Transport properties and lithium insertion study in the p-type semi-conductors AgCuO2 and AgCu0.5Mn0.5O2

The transport properties and lithium insertion mechanism into the first mixed valence silver–copper oxide AgCuO2 and the B-site mixed magnetic delafossite AgCu0.5Mn0.5O2 were investigated by means of four probes DC measurements combined with thermopower measurements and in situ XRD investigations. AgCuO2 and AgCu0.5Mn0.5O2 display p-type conductivity with Seebeck coefficient of Q 1⁄4 +2.46 and +78.83mV/K and conductivity values of s 1⁄4 3.2 10 1 and 1.8 10 4 S/cm, respectively. The high conductivity together with the low Seebeck coefficient of AgCuO2 is explained as a result of the mixed valence state between Ag and Cu sites. The electrochemically assisted lithium insertion into AgCuO2 shows a solid solution domain between x 1⁄4 0 and 0.8Li followed by a plateau nearby 1.7V (vs. Li/Li) entailing the reduction of silver to silver metal accordingly to a displacement reaction. During the solid solution, a rapid structure amorphization was observed. The delafossite AgCu0.5Mn0.5O2 also exhibits Li/Ag displacement reaction in a comparable potential range than AgCuO2; however, with a prior narrow solid solution domain and a less rapid amorphization process. AgCuO2 and AgCu0.5Mn0.5O2 provide a discharge gravimetric capacity of 265 and 230mAh/g above 1.5V (vs. Li/Li), respectively, with no evidence of a new defined phases. & 2008 Elsevier Inc. All rights reserved.