weakening of the interaction of cation with fluorine of host polymer matrix. Also, the
porous structure as evidenced in FESEM provides some additional conducting
pathways in the same volume favorable for ion transport, and space charge region
buildup occurs due to the more free charge carriers’ availability. At high content, the
interpenetrating networks are formed due to the overlapped space charge regions and
hence the ion conducting pathways. Also, the transference number of Li
+ was
increased from 0.23 to 0.70 on the addition of nanowire and may be due to the
increased number of free ions via the dual interaction of acidic sites with fluorine of
polymer host as well as an anion (PF 6
À ). The electrochemical stability window of the
synthesized composite polymer electrolyte was 4.8 V, and no effect of a surface
group of the nanofiller was observed on the stability window.
Another report based on Mg 2 B 2 O 5 nanowires (Av. diameter ~270 nm) with
PEO–LiTFSI was reported by Sheng et al. (2018). The advantages with Mg 2 B 2 O 5
NWs are the hardness of 15.4 GPa and Young’s modulus of 125.8 GPa (Tao and Li
2008). The highest ionic conductivity was 1.53 Â 10
À4 S cm
À1 (at 40
C) and
3.7 Â 10
À4 S cm
À1 (at 50
C) for 10 wt. % Mg 2 B 2 O 5 nanowires. The enhancement
was attributed to the coordination interaction of anion (TFSI
À ) with Mg 2 B 2 O 5
nanowires, and it enhances the salt dissociation which increases the number of
lithium–ions for migration (Fig. 8.24a). Another reason may be the reduction of
the crystallinity and reorganization tendency after incorporation of NW which promotes faster segmental motion as evidenced by the XRD and DSC analysis. The
lithium transference number (t Li
+ ) was 0.44 and is much higher as compared to pure
PEO which (t Li
+
¼ 0.19). The voltage stability window was 4.7 V and is superior to
NW free system which shows 4.25 V.
The maximum strength was 2.29 MPa, and mechanical properties were improved
after addition of NW. The prepared system shows excellent flame-retardant performance. Figure 8.24–e shows the electrochemical performance of Li–ion battery
assembled using PEO–LiTFSI–Mg 2 B 2 O 5 . The discharge and charge voltage plateaus are around 3.35 and 3.50 V (at 0.2
C), and overpotential between charge–
discharge plateau increases with the increase of current density (Fig. 8.24b). Figure 8.24 c shows the performance with NW and without NW. The polymer electrolyte system with NW displays the specific discharge capacity of about
158 (at 0.2
C), 140 (at 0.4
C), 124 (at 0.8
C), 117 (at .0
C), and 72 mAh g
À1
(at 2.0
C), while without NW, the specific discharge capacity is 139 (at 0.2
C),
121 (at 0.4
C), 92 (at 0.8
C), 75 (at 1.0
C), and 37 mAh g
À1 (at 2.0
C). It
concluded that the addition of NW increases the cyclic stability and capacity
independent of current rate. Figure 8.24d shows the impedance study of the battery
with and without NW. The addition of NW reduces both charge–transfer resistance
(R ct ) and ohmic resistance (R o ) which indicates the increase of ionic conductivity
with NW. Figure 8.24 e shows the stable specific capacity nearly 120 mAh g
À1 in
230 dischargeÀcharge cycles (at 1.0
C, 50
C) with a coulombic efficiency of
100%. The inset in the Fig. 8.24e shows a lightening LED with present battery
(shape of “I”).
8 Polymer Nanocomposites: Synthesis and Characterization
307
porous structure as evidenced in FESEM provides some additional conducting
pathways in the same volume favorable for ion transport, and space charge region
buildup occurs due to the more free charge carriers’ availability. At high content, the
interpenetrating networks are formed due to the overlapped space charge regions and
hence the ion conducting pathways. Also, the transference number of Li
+ was
increased from 0.23 to 0.70 on the addition of nanowire and may be due to the
increased number of free ions via the dual interaction of acidic sites with fluorine of
polymer host as well as an anion (PF 6
À ). The electrochemical stability window of the
synthesized composite polymer electrolyte was 4.8 V, and no effect of a surface
group of the nanofiller was observed on the stability window.
Another report based on Mg 2 B 2 O 5 nanowires (Av. diameter ~270 nm) with
PEO–LiTFSI was reported by Sheng et al. (2018). The advantages with Mg 2 B 2 O 5
NWs are the hardness of 15.4 GPa and Young’s modulus of 125.8 GPa (Tao and Li
2008). The highest ionic conductivity was 1.53 Â 10
À4 S cm
À1 (at 40
C) and
3.7 Â 10
À4 S cm
À1 (at 50
C) for 10 wt. % Mg 2 B 2 O 5 nanowires. The enhancement
was attributed to the coordination interaction of anion (TFSI
À ) with Mg 2 B 2 O 5
nanowires, and it enhances the salt dissociation which increases the number of
lithium–ions for migration (Fig. 8.24a). Another reason may be the reduction of
the crystallinity and reorganization tendency after incorporation of NW which promotes faster segmental motion as evidenced by the XRD and DSC analysis. The
lithium transference number (t Li
+ ) was 0.44 and is much higher as compared to pure
PEO which (t Li
+
¼ 0.19). The voltage stability window was 4.7 V and is superior to
NW free system which shows 4.25 V.
The maximum strength was 2.29 MPa, and mechanical properties were improved
after addition of NW. The prepared system shows excellent flame-retardant performance. Figure 8.24–e shows the electrochemical performance of Li–ion battery
assembled using PEO–LiTFSI–Mg 2 B 2 O 5 . The discharge and charge voltage plateaus are around 3.35 and 3.50 V (at 0.2
C), and overpotential between charge–
discharge plateau increases with the increase of current density (Fig. 8.24b). Figure 8.24 c shows the performance with NW and without NW. The polymer electrolyte system with NW displays the specific discharge capacity of about
158 (at 0.2
C), 140 (at 0.4
C), 124 (at 0.8
C), 117 (at .0
C), and 72 mAh g
À1
(at 2.0
C), while without NW, the specific discharge capacity is 139 (at 0.2
C),
121 (at 0.4
C), 92 (at 0.8
C), 75 (at 1.0
C), and 37 mAh g
À1 (at 2.0
C). It
concluded that the addition of NW increases the cyclic stability and capacity
independent of current rate. Figure 8.24d shows the impedance study of the battery
with and without NW. The addition of NW reduces both charge–transfer resistance
(R ct ) and ohmic resistance (R o ) which indicates the increase of ionic conductivity
with NW. Figure 8.24 e shows the stable specific capacity nearly 120 mAh g
À1 in
230 dischargeÀcharge cycles (at 1.0
C, 50
C) with a coulombic efficiency of
100%. The inset in the Fig. 8.24e shows a lightening LED with present battery
(shape of “I”).
8 Polymer Nanocomposites: Synthesis and Characterization
307