Abstract
Sintered ceramics of Ca0.9A0.1MnO3-δ(A = La, Nd, Sm, Gd and Y) were studied on their cathode properties in LiOHaq. solution. After firing, the samples were obtained as high conductivity sintered (porous) materials composed of an orthorhombic perovskite-type phase. Next, charge discharge performances of the electrodes consisting of the sintered sample were investigated. The discharge capacity of Ca0.9Y0.1MnO3-δwas 185 mAh·g-1on the 1st cycling, and the 1st charging was possible by 130 mAh·g-1. However, the 2nd discharge capacity remarkably decreased to lower than 50 mAh·g-1. Considering no obvious charging property on the previous La-substituted sample of Ca0.9La0.1MnO3-δ, it would mean that change of the substituent for CaMnO3 affects the electrochemical property. The roll of lithium ions, the effect of the cut-off potential range on the cycle performance would be discussed leading to the charge/discharge results of the cell (-)Zn/LiOHaq./Ca0.9Y0.1MnO3-δ(+).
Highlights
When lanthanum is partially substituted for calcium sites in the perovskite-type oxide of CaMnO3, high electronic conductivity is observed at room temperature due to the valence change of manganese and the easy change of oxygen content in the lattice [1] [2]
The crystal lattices somewhat changed depending on the ionic radius of A element; Ca0.9Y0.1MnO3−δ showed the most packed unit lattice among them and Ca0.9La0.1MnO3−δ the most open parallel structure, which coincided with the size of substituting elements [16]
Assuming the end potential of discharge as −800 mV, the specific discharge capacity was calculated to be 200 mAh∙g−1, which was the completely the same as that we previously reported in the comparative experiments
Summary
When lanthanum is partially substituted for calcium sites in the perovskite-type oxide of CaMnO3, high electronic conductivity is observed at room temperature due to the valence change of manganese and the easy change of oxygen content in the lattice [1] [2] This oxide is a candidate for air electrode of SOFCs [3] and/or active material in alkaline [4]-[11] and sea water batteries [12]. We synthesized high conductivity perovskite-type Ca0.9A0.1MnO3−δ (A = Y, Sm, Gd and so on) in porous state by a sintering method, and investigated the electrochemical properties, especially the rechargeability of the porous ceramic sample as a cathode material in LiOHaq. solution
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