Yoko Hase

Catalytic Cycle Employing a TEMPO-Anion Complex to Obtain a Secondary Mg-O2 Battery.

Nonaqueous Mg-O2 batteries are suitable only as primary cells because MgO precipitates formed during discharging are not decomposed electrochemically at ambient temperatures. To address this problem, the present study examined the ability of the 2,2,6,6-tetramethylpiperidine-oxyl (TEMPO)-anion complex to catalyze the decomposition of MgO. It was determined that this complex was capable of chemically decomposing MgO at 60 °C. A catalytic cycle for the realization of a rechargeable Mg-O2 electrode was designed by combining the decomposition of MgO via the TEMPO-anion complex and the TEMPO-redox couple. This work also demonstrates that a nonaqueous Mg-O2 battery incorporating acrylate polymer having TEMPO side units in the cathode shows evidence of being rechargeable.

A highly efficient Li2O2 oxidation system in Li–O2 batteries

A novel indirect charging system that uses a redox mediator was demonstrated for Li-O2 batteries. 4-Methoxy-2,2,6,6-tetramethylpiperidinyl-1-oxyl (MeO-TEMPO) was applied as a mediator to enable the oxidation of Li2O2, even though Li2O2 is electrochemically isolated. This system promotes the oxidation of Li2O2 without parasitic reactions attributed to electrochemical charging and reduces the charging time.

Coupling of nitroxyl radical as an electrochemical charging catalyst and ionic liquid for calcium plating/stripping toward a rechargeable calcium–oxygen battery

There are two problems to overcome to realize a non-aqueous rechargeable calcium–oxygen battery: lack of a catalyst for decomposing calcium oxide (CaO) as the main discharge product, and irreversible deposition/dissolution of Ca2+ at the anode. First, the catalytic capability of 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO)–anion complex to decompose CaO at the O2 electrode was examined. Charge transfer from the TEMPO–anion complex to CaO occurred, leading to effective decomposition of CaO. Second, the deposition/dissolution behavior of Ca2+ was investigated in N,N-diethyl-N-methyl-N-(2-methoxyethyl) ammonium bis(trifluoromethanesulfonyl) amide at 60 °C. We observed partially reversible Ca plating/stripping under a high sweep rate in the ionic liquid. Finally we fabricated a rechargeable Ca–O2 battery using the TEMPO catalyst for the cathode, Ca chips for the anode, and an ionic liquid, and demonstrated that the battery showed repeated discharge/charge performance.