Charge Compensation Mechanism Research Articles

Crystal Growth and Spectroscopy of Yb2+-Doped CsI Single Crystal

The single crystals of CsI-Yb2+ were grown, and their spectroscopic studies were conducted. The observed luminescence in CsI-Yb2+ is due to 5d–4f transitions in Yb2+ ions. Using time-resolved spectroscopy, spin-allowed and spin-forbidden radiative transitions of ytterbium ions at room temperature were found. The excitation spectra of Yb2+ luminescence bands were obtained in the range of 3–45 eV. The mechanism of charge compensation of Yb2+ ions in a CsI crystal was also studied, the spectrum of the thermally stimulated depolarization current was measured, and the activation energies of the two observed peaks were calculated. These peaks belong to impurity–vacancy complexes in two different positions. The charge compensation of Yb2+ occurs via cation vacancies in the nearest-neighbor and next-nearest-neighbor positions.The Yb2+ ions are promising dopants for CsI scintillators and X-ray phosphors in combination with SiPM photodetectors.

Understanding the Correlation between Electrochemical Performance and Operating Mechanism of a Co-free Layered-Spinel Composite Cathode for Na-Ion Batteries.

Compositing different crystal structures of layered transition metal oxides (LTMOs) is an emerging strategy to improve the electrochemical performance of LTMOs in sodium-ion batteries. Herein, a cobalt-free P2/P3-layered spinel composite, P2/P3-LS-Na1/2Mn2/3Ni1/6Fe1/6O2 (LS-NMNF), is synthesized, and the synergistic effects from the P2/P3 and spinel phases were investigated. The material delivers an initial discharge capacity of 143 mAh g-1 in the voltage range of 1.5-4.0 V and displays a capacity retention of 73% at the 50th cycle. The material shows a discharge capacity of 72 mAh g-1 at 5C. This superior rate performance by the material could be by virtue of the increased electronic conductivity contribution of the incorporated spinel phase. The charge compensation mechanism of the material is investigated by in operando X-ray absorption spectroscopy (in a voltage range of 1.5-4.5 V vs Na+/Na), which revealed the contribution of all transition metals toward the generated capacity. The crystal structure evolution of each phase during electrochemical cycling was analyzed by in operando X-ray diffraction. Unlike in the case of many reported P2/P3 composite cathode materials and spinel-incorporated cobalt-containing P2/P3 composites, the formation of a P'2 phase at the end of discharge is absent here.

Hydrothermal vs. Electrochemical reduction of graphene oxide: A physico-chemical and quartz crystal microbalance study

Reduced Graphene Oxide possesses numerous interesting properties, making it one of the most studied materials today. By this way, applications in various fields, including fundamental research, can be found. Nevertheless, the complexity of reduced Graphene Oxide lies in its fabrication process which defines their properties. In this paper, two fabrication methods -electrochemical and hydrothermal reduction of graphene oxide - were compared using physico-chemical and electrogravimetric analysis. Our findings reveal significant morphological differences between the two methods, accompanied by different electrochemical behaviors, when tested in aqueous electrolyte (i.e. 0.5 M Na2SO4). Specifically, electrochemically reduced graphene oxide exclusively involves sodium (whether hydrated or not) in its charge compensation mechanism, whereas hydrothermally reduced graphene oxide also involves proton in sodium sulfate solution.

Prussian Blue Analogues for Sodium-Ion Battery Cathodes: A Review of Mechanistic Insights, Current Challenges, and Future Pathways.

Prussian blue analogues (PBAs) have emerged as highly promising cathode materials for sodium-ion batteries (SIBs) due to their affordability, facile synthesis, porous framework, and high theoretical capacity. Despite their considerable potential, practical applications of PBAs face significant challenges that limit their performance. This review offers a comprehensive retrospective analysis of PBAs' development history as cathode materials, delving into their reaction mechanisms, including charge compensation and ion diffusion mechanisms. Furthermore, to overcome these challenges, a range of improvement strategies are proposed, encompassing modifications in synthesis techniques and enhancements in structural stability. Finally, the commercial viability of PBAs is examined, alongside discussions on advanced synthesis methods and existing concerns regarding cost and safety, aiming to foster ongoing advancements of PBAs for practical SIBs.

Dual-ion regulation of coordination chemistry for high-voltage stabilized P2-type cathode

P2-Na2/3Ni1/3Mn2/3O2 has shown great potential as cathode material for sodium-ion batteries with its high theoretical capacity and energy density. However, severe structural changes are induced by charging P2-Na2/3Ni1/3Mn2/3O2 above 4.2 V, resulting in rapid capacity decay and poor kinetic capability. In this study, we propose a Zn/Ti synergistic modification strategy to stabilize the P2-type cathode under high voltage. It is found that the P2-O2 phase transition with large volume change is replaced by a milder P2-Z phase transition with the noteworthy improvement in structural stability and Na+ diffusion kinetics, due to the disordered Na+/vacancy and the suppressed of the sliding of transition metal layers, as disclosed by density functional theory calculations and in-situ X-ray diffraction. Concurrently, The phenomenon of Ni and O reductive coupling is inhibited by regulating local O coordination owing to the incorporation of a strong Ti−O covalence bond, leading to the more reversible charge compensation mechanism and the inhibited lattice O evolution, as clearly revealed by ex-situ X-ray absorption spectroscopy and Differential Electrochemical Mass Spectrometry. Consequently, we obtained a stable P2-Na0.67Zn0.05Ni0.28Mn0.52Ti0.15O2 cathode, achieving an average discharge voltage of 3.62 V at 0.1 C and a capacity retention of 80% after 500 cycles at 2 C. This research provides valuable insights into the enhancement of sodium-ion battery cathode materials by utilizing different functional ions in synergy.

Structural Behaviour and Charge-Compensation Mechanism in Li2Fe1−xCoxSeO Solid Solutions during Reversible Delithiation

The constantly growing demand for renewable electrical energy keeps the continuation of battery-related research imperative. In spite of significant progress made in the development of Na- and K-ion systems, Li-ion batteries (LIBs) still prevail in the fields of portative devices and electric or hybrid vehicles. Since the amount of lithium on our planet is significantly limited, studies dedicated to the search for and development of novel materials, which would make LIBs more efficient in terms of their specific characteristics and life lengths, are necessary. Investigations of less industry-related systems are also important, as they provide general knowledge which helps in understanding directions and strategies for the improvement of applied materials. The current paper represents a comprehensive study of cubic Li2Fe1−xCoxSeO compounds with an anti-perovskite structure. These solid solutions demonstrate both cationic and anionic electrochemical activity in lithium cells while being applied as cathodes. Cobalt cations remain inactive; however, their amount in the structure defines if the Se0/Se2− or Fe3+/Fe2+ redox couple dominates the charge compensation mechanism upon (de)lithiation. Apart from that, cobalt affects the structural stability of the materials during cycling. These effects were evaluated by means of operando XRD and XAS techniques. The outcomes can be useful for both fundamental and practice-relevant research.

Designing a 3D framework NaVOPO4 as a high-power, low-strain and long-life positive electrode material for Na-ion batteries

Advances in sodium-ion batteries hugely rely on perfecting the performance of active electrode materials. In this paper, we offer a new NaVOPO4 polymorph adopting a KTiOPO4-type framework as a promising high-rate, low-strain and long-life positive electrode material for sodium-ion batteries. NaVOPO4 is prepared via a facile hydrothermally-assisted solid-state ion exchange. The crystal structure is refined based on synchrotron X-ray powder diffraction (XRD) and validated by X-ray absorption spectroscopy (XAS), transmission electron microscopy analysis and density functional theory (DFT) calculations. The electrochemical performance of NaVOPO4 is evaluated through galvanostatic charge/discharge tests, cyclic voltammetry, potentiostatic intermittent titration and electrochemical impedance spectroscopy. A carbon-coated NaVOPO4 demonstrates a specific capacity of ∼110 mAh g–1 at a C/10 rate at an average potential of ∼3.93 V vs. Na+/Na. The material exhibits decent capacity retention and rate capability, maintaining over 74 % of the initial capacity after 1000 cycles at a C/2 rate and around 87% at a 2C charge/discharge rate. Diffusion coefficients of 10–11 cm2 s–1 and DFT-calculated energy barriers of ∼0.15–0.35 eV indicate fast Na+ ion diffusion within the NaVOPO4 framework. The vanadium oxidation state and charge compensation mechanism in NaVOPO4 are studied by XAS and DFT. Moreover, the operando XRD analysis coupled with DFT elucidates several phase transitions occurring in NaVOPO4 with an exceptionally low volume variation of 2.4% in total, highlighting the reversibility and structural stability during Na+ de/insertion. Overall, NaVOPO4 exhibits attractive electrochemical performance and stability, making it a potential candidate for sodium-ion battery cathode materials.

Depth-Resolving the Charge Compensation Mechanism from LiNiO2 to NiO2

Depth-Resolving the Charge Compensation Mechanism from LiNiO₂ to NiO₂

Probing the account of phase transition upon electrochemical cycling of the P2-Na0.67Ni0.15Fe0.2Mn0.65O2 layered oxide cathodes for sodium-ion batteries

Layered P2-Na0.67Ni0.15Fe0.2Mn0.65O2 (P2-NFM) cathode material has attracted great attention in sodium-ion batteries due to its high theoretical capacity, low cost, and environmental friendliness. However, P2-NFM exhibits irreversible phase transition and slip of transition metal layers in the high voltage range during charging process, leading to a gradually declined performance of the cathode material. It is therefore necessary to investigate the mechanism of phase transition of P2-NFM as well as the effect of phase transition on its performance. Herein, utilizing ex situ x-ray diffraction spectroscopy and x-ray photoelectron spectroscopy, the crystal structure and TM (transition-metal) bonding changes caused by phase transition are elucidated. It is found that P2-NFM is prone to undergo an irreversible P2-O2 phase transition at high voltage, causing changes in lattice parameters and rapid capacity decay. The irreversible phase transition is mainly due to he dynamic transformation of valence states of Fe and Ni in P2-NFM materials at high voltage. It is this process that results in irreversible fluctuations in the bond lengths between these elements and oxygen, consequently instigating interlayer slip within the material. Besides, the charge compensation mechanism of P2-NFM has been elucidated based on the study of its initial charging process. Results show that the charge compensation is mainly contributed by Ni and Fe in the high voltage range, while by a small amount of Mn in the low voltage range. It reveals the essential cause of the adverse phase transition of P2-NFM materials and points out the direction for improving the cycling stability of these layered oxide materials.

High-temperature transport properties of entropy-stabilized pyrochlores

In this report, the high-temperature transport properties of (Dy1−xCax)(Zr0.2Hf0.2Sn0.2Ti0.2Ge0.2)O7 pyrochlore oxides with x = 0, 0.05, and 0.1 are studied in dry and humid air. The phase composition and crystal structure were determined by using x-ray and neutron diffraction. The addition of calcium to the structure caused an increase in the concentration of oxygen vacancies, indicating an ionic charge compensation mechanism. Electrical studies allowed us to determine the total electrical conductivity as a function of the synthesis atmosphere and pH2O. The electrical conductivity turned out to be at the level of ∼10−3 S/cm at 800 °C, and only a slight effect of the presence of protonic defects in the structure on the total electrical conductivity was observed. In general, the samples had a low electrical conductivity with a relatively high activation energy of conduction.

Lead-free (K0.5Na0.5)NbO3 co-substituted with Ta5+ and Er3+: Structural, optical, dielectric and electrical properties

The lead-free K0.5Na0.5NbO3 (KNN) ceramics co-substituted with 0.05 mol Ta5+ and x mol Er3+ ions (K, Na) (1-3x) ErxNb0.95Ta0.05O3, with x = 0.00 to 0.05, have been successfully manufactured by using the solid-state reaction. The XRD results showed that the ceramics crystalize in pure perovskite with a trace of secondary phase, for low Er levels (x ≤ 0.02). Above this rate, the presence of secondary phases became more significant. The optical band gap energy of the synthesis samples has been determined using UV–vis absorbance spectra using Tauc's relation. The Ta and Er co-substitution leads to decrease the Eg of KNN material. The grain size is found to be minimal ≈490 nm and 240 nm of sintered pellets at x = 0.02 and 0.05 of Er content respectively with a high density. The dielectric study of (K, Na) (1-3x) ErxNb0.95Ta0.05O3 ceramics was carried out and double peaks were observed in relative permittivity versus temperature data for pure KNN and KNNTa corresponding to orthorhombic-tetragonal-cubic phase transitions. While for Er doped-KNNTa samples only a broad ferroelectric-paraelectric phase transition is observed and it shifted to the high temperature with increasing Er content. This broad peak observed in dielectric data for x = 0.02 of Er content is due to inhomogeneity and will certainly open new applications in microwave dielectrics. The ac conductivity variation of KNErNTa ceramics with diverse Er concentration was analyzed according to the charge compensation mechanism. However, for KNNTa, a decrease in conductivity values is attributed to the reduction in leakage current density. Meanwhile, at x = 0.01 and 0.02 of Er concentration, Er-doped KNNTa became semi-conductor. Further investigation revealed that the resistance of grains and grains boundaries are both minimal for x = 0.02 sample which are responsible for the increase of ac conductivity. For high Er concentration ≥0.03, the RG and RGB values increase along with decrease of conductivity value related to the increase in grain size found in SEM micrographs.

Unveiling charge compensation mechanisms in Na2/3MgxNi1/3-xMn2/3O2 cathode materials: insights into cationic and anionic redox

P2-type Na2/3Ni1/3Mn2/3O2 cathode material for sodium-ion batteries exhibits negligible voltage hysteresis during charge and discharge cycles, with oxygen redox mechanisms playing a pivotal, non-negligible role. Conversely, for the Na2/3Mg1/3Mn2/3O2 material featuring Mg substitution for Ni, O redox largely governs the entire charge and discharge process, accompanied by a pronounced voltage hysteresis. Upon combining these two materials – Na2/3MgxNi1/3-xMn2/3O2 – the transition metal and O redox processes, constituting the charge compensation mechanism, become paramount. These phenomena underscore the transition metal's influence on anionic redox, a topic with limited in-depth exploration in the existing literature. Within this study, we synthesized two materials, Na2/3Mg1/9Ni2/9Mn2/3O2 and Na2/3Mg2/9Ni1/9Mn2/3O2 (Mg-0.11, Mg-0.22), subsequently probing their transition metal and oxygen redox contributions to electrochemical capacity during the initial and 10th cycle charge and discharge processes by synchrotron-based mapping of resonant inelastic X-ray scattering and soft X-ray Absorption Spectroscopy. Our findings corroborate the presence of similar O redox contributions in the Mg-substituted materials. Intriguingly, the Mg-0.11 material exhibits a substantial enhancement in O redox following ten cycles, warranting further investigation due to its exceptional multiplicity, cycling performance, minimal voltage hysteresis, and potential impact on advancing sodium-ion battery commercialization.

Structures and Properties of High-Concentration Doped Th:CaF2 Single Crystals for Solid-State Nuclear Clock Materials.

Thorium-doped vacuum ultraviolet (VUV) transparent crystals is a promising candidate for establishing a solid-state nuclear clock. Here, we report the research results on high-concentration doping of 232Th:CaF2 single crystals. The structures, defects, and VUV transmittance performances of highly doped Th:CaF2 crystals are investigated by theoretical and experimental methods. The defect configurations formed by Th and the charge compensation mechanism (Ca vacancy or interstitial F atoms) located at its first nearest neighbor position are mainly considered and studied. The preferred defect configuration is identified according to the doping concentration dependence of structural changes caused by the defects and the formation energies of the defects at different Ca or F chemical potentials. The cultivated Th:CaF2 crystals maintain considerable high VUV transmittance levels while accommodating high doping concentrations, showcasing an exceptional comprehensive performance. The transmittances of 1-mm-thick samples with doping concentrations of 1.91 × 1020 and 2.76 × 1020 cm-3 can reach ∼62% and 53% at 150 nm, respectively. The VUV transmittance exhibits a weak negative doping concentration dependence. The system factors that may cause distortion and additional deterioration of the VUV transmittance are discussed. Balancing and controlling the impacts of various factors will be of great significance for fully exploiting the advantages of Th:CaF2 and other Th-doped crystals for a solid-state nuclear optical clock.

Nonlinear properties and structural rearrangements in thermally poled niobium germanate glasses

Second order nonlinear optical properties and structural rearrangements in GeO2Na2ONb2O5 glasses were achieved by thermal poling. The effects of applied voltage as well as sodium and niobium contents on nonlinear optical (NLO)-active layer were investigated. Structural rearrangements in the anodic microlayer were investigated and occur due to sodium depletion promoting variation in bridging/non-bridging oxygen ratio and formation of a more polymerized network. Quantitative analysis of second harmonic generation signals confirm the electrooptical origin of the nonlinear optical response described by the electric-field-induced second harmonic model. χ(2) susceptibility values range from 0.42 to 0.76 pm/V depending on the niobium content. Lastly, the charge compensation mechanism with increasing applied voltage was described in detail. A progressive decrease in χ(2) for higher voltages was observed due to a greater poled thickness than expected by classical electrostatic models. In this case, the compensation mechanism occurs due to structural rearrangement, redox reactions, and motion of negative charges.

Optoelectronic Synapse Based on 2D Electron Gas in Stoichiometry-Controlled Oxide Heterostructures.

Emulating synaptic functionalities in optoelectronic devices is significant in developing artificial visual-perception systems and neuromorphic photonic computing. Persistent photoconductivity (PPC) in metal oxides provides a facile way to realize the optoelectronic synaptic devices, but the PPC performance is often limited due to the oxygen vacancy defects that release excess conduction electrons without external stimuli. Herein, a high-performance optoelectronic synapse based on the stoichiometry-controlled LaAlO3 /SrTiO3 (LAO/STO) heterostructure is developed. By increasing La/Al ratio up to 1.057:1, the PPC is effectively enhanced but suppressed the background conductivity at the LAO/STO interface, achieving strong synaptic behaviors. The spectral noise analyses reveal that the synaptic behaviors are attributed to the cation-related point defects and their charge compensation mechanism near the LAO/STO interface. The short-term and long-term plasticity is demonstrated, including the paired-pulse facilitation, in the La-rich LAO/STO device upon exposure to UV light pulses. As proof of concepts, two essential synaptic functionalities, the pulse-number-dependent plasticity and the self-noise cancellation, are emulated using the 5×5 array of La-rich LAO/STO synapses. Beyond the typical oxygen deficiency control, the results show how harnessing the cation stoichiometry can be used to design oxide heterostructures for advanced optoelectronic synapses and neuromorphic applications.

Crystal structure, infrared spectroscopy and thermodynamic properties of a manganese member of the ellenbergerite family

We report on the structural features of Mn6.75[H1.20(VO4)]4-2z(V2O7)z (z = 0.15), which clarified the mechanism of negative charge compensation of the framework. The compound undergoes phase transition at TN = 42.5 K into canted AF state.

Voltage-dependent charge compensation mechanism and cathode electrolyte interface stability of the lithium-ion battery cathode materials LiCoO2 and LiNi1/3Mn1/3Co1/3O2 studied by photoelectron spectroscopy

Charge state dependent core level spectroscopy after in vacuo scratching reveals the electronic structure reasons for the high voltage limits of the relevant Li-ion battery cathode materials LiCoO2 (LCO) and LiNi1/3Mn1/3Co1/3O2 (NMC333).

Electrochemical Storage Behavior of a High-Capacity Mg-Doped P2-Type Na2/3Fe1-yMnyO2 Cathode Material Synthesized by a Sol-Gel Method.

Grid-scale energy storage applications can benefit from rechargeable sodium-ion batteries. As a potential material for making non-cobalt, nickel-free, cost-effective cathodes, earth-abundant Na2/3Fe1/2Mn1/2O2 is of particular interest. However, Mn3+ ions are particularly susceptible to the Jahn-Teller effect, which can lead to an unstable structure and continuous capacity degradation. Modifying the crystal structure by aliovalent doping is considered an effective strategy to alleviate the Jahn-Teller effect. Using a sol-gel synthesis route followed by heat treatment, we succeeded in preparing an Mg-doped Na2/3Fe1-yMnyO2 cathode. Its electrochemical properties and charge compensation mechanism were then studied using synchrotron-based X-ray absorption spectroscopy and in situ X-ray diffraction techniques. The results revealed that Mg doping reduced the number of Mn3+ Jahn-Teller centers and alleviated high voltage phase transition. However, Mg doping was unable to suppress the P2-P'2 phase transition at a low voltage discharge. An initial discharge capacity of about 196 mAh g-1 was obtained at a current density of 20 mAh g-1, and 60% of rate capability was maintained at a current density of 200 mAh g-1 in a voltage range of 1.5-4.3 V. This study will greatly contribute to the ongoing search for advanced and efficient cathodes from earth-abundant elements for rechargeable sodium-ion batteries operable at room temperature.

Increasing the Sodium Content in P2-Type Layered Oxides As Cathode Materials for Sodium-Ion Batteries

P2-type layered oxides exhibit superior Na ion conductivity and structural stability compared to their O3 analogues, making them promising candidate materials for next generation batteries. However, their lower initial Na contents (Na/transition metals < 1) restrict their capacity during the first charge process, and the transitions between P- and O2-type structures during cycling further deteriorate their stability.[1,2] Our work aims to increase the Na inventory in pristine cathode compositions, especially relevant for full cell systems, while maintaining their cycling stability. We started with the well-studied P2 material Na2/3Ni1/3Mn2/3O2 and have worked on incorporating Li in the transition metal layers to stabilize the structure, while at the same time increasing the Na content.[3,4] In this respect, a great challenge is to control the phase formation during the synthesis. When the Na content exceeds a certain limit, an O3 structure is more likely to form than a P2 structure.[1] On the other hand, at too low temperatures, a P3 polymorph is preferred.[5] By regulating the synthesis conditions, Na contents have been successfully increased in a series of materials between two end compositions, Na2/3Ni1/3Mn2/3O2 and Na5/6Li5/18Mn13/18O2.In this presentation, we report on unpublished in situ XRD characterizationsof these compositions during their solid-state synthesis, as well as on their crystal structures and electrochemical behavior, which involves varying amount of Ni redox. These time-resolved studies of structural evolutions provide guidance for further synthesis of desired phases and compositions. Along with the electrochemical results, we also aim to answer the questions on the charge compensation mechanisms that sustain the electrochemical performance as the amount of Li increases and Ni decreases. Finally, we also explore which amount of Li substitution can best balance the structural stability and capacity retention of the cathode material.

Development of Novel High Capacity Fluoride Ion Battery Cathode Utilizing Anion Redox of Sulfur

All-solid-state fluoride-ion batteries (FIBs), which are based on the shuttling of fluoride ions, have been considered as one of the promising alternates for next-generation energy storage devices because of high theoretical energy density and safety. Benefiting from the multi-covalent fluorination process, metal/metal fluorides (M/MFx) have been firstly utilized as electrode materials for FIBs with high theoretical energy densities.[1] However, M/MFx systems suffer from exceptionable volume expansion upon fluorination process due to the close-packed metal atoms, which would cause blockage of the F- diffusion pathway, resulting in devastating damage to the electrode-electrolyte interfaces. To solve these problems, cathode materials that utilize topotactic fluoride ion intercalation reactions, similar to the electrode materials applied in lithium-ion secondary batteries, are being developed.[2] Cathode materials that utilize topotactic intercalation of fluoride ions are often composed of heavier elements than the cathodes of lithium-ion batteries that use the same type of reaction mechanism, and effective anion redox is required if capacity is to be increased beyond that of lithium-ion secondary batteries.In this research, we investigated Sr2F2Fe2OS2 (SFFOS) compound with a layered structure as a novel cathode material for all-solid-state FIBs, and evaluated its electrochemical properties and elucidated the charge compensation mechanism using anion redox of sulfur.SFFOS was synthesized by a solid-state reaction under vacuum environment using SrF2, SrO, Fe, and S.[3] SFFOS/La0.9Ba0.1F2.9/vapor grown carbon fiber (VGCF) was used as the composite cathode, La0.9Ba0.1F2.9 as the electrolyte and Pb/PbF2/ La0.9Ba0.1F2.9/VGCF as the composite anode to construct the electrochemical cell. Charge-discharge measurements were carried out in the cut-off voltage range of -1.5 to 1.5 V at 140°C. Ex-situ X-ray Diffraction (XRD), X-ray absorption spectroscopy (XAS) measurements of Fe K-edge, S K-edge, O K-edge and F K-edge were carried out under different state of charge during the 1st and the 2nd cycle.SFFOS showed reversible intercalation/de-intercalation of fluoride ions and a capacity of ~6.1 fluoride ions per unit cell (403 mAh g-1). The charge compensation mechanism was revealed for SFFOS by XAS measurements, where S redox contributed to the whole voltage range from -1.5 V to 1.5 V vs. Pb/PbF2, and Fe+2/+3 redox contributed from the middle SOC. The S-S dimers were formed upon charging, which was similar to the trapped O2 molecules observed in lithium-excess metal oxide during charge process[4]. Not only can the F- anions insert around Fe to form Fe-F bonds, but the excess F- anions can also occupy the Sr-S interstitial layers in the original lattice. Compared to the Fe-based layered oxide Sr3Fe2O5, the Fe-based oxysulfide SFFOS showed a lower average voltage but a higher specific capacity. We believe that this study could provide a new understanding of sulfur-based charge compensation and electrochemical fluorination reactions. Reference s : [1] D. Zhang, K. Yamamoto, Y. Uchimoto et al., J. Mater. Chem. A, 2021, 9, 406–412.[2] Y. Wang, K. Yamamoto, Y. Uchimoto, et al., Chem. Mater., 2022, 34, 609–616.[3] Kabbour H, Janod E, Corraze B, et al ., J. Am. Chem. Soc., 2008, 130(26): 8261-8270.[4] R. A. House, P. G. Bruce, et al., Nat. Energy 2020, 5, 777–785. Figure 1