid Polymer electrolytes are versatile, highly processible and electrochemically compatible with solid electrode materials. The versatility of these materials is a result of the existence of many possible conductive polymer‐salt, polymer‐polymer and salt‐salt combinations. Despite the wide array of available lithium salts, most polymer electrolyte materials are made using lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) due to its long history of achieving relatively high ionic conductivities in polymer electrolyte systems with the most famous being poly(ethylene oxide) (PEO). It is however possible that better ionic conductivities can be achieved with different salts and/or in polymer matrices containing different functional groups. This is because ionic conductivity in polymer electrolytes is partially based on the ability of the polymer matrix to dissolve and bond to the salt. These interactions impact local‐scale ion mobility which can be measured via NMR spectroscopy using pulsed field gradient experiments. In this work, polymer electrolytes are prepared using PEO, hydrogenated nitrile butadiene rubber and poly(propylene) carbonate. Ion mobility, lithium conductivity and salt‐polymer interactions are investigated to compare interactions between LiTFSI and lithium cyano(trifluorosulfonyl)imide in polymers with common salt‐dissociating functional groups such as ethyl, nitrile and carbonate to determine the impact of these interactions on ionic conductivity.

Visible and near-infrared modulating tungsten suboxide nanorods electrochromic films in acidic aqueous electrolytes

Proton-based aqueous electrolytes can be used to achieve high performance electrochromic nanocrystal thin films due to their small ion size. However, acidic aqueous electrolyte systems have not yet been explored in near-infrared (NIR) absorbing plasmonic tungsten oxide nanocrystal films. Here, we demonstrate tungsten suboxide nanorod films with excellent visible and NIR modulation performance in the H+-based aqueous electrolytes, thanks to their mesoporous structure, nanosized domains, and open tunnel structure. Colloidally synthesized WO2.83 nanorods with an average width of 6 nm and length of 48 nm were converted to WO2.90 nanorod film via annealing in air, while still preserving open tunnels. These films exhibit fast switching speed (tc = 0.9 s, tb = 2.1 s), excellent cycling stability over 2500 cycles, wide optical modulation up to ΔT = 53.8 % in the NIR region, and a high coloration efficiency (CE) of 167 cm2 C⁻1 at 1300 nm. Additionally, introducing a thin spacer (25 μm) reduced intrinsic NIR absorption from water, thereby enhancing the NIR modulation properties. These highly performing aqueous proton-electrolytes-based electrochromic devices open new possibilities for implementing visible and NIR electrochromism.

Si particle size blends to improve cycling performance as negative electrode for all-solid-state lithium-ion battery

Silicon negative electrodes dramatically increase the energy density of lithium-ion batteries (LIBs), but there are still many challenges in their practical application due to the limited cycle performance of conventional liquid electrolyte systems. In this study, we clarified that the use of an inorganic solid electrolyte improves the cycle performance of the LIB with the Si negative electrode and the size of Si particles influenced the properties of the all-solid-state LIB. The all-solid-state LIB using micro-sized silicon (mSi) particles as the negative electrode active material showed a large initial discharge capacity (2400 mAh g-1), but the discharge capacity decreased as charge/discharge cycles increased. In contrast, the all-solid-state LIB using nano-sized silicon (nSi) particles showed a low initial discharge capacity (1000 mAh g-1), but the discharge capacity increased for the initial 20 charge/discharge cycles. The cross-sectional images analyzed by scanning electron microscopy showed that for mSi particles, cracks and voids occurred due to volumetric changes during charging and discharging, interrupting the flow path of ions and electrons, whereas for nSi particles, the contact with the solid electrolyte and conductive material was improved. Moreover, the all-solid-state LIB using the negative electrode of nSi: mSi = 7: 3 (mass ratio) showed higher initial discharge capacity and longer cycle performance than that using mSi and nSi.

A novel multifunctional electrolyte system for high performance Li-ion batteries

Lithium-ion batteries have advantages such as environmental protection and sustainable use, but the widespread application of lithium-ion battery-powered vehicles is limited by the inability to quickly charge and extreme ambient temperatures, and reasonable design of electrolyte components can effectively solve these problems. Here, a novel fluoroethylene carbonate (FEC)/ethyl acetate (EA) based electrolyte containing lithium difluorophosphate (LiPO2F2, 2 wt%) and lithium bis(fluorosulfonyl)imide salt (LiFSI, 1.0 M) is first reported. The electrolyte containing these components has the characteristics of low freezing point, low viscosity and high ionic conductivity. Especially, due to the preferential decomposition of FEC, LiFSI and LiPO2F2, uniform multiphase inorganic LiF and Li3N species are formed on the electrode surface with enhanced robustness and ion transfer kinetics. So, the graphite||LiNi0.5Co0.2Mn0.3O2&LiMn2O4 (Gr||LMO&NCM523) batteries in the designed electrolyte maintain high capacity and coulombic efficiency (100 %) after 200 times at 1C charge and discharge current density at 25 °C and 45 °C. At −20 °C, the batteries have a coulombic efficiency of 50 % and capacity of 38.0 mA h g−1 after 200 charging and discharging cycles, showing excellent low-temperature fast dynamics. Our work supplies an efficient way to accelerate the engineering application of Li-ion batteries.

Aqueous lithium-ion battery of dual electrolytes separated by cation-exchange membrane with enhanced rate capability for thick electrodes

Aqueous lithium-ion batteries (ALIBs) have received increasing attention because of their high safety. An aqueous electrolyte system compatible with a wider electrochemical window and high ionic conductivity is desired to increase the industrial potential of ALIBs. In this study, a dual-electrolyte system separated by a perfluorosulfonated cation-exchange membrane (CEM) was designed to demonstrate a 2 V-class ALIB. The specific compositions of the cathode and anode electrolytes to be stable in facing via the CEM were experimentally determined, where each electrolyte pH was adjusted for the lithiation/delithiation of LiMn2O4 and TiO2, together with a high ionic conductivity of >70 mS/cm. The pH difference successfully suppressed water splitting, which enabled stable battery operation in the 1.5–2.8 V range with >99 % Coulombic efficiency. The optimized cathode and anode electrolytes also exhibited better rate performances even in a thick electrode layer over 50 mg/cm2 of the active material loading than a conventional concentrated electrolyte of 21 mol/kg LiTFSI (9 mS/cm). The present system, which employs the aqueous electrolytes with smaller lithium salts and favorable ionic conductivities should increase the industrial potential of low-cost aqueous lithium-ion batteries.

Study on a new molten salt for electrolytic preparation of Ti: dissolution mechanism and kinetic analysis of TiO2 in NaCl-KCl-K2TiF6

Understanding the dissolution behavior and reaction rate of TiO2 in the NaCl-KCl-K2TiF6 electrolyte system is paramount for the advancement of a novel titanium metal production process. Initially, the liquidus temperature of the electrolyte system decreases with an increase in K2TiF6 content or the addition of a small amount of TiO2. Kinetic analysis reveals that the dissolution of TiO2 in the electrolyte follows a zero-order reaction for the first 30 min, with an activation energy of 2.46 × 105 (J/mol). The saturation concentration of TiO2 is reached at 300 min, and higher reaction temperatures or increased K2TiF6 content enhance the solubility of TiO2 in the electrolyte. In addition, the regression equation Y = − 25.02096 + 1.06412x1 + 0.0362x2 among the solubility of TiO2 (Y), the ratio of fluoride to chloride in electrolyte (x1) and experimental temperature (x2) was established by multivariate regression model. The analysis indicates that TiO2 dissolves in the electrolyte system as a complex K2NaTiOF5, releasing TiOF2 gas during the reaction. Finally, characterization studies on the elemental composition, chemical state, molecular structure, and material morphology of K2NaTiOF5 complex and TiOF2 gas reveal even distribution of elements. The K2NaTiOF5 complex molecules exhibit irregularly polygonal dispersion, while TiOF2 exists as agglomerated particles.