Biomedical Engineering Reference
In-Depth Information
lower than that of other transition metals such as manganese,
nickel, and iron, and this leads to a much higher cost. On the
other hand, the structure of LiCoO
is not as stable as that of other
2
cathode materials (e.g., LiFePO
), and it undergoes performance
degradation or even failure when overcharged [37, 38].
Therefore, it still is highly desired to search for alternative
materials to replace LiCoO
2
4
. One of the candidates is LiNiO
2
, which
shares the same layered structure as LiCoO
2
. Compared with
is lower in cost and higher in energy density;
however, it also suffers from serious structural instability [39,
40]. Element doping of cobalt can effectively increase the degree
of
LiCoO
2
, LiNiO
2
ordering,
thus
enhancing
its
structural
stability;
the
same holds for LiMnO
, which can achieve a higher capacity
2
as
well
as
a
better
rate
capability
through
the
addition
of
cobalt
and
nickel
to
form
a
composition
of
Li(Ni
Mn
1/3
Co
)O
[41-43].
1/3
1/3
2
6.3.2 Spinel Structured Oxide
, which forms a
spinel structure, and this structure enables manganese to occupy
the octahedral sites while lithium predominantly occupies the
tetrahedral sites [44]. LiMn
Another promising cathode material is LiMn
O
2
4
O
4
has a lower cost and enhanced
2
, but it also has some limitations
[45]. One of its limitations comes from the phase change during
the charge/discharge cycling, which will then be responsible for
its capacity fade [46, 47]. Doping has been widely used to improve
the electrochemical performance of LiMn
safety compared with LiCoO
2
. For example, the
addition of iron may lead to an enhancement in the charge
plateau of LiMn
O
2
4
at high voltages, the addition of cobalt may
help to stabilize the spinel structure of LiMn
O
2
4
, thus bettering
the capacity retention upon cycling, and the addition of nickel
can improve the capacity of LiMn
2
O
2
4
by decreasing its lattice
parameters [48-50]. Other doping atoms, such as aluminum,
can also be used to improve the electrochemical performance
of LiMn
O
4
O
.
2
4
 
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