Abstract:
Lithium manganese oxide LiMn2O4
is recently one of the most intensively studied cathode
materials for lithium ion batteries, due to its low cost and non-toxic nature when compared
with other layered oxides such as LiCoO2 and LiNiO
2
. However, LiMn2O4
shows severe
capacity fading with cycling as compared to LiCoO2
. Different methods are employed to
minimize the aforementioned problems. Spinel LiMn1.977M0.023O4 (M = Cerium, Cu) cathode
materials were synthesized by sol-gel method using citric acid as a chelating agent. The
materials were characterized by using TGA/DTA, XRD, FT-IR spectroscopy, Raman
spectroscopy and inductance, capacitance & resistance (LCR) meter. The TGA/DTA result
indicates that exothermic peaks, large weight loss regions, which are attributed to the
decomposition of nitrate precursors, are identified. The XRD results of both materials revile
the formation of pure spinel phases with Fd-3m space group without any secondary phases or
impurities. It is also found that the lattice constant of spinel LiMn1.977
Ce0.023O4
(8.26 Å) is
larger than that of LiMn
1.977
Cu0.023O4 (8.249 Å). The FT-IR spectroscopy study shows that
Ce
3+
and Cu
2+
sabstituted spinels exhibit two strong absorbation spectral bands, which are
responsible for the formation of the synthesized materials. Similar results are also found from
Raman spectroscopy study. The room temperature conductivity of both samples is found to
be 3.0 x 10
-5
S/cm for LiMn1.977
Ce0.023O4
electrode and 2.58 x 10
-5
S/cm for
LiMn1.977
Cu0.023O4
electrode. From the dielectric constant ε′ as a function of frequency study,
it is observed that value of ε′ maximum at lower frequencies and it begins to drop and
becomes constant at higher frequencies.
