V. Focused Fundamental Research - EERE - U.S. Department of ...

V.C.11 Polymer-Coated Layered SiOx-Graphene Nanocomposite Anodes (PSU)
Wang, Hickner – PSU
commercial binder of PVDF at a weight ratio of 8:1:1 and
pasted on Cu foils. Figure V - 114a shows the discharge
and charge curves during the first five cycles in a coin-type
half-cell at a rate of 200 mA/g. The Si-graphene
nanocomposite anode shows first discharge and charge
capacities of 1461 and 1238 mAh/g, that is, a coulombic
efficiency of 85%. The electrode maintains a capacity over
1300 mAh/g in the following cycles with the coulombic
efficiency of ca. 96%. In addition, we also investigated the
cycling performance of Si-graphene nanocomposites at a
high current density of 2000 mAh/g (Figure V - 114b). At
the first cycle, Si-graphene nanocomposites show a
specific discharge capacity of approximately 863 mAh/g
and charge capacity of 751 mAh/g (i.e., the coulombic
efficiency of 87%). With increase in cycling number, the
capacity of Si-graphene nanocomposites remains relatively
constant (900~1000 mAh/g) with the coulombic efficiency
of over 97%, indicating that these Si-graphene anodes have
good cycling stability. Further investigation on the anode
performance of Si-graphene nanocomposites is still
underway.
A series of PEO and trimethoxy silane-based binders
have been synthesized. An example chemical structure of
these polymers is shown in Figure V - 115. These types of
polymers have been made in random and block
architectures. Also, other functional groups such as
quaternary ammonium groups and sulfonate groups have
been explored as the Si-binding moiety. In addition,
mechanically robust binders composed of RADEL ®
poly(sulfone) variants have also been synthesized.
(a)
(b)
Specific capacity (mAh/g) Voltage vs. Li/Li + (V)
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
1200
1000
800
600
400
200
0
C rate: 200 mA/g
1st cycle
2nd cycle
3rd cycle
4th cycle
5th cycle
0 200 400 600 800 1000 1200 1400
Specific capacity (mAh/g)
C rate: 2000 mA/g
Li de-insertion
Li insertion
Coulombic efficiency
0 2 4 6 8 10 12 14 16 18 20
Cycle number
Figure V - 114: (a) Charge-discharge curves of Si-graphene nanocomposites at a rate of 200 mA/g between 0.01 and 1.5 V; (b) Cycling performance of Sigraphene
nanocomposites at a high current density of 2000 mA/g.
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
Coulombic efficiency
O
O
O
O
O
Figure V - 115: Silane-PEO containing copolymers.
H3 CO Si OCH3
OCH 3
Energy Storage R &D 578 FY 2011 Annual Progress Report