Electrolytes For Lithium Batteries Research Articles

Ion Networks in Water-based Li-ion Battery Electrolytes.

ConspectusWater-in-salt electrolytes (WiSEs) are promising electrolytes for next-generation lithium-ion batteries (LIBs), offering critical advantages like nonflammability and improved safety. These electrolytes have extremely high salt concentrations and exhibit unique solvation structures and transport mechanisms dominated by the formation of ion networks and aggregates. These ion networks are central to the performance of WiSEs, govern the transport properties and stability of the electrolyte, deviating from conventional dilute aqueous or organic electrolytes.The availability of free water molecules is significantly reduced in WiSEs, leading to a shift in the solvation environment. Lithium ions (Li+) typically travel with their solvation shells in dilute solutions and form stronger interactions with anions, resulting in the formation of complex ion aggregates. Despite the high viscosity of WiSEs, they exhibit surprisingly high ionic conductivity attributed to the decoupling of viscosity and ionic mobility. Instead of moving through free water, Li+ ions are transported along the pathways formed by the ion networks, minimizing direct solvent interaction and enhancing mobility.Advanced spectroscopic techniques, such as infrared IR pump-probe (IR-PP) and two-dimensional IR (2D-IR) spectroscopy, and molecular dynamics (MD) simulations have illuminated the critical role of these ion networks in facilitating transport. These studies have shown that even at extreme salt concentrations, some water molecules retain properties similar to bulk water, essential for fast ion movement. In WiSEs, bulk-like water molecules form transient hydrogen-bond networks that serve as conduits for Li+ ions, while anion-bound water molecules play a less active role in transport due to their slower dynamics.As the salt concentration increases, the structure of WiSEs becomes more dominated by 3D ion networks. MD simulations reveal that these networks, stabilized by chaotropic anions such as bis(trifluoromethanesulfonyl)imide (TFSI-), disrupt the hydrogen-bonding network of water and provide a stable, interconnected structure that supports the movement of Li+ ions. The formation of these extensive ion networks is critical for maintaining ionic mobility and the electrochemical stability of the electrolyte.The shift from traditional vehicular transport mechanisms to structural diffusion is a hallmark of WiSEs. Li+ ions no longer move with their solvation shells but hop between coordination sites within the ion network. This structural diffusion mechanism enables high ionic mobility despite the reduced presence of water and the increased viscosity of the solution. In conclusion, the formation of ion networks and aggregates in WiSEs not only stabilizes the electrolyte but also drives an unconventional ion transport mechanism. By understanding and controlling these aggregates, WiSEs offer a pathway toward safer, high-performance electrolytes for LIBs and other aqueous energy storage technologies.

Composite solid-state electrolytes for all solid-state lithium batteries: progress, challenges and outlook

Composite solid-state electrolytes (CSEs) with multiple phases offer greater flexibility to customize and combine the advantages of single-phase electrolytes, making them promising candidates for commercial all-solid-state batteries (ASSBs).

Spray-Flame Synthesis (SFS) and Characterization of Li1.3Al0.3-xYxTi1.7(PO4)3 [LA(Y)TP] Solid Electrolytes.

Solid-state electrolytes for lithium-ion batteries, which enable a significant increase in storage capacity, are at the forefront of alternative energy storage systems due to their attractive properties such as wide electrochemical stability window, relatively superior contact stability against Li metal, inherently dendrite inhibition, and a wide range of temperature functionality. NASICON-type solid electrolytes are an exciting candidate within ceramic electrolytes due to their high ionic conductivity and low moisture sensitivity, making them a prime candidate for pure oxidic and hybrid ceramic-in-polymer composite electrolytes. Here, we report on producing pure and Y-doped Lithium Aluminum Titanium Phosphate (LATP) nanoparticles by spray-flame synthesis. The as-synthesized samples consist of an amorphous component and anatase-TiO2 crystalline particles. Brief annealing at 750-1000 °C for one hour was sufficient to achieve the desired phase while maintaining the material's sub-micrometer scale. Rietveld analysis of X-Ray diffraction data demonstrated that the crystal volume increases with Y doping. At the same time, with high Y incorporation, a segregation of the YPO4 phase was observed in addition to the desired LATP phase. Another impurity phase, LiTiOPO4, was observed besides YPO4 and, with higher calcination temperature (1000 °C), the phase fraction for both impurities also increased. The ionic conductivity increased with Y incorporation from 0.1 mS/cm at room temperature in the undoped sample to 0.84 mS/cm in the case of LAY0.1TP, which makes these materials-especially considering the comparatively low sintering temperature-highly interesting for applications in the field of solid-state batteries.

Boosting cation mobility in sol-gel derived organic-inorganic hybrid solid electrolytes through physical conditioning.

Organic-inorganic hybrid materials are explored for application as solid electrolytes for lithium-ion batteries. The material consists of a porous silica network, of which the pores are infiltrated by poly(ethylene oxide) and lithium perchlorate. The synthesis involves two steps: First, the inorganic backbone is created by the acid-catalyzed sol-gel synthesis of tetraethyl orthosilicate to ensure continuity of the backbone in three dimensions. In the second step, the polymer and salt are imbued into the porous backbone via solvent exchange. During drying, the cylindrical disk-shaped specimens shrink mainly in the radial direction, which results in spatially non-uniform structural developments. While this inhomogeneity is not discernible in the material's chemical compositional or thermal properties, it is manifest in its ionic conductivity and adiabatic elastic modulus. The ionic conductivity in the center of the specimens is projected to be between one and two orders of magnitude higher than the measured average across the sample diameter. The process that yields a structure with enhanced ionic mobility during post-synthesis physical conditioning is inferred from careful analysis and numerical interpretation of measurable quantities, and the implications for the design of nanostructured hybrid electrolytes with high ionic conductivity are discussed.

Machine Learning Prediction of Physicochemical Properties in Lithium-Ion Battery Electrolytes With ActiveLearning Applied to Graph Neural Networks.

Accurate prediction of physicochemical properties, such as electronic energy, enthalpy, free energy, and average vibrationalfrequencies, is critical for optimizing lithium-ion battery (LIB) performance. Traditional methods like density functional theory(DFT) are computationally expensive and inefficient for large-scale screening. In this study, we apply active learningontop of graph neural networks (GNNs) to efficiently predict these properties. By focusing on uncertain data points, active learning reduces training data size while maintaining high accuracy. Applied to the LIBE and MPcules datasets, the model achieved an R-squared (R2) values of 0.9977 with a mean absolute error (MAE) of 9.66 Ha for electronic energy and an R2 values of 0.957 with an MAE of 13.94 cm-1 for average vibrational frequencies. SHapley Additive exPlanations (SHAP) provided insights into key features influencing predictions, such as atomic number and spin multiplicity. This approach enhances both predictive accuracy and model interpretability, offering a scalable solution for LIB electrolyte discovery.

Effect of Additives With Phenyl and Acid Anhydride Functional Groups on the Wide Temperature Operation Performance of LiNi0.8Co0.1Mn0.1O2||SiO/Graphite Pouch Cells

ABSTRACTHigh‐nickel LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode paired with silicon‐based graphite (SiO/Gr) is pivotal for enhancing the energy density of lithium‐ion batteries (LIBs). However, the high reactivity of NCM811 with the electrolyte and the volumetric expansion issues associated with SiO/Gr pose significant challenges to their practical application. To settle these issues, we explore the impact of additives with phenyl and acid anhydride moieties on the performance of NCM811‖SiO/Gr pouch cells across a wide temperature range of −20°C~60°C. Acid anhydride additives are capable of diminishing the internal resistance in NCM811‖SiO/Gr pouch cells, as well as curbing gas evolution and thickness increase during the operational phase. Notably, the batteries enriched with citraconic anhydride (CAn) and succinic anhydride (SAn) additives after 120 cycles at 45°C demonstrated enhanced capacity retention from 83.2% to 88.1% and 85.5%, respectively. Intriguingly, the inclusion of phenyl‐containing additives in the electrolyte was found to be advantageous for NCM811‖SiO/Gr pouch cells' low‐temperature performance. Furthermore, neither type of functional group significantly enhanced performance at room conditions. Consequently, the combination of additives is necessary to fulfill the stringent requirements of LIBs for extreme environment applications. This work guides designing composite electrolytes for high energy density wide temperature operation LIBs.

Revealing Lithium Ion Transport Mechanisms and Solvation Structures in Carbonate Electrolytes.

Optimizing lithium-ion battery (LIB) electrolytes is essential for high-current applications such as electric vehicles, yet experimental techniques to characterize the complex structural dynamics responsible for the lithium transport within these electrolytes are limited. In this study, we used ultrafast infrared spectroscopy to measure chemical exchange, spectral diffusion, and solvation structures across a wide range of lithium concentrations in propylene carbonate-based LiTFSI (lithium bis(trifluoromethanesulfonimide) electrolytes, with the CN stretch of phenyl selenocyanate as the long-lived vibrational probe. Phenyl selenocyanate is shown to be an excellent dynamical surrogate for propylene carbonate in Li+ solvation clusters. A strong correlation between exchange times and ionic conductivity was observed. This correlation and other observations suggest structural diffusion as the primary transport mechanism rather than vehicular diffusion. Additionally, spectral diffusion observables measured by the probe were directly linked to the desolvation dynamics of the Li+ clusters, as supported by density functional theory and molecular dynamics simulations. These findings provide detailed molecular-level insights into LIB electrolytes' transport dynamics and solvation structures, offering rational design pathways to advanced electrolytes for next-generation LIBs.

Phthalocyanine-based solid-state electrolyte for high-capacity and long-life lithium-ion batteries

A new solid-state electrolyte (SSE) with low energy activation for lithium-ion conduction was designed and tested in an all-solid-state battery configuration with a lithium metal anode and a lithium iron phosphate (LiFePO[Formula: see text] cathode. The aromatic character of the phthalocyanine-based SSE facilitates cell stabilization against lithium metal dendrites, and the low energy of activation enables battery cycling at -20[Formula: see text]C. The use of the phthalocyanine-based SSE necessitated the development of an in-situ process for the formation of an effective solid electrolyte interphase (SEI) layer between the anode and the SSE. Such a procedure enabled battery cycling over a 12-to-16-month time frame. The cells delivered high discharge capacities of up to 291.3 mAh/g at 23[Formula: see text]C and 194.5 mAh/g at -20[Formula: see text]C. All cells were fabricated in a dry room via simple solution casting of the soluble SSE onto either an aerosol-jet-deposited or tape-cast LiFePO4 cathode.

Synergistic Advancements of Acrylate-Grafted Poly(vinylidene Fluoride-co-hexafluoropropylene) Gel Polymer Electrolytes for Lithium-ion Batteries

Synergistic Advancements of Acrylate-Grafted Poly(vinylidene Fluoride-co-hexafluoropropylene) Gel Polymer Electrolytes for Lithium-ion Batteries

Machine Learning Assisted Prediction of Donor Numbers: Guiding Rational Fabrication of Polymer Electrolytes for Lithium-Ion Batteries.

Polymer electrolytes are of interest in high-energy-density batteries. However, how the intrinsic electron-donating capability of polymer segments involved in coordination affects lithium-ion dissociation/transmission and rationally guides the design and fabrication of electrolytes is a highly exploratory topic. This study proposes a workable method that integrates machine learning with density functional theory to predict donor numbers (DN) for polymer building units. Using this approach, polymer chains with optimized DN are designed, effectively modulating the solvation structure of lithium-ion. Molecular dynamics simulations confirm the positive impact of polymer chains on rapid transport of lithium ions. Experimental validation of the proposed zwitterionic polymer electrolyte (ZPE) showcases satisfactory parameters: ion conductivity (0.59 mS cm-1), ion migration numbers (0.82), and activation energy (0.016 eV). Electrochemical analysis on Li|ZPE|Li symmetric batteries demonstrate sustained plating/stripping performance exceeding 3000 hours at a current density of 0.2 mA cm-2. Assembled NCM|ZPE|Li batteries exhibit stable cycling over 1400 cycles at 4.3 V, with a capacity retention ratio of 92.3 %. Moreover, even under ultra-high voltages of 4.5 V and 4.7 V, NCM|ZPE|Li batteries display stable cycling performances. This approach offers a paradigmatic strategy for polymer molecule design, advancing sustainable battery technologies.

In Situ Characterization of the Oxidation Behavior of Carbonate-Based Electrolytes for Lithium-Ion Batteries by Scanning Electrochemical Microscopy

In Situ Characterization of the Oxidation Behavior of Carbonate-Based Electrolytes for Lithium-Ion Batteries by Scanning Electrochemical Microscopy

Electrostatic Aspect of the Proton Reactivity in Concentrated Electrolyte Solutions.

Water-in-salt electrolytes with a surprisingly large electrochemical stability window of ≤3 V have revived interest in aqueous electrolytes for rechargeable lithium-ion batteries. However, recent reports of acidic pH measured in concentrated electrolyte solutions appear to be in contradiction with the suppressed activity of the hydrogen evolution reaction (HER). Therefore, the fundamental thermodynamics of proton reactivity in concentrated electrolyte solutions remains elusive. In this work, we have used density functional theory-based molecular dynamics (MD) simulations and the proton insertion method to investigate how the HER potential shifts in concentrated LiCl solutions under both acidic and alkaline conditions. Our results show that the intrinsic HER activity increases significantly with the salt concentration under acidic conditions but remains relatively constant under alkaline conditions. Moreover, by leverage over finite-field MD simulations, it is found that a determining factor for the HER activity is the Poisson potential of the liquid phase, which increases in concentrated electrolyte solutions with comparable values from both density functional theory and point-charge models.

Hydrogen-bonded organic framework-ionic liquid composite quasi-solid electrolyte for high-performance lithium battery

Hydrogen-bonded organic framework-ionic liquid composite quasi-solid electrolyte for high-performance lithium battery

Effect of ionic wind on the sample distribution in corona discharge ion mobility spectrometry

Ionic wind generated during corona discharge (CD) can significantly influence the airflow field within Ion Mobility Spectrometry (IMS), yet its impact is often overlooked. This study delves into the impact of ionic wind on sample distribution, emphasizing the need to balance reactant ion density and ionic wind intensity, which leads to sample dilution. To mitigate this issue, an axial injection mode employing a hollow needle was proposed, thereby improving the sensitivity and recovery performance of CD-IMS. As a result, the limit of detection of dimethyl methylphosphonate (DMMP) monomer is lowered from 15 ppbv to 5 ppbv. Furthermore, this technique was successfully applied to the detection of lithium battery electrolyte leaks, with carbonate concentrations as low as 10 mg/L or 1 nL being detected within 5 s. Such findings underscore the technique's applicability for swift and sensitive monitoring of battery safety.

Redox Reaction of Some Nitroxyl Radicals in 1-Butyl-1-Methylpyrrolidinium Bis(fluorosulfonyl)amide in the Presence and Absence of Lithium Ion

Ionic liquids composed of bis(fluorosulfonyl)amide (FSA–) have been investigated as the promising electrolytes for rechargeable lithium batteries due to their high conductivity and low viscosity dependence on the Li salt concentration. Despite many reports on FSA–-based ionic liquids as the electrolytes for rechargeable lithium and sodium batteries, a few studies have been reported on the electrode reactions of redox species. The redox reactions of Ag+/Ag and ferrocenium (Fc+)/ferrocene (Fc) were investigated in BMPFSA (BMP+ = 1-butyl-1-methylpyrrolidinium)[1]. It was reported that the donor ability of FSA– was found to be lower than that of bis(trifluoromethylsulfonyl)amide (TFSA–) from the potential difference between Ag+/Ag and Fc+/Fc. 2,2,6,6,-Tetramethylpiperidine-1-oxyl (TEMPO) is one of the typical niroxyl radicals with redox activity. In the present study, the redox reactions of TEMPO and 4-oxo-TEMPO were investigated in BMPFSA in the presence and absence of lithium ion.The redox reactions of TEMPO+/TEMPO and 4-oxo-TEMPO+/4-oxo-TEMPO were observed on a Pt electrode in BMPFSA by cyclic voltammetry. The formal potential of TEMPO+/TEMPO was lower than that of 4-oxo-TEMPO+/4-oxo-TEMPO. The formal potential of TEMPO+/TEMPO in the presence of Li+ was higher than that in the absence of Li+, suggesting that the interaction between TEMPO and Li+ affected the thermodynamic properties of the redox species. The diffusion coefficients and the standard rate constants were evaluated by chronoamperometry and electrochemical impedance spectroscopy, respectively. The diffusion coefficient and the standard rate constant were suggested to be controlled not only by the viscosity but also by the interaction between the nitroxyl radicals and Li+.Reference[1] S. Kato, N. Serizawa, and Y. Katayama, J. Electrochem. Soc., 170, 046504 (2023).

Interphase-Controlled Composite Electrolyte Based on LLZTO-Ionic Liquid for All Solid-State Battery

Solid-state electrolytes (SSEs) are promising alternatives to conventional liquid organic electrolytes in lithium-ion batteries (LIBs), primarily due to their non-flammability and potential to reduce battery size. SSEs are categorized into three types: solid polymer electrolytes (SPEs), inorganic ceramic electrolytes (ICEs), and composite solid electrolytes (CSEs). Solid polymer electrolytes (SPEs) offer good interface contact with electrodes but suffer from low ionic conductivity and poor mechanical stability. In contrast, inorganic ceramic electrolytes (ICEs) exhibit high ionic conductivity and excellent mechanical stability but have weak electrode contact due to stiffness. Composite solid electrolytes (CSEs) aim to combine the advantages of both SPEs and ICEs, utilizing inorganic filler and polymer host to enhance conductivity, mechanical stability, and electrode contact. Understanding the mechanisms behind the enhanced ionic conductivity of CSEs is important to getting the key. Previous studies have investigated various factors, including the type and morphology of fillers, with active fillers showing promise in improving conductivity by facilitating extra Li-ion transport and maintaining the amorphous phase of the polymer. However, the exact cause of enhanced conductivity remains unclear.This study proposes the use of ionic liquids to exclude the amorphous effect of polymers and compares the ionic conductivity with active fillers. Additionally, nanoparticles are introduced to form a solid phase without additional solvents, enhancing filler-polymer contact and promoting thixotropy in the electrolyte, which improves safety and stability. To investigate the interphase effect between filler and matrix, our study focuses on controlling the vacancy concentration on the filler surface using garnet-type oxide as the filler material. X-ray photoelectron spectroscopy (XPS) analysis reveals a difference in oxygen vacancy (O-v) concentration between raw material and filled powder, indicating the influence of surface vacancies on ionic conductivity. Experimental results show that the addition of fillers increases the ionic conductivity of electrolytes, with lower oxygen vacancy concentrations leading to higher ionic conductivity. Distribution of relaxation time (DRT) analysis indicates low resistance in the electrolyte at most timescales, especially showing low diffusion resistance, suggesting improved ion transport properties. COMSOL Multiphysics simulations prove consistent electrolyte current density from the whole electrolyte, inducing uniform ion flux to electrodes. Laser-induced breakdown spectroscopy (LIBS) and XPS depth profiles confirm thin and uniform growth of the solid electrolyte interphase (SEI) layer, contributing to cycle stability.Overall, our study provides insights into the role of surface-controlled fillers in enhancing electrochemical properties and understanding ion-conduction mechanisms in composite solid electrolytes (CSEs). We explore the interphase effect between filler and matrix using Li conductive oxide. Vacancies on the filler surface impact electrolyte properties; fewer vacancies correlate with improved ionic conductivity and stability. Results show enhanced conductivity in surface-controlled electrolytes compared to host or composite electrolytes. Oxygen-filled electrolytes demonstrate superior thermal and electrochemical stability, promoting uniform SEI layer formation and enhancing specific capacity and cycle stability in Li metal half-cells. These findings contribute to developing safer, more efficient solid-state batteries for various applications. Figure 1

Advancement of Ionic Complexes Based on Multivalent Carbon Dot Polyanions for Applications in Electrochemical Systems

Carbon dots, also known as carbon quantum dots or graphene quantum dots (C-dots), have garnered significant attention due to their promising applications in various fields such as energy, catalysis, bioimaging, and nanomedicine. Typically, C-dots exhibit zero-dimensional characteristics with hybridized carbon structures at the core and functional groups like hydroxyl and carboxyl at the edges.In this talk, I will highlight our recent advancements in utilizing ionic complexes based on C-dots for electrochemical applications, serving as supporting electrolytes and anionic dopants. We've developed nano-sized multivalent C-dot polyanions through a hydrothermal oxidation process of carbon nanofibers, forming complexes with alkali cations such as Li+, Na+, and K+. Consequently, we investigated the potential applications of ionic complexes based on C-dot as electrolytes for lithium-ion batteries and electrochromic devices. The ionic complexes demonstrate low Coulombic energy, exceptional thermal/electrochemical stability, and good ionic conductivity when dissolved in both aqueous and organic solvents. Molecular dynamics simulation with the electrochemical characterization reveals that the ionic complexes provide highly abundant free metal cations with highly stable C-dot polyanions and negligible ion pairs in solution. Furthermore, we have successfully implemented a novel approach to fabricate nanoarchitectures based on C-dots as an electrode-active material with outstanding electrochemical catalytic activity which is suitable for electrochemical biosensors and H2O2 reduction. Figure 1

Ether-Functionalized Phosphonium Ionic Liquids: Molecular Dynamics, Ion Conformation, and Intermolecular Interaction

Ionic liquids have many potential applications because they have non-flammability, high thermal stability, high ionic conductivity, and so on. Among various types of ionic liquids, quaternary-phosphonium-cation-based ionic liquids (P-ILs) have better physicochemical properties such as ionic conductivity, potential window compared with corresponding quaternary-ammonium-cation-based ionic liquids (N-ILs). Therefore, we have considered that P-ILs are better suitable for applications in electrochemical devices such as electrolytes for lithium-ion batteries than N-ILs [1].Recently, we spectroscopically demonstrated that such higher ionic conductivity for P-ILs can be explained by weaker intermolecular interaction between anion and cation [2]. This provided us a consideration that molecular interactions are controlling factors in translational motion of ions. For deeper discussion, we focused on the ether-functionalized P-ILs displayed in the Figure 1 because ether structure in phosphonium cations enhanced ionic conductivity and investigated by pulsed field gradient NMR (PFG-NMR), Raman, and terahertz spectroscopies.Based on the PFG-NMR, we calculated transport number of each ion specie and found that transport number of P111(1O1) cation was slightly higher than that for P1113 cation. In Raman spectroscopy, we obtained enthalpy change in conformational change of anion (ΔH) and demonstrated that ΔH for P111(1O1)cation was somewhat lower than that for P1113 cation. Terahertz spectroscopy indicated the weaker intermolecular interaction of P111(1O1) cation with anion than that of P1113 cation. Despite these differences in P111X cations, such ether group effects were hardly observed in P222X cations, which would be due to the different symmetry of cation and steric hindrance.

All-Solid-State Lithium–Sulfur Batteries Enabled By Single-Ion Conducting Particle Electrolytes

The demand for safer alternatives to liquid electrolytes in lithium-ion batteries has stimulated the development of all-solid-state lithium batteries. These advanced batteries aim to mitigate potential hazards associated with flammability and dendrite formation during operation. Additionally, the integration of solid-state electrolytes creates opportunities to improve the energy and power densities of lithium batteries by enabling the direct utilization of lithium metal as the anode. In this study, we designed solid-state hybrid electrolytes with single-ion conducting properties by co-assembling binary polymer nanoparticles with large surface areas and excellent thermodynamic compatibility. These electrolytes were developed by synthesizing two distinct types of core–shell polymer nanoparticles with mechanically robust cores and shells capable of facilitating Li+ transport. By controlling the nanoparticle size and number, we created superlattices that optimized the Li+ concentration and transport. The electrolytes exhibited a remarkable ionic conductivity (10-4 S cm-1), lithium transference number (0.94), electrochemical stability (up to 6 V), and modulus (0.12 GPa) at 25 °C. The mechanical strength of these electrolytes depended minimally on temperature at 25–150 °C because of the robustness of the cores. These results unequivocally establish the remarkable superiority of the BNPs electrolyte, which avoid the conventional trade-off between conductivity and mechanical strength through the unique design of superlattice structures, thereby representing a significant breakthrough in the field of solid-state single-ion electrolytes. When implemented in Li–S batteries with no liquids, they demonstrated a stable discharge capacity exceeding 1008 mAh g-1, a cycle life of over 200 cycles, and a rate capability with a discharge capacity of 627 mAh g-1 at 3C. Our findings will pave the way for the safe operation of future high-energy-density lithium batteries utilizing solid-state hybrid electrolytes. Figure 1

Composition and Conductivity Evaluation of Cathode Active Materials/Solid Electrolytes for Lithium-Ion Batteries

Solid-state batteries have attracted considerable attention as innovative secondary batteries for future electric energy societies due to their high safety and energy density. In particular, sulphide-based solid electrolytes are positioned as promising materials for solid-state batteries due to their excellent ion conductivity properties. However, a challenge exists with sulfide-based solid electrolytes, as high lithium-ion conductivity resistance occurs upon contact with the positive electrode active material due to the formation of a lithium-ion deficiency layer. Previous studies have shown that reducing interface resistance can be reduced by coating the active material with lithium-ion conductors such as LiNbO3. It is believed that by structuring the active material and solid electrolyte to conduct ions through a buffer layer, the lithium ion deficiency can be reduced, and the electrical potential barrier of lithium ions near the interface can be suppressed. However, the ion conduction mechanism at the interface between the active material and solid electrolyte formed by uniformly coating of the active material has not been sufficiently elucidated.This study aims to elucidate the ion conduction mechanism at the interface between the positive electrode active material crystal and the solid electrolyte by achieving uniform coating of a buffering layer. We aim to achieve uniform coating driven by the evaporation of a mixed solution of LiTaO3 dispersed in water and LiCoO2 crystals. Furthermore, by preparing electrodes using only binders without the use of conductive agents via a paste method, we aim to reduce factors related to resistance and elucidate the ion conduction mechanism at specific interfaces.For the coating of the buffer layer on the active material crystal, a LiTaO3 water solution obtained from an external source was prepared, and a LiCoO2 crystal dispersion solution was prepared, and the influence on coating under different conditions of LiTaO3 concentration and heat treatment temperature for LiCoO2 crystals was investigated.Scanning electron microscope (SEM) observations showed no change in the coating morphology under temperature conditions of 300 to 500°C. Additionally, X-ray photoelectron spectroscopy (XPS) showed no change in the dependence of the Ta bonding state on temperature conditions. However, it was confirmed that the weight ratio of Ta coated on the surface increased with the increasing concentration of LiTaO3. Subsequently, electrodes were prepared using slurry from synthesized active material/buffering layer composites, and ion conduction resistance was measured using impedance measurements. Ion conduction resistance dependent on the amount of coating was observed in composites synthesized at 400°C and 500°C. In composites synthesized at 300°C, a tendency for higher ion conduction resistance with less coating and an overall high resistance value were observed. Moreover, differential relaxation time (DRT) analysis revealed that the relaxation frequency of the main resistance component changed with increasing heat treatment temperature. However, no shift in relaxation frequency of resistance components was observed with coating amount.From these results, it was revealed that coating crystal morphology changes depending on the temperature conditions and coating amount changes depending on the concentration. Furthermore, synthesis of composites at high temperatures reduced Li-ion conduction resistance. This is believed to be due to atomic diffusion occurring at high temperatures during heat treatment, resulting in Ta bonding to the CoO2 structure on the surface of LiCoO2, continuously joining the interfaces. Additionally, it is believed that the reduction in grain boundary resistance occurred due to particle densification. In the future, solid-state batteries using sulfide-based solid electrolytes will be fabricated to investigate the suppression of lithium-ion conduction resistance and its conduction mechanism.AcknowledgementThis work was supported in part by Grant-in-Aid for Scientific Research (22H01847), Aichi Priority Research Program, the Strategic Innovation Program (SIP) of the Cabinet Office and by joint researches with industries.