Cathode and Anode Materials for Na-Ion Battery - Low-cost Nanomaterials: Toward Greener and More Efficient Energy Applications - page 409

Fig. 25 The initial two discharge/charge profiles of the a Sn/C and b Sb/C nanocomposite
electrodes between 0.0 and 1.2 V versus Na/Na + at a current rate of 100 mA g -1 [ 62 ]

Fig. 26 Cycling
performance of the SnSb/C
nanocomposite electrode at a
cycling rate of 100 mA g -1
[ 62 ]

Xiao et al. first studied the Na storage properties in Sn and Sb (Fig. 25 )[ 62 ]. As
shown in Fig. 25 a, the voltage profiles of Sn/C nanocomposites clearly showed
two discharge and four charge plateaus, reflecting the stepwise Na-Sn alloy phase
transition processes, similar to the calculated theoretical data (Fig. 24 ). The Sn/C
electrode delivered a high reversible capacity of 509 mAh g -1 (Fig. 25 a). After
deducting the capacity associated with carbon black, Sn individually can offer a
capacity of 653 mAh g -1 , which is about 77.1 % of the theoretical capacity of
847 mAh g -1 based on Na 15 Sn 4 . The Sb/C electrode also showed high initial
capacity of 494 mAh g -1 (Fig. 25 b). Sb individually can offer a capacity of
631 mAh g -1 , which is equivalent to 95.6 % of the theoretical capacity based on
Na 3 Sb (660 mAh g -1 ). But both electrodes exhibited a rapid decrease in capacity
with cycling [ 62 ]. This situation is commonly found in Li-alloy electrode,
resulting from severe volume changes of the electrode during the alloying/deal-
loying processes which cause the pulverization of the metal particles, the loss of
the electric conducting between the active materials. However, the SnSb/C com-
posite exhibited high reversible capacity of 544 mAh g -1 and particularly excel-
lent cycling capability with 80 % of capacity retention over 50 cycles (Fig. 26 )
[ 62 ]. It is proposed that when discharged to 0.4 V, Na ions insert into the SnSb