Dense Electrolyte Research Articles

Inorganic-Dominated Interphase Enabled by Tuning Solvation Configuration for 4.8 V Lithium-Ion Batteries.

Constructing a dense inorganic component-dominated cathode electrolyte interphase (CEI) to meet the long-term cycling requirements of ultrahigh voltage cathodes has been a crucial challenge. Nevertheless, this goal is difficult to achieve in traditional electrolyte compositions due to the inevitable decomposition of organic solvents. Herein, by utilizing the localized mismatch between the strongly coordinating hexafluorophosphate anion (PF6-) and the weakly coordinating solvent 1,1,1-trifluoro-N,N-dimethylmethanesulfonamide (TFDMSA), abundant aggregates (AGGs) emerged under a regular Li salt concentration of 1 m lithium bis(fluorosulfonyl)imide (LiFSI) + 0.1 m LiPF6 in TFDMSA. This anion-rich Li+ solvation structure results in an inorganic-dominated LiF-rich CEI to suppress phase transitions of lithium-rich manganese-based cathode materials (LLMO). Consequently, the prepared LLMO||Li half-cells demonstrate a capacity retention of 80.7% after 350 cycles at 4.8 V. This work advances the practical application of new electrolyte systems by proposing a new approach to construct anion-dominated Li+ solvation structures in local environments.

Correlation and application of thermal expansion coefficient/elastic modulus for co-sintered composite cermet/ceramic materials

Deformation and stress concentration appearing during high-temperature sintering process significantly affect production quality of solid oxide cell (SOC), due to mismatched mechanical and thermophysical properties of the sintered electrode and electrolyte. In this study, a coarse-grained molecular dynamics (CG-MD) method is developed to evaluate and correlate coefficient of thermal expansion (CTE) and elastic modulus during the entire co-sintering process (including temperature-increasing, −insulation, and -decreasing stages). It is revealed that, in the sintered porous cermet electrode, CTE primarily exhibits an increasing trend until temperature-decreasing stage. Compared to the constant values commonly applied in the literature, the elastic modulus experiences a decay trend with a reduction of 32.14 % in the porous electrode and 9.68 % reduction in the dense electrolyte. The obtained CTE and elastic modulus are correlated with the sintering parameters and further applied to a macroscopical model for predicting overall sintering warpage and stress in a co-sintered SOC half-cell composed of a thick porous electrode and a thin dense layer. The varied CTE is identified as the main factor influencing warpage deformation, while the elastic modulus as a more significant impact on the von Mises stress during the co-sintering of the half-cell. Analysis is further conducted by orthogonal testing method for sintering temperature, sintering time, material content and diameter ratio of the porous cermet nanoparticles, aiming to optimize the varied CTE and elastic modulus, particularly during the temperature-insulation process. Subsequently, the optimized properties are implemented, and it is found that, after sintering insulation for 120 min, the maximum warpage displacement is about 7.34 mm, which represents a decrease of approximately 14.11 %; while the von Mises stress is observed to be 379.24 MPa, which indicates a reduction of around 37.33 % compared with the predictions by the constant properties.

Plasma-sprayed dense yttria-stabilized zirconia electrolyte for metal-supported solid oxide fuel cells

Plasma-sprayed dense yttria-stabilized zirconia electrolyte for metal-supported solid oxide fuel cells

Lithium resurrection: Synergistic thermal-decomposition and electric-drive strategy enabling inactive lithium fully recycling

Traditional pyrometallurgy and hydrometallurgy processes primarily focus on the recovery of valuable metals (Co, Ni, etc.) from spent lithium-ion batteries. However, these methods are not economical for recycling cheap LiFePO4. Herein, a synergistic thermal-decomposition and electric-drive strategy is proposed to recover the whole spent LiFePO4 electrode by in-situ recovering the inactive lithium (dead lithium and trapped interlayer lithium). Firstly, the organic components in the dense solid electrolyte interface (SEI) are effectively decomposed through thermal-decomposition processing, exposing the dead lithium encapsulated within the SEI and recovering the electron channels between the dead lithium and graphite. Leveraging the difference between the Gibbs free energy of the dead lithium and graphite as the driving force facilitates the dead lithium inserting into the anode. Then, fully utilizing the remaining discharge capacity of the spent LiFePO4 cell, the inactive lithium is reinserted into LiFePO4 lattice during the electric-drive process. Consequently, the reactivated lithium content increases by more than 16%, reaching a capacity of 134.2 mA h g−1 compared to 115.2 mA h g−1 from degraded LiFePO4, allowing for effective participation in the subsequent cycling. This work provides new perspectives on highly profitable cycles with low energy and material consumption and a low carbon footprint.

Colloidal route towards sodium ionic conductor (NASICON) 3D complex solid electrolyte structures fabricated by Direct Ink Writing (DIW)

Progressing towards a sustainable energy model, safer new generation high-performance energy storage devices with large energy density and power are needed. In this sense, the improvement in terms of efficiency and sustainability has led to the interest in solid-state batteries (SSBs). Lately, sodium-ion batteries (SIBs) have become an emerging alternative due to the abundance of raw materials, low cost, and improvements in terms of fast sodium-ion conductor solid electrolytes (SCSEs). Among all the SCSEs, the sodium superionic conductor (NASICON) type electrolyte is one of the most well-known electrolytes, being widely developed in terms of synthesis and materials. However, the processing and manufacturing of these electrolytes have gone almost unnoticed, without considering that well-designed structures of electrodes/electrolytes are the bridge toward turning advanced energy materials into high-performance devices. This work presents the fabrication of 3D complex structures based on NASICON sodium solid electrolytes, obtained for the first time by direct ink writing (DIW). Through a colloidal route, fine NASICON phase powder with high pureness was prepared, enabling the manufacturing of intricate NASICON-printed electrolytes in a one-step fabrication process. By optimizing the ink, a dense electrolyte layer, acting as an ionic conductor and separator, was inserted between two complex porous pattern layers obtaining a device with a total height below 1.15 mm. Further, the densification of the 3D electrolyte was enhanced, reaching high ionic conductivities at room temperature (3.10-4 S·cm-1). Thus, a high-performance sodium ion conductor NASICON solid electrolyte with shorter diffusion pathways and larger interfacial surface areas between electrode/electrolyte was obtained, improving the overall electrochemical performance of the device by a 3D layer-by-layer design.

Fabrication of Dense Electrolyte for Metal-Supported Solid Oxide Fuel Cells By Plasma Spray Method

Metal-supported SOFCs (MS-SOFCs) have attracted attention because of their potential for low cost and high mechanical robustness. However, the conventional cell fabrication process is not easily applied to MS-SOFCs. The difficulty of MS-SOFC fabrication is especially to form a dense electrolyte without oxidation and diffusion of the metal support. We’ve tried to use a plasma spray method to prepare the metal supported cells. Then, apparently dense electrolyte layer could be fabricated using doped lanthanum gallate instead of yttria stabilized zirconia. In this paper, electrochemical performance and gas tightness of the cells were evaluated to consider the applicability of plasma spray for MS-SOFC fabrication.A prepared MS-SOFC consists of porous metal substrate (SUS430), NiO-YSZ anode, Sr-, Mg-doped lanthanum gallate (LSGM9182), and conventional cathode (LSCF6428). The cell components, except for the porous substrate, were deposited by atmospheric pressure plasma spray (APS). Gas tightness of the cell was confirmed by open circuit voltage (OCV) measurement. Cell performance was evaluated by current-voltage measurement and impedance measurement. Post-analysis of the cell was conducted by SEM/EDS.The measured OCV was confirmed to be equivalent to theoretical value in humidified hydrogen at 973 K. It means the fully dense electrolyte layer could be prepared by plasma spray. Current density of I-V measurement was 0.6 Acm-2 at 0.5 V at 973 K. The impedance results showed larger over potential of anode reaction. This might be caused by anode electrochemical reaction and gas diffusion through anode and substrate layer. Further development of plasma spray anode is necessary for practical application; however, this study confirmed the possibility of the plasma spray method to fabricate the dense electrolyte for MS-SOFCs.This research was financially supported by NEDO.

Influence of the Transition Metal Doping on the Properties of Sr2Fe1.5Mo0.5O6 Double Perovskite for Solid Oxide Fuel Cells

The increase in environmental awareness has led to a significant worldwide trend for the development of alternative energy sources other than conventional use of the fossil fuels. One of the alternatives is the use of Solid Oxide Fuel Cells (SOFCs), which are capable of converting chemical energy of the fuel into electricity. In SOFCs, dense electrolyte is covered with two porous electrodes. So far, the most widely used fuel electrode material is Ni-YSZ composite, which degrades significantly when is fed with the fuels other than hydrogen. Thus, the development of a substation for Ni cermet is desirable. Among many materials, one may find perovskite families, which are known for their high stability and ionic conductivity. Unfortunately, their catalytic performance is rather low and needs to be increased. This can be done by introducing catalytically active materials as dopants and force them to form nanoparticles via the exsolution phenomenon. Main advantages of exsolving nanoparticles, rather than their deposition, are better connection with the surface and lower tendency for agglomeration.Perovskites may be divided into several sub-groups and one of them are double perovskites with general formula of A2BB’O6. Strontium ferrite molybdate (SFM – Sr2Fe1.5Mo0.5O6) is one of the most prominent compounds in this family. It is well known for its high ionic and electronic conductivity as well as stability in both reducing and oxidizing atmospheres. Those properties make it a promising material for not only the anode, but also a cathode, hence SFM-based compounds can be considered prominent candidates for symmetrical fuel cells. On the other hand, our previous work has shown that, in highly reducing atmospheres, this double perovskite can partially transform into the Ruddlesden-Popper layered perovskite. This transition could increase the amount of exsolved nanoparticles due to internal strain.Herein, the SFM-based compounds were co-doped with La at A-site and one of transition metals - Co or Ni, (with x being doping level within 5-20 mol.%) - giving the composition of La0.3Sr1.7Fe1.5-0.75xMo0.5-0.25xMexO6. Fixed Fe:Mo ratio was maintained to prevent formation of either Fe-, or Mo-rich phases. Based on our previous studies, La-doping was found to suppress the phase transition and to simultaneously increase the electrical conductivity. Transition metals were incorporated during the synthesis to boost the catalytic performance of the compound. After the reduction at 800 °C in hydrogen, the surface of the grains was almost fully covered with nanoparticles of one metal (Co or Ni) or bimetallic alloys with co-exsolved iron. Even small amount (10 mol.%) of introduced transition metal resulted in enormous amount of nanoparticles. The electrical conductivity measurements were performed in both air and hydrogen. It was found that the mechanism of electrical conductivity is different in both atmospheres: in the air, the electrical conduction occurs by the polaron hopping mechanism through Fe/Mo-O-Fe/Mo bonds. Selected samples underwent several cycles of electrical measurements in air and hydrogen, alternately, to determine their stability for several redox cycles and to study the degradation. To better understand how Fe3+/4+-Mo5+/6+ redox pairs are influenced by transition doping, the XPS technique was used for as-synthesized and reduced compounds. After the reduction, both iron and transition metals were present also in Me0 form, hence the amount of Mo6+ cations increased. Finally, TPR/TPO measurements were performed to understand the reducibility of the compounds and to have a better understanding of the formation of exsolved nanoparticles. Acknowledgements: The research project was supported by the National Science Center under grant No. NCN 2022/45/N/ST5/02933.

Enabling Lithium-Free Batteries through Newly Developed Lithium-Garnet with Mixed Ion and Electron Conduction

Garnet structured solid electrolyte with a lithium-metal anode and high voltage cathode is a promising battery system owing to its inherent safety with high energy density. However, integrating thick metallic lithium with garnet solid electrolyte is not viable for a scalable process due to its complexity and the excess volume of lithium-metal compared to the lithiated cathode. To overcome these challenges, “lithium-free” batteries fabricated in a discharged state of the battery with only the current collector at the anode side is garnering increasing attention.1 The major drawback of a “lithium-free” battery with a garnet solid electrolyte is the limited lithium plating capacity and poor coulombic efficiency. To address this, we developed a mixed ion electron conducting (MIEC) garnet with comparable lithium-ion and electron conductivity at room temperature.2 We demonstrate that with a porous MIEC framework supporting a thin dense garnet solid electrolyte the cells can be cycled with no dendrite-induced shorting, at room temperature and sub-zero temperature without any stack pressure. Through various electrochemical characterization and electron microscopy the role of porous MIEC was elucidated. Huang, Wen‐Ze, Chen‐Zi Zhao, Peng Wu, Hong Yuan, Wei‐Er Feng, Ze‐Yu Liu, Yang Lu et al. "Anode‐free solid‐state lithium batteries: a review." Adv. Energy Mat. 12, 2201044 (2022).Alexander, George V., Changmin Shi, Jon O’Neill, and Eric D. Wachsman. "Extreme lithium-metal cycling enabled by a mixed ion-and electron-conducting garnet three-dimensional architecture." Nat. Mat. 22, 1136-1143 (2023).

Improvement of ionic conductivity and relative density of Li6.4La3Zr1.4Ta0.6O12 electrolytes by optimization of composition and sintering aid

Introduction All-solid-state lithium metal batteries (ASSLMBs) are expected to have high energy density. Among various solid electrolytes, oxide-based solid electrolytes have attracted attention in recent years due to their higher air stability compared to sulfide-based solid electrolytes. However, oxide-based solid electrolytes exhibit lower ionic conductivity compared to sulfide-based or liquid electrolytes, leading to inferior high-rate cycle performance. Additionally, when the relative density of solid electrolytes is low, the formation of lithium dendrites through structural defects in the solid electrolyte causes short circuits. Therefore, improving the ionic conductivity and relative density of solid electrolytes is essential for enhancing the performance of oxide-based all-solid-state batteries.In our previous research, we increased the relative density of lithium lanthanum zirconium tantalate (Li6.4La3Zr1.4Ta0.6O12, LLZT) solid electrolytes to 99.3% by co-doping LLZT with alumina (Al2O3)1) and lithium tungstate (Li2WO4)2). The increase in relative density resulted in improved short-circuit resistance performance. However, the drawback of adding these sintering aids is the reduction in ionic conductivity of LLZT due to the substitution effect on the solid electrolyte. According to the paper by N. Hayashi et al., reducing the amount of lanthanum in LLZ-CaBi solid electrolytes can improve ionic conductivity and relative density3). In this study, we attempted to enhance the ionic conductivity and relative density of LLZT by reducing the amount of lanthanum in the raw materials. Experimental The Li6.4La3-xZr1.4Ta0.6O12-1.5x (x=0, 0.03, 0.06, 0.09, 0.12,0.15) powders were synthesized via solid-state synthesis method. Lithium carbonate, lanthanum oxide, zirconium oxide, and tantalum oxide were used as raw materials. The raw materials were mixed and then heated at 900°C for 12 hours to synthesize LLZT powder. During the weighing process, lithium carbonate was added in excess by 20% of the target composition to account for lithium carbonate volatilization. LLZT powder and sintering aids were mixed using a planetary ball mill, and then the powder was pressed into pellets at 98 MPa. The pellets were sintered at 1150°C for 5 hours. Next, dry polishing was conducted to adjust the thickness of LLZT to 0.8 mm, and Au blocking electrodes were sputtered on both sides of LLZT to perform AC impedance. AC impedance measurements were performed at 30°C with an applied voltage of 10 mV over a frequency range from 1 MHz to 1 Hz. Li metal electrodes (diameter 6 mm) were attached to both sides of the Au thin film on LLZT to fabricate Li-Au|LLZT|Au-Li symmetric cells to conduct short-circuit test. In the short-circuit tests, charge-discharge cycles were repeated every 30 minutes, with the current density increasing by 0.1 mA cm- 2 every 20 cycles at 60°C. Results and Discussion Table 1 shows the relative density, resistance, and ionic conductivity of as-prepared LLZT without sintering aid. Decreasing the amount of lanthanum led to improvements in both relative density and ionic conductivity. The highest relative density achieved at x=0.06 and 0.09. Additionally, at x=0.06, bulk ionic conductivity was measured at 1.12 mS, and total ionic conductivity at 0.976 mS. The low grain boundary resistance at x=0.06 is believed to be due to the reduction in voids resulting from the improved relative density. For samples with x=0.09 and above, a gradual decrease in both relative density and ionic conductivity was observed.Figure 1 depicts the XRD patterns of LLZT from 20° to 22°. Pronounced peaks of Li2ZrO3 were observed in samples with x=0.12 and x=0.15. This is believed to result from the reaction of excess lithium, zirconium, and oxygen due to the reduction in lanthanum. Previous our studies have shown that Li2ZrO3 suppresses abnormal grain growth in LLZT particles and improves relative density. Therefore, the enhancement in relative density is likely attributed to Li2ZrO3.Figure 2 shows cross-sectional SEM images of LLZT. Abnormal grain growth and voids were observed in samples with x=0 and 0.03, while samples with x=0.06 and above exhibited no abnormal grain growth, indicating that dense solid electrolytes were successfully fabricated. This is considered evidence of abnormal grain growth suppression due to the formation of Li2ZrO3.In addition to the above, the reasons for the enhancement in bulk ionic conductivity, the characteristics of LLZT (x=0.06) added sintering aids, and the results of short-circuit tests will be discussed in more detail on the poster.

(Invited) Mechanistic Studies on Electrode/Electrolyte Interfaces in Li-Ion Batteries Using in-Situ Neutron Reflectometry

A thorough understanding of electrochemical interfaces is critical for the development of next-generation energy storage/conversion devices with high energy densities and long-life operations. The direct observation of structural changes provides invaluable information about charge transfer, ionic diffusion, and side reactions in electrochemical reaction processes. Neutron reflectometry is a powerful technique for gaining a nanoscopic understanding of solid/liquid interfaces as a function of depth. Neutrons are capable of providing electrochemical interfaces owing to their strong penetrating power through the substrate. In addition, lithium can be sensitively detected by neutrons because the scattering length of lithium is significant in comparison with that of other elements in the electrode for neutrons, whereas it is small and almost invisible to X-rays. The depth profile of the neutron scattering length density (SLD) obtained by analyzing the reflectivity profile can reveal the distribution of diffusing ions at the interface. Our previous studies on electrode/electrolyte interfaces using neutron reflectometry have mainly focused on the electrode-side interface (surface structural changes and/or surface electrolyte interphases) (1-3). There are no reports of neutron reflectometry used to discuss the depth distribution on the liquid-electrolyte side. In this study, we elucidate lithium transfer by directly observing structural changes within the cathode, through the interface, and into the electrolyte using in situ neutron reflectometry conducted on a time-of-flight reflectometer (J-PARC, BL16 SOFIA) (4, 5). We studied two different films—a Li2ZrO3-modified film and an unmodified LiCoO2 film—and found that the modified film exhibited a superior rate capability. In situ NR studies indicated that surface modification facilitates the formation of a dense cathode electrolyte interphase (CEI), primarily composed of inorganic species. In contrast, the unmodified surface was covered by a relatively sparse electrolyte-impregnated CEI. These structural observations suggest that lithium desolvation during intercalation occurs primarily on the CEI and LiCoO2 surfaces of the modified and unmodified films, respectively. The fast desolvation of Li on the CEI may contribute to the superior rate capability of the surface-modified cathodes. This suggests a mechanism of fast intercalation achieved by surface modification of low-ionically conductive oxides. The simultaneous detection of chemical composition and morphological information is a powerful way to elucidate the dynamics at cathode/liquid electrolyte interfaces suitable for high-power operation. Furthermore, neutron reflectometry is useful for understanding interfacial phenomena in all-solid-state batteries (6).References M. Hirayama, M. Yonemura, K. Suzuki, N. Torikai, H. Smith, E. Watkinsand, J. Majewski and R. Kanno, Electrochemistry, 78, 413 (2010). M. Hirayama, T. Shibusawa, R. Yamaguchi, K. Kim, S. Taminato, N. L. Yamada, M. Yonemura, K. Suzuki and R. Kanno, J. Mater. Res., 31, 3142 (2016). T. Minato, H. Kawaura, M. Hirayama, S. Taminato, K. Suzuki, N. L. Yamada, H. Sugaya, K. Yamamoto, K. Nakanishi, Y. Orikasa, H. Tanida, R. Kanno, H. Arai, Y. Uchimoto and Z. Ogumi, J. Phys. Chem. C (2016). H. Zhou, J. Izumi, S. Asano, K. Ito, K. Watanabe, K. Suzuki, F. Nemoto, N. L. Yamada, K. Aso, Y. Oshima, R. Kanno and M. Hirayama, Adv. Ener. Mater., 13, 2302402 (2023). J. Nakayama, H. Zhou, J. Izumi, K. Watanabe, K. Suzuki, F. Nemoto, N. L. Yamada, R. Kanno and M. Hirayama, Adv. Mater. Inter., 11, 2300780 (2024). S. Asano, J.-I. Hata, K. Watanabe, K. Shimizu, N. Matsui, N. L. Yamada, K. Suzuki, R. Kanno and M. Hirayama, ACS Appl. Mater. Inter., 16, 7189 (2024).

(Invited) Understanding the Degradation of Oxide Ion Diffusivity in YSZ Electrolyte for Practical SOC

Yttria-stabilized zirconia (YSZ) is the most common and the most reliable electrolyte material for solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs), collectively referred to as solid oxide cells (SOCs). Typical SOCs for practical applications are of the fuel-electrode-supported cell variety because these type of cells could be operated under high current densities. Here, the YSZ electrolyte is co-sintered with porous NiO-YSZ support at temperatures as high as 1400 °C to obtain dense electrolyte layer on the anode. In this process, NiO is expected to diffuse into the YSZ electrolyte. The influence of dissolved NiO into YSZ electrolyte has been investigated in AIST [1-3]. For the YSZ electrolyte with intentionally dissolved NiO, the phase transformation from cubic phase to tetragonal phase is accelerated in the lower oxygen potential range where NiO is reduced to Ni metal in the YSZ electrolyte, consequently, degradation in the conductivity of YSZ electrolyte occurs. In this study, the influence of co-sintering process of YSZ electrolyte with the NiO-YSZ support, i.e. NiO diffusion into YSZ electrolyte under co-sintering process, and its influence on the oxide ion diffusivity of YSZ electrolyte are examined.YSZ electrolyte layers were prepared on the NiO-YSZ substrates by screen-printing method or dip-coating method, and then co-sintered at high temperatures between 1370 °C to 1550 °C. The co-sintered YSZ/NiO-YSZ half-cells were reduced under dry H2 flow for 5 to 300 hours. The crystal structure and Ni distribution of the YSZ electrolyte layer were analyzed using Raman spectroscopy and high-spatial-resolution SIMS (secondary ion mass spectrometry), respectively. Lastly, the oxide ion diffusivity of the YSZ electrolyte layer was obtained using the oxygen isotope exchange method and high-spatial-resolution SIMS technique.By co-sintering of YSZ electrolyte and NiO-YSZ support, NiO uniformly diffused into YSZ electrolyte layer, and the amount of dissolved Ni (NiO) increased with increasing sintering temperature. When the half-cell was reduced at 900 °C, a phase transformation of the YSZ electrolyte was clearly observed, moreover, the oxide ion diffusivity of the YSZ electrolyte also decreased. By reduction of the half-cell at 700 °C, such phase transformation could not be observed, however, the oxide ion diffusivity is slightly but clearly decreased. In the presentation, the mechanisms of phase transformation and conductivity degradation will be discussed. H. Yokokawa et. al., Fuel Cells, 19 (2019) 311–339.T. Ishiyama, H. Kishimoto, K. D. Bagarinao, K. Yamaji, T. Horita, H. Yokokawa, ECS Transactions, 78 (2017) 321–326.T. Shimonosono, H. Kishimoto, M.E. Brito, K. Yamaji, T. Horita, H. Yokokawa, Solid State Ionics,225, 69 (2012).

Manufacturing of Proton Conducting Solid-Oxide Electrolysis Cells Based on Yttrium‐Doped Barium Zirconate Electrolyte

Proton-conducting solid oxide electrolysis cell (P-SOEC) has been recently recognized as a promising technology for delivering fast hydrogen production at lower temperature range to hold the promise of utilizing cheaper stack materials and reducing degradation. The current P-SOEC technology has been progressed into a new development stage with promising technical accomplishments. The operating temperatures have been effectively pushed down to 500~600°C to enable use of cheaper interconnects and to improve material system compatibility. However, the P-SOEC development is in its early stage due to low technology readiness level limited by several technical issues lying in material system, thermal processing, and efficiency. Based on comprehensive considerations on efficiency and durability, BaZr0.8Y0.2O3 (BZY) is considered as stable electrolyte candidate for electrolysis operation under extremely high steam concentration. However, the manufacturing of BZY electrolyte in half cells is challenging due to the refractory nature on sintering. In this work, we demonstrate the recent efforts in manufacturing BZY based P-SOEC for achieving the dense electrolyte with less sacrifice in proton conductivity. Several approaches are utilized and compared for validating the sintering activity and resulted properties. This work paves a solid foundation for our further investigation on electrolysis behaviors to meet the requirements on performances and durability.

Preparation of Y2O3-Stabilized ZrO2 Film By Warm Isostatic Press (WIP) Method for Metal-Support Solid Oxide Fuel Cells (SOFCs)

Solid Oxide Fuel Cells (SOFCs) are attracting as highly efficient power generator and almost no air pollutant emitted. So, SOFCs are now practically used, however, current SOFCs are consisted of all ceramics and so reliability and cost are the issues. Metal support SOFC (MS-SOFCs) is used porous metal for substrate and so high mechanical strength and also easy gas sealing is expected. However, preparation of dense electrolyte film on porous metal substrate is now the most significant issue to solve. In this study, we proposed oxide dense plate of NiO-NiFe2O4 as precursor of MS-SOFCs and after deposition of dense electrolyte film, dense oxide disc of NiO-NiFe2O4 is changed to porous Ni-Fe porous support by reduction in H2 stream[1]. For making thin film of Y2O3 stabilized ZrO2(YSZ), warm isostatic press (WIP) was used by using YSZ tape prepared by tape casting method. Commercial YSZ powder (TOSOH TZ8Y) was used after ball mill treatment and after making slurry, YSZ green sheet was obtained by tape casting of YSZ slurry on plastic film and then the obtained YSZ film was transcribed onto NiO-NiFe2O4 substrate with warm isostatic press (WIP) at 353K. After co-sintered at 1473K for 6 h, dense YSZ film with 10mm was obtained followed by reaction in H2 stream at 973K. Sm0.5Sr0.5CoO3 was used as cathode. After reduction, change in size and porosity of NiO-NiFe2O4 were less than 6% and 39%, respectively. Figure 1 shows power generation property of the obtained Ni-Fe supported YSZ cell at 973 K. The open circuit potential was closed to the theoretical value of 1.03 V and reasonable power density of 340mW/cm2 was achieved at 973K. Slightly lower OCV may be results of Fe diffusion into YSZ cell and so, functional inter layer to prevent elemental diffusion was also investigated in this study. This study reveals that metal support YSZ can be obtained by WIP method.Acknowledgement; This study was financially supported by New Energy and Industrial Technology Development Organization (NEDO,JPNP20003), Japan Ju, Y‐W., S. Ida, and T. Ishihara. Fuel Cells6 (2012): 1064-1069. Figure 1 Power generation curves of metal support SOFC using YSZ film prepared with WIP method. Figure 1

High ionic conductive sodium β-alumina (SBA) and SBA-NaPF6 composite solid electrolytes prepared by cold sintering process

Sodium β-alumina (SBA) electrolytes are among the most excellent candidates for all-solid-state batteries due to their high electrochemical performances and low cost of sodium resources. However, thermally sintering at above 1400 °C is required to fabricate high dense SBA electrolytes, thus giving rise to a huge energy consumption. Here, dense SBA electrolytes and (1-x)SBA-xNaPF6 (x = 5, 10, 15, 20 wt%) composites were fabricated using cold sintering process (CSP) below 300 °C with 2 mol/L NaOH solution as transient chemistry. The ionic conductivity of SBA electrolytes is significantly enhanced from 5.53×10-6 S cm-1 to 5.91 × 10−4 S cm−1 as 15 wt% NaPF6 was introduced to the composite, which is comparable with the SBA sintered above 1400 °C. CSP may provide a promising approach for the fabrication of solid-state electrolytes by avoiding the detrimental impact of high temperature heat treatment.

Co-solvent electrolyte-induced zinc anode surface reconstruction for high performance zinc ion batteries

The progress of rechargeable zinc (Zn) ion batteries (RZBs) has been significantly impeded by the occurrence of side reactions and dendritic issues on Zn anodes, which are attributed to the intricate reaction kinetics observed in aqueous electrolytes. Herein, we propose a co-solvent electrolyte comprising a combination of N, N-dimethylformamide (DMF) and Dimethyl sulfoxide (DMSO). This electrolyte reconstructs the surface of the Zn anode and generates a dense and robust solid electrolyte interface (SEI), which promotes uniform Zn2+ deposition and enhances Zn2+ transport kinetics. The DFT further shows that the electrolyte has a unique solvated structure which enables uniform Zn2+ deposition and the creation of stable SEI. By utilizing these advantages, the co-solvent electrolyte is capable of enduring uninterrupted cycling for more than 4000 h at a current density of 1 mA cm−2, and for over 2000 h at a current density of 5 mA cm−2. Furthermore, the Zn||NH4V4O10 full cell demonstrated exceptional electrochemical performance with regard to charge/discharge capacity and cycle stability. This study showcases the effectiveness of non-aqueous electrolytes, which will enable the progress of secure and high-capacity RZBs.

Exploring the Potential of Cold Sintering for Proton-Conducting Ceramics: A Review.

Proton-conducting ceramic materials have emerged as effective candidates for improving the performance of solid oxide cells (SOCs) and electrolyzers (SOEs) at intermediate temperatures. BaCeO3 and BaZrO3 perovskites doped with rare-earth elements such as Y2O3 (BCZY) are well known for their high proton conductivity, low operating temperature, and chemical stability, which lead to SOCs' improved performance. However, the high sintering temperature and extended processing time needed to obtain dense BCZY-type electrolytes (typically > 1350 °C) to be used as SOC electrolytes can cause severe barium evaporation, altering the stoichiometry of the system and consequently reducing the performance of the final device. The cold sintering process (CSP) is a novel sintering technique that allows a drastic reduction in the sintering temperature needed to obtain dense ceramics. Using the CSP, materials can be sintered in a short time using an appropriate amount of a liquid phase at temperatures < 300 °C under a few hundred MPa of uniaxial pressure. For these reasons, cold sintering is considered one of the most promising ways to obtain ceramic proton conductors in mild conditions. This review aims to collect novel insights into the application of the CSP with a focus on BCZY-type materials, highlighting the opportunities and challenges and giving a vision of future trends and perspectives.

Role of Sintering Aids in Electrical and Material Properties of Yttrium- and Cerium-Doped Barium Zirconate Electrolytes

Ceramic proton conductors have the potential to lower the operating temperature of solid oxide cells (SOCs) to the intermediate temperature range of 400–600 °C. This is attributed to their superior ionic conductivity compared to oxide ion conductors under these conditions. However, prominent proton-conducting materials, such as yttrium-doped barium cerates and zirconates with specified compositions like BaCe1−xYxO3−δ (BCY), BaZr1−xYxO3−δ (BZY), and Ba(Ce,Zr)1−yYyO3−δ (BCZY), face significant challenges in achieving dense electrolyte membranes. It is suggested that the incorporation of transition and alkali metal oxides as sintering additives can induce liquid phase sintering (LPS), offering an efficient method to facilitate the densification of these proton-conducting ceramics. However, current research underscores that incorporating these sintering additives may lead to adverse secondary effects on the ionic transport properties of these materials since the concentration and mobility of protonic defects in a perovskite are highly sensitive to symmetry change. Such a drop in ionic conductivity, specifically proton transference, can adversely affect the overall performance of cells. The extent of variation in the proton conductivity of the perovskite BCZY depends on the type and concentration of the sintering aid, the nature of the sintering aid precursors used, the incorporation technique, and the sintering profile. This review provides a synopsis of various potential sintering techniques, explores the influence of diverse sintering additives, and evaluates their effects on the densification, ionic transport, and electrochemical properties of BCZY. We also report the performance of most of these combinations in an actual test environment (fuel cell or electrolysis mode) and comparison with BCZY.

Self-forming Na3P/Na2O interphase on a novel biphasic Na3Zr2Si2PO12/Na3PO4 solid electrolyte for long-cycling solid-state Na-metal batteries

A novel biphasic Na3Zr2Si2PO12/Na3PO4 solid electrolyte is proposed to effectively address critical anode interface challenges for solid-state Na-metal batteries (SSSMBs). The Na3PO4 phase, at an optimal composition of ∼20 mol%, transforms the interface chemistry throughout the NZSP electrolyte, which results in dense electrolytes with high Young's modulus, rapid ion transport (6.2 × 10−4 S cm-1) at low activation barrier (0.19 eV), negligible electronic conductivity, and excellent sodiophilicity. The AIMD/DFT calculations and XPS analysis reveal a self-formed, (electro)chemically stable mixed Na+/electron-conducting interphase, comprising Na3P and Na2O, at the Na anode interface. The interphase not only homogenizes the Na+ flux distribution and accelerates the interfacial charge transport, but prevents continuous interfacial reactions, thereby stabilizing the anode interface against dendrite formation. Benefiting from the low-impedance, dendrite-free anode interface, Na symmetric cells demonstrate a low interface resistance of 12.7 Ω cm2 and exceptional cyclability of 3000 h. Additionally, full cells with Na3V2(PO4)3 cathodes achieve 93 % capacity retention after 550 cycles at 0.5 C. This research comprehensively elucidates and leverages the critical advantages of Na3PO4 in enhancing the bulk and interface properties of Na3Zr2Si2PO12 solid electrolytes. The design strategy of biphasic solid electrolytes presented here offers new insights into the developing high-performance solid electrolytes for advanced SSSMBs.

Achievable dual-strategy to stabilize Li-rich layered oxide interface by a one-step wet chemical reaction towards long oxygen redox reversibility

Oxygen release and electrolyte decomposition under high voltage endlessly exacerbate interfacial ramifications and structural degradation of high energy-density Li-rich layered oxide (LLO), leading to voltage and capacity fading. Herein, the dual-strategy of CrxB complex coating and local gradient doping is simultaneously achieved on LLO surface by a one-step wet chemical reaction at room temperature. Density functional theory (DFT) calculations prove that stable B–O and Cr–O bonds through the local gradient doping can significantly reduce the high-energy O 2p states of interfacial lattice O, which is also effective for the near-surface lattice O, thus greatly stabilizing the LLO surface. Besides, differential electrochemical mass spectrometry (DEMS) indicates that the CrxB complex coating can adequately inhibit oxygen release and prevents the migration or dissolution of transition metal ions, including allowing speedy Li+ migration. The voltage and capacity fading of the modified cathode (LLO-CrB) are adequately suppressed, which are benefited from the uniformly dense cathode electrolyte interface (CEI) composed of balanced organic/inorganic composition. Therefore, the specific capacity of LLO-CrB after 200 cycles at 1C is 209.3 mA h g−1 (with a retention rate of 95.1%). This dual-strategy through a one-step wet chemical reaction is expected to be applied in the design and development of other anionic redox cathode materials.

Wet Chemical Method ZnF2 Interlayer for High Critical Current Density Lithium Metal Batteries Utilizing Ba and Ta–Doped Li7La3Zr2O12 Garnet Solid Electrolyte

AbstractLi metal batteries with garnet‐type solid electrolytes have the potential to increase specific energy and power densities of current Li‐ion batteries. Li metal batteries have been hampered by the poor wettability of solid electrolyte with elemental lithium. Here, to resolve the solid garnet electrolyte/Li interface issue, a scalable, cost‐effective, and efficient surfactant‐assisted wet‐chemical strategy is developed. A ZnF2 interlayer coating is applied on Ba and Ta ‐co‐doped Li7La2.75Ba0.25Zr1.75Ta0.25O12 that formed LiF and Li‐Zn alloy upon contact with molten Li. Conformal contact applying a homogenous surfactant‐assisted ZnF2 coating reduced the interfacial resistance from 87 to 15.5 Ω cm2 which enhanced critical current density to a record high value of 5 mA cm−2 at room temperature. Dense and Li2CO3 free garnet solid electrolyte assisted in achieving long‐term stability for 1000 cycles at 1 mA cm−2. Interface stabilized Li/ZnF2‐ solid electrolyte/liquid electrolyte/LiFePO4 cell displayed a 90% capacity retention over 800 cycles at 0.2 C, with Coulombic efficiency of 99% as well as excellent cycle stability at 1 C, with ≈91% of capacity retention for 500 cycles. Using a new design principle for Li anode interfaces, next‐generation power‐intensive and stable solid‐state Li metal batteries can be developed.