A highly active and durable lanthanum strontium cobalt ferrite cathode for Intermediate-Temperature solid Oxide fuel cel

Solid oxide fuel cells (SOFCs) are promising techniques for high energy efficiency, fuel flexibility, and low pollutant emissions. For commercialization of SOFCs, it is required to decrease the operating temperature. At this intermediate temperature region, the cathodic polarization resistance significant due to the thermally activated oxygen reduction reaction (ORR). To compensate this, highly active cathode materials have been considered and lanthanum strontium cobalt ferrite (LSCF6428, La0.6Sr0.4Co0.2Fe0.8O3-δ) has been attracted as a cathode material for SOFCs because of its high mixed electronic and ionic conducting (MIEC) nature. However, one of the major concerns of LSCF6428 is the degradation during the long-term operation. Currently, Sr segregation has been reported as one of the major reasons for the LSCF degradation. In this study, we investigated LSCF2882 (La0.2Sr0.8Co0.8Fe0.2O3-δ) and compared with LSCF6428 as a SOFC cathode. X-ray diffraction (XRD) and Rietveld refinement were applied to analyze phase structures. By electrical conductivity relaxation (ECR) technique, Oxygen surface exchange coefficients (kchem) and chemical diffusion coefficients (Dchem) of LSCF2882 were evaluated and we observed enhancements compare to LSCF6428. For interpretation of enhanced oxygen transport kinetics, we tried to visualize the interstitial oxygen conduction pathways and the bond valence sum (BVS) mapping method was utilized by Valence program. BVS mapping results show clearly demonstrating the 3D network of the interstitial pathways at 600oC in LSCF2882. Electrochemical performances were investigated by EIS (Electrochemical Impedance Spectroscopy) and single cell performance was also evaluated. In addition, long-term stability test was performed for over 500 hours. LSCF2882 showed better performances and it exhibited no degradation during the stability test. Please click Additional Files below to see the full abstract

Prototype System of Rocking-Chair Zn-Ion Battery Adopting Zinc Chevrel Phase Anode and Rhombohedral Zinc Hexacyanoferrate Cathode

Zinc-ion batteries (ZIBs) have received attention as one type of multivalent-ion batteries due to their potential applications in large-scale energy storage systems. Here we report a prototype of rocking-chair ZIB system employing Zn2Mo6S8 (zinc Chevrel phase) as an anode operating at 0.35 V, and K0.02(H2O)0.22Zn2.94[Fe(CN)6]2 (rhombohedral zinc Prussian-blue analogue) as a cathode operating at 1.75 V (vs. Zn/Zn2+) in ZnSO4 aqueous electrolyte. This type of cell has a benefit due to its intrinsic zinc-dendrite-free nature. The cell is designed to be positive-limited with a capacity of 62.3 mAh g−1. The full-cell shows a reversible cycle with an average discharge cell voltage of ~1.40 V, demonstrating a successful rocking-chair zinc-ion battery system

Re-evaluating the Magnesium-ion Storage Capability of Vanadium Dioxide, VO2(B): Uncovering the Influence of Water Content on the Previously Overestimated High Capacity

Magnesium batteries have emerged as a promising alternative to lithium-ion batteries due to their theoretical high energy density and abundant magnesium resources. Vanadium dioxide, VO2(B), has been reported as a high-capacity cathode material for magnesium batteries. However, the electrochemical intercalation mechanism requires further elucidation due to a limited understanding of the structure-property relationship. In this study, we re-evaluated the magnesium storage capability of the material, with a particular focus on the influence of water content in nonaqueous electrolytes. The higher discharge capacity of 250 mAh g−1 is achieved exclusively in the wet electrolyte with 650 ppm water content. A significantly lower capacity of 51 mAh g−1 was observed in the dry electrolyte solution containing 40 ppm water content. Through X-ray structural and elemental analyses, as well as magnesium-ion diffusion pathway analysis using bond-valence-energy-landscape calculations, the restricted capacity was clarified by examining the reaction mechanism. According to this study, the impressive capacity of magnesium-ion battery cathodes may be exaggerated due to the involvement of non-magnesium-ion insertion unless the electrolytes′ water content is appropriately regulated. © 2023 Wiley-VCH GmbH.FALS

H2V3O8 as a High Energy Cathode Material for Nonaqueous Magnesium-Ion Batteries

Magnesium-ion batteries (MIBs) suffer from a low energy density of cathode materials in a conventional nonaqueous electrolyte, contrary to the expectation due to the divalent Mg ion. Here, we report H2V3O8, or V3O7·H2O, as a high-energy cathode material for MIBs. It exhibits reversible magnesiation-demagnesiation behavior with an initial discharge capacity of 231 mAh g-1 at 60 °C, and an average discharge voltage of 1.9 V vs Mg/Mg2+ in an electrolyte of 0.5 M Mg(ClO4)2 in acetonitrile, resulting in a high energy density of 440 Wh kg-1. The structural water remains stable during cycling. The crystal structure for Mg0.97H2V3O8 is determined for the first time. Bond valence sum difference mapping shows facile conduction pathways for Mg ions in the structure. The high performance of this material with its distinct crystal structure employing water-metal bonding and hydrogen bonding provides insights to search for new oxide-based stable and high-energy materials for MIBs. © 2018 American Chemical Society.1

Calcium Molybdenum Bronze as a Stable High-Capacity Cathode Material for Calcium-Ion Batteries

Calcium-ion batteries (CIBs) are gaining increasing attention due to their theoretically high capacity, owing to the divalency of calcium, and low cost. However, only a few calcium insertion electrode materials are reported, and most of them exhibit low capacity or poor cyclability in nonaqueous electrolytes. Herein, we demonstrated high-performance calcium molybdenum bronze Ca0.13MoO3·(H2O)0.41 as a potential CIB cathode material at room temperature, with a reversible discharge capacity of 192 mAh g-1 at 86 mA g-1, an average voltage of 2.4 V (vs Ca/Ca2+), and excellent cyclability. This work provides the feasibility of developing high-capacity CIB cathode materials. Copyright © 2020 American Chemical Society.1

Double-Sheet Vanadium Oxide as a Cathode Material for Calcium-Ion Batteries

Calcium-ion batteries (CIBs) are theoretically considered one of the potential post-lithium-ion battery technologies. However, only a few host materials are known to intercalate Ca ions. Herein, we demonstrate the use of double-sheet vanadium oxide V2O5 ⋅ 0.63H2O as a high-performance cathode material for CIBs. The vanadium oxide was synthesized via an electrochemical oxidation process on a graphite foil substrate. The material exhibited a high reversible capacity of 204 mAh g−1 at a 0.1 C rate in an aqueous electrolyte, with an average discharge voltage of 2.76 V vs. Ca/Ca2+, and a capacity retention of 86% after 350 cycles. The reaction mechanism can be described as a combination of diffusion-controlled intercalation and surface-limited pseudo-capacitance reactions. This study provides a new type of Ca host material, motivating further development of new CIB cathode materials. © 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim1

Layered Iron Vanadate as a High-Capacity Cathode Material for Nonaqueous Calcium-Ion Batteries

Calcium-ion batteries represent a promising alternative to the current lithium-ion batteries. Nevertheless, calcium-ion intercalating materials in nonaqueous electrolytes are scarce, probably due to the difficulties in finding suitable host materials. Considering that research into calcium-ion batteries is in its infancy, discovering and characterizing new host materials would be critical to further development. Here, we demonstrate FeV3 O9·1.2H2 O as a high-performance calcium-ion battery cathode material that delivers a reversible discharge capacity of 303 mAh g−1 with a good cycling stability and an average discharge voltage of ~2.6 V (vs. Ca/Ca2+ ). The material was synthesized via a facile co-precipitation method. Its reversible capacity is the highest among calcium-ion battery materials, and it is the first example of a material with a capacity much larger than that of conventional lithium-ion battery cathode materials. Bulk intercalation of calcium into the host lattice contributed predominantly to the total capacity at a lower rate, but became comparable to that due to surface adsorption at a higher rate. This stimulating discovery will lead to the development of new strategies for obtaining high energy density calcium-ion batteries. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.TRU

Electrochemical Exchange Reaction Mechanism and the Role of Additive Water to Stabilize the Structure of VOPO 4 ⋅2 H 2 O as a Cathode Material for Potassium-Ion Batteries

VOPO 4 ⋅2 H 2 O is demonstrated as a cathode material for potassium-ion batteries in 0.6 m KPF 6 in ethylene carbonate/diethyl carbonate, and its distinct exchange reaction mechanism between potassium and crystal water is reported. In an anhydrous electrolyte, the cathode shows an initial capacity of approximately 90 mAh g −1 , with poor capacity retention (32 % after 50 cycles). In contrast, the capacity retention dramatically improved (86 % after 100 cycles) in a wet electrolyte containing 0.1 m of additive water. VOPO 4 ⋅2 H 2 O contains two types of water (structural and crystal). Upon discharge, potassium ions are intercalated whereas the crystal water is simultaneously de-intercalated from the structure. Upon charging, a completely reverse reaction takes place in the wet electrolyte, resulting in high stability of the host structure and excellent cyclability. However, in the anhydrous electrolyte, some portion of the extracted crystal water molecules cannot be reinserted into the host structure because they are distributed over the anhydrous electrolyte. Keeping some concentration of water in the electrolyte turns out to be was the key to achieving such high reversibility. The potassium ions (90 %) and proton or hydronium ions (10 %) seem to be co-intercalated in the wet electrolyte. This work provides a general insight into the intercalation mechanism of crystal-water-containing host materials. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim1

Rhombohedral Potassium-Zinc Hexacyanoferrate as a Cathode Material for Nonaqueous Potassium-Ion Batteries

Rhombohedral potassium-zinc hexacyanoferrate K 1.88 Zn 2.88 [Fe(CN) 6 ] 2 (H 2 O) 5 (KZnHCF) synthesized using a precipitation method is demonstrated as a high-voltage cathode material for potassium-ion batteries (PIBs), exhibiting an initial discharge capacity of 55.6 mAh g -1 with a discharge voltage of 3.9 V versus K/K + and a capacity retention of 95% after 100 cycles in a nonaqueous electrolyte. All K ions are extracted from the structure upon the initial charge process. However, only 1.61 out of 1.88 K ions per formula unit are inserted back into the structure upon discharge, and it becomes the reversible ion of the second cycle onward. Despite the large ionic size of K, the material exhibits a lattice-volume change (3%) during a cycle, which is exceptionally small among the cathode materials for PIBs. The distinct feature of the material seems to come from the unique porous framework structure built by ZnN 4 and FeC 6 polyhedra linked via the CN bond and a Zn/Fe atomic ratio of 3/2, resulting in high structural stability and cycle performance. © 2019 American Chemical Society.1

Electrochemical lithium intercalation chemistry of condensed molybdenum metal cluster oxide: LiMo4O6

The electrochemical lithium-ion intercalation properties of molybdenum metal-cluster oxide LixMo4O6 (0.33 ≤ x ≤ 1.0) in an organic electrolyte of 1.0 M LiPF6 in ethylene carbonate/dimethyl carbonate (1:2 v/v) were characterized for the first time. Li0.66Mo4O6 (tetragonal, P4/mbm, a = 9.5914(3) Å, c = 2.8798(1) Å, V = 264.927(15) Å3, Z = 2) was prepared via ion-exchange of indium and lithium ions from InMo4O6 (tetragonal, P4/mbm, a = 9.66610(4) Å, c = 2.86507(2) Å, V = 267.694(2) Å3, Z = 2), which was first synthesized from a stoichiometric mixture of In, Mo, and MoO3 via a solid-state reaction for 11 h at 1100 °C. Then, Li0.33Mo4O6 was obtained via electrochemical charge of the electrode at 3.4 V vs. Li. The electrochemical lithium-ion insertion into Li0.33Mo4O6 occurs stepwise: three separate peaks were observed in the cyclic voltammogram and three quasi-plateaus in the galvanostatic profile, indicating a complicated intercalation mechanism. However, examination of the structural evolution of LixMo4O6 during the electrochemical cycle indicated a reversible reaction over the measured voltage range (2.0–3.2 V) and x range (0.33 ≤ x ≤ 1.00). Despite the excellent electrochemical reversibility, LixMo4O6 showed poor rate performance with a low capacity of 36.3 mAh g−1 at a rate of 0.05 C. Nonetheless, this work demonstrates a new structural class of lithium cathode materials with condensed metal clusters and 1D tunnels, and provides a host material candidate for multivalent-ion batteries. © 2017 Elsevier Inc.