Nowadays, lithium-ion batteries have been intensively
researched to meet an increasing need for new applications such
as electric vehicles (EVs), hybrid electric vehicles (HEVs) and plugin
hybrid electric vehicles (PHEVs) and stationary storage [1–4].
LiCoO2 with layered a-NaFeO2 structure (Space Group R3m), as the
first commercial lithium-ion battery cathode material, is mainly
used in the 3C market, its good cycling performance and the higher
actual capacity (about 140 mAh g1
) are closely related to the
layered structure [5–7]. It is to say, LiMO2 compound (M: transition
metal) with the layered structure is an ideal cathode materials.
Unfortunately, LiCoO2 is poor in thermal stability and cobalt is not
only poisonous but also costly, which hinder its further applications
in larger device. Compared to Co element, Mn element is
cheap and abundant. But LiMnO2 with layered a-NaFeO2 structure
is instability, which cannot be synthesized by conventional
methods [8].
Other structure cathode materials, such as spinel structure
LiMn2O4 and olivine structure LiFePO4 have drawn lots of attention
for its stability in both structurally and thermally. However, low
capacity of LiMn2O4 and LiFePO4 (whose theoretical capacity is
148 mAh g1 and 170 mAh g1 respectively) cannot meet the
increasing demand for high capacity lithium ion batteries [9].
In 2001, Ohzuku and Makimura reported a ternary transition
metal oxide, Li[Ni1/3Co1/3Mn1/3]O2, as cathode material, which
adopts layereda-NaFeO2 structure withR3mspace group [10]. Over
the last few years, a series of ternary transition metal oxide such as
Li[Ni0.5Co0.2Mn0.3]O2, Li[Ni0.4Co0.2Mn0.4]O2, and Li[Ni0.7Co0.15Mn0.15]O2
has developed into a strong candidate for applications
in high power rechargeable Li-ion batteries, due to its
superior thermal stability and reversible capacity [11]. In these
ternary transition metal oxides, the total content of cobalt and
nickel is more than 60%. From a cost point of view, these materials
are still relatively expensive