  This paper presents synthesis methods and multifunctional properties of
porous Co3O4 nanoplatelets and nanowires. Surprisingly, significantly superior
Li-ion battery performance compared to other cathode materials is exhibited in
the same samples as room temperature ferromagnetism (RTFM). Microstructure
observations, and properties measurements and analysis indicate that the
as-prepared Co3O4 nanostructures exhibit a spontaneous transformation of their
morphology, showing a predominantly {110} plane orientation and preferentially
presenting the Co3+ species at the surface at appreciate preparation condition.
More Co3+ in an octahedral (O) position exposed on the surface is associated
with more Co3+ being Co3+|\cdot (Co3+ with trapped charge carriers) or reduced
to Co2+ in the O position due to surface defects or oxygen vacancies, which is
possibly the mechanism of excellent electric transport properties then high
Li-battery performance; at the same time, reduced to Co2+ or free charge
carriers trapped by Co3+|\cdot in the O position are the role of charge
carries- mediate ferromagnetism, may be the origin of RTFM as well. These
results further show the importance of modifying the nanostructure of surfaces
in the preparation of transition metal oxides as multidisciplinary functional
materials.
