Biomedical Engineering Reference
In-Depth Information
6.2.3 Alloys
It is well known that many metals and alloys can store a large
quantity of lithium through the electrochemical alloying reaction;
for example, Li
Sn gives a lithium storage capacity of 992 mAh g
-
,
1
4.4
nearly triple that of conventional graphite (in the form of LiC
6
, with
a theoretical capacity of 372 mAh g
-
), and Li
4.4
Si can even provide a
1
capacity of 4200 mAh g
. These materials exhibit a great potential
in substituting graphite to become the next-generation anode
materials used in high-energy lithium-ion batteries. However,
the significant volume expansion during lithiation/delithiation
cycle, which leads to the pulverization of electrode materials and
very rapid capacity decay, brings a huge problem to their practical
applications [14, 29, 30]. To conquer this problem, much work has
been done, and one of the most promising methods is the
introduction of carbon matrix into a nanocomposite electrode
material. For example, Derrien et al. [31]
-
1
have demonstrated
the use of Sn-C composite (i.e., Sn nanoparticles dispersed in
the carbon matrix, which acts as a buffer) can effectively
relieve the strain associated with volume variations of tin
while preventing the aggregation of Sn nanoparticles upon cycling
and hence leads to a much improved anode material with large
capacity of ca. 500 mAh g
over several hundred cycles.
When referring to carbon matrix, hollow carbon spheres can
always be considered a favorable candidate, and recent work [30]
has proved that by encapsulating tin nanoparticles into hollow
carbon spheres with a uniform size, anode materials with high
specific capacity and good cycling performance will be obtained, as
explained in detail below.
-
1
6.2.4 Transiion Metal Oxides
After 2000, the use of transition metal oxides as anode materials
for lithium-ion batteries became more and more popular [32].
However, most of the materials consisting of transition metal oxides
suffer from a high overpotential (voltage difference between the
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