Page 372 - Polymer-based Nanocomposites for Energy and Environmental Applications

Nanofibrous composites for sodium-ion batteries 339

600 CNF@NPC
Specific capacity (mAh/g) 400 50 200 1000 200 50 mA g −1
CNF

200

1µm −200 0 100 500 500 100
0 20 40 60 80
(A) (B) Cycle number

Na+
Na+
Na+ Na+
Na+ Na+
Na+
Na+
e− Redox reaction with
Na+
functional groups
Na+ Absorbed Na+
Carbon nanofiber
(C) N-doped porous carbon

Fig. 12.3 (A) SEM image of N-doped CNF, (B) cycling performances of N-doped and pure
CNF, and (C) schematic representation of the working mechanism of the N-doped anode in a
Na-ion cell.
Adapted with permission from Zhang Z, Zhang J, Zhao X, Yang F. Core-sheath structured
porous carbon nanofiber composite anode material derived from bacterial cellulose/polypyrrole
as an anode for sodium-ion batteries. Carbon 95;2015:552–9.

that dropped to 731 mAh/g after 55 cycles at 0.1 A/g. Regardless the low cycling
stability, these CNFs exhibited 5.5 times larger capacity than normally N-doped CNFs
or 29 times larger than pure P cycled under the same conditions.
Sn-based compounds are among the most promising anode materials for NIB.
Among them, its oxide (SnO 2 ) can provide the highest theoretical volumetric capacity
3
of approximately 10,000 mAh/cm , while its alloy with phosphorus (Sn 4 P 3 ) can pro-
vide the highest volumetric and gravimetric energy densities [10]. SnO 2 embedded
into PCNFs by electrodeposition provides initial capacity of about 500 mAh/g at
0.05 A/g and sharp capacity loss after 40 cycles [37]. The same anode covered with
a thin carbon layer by CVD gives capacity of 493 mAh/g at 0.05 A/g and capacity
retention of about 83% after 100 cycles. In another approach, SnO 2 nanofibers were
obtained by electrospinning of polymer solution containing SnCl 2 followed by calci-
nation and covered with thin carbon layer by a hydrothermal process [38]. Such SnO 2
nanofibers are partially reduced to Sn by a thermal treatment in inert atmosphere
forming and SnO 2 /Sn nanoparticles that can accommodate the volume expansion