Magnesium-ion batteries are considered as a new rechargeable
battery system comparable to lithium-ion batteries.
1–4) Magnesium that would be used as an active
material for an anode is possible to provide a considerably
high energy density due to its high electrochemical equivalence
and considerably negative electrode potential. Therefore,
if an excellent cathode material can be sought somehow,
rechargeable magnesium-ion batteries can be realized in
future. In this work, we focus on a spinel-type MgCo2O4 as
a candidate for a cathode material, in which the following
cathode reaction is supposedalso in this case the valence of cobalt is expected to
change as well as LiCoO2. Both of high electronic conductivity
and high ionic conductivity are indispensable to be
used as a cathode material. It has been reported that the
crystal structure of MgCo2O4 is partially inversed spinel.5) In
this work, we devote to investigate the electrical properties of
MgCo2O4 to examine the feasibility of its use as a cathode
material.