Electrochemical performance of a lead fluoride electrode mixed with carbon in an electrolyte containing triphenylboroxine as an anion acceptor for fluoride shuttle batteries

In fluoride shuttle batteries (FSBs), the addition of an anion acceptor (AA) is required to dissolve the supporting electrolyte salt in an organic solvent. Based on theoretical calculations and practical experiments, the effectiveness of triphenylboroxine (TPhBX) as an AA for FSB was verified. Using an electrolyte with TPhBX as an AA, the specific capacities of the following two types of lead fluoride (PbF₂) electrodes were evaluated: (i) PbF₂ pulverized using a ball mill, (ii) pulverized PbF₂ mixed with carbon using a ball mill. The experimental results indicate that mixing PbF₂ with carbon using a ball mill increases the specific capacity of PbF₂ electrode

Electrochemical properties of lead fluoride electrode in fluoride shuttle battery

Recently, the reversible discharge and charge reaction of BiF₃ electrode for fluoride shuttle battery (FSB) that can be used as a promising candidate for next-generation battery are observed using a liquid-based electrolyte. In this study, we investigate the electrochemical performance of PbF₂ as an active material for the FSB. To increase the electronic conductivity, the PbF₂ was mixed with carbon, and the composite material between PbF₂ and carbon, PbF₂/C, is formed. High discharge and charge capacities are obtained for PbF₂/C during the first cycle. Although the discharge and charge capacities gradually decreased, the discharge and charge reactions occurred in the second and third cycles. To confirm the progress of the discharge and charge reactions, the crystal structure change of the active material during discharging and charging in the first and second cycles is evaluated using X-ray diffraction (XRD). From the XRD results, the formation of Pb and PbF₂ during discharging and charging can be confirmed, indicating that the discharge (PbF₂ + 2e− → Pb + 2F−) and charge (Pb + 2F− → PbF₂ + 2e−) reactions progress in both the first and second cycles

Improved electrochemical performances in a bismuth fluoride electrode prepared using a high energy ball mill with carbon for fluoride shuttle batteries

Bismuth fluoride (BiF₃) is a promising positive electrode material for fluoride shuttle batteries (FSBs) owing to its high theoretical specific capacity (302 mA h g⁻¹). However, it exhibits low practical capacity. The methods for preparing the electrode are known to have significant effects on battery performance. The mixture between BiF₃ and carbon, BiF₃/C, prepared by high energy ball milling method has been already approved in lithium ion batteries. With this method, a significant improvement over the discharge and charge capacities of the BiF₃/C electrode has been achieved. In this work, for the first time, BiF₃/C electrode has been used for FSB. Using BiF₃/C electrode significantly increased the discharge and charge capacities. To confirm the progress of the discharge and charge reactions of BiF3/C electrode, the crystal structure of active materials and oxidation state of Bi for the BiF₃/C electrode during discharging and charging has been investigated by X-ray diffraction and X-ray absorption fine structure. The results reveal that, with higher capacity values, discharge and charge reactions related to BiF₃/C have been realized

Oxidation behaviour of lattice oxygen in Li-rich manganese-based layered oxide studied by hard X-ray photoelectron spectroscopy

The oxidation/reduction behaviours of lattice oxygen and transition metals in a Li-rich manganese-based layered oxide Li[Li0.25Ni0.20Mn0.55]O1.93 are investigated by using hard X-ray photoelectron spectroscopy (HAX-PES). By making use of its deeper probing depth rather than in-house XPS analyses, we clearly confirm the formation of O- ions as bulk oxygen species in the active material. They are formed on the 1st charging process as a charge compensation mechanism for delithiation and decrease on discharging. In particular, the cation-anion dual charge compensation involving Ni and O ions is suggested during the voltage slope region of the charging process. The Ni ions in the material are considered to increase the capacity delivered by a reversible anion redox reaction with the suppression of O2 gas release. On the other hand, we found structural deterioration in the cycled material. The O- species are still observed but are electrochemically inactive during the 5th charge-discharge cycle. Also, the oxidation state of Ni ions is divalent and inactive, although that of Mn ions changes reversibly. We believe that this is associated with the structural rearrangement occurring after the activation process during the 1st charging, leading to the formation of spinel- or rocksalt-like domains over the sub-surface region of the particles

Atomic defects in titanium dioxide.

The functionality of solid materials is defined by the type and ordering of the constituent atoms. By introducing defects that perturb the ordered structure, new functionality is created within the solid material. Atomic defects in titanium dioxide, such as oxygen vacancies, atomic hydrogen, and interstitial Ti, typically create new functionality. However, the fundamental physical properties of atomic defects in TiO2 are not fully understood and still remain controversial. In this account, the progress and issues for debate regarding the physical properties, electronic structure, and manipulation mechanisms of atomic defects in TiO2 as well as their interaction with gold nanoclusters are described

Surface and interface sciences of Li-ion batteries

The application potential of Li-ion batteries is growing as demand increases in different fields at various stages in energy systems, in addition to their conventional role as power sources for portable devices. In particular, applications in electric vehicles and renewable energy storage are increasing for Li-ion batteries. For these applications, improvements in battery performance are necessary. The Li-ion battery produces and stores electric power from the electrochemical redox reactions between the electrode materials. The interface between the electrodes and electrolyte strongly affects the battery performance because the charge transfer causing the electrode redox reaction begins at this interface. Understanding of the surface structure, electronic structure, and chemical reactions at the electrode–electrolyte interface is necessary to improve battery performance. However, the interface is located between the electrode and electrolyte materials, hindering the experimental analysis of the interface; thus, the physical properties and chemical processes have remained poorly understood until recently. Investigations of the physical properties and chemical processes at the interface have been performed using advanced surface science techniques. In this review, current knowledge and future research prospects regarding the electrode–electrolyte interface are described for the further development of Li-ion batteries

Triphenylboroxine and Triphenylborane as Anion Acceptors for Electrolyte in Fluoride Shuttle Batteries

For liquid-based fluoride shuttle batteries, electrolyte composed of organic solvent and supporting electrolyte salt is developed. To increase the solubility of supporting electrolyte salt in organic solvent, anion acceptors (triphenylboroxine or triphenylborane) are added. The addition of anion acceptor greatly increases the solubility of supporting electrolyte salt, and discharge-charge reaction of BiF₃ electrode is confirmed in the prepared electrolytes. A supporting electrolyte salt (Cesium fluoride (CsF)) dissolves sparingly in an organic solvent (bis[2-(2-methoxyethoxy)ethyl]ether (tetraglyme: G4)); however, the solubility of the CsF in the G4 is greatly increased by addition of an anion acceptor (triphenylboroxine or triphenylborane). Using the developed electrolyte for fluoride shuttle battery, discharge and charge reactions of a metal fluoride electrode can be progressed

Charge and Discharge Reactions of a Lead Fluoride Electrode in a Liquid‐Based Electrolyte for Fluoride Shuttle Batteries:‐The Role of Triphenylborane as an Anion Acceptor‐

This article also appears in: Electro, Physical & Theoretical ChemistryLead fluoride (PbF₂) is a promising electrode material for fluoride shuttle batteries (FSBs) owing to its high theoretical capacity (219 mAh g⁻¹). In this study, the discharge and charge capacities of a PbF₂ electrode were measured using a bis[2‐(2‐methoxyethoxy)ethyl] ether containing cesium fluoride and triphenylborane as an electrolyte. A high specific capacity was maintained during both the discharge and charge processes in the first cycle, but the capacity decreased from the first charge process to the following discharge process. To clarify the electrochemical reaction mechanism, the dissolution and change in the electronic state of Pb at the PbF2 electrode during the discharge and charge processes were evaluated via atomic absorption spectrometry (AAS) and X‐ray photoelectron spectroscopy (XPS). The results obtained from AAS and XPS indicated that Pb was formed during the discharge process. Conversely, the formation of PbF₂ and dissolution of Pb coexisted within the wide range of charge process. The PbF₂ could react in the following cycle, but the dissolved Pb was unable to contribute to the following discharge/charge reaction. Therefore, after the initial charge process, the capacity decreased

Difference of rate performance between discharge and charge reactions for bismuth fluoride electrode in lithium-ion battery

The conversion-based BiF₃ is a promising cathode material for lithium-ion batteries due to its high theoretical capacity (302 mAh g⁻¹). Nanocomposites of BiF₃ and carbon (BiF₃/C) are known to improve the electrochemical performance by increasing the electronic conductivity of the electrode. Here we investigate the electrochemical performance of BiF3/C at high C-rates. In particular, we newly investigate the difference of high C-rate performance between discharge and charge reactions. The discharge and charge capacities in the first cycle were almost the same at 0.1 C. In contrast, the discharge capacity was higher than charge capacity at 10 C. Further, during cycling at 10 C, the charge capacity drastically decreased, but the discharge capacity remained high. The rate performance of the discharge reaction was higher than that of the charge reaction, especially after cycling

Atomic-level viscosity distribution in the hydration layer

界面で流動性を失う水分子の直接可視化に成功 --原子間力顕微鏡による炭酸カルシウム表面の水和水の粘性測定--. 京都大学プレスリリース. 2019-03-29.Viscosity of the solvation structures is crucial for the development of energy-efficient biochemical and electrochemical devices. Elucidating their subnanoscale distributions can cause the formation of a sustainable energy society. Here, we visualize the three-dimensional damping distribution on a CaCO3 surface composing binary ion species using ultra-low-noise frequency-modulation atomic force microscopy. With the support from molecular dynamics simulation, we found a strikingly large damping at the calcium sites, which demonstrates the capability of this methodology to visualize molecular-scale viscosity in the hydration layers, which will expedite the evolutions of various functional devices