Atsushi Inoishi

High capacity of an Fe–air rechargeable battery using LaGaO3-based oxide ion conductor as an electrolyte

Rapid growth and improved functions of mobile equipment present the need for an advanced rechargeable battery with extremely high capacity. In this study, we investigated the application of fuel cell technology to an Fe-air rechargeable battery. Because the redox potential of Fe is similar to that of H(2), the combination of H(2) formation by the oxidation of Fe with a fuel cell has led to a new type of metal-air rechargeable battery. By decreasing the operating temperature, a deep oxidation state of Fe can be achieved, resulting in enlarged capacity of the Fe-air battery. We found that the metal Fe is oxidized to Fe(3)O(4) by using H(2)/H(2)O as mediator. The observed discharge capacity is 817 mA h g(-1)-Fe, which is approximately 68% of the theoretical capacity of the formation of Fe(3)O(4), 1200 mA h g(-1)-Fe, at 10 mA cm(-2) and 873 K. Moreover, the cycle stability of this cell is examined. At 1073 K, the cell shows a discharge capacity of ca. 800 mA h g(-1)-Fe with reasonably high discharge capacity sustained over five cycles.

Ni–Fe–Ce(Mn,Fe)O2 cermet anode for rechargeable Fe–Air battery using LaGaO3 oxide ion conductor as electrolyte

There is a strong demand for the development of a large capacity rechargeable battery in various fields. Recently, we proposed the combination of solid oxide fuel cell technology with Fe–air battery concepts using H2/H2O as a redox mediator and a LaGaO3-based oxide as an electrolyte. Because large internal resistance and large degradation during charge and discharge cycles were observed on the anode, there is a strong demand for improvements in discharge potential and cycle stability. This study investigates the use of a cermet anode consisting of a Ni–Fe alloy combined with an oxide ion conductor. It was observed that by using a cermet anode of Ni–Fe combined with Ce0.6Mn0.3Fe0.1O2 (CMF), the observed capacity of the cell was improved to 1163 mAh g−1 Fe−1 at 10 mA cm−2 and 873 K. This is about 97% of the theoretical capacity by assuming the formation of Fe3O4 (1200 mAh g−1 Fe−1). Cycle stability of the cell was also considerably improved with the use of a Ni–Fe–CMF anode compared to a Ni–Fe anode because of the suppressed aggregation provided by the mixing of Ni with CMF.

A rechargeable Si–air solid state oxygen shuttle battery incorporating an oxide ion conductor

Herein, we report a new type of Si–air rechargeable battery incorporating an oxide ion conducting electrolyte, based on the oxygen shuttle concept. A cell designed in this manner and employing Ca stabilized ZrO2 exhibited stable charge–discharge over 20 cycles at 1073 K and achieved a discharge capacity of approximately 600 mA h gSi−1.

Low temperature operation of a solid-oxide Fe–air rechargeable battery using a La0.9Sr0.1Ga0.8Mg0.2O3 oxide ion conductor

We investigated a catalyst for oxidation of Fe powder using steam and it was applied to a Fe–air rechargeable battery based on the low temperature operating Solid Oxide Fuel Cells technology. Stable charge–discharge cycling over 20 cycles was achieved at 673 K.

Discharge Performance of Solid-State Oxygen Shuttle Metal–Air Battery Using Ca-Stabilized ZrO2 Electrolyte

The effects of metal choice on the electrochemical performance of oxygen-shuttle metal-air batteries with Ca-stabilized ZrO2 (CSZ) as the electrolyte and various metals as the anodes were studied at 1073 K. The equilibrium oxygen partial pressure (P O 2) in the anode chamber was governed by the metal used in the anode chamber. A lower-P O 2 environment in the anode decreased the polarization resistance of the anode. The oxidation of oxide ions to oxygen in the anode is drastically enhanced by the n-type conduction generated in the CSZ electrolyte when it is exposed to a reducing atmosphere. A high discharge potential and high capacity can be achieved in an oxygen-shuttle battery with a Li or Mg anode because of the fast anode reaction compared to that of cells with a Zn, Fe, or Sn anode. However, only the mildly reducing metals (Zn, Si, Fe, and Sn) can potentially be used in rechargeable metal-air batteries because the transport number of the CSZ electrolyte must be unity during charge and discharge. Oxygen shuttle rechargeable batteries with Fe, and Sn electrodes are demonstrated.

A single-phase all-solid-state lithium battery based on Li1.5Cr0.5Ti1.5(PO4)3 for high rate capability and low temperature operation

We report a battery made from a single material using Li1.5Cr0.5Ti1.5(PO4)3 as the anode, cathode and electrolyte. A high rate capability at room temperature and very low-temperature operation (233 K) were possible as a result of the superior ionic conductivity and low interfacial resistance obtained from the single-phase cell design.

A dense La(Sr)Fe(Mn)O3−δ nano-film anode for intermediate-temperature solid oxide fuel cells

To achieve high power density in intermediate-temperature solid oxide fuel cells (IT-SOFCs), we introduce a dense La(Sr)Fe(Mn)O3−δ (LSFM) nano-film anode between a Ni–Fe metallic substrate and a LaGaO3-based oxide electrolyte. Although a three-phase boundary (TPB) is believed to be required for anode active sites, the cell with the LSFM mixed-conductor thin-film anode exhibited much improved power density compared with that of the cell with a simple porous Ni–Fe anode. The maximum power density of the cell with the LSFM film was approximately 3.0 W cm−2 at 973 K. The improved power density was primarily attributed to the enhanced anodic activity. Furthermore, we observed that the dense LSFM thin-film anode is effective in increasing the fuel utilization of a Ni–Fe metallic anode supported cell. This suggests that a two-phase boundary (anode and gas phase) at the LaFeO3 perovskite is highly active towards the anodic reaction.

Solid-oxide Fe–air rechargeable battery using Fe–Ce(Mn, Fe)O2 for low temperature operation

The effects of Ce0.6Mn0.3Fe0.1O2 (CMF) mixed with Fe for increasing redox properties were investigated in this study, and it was found that the reaction rate constant of Fe oxidation and reduction can be much increased through mixing with CMF. At 673 K, the oxidation rate constant of the Fe powder was higher than that of Fe without added CMF by an order of magnitude and the oxidation degree of the Fe is also increased from 10 to 80% at the initial time. When CMF mixed with Fe was set into the fuel chamber of a solid state Fe–air rechargeable battery, Ni–Fe/La0.9Sr0.1Ga0.8Mg0.2O3/Ba0.6La0.4CoO3, a discharge potential of ca. 1 V and a discharge capacity of 600 mA h gFe−1 was achieved at 673 K which is similar to the operating temperature of Na–S batteries. A stable discharge capacity was sustained over 20 cycles. In addition, the observed energy density of the present cell, 600 W h kgFe−1, was larger than that of the Na–S battery by 5 times and that of the redox flow battery by 30 times, and the efficiency of charging and discharging is almost the same. Since the Fe–air rechargeable battery is highly safe and environmentally compatible, it is promising for use as a stationary large capacity rechargeable battery, as an alternative to Na–S or redox flow batteries.

Proton-Driven Intercalation and Ion Substitution Utilizing Solid-State Electrochemical Reaction

The development of an unconventional synthesis method has a large potential to drastically advance materials science. In this research, a new synthesis method based on a solid-state electrochemical reaction was demonstrated, which can be made available for intercalation and ion substitution. It was referred to as proton-driven ion introduction (PDII). The protons generated by the electrolytic dissociation of hydrogen drive other monovalent cations along a high electric field in the solid state. Utilizing this mechanism, Li+, Na+, K+, Cu+, and Ag+ were intercalated into a layered TaS2 single crystal while maintaining high crystallinity. This liquid-free process of ion introduction allows the application of high voltage around several kilovolts to the sample. Such a high electric field strongly accelerates ion substitution. Actually, compared to conventional solid-state reaction, PDII introduced 15 times the amount of K into Na super ionic conductor (NASICON)-structured Na3-xKxV2(PO4)3. The obtained materials exhibited a thermodynamically metastable phase, which has not been reported so far. This concept and idea for ion introduction is expected to form new functional compounds and/or phases.

Reversible Solid State Fe-Air Rechargeable Battery Using LaGaO3 Based Oxide Ion Conducting Electrolyte

The combination of solid oxide fuel cell technology with Fe-air battery concept was proposed by using H2/H2O as a redox mediator and LaGaO3 based oxide for electrolyte. Since large internal resistance and large degradation during charge and discharge cycles are observed on anode, improvement in discharge potential and cycle stability are strongly required by improving stability of anode. In this study, cermet anode consisting of Ni-Fe alloy combined with oxide ion conductor was investigated. It was found that by using cermet anode of Ni-Fe combined with Ce0.6Mn0.3Fe0.1O2 (CMF), the observed energy density of the cell is improved to be 1109 Wh/Kg-Fe at 10 mA/cm2, 873 K, which is about 92% of the theoretical energy density assuming the formation of Fe3O4 (1290 Wh/Kg-Fe). Cycle stability was also much improved on the cell using Ni-Fe-CMF anode comparing with that of Ni-Fe metal because of suppressed aggregation of Ni by mixing with CMF. Electrochemical charge-discharge measurement at 773 K showed excellent cycle stability over 30 cycles with high energy density (Round trip efficiency is higher than 80 %). The excellent performance and stability with operating at lower temperature promise this Fe-air solid oxide battery as the next generation energy storage device for averaging electricity and electric vehicle.