Nondestructive testing of defects in adhesive joints

in Fig. 8. The cell based on the PEs with
BaTiO3 delivers charge and discharge capacities
of 164 mAh/g, which correspond to 96.5%
utilization of the active material. The
performance of the cell with PEs containing
Al2O3 and SiO2 is slightly lower as the discharge
capacities of 153 and 156 mAh/g are obtained,
respectively.
Fig. 7. AC impedance spectra of polymer electrolytes
based on electrospun P(VdF-HFP) membranes with
different ceramic fillers (Li/NCPE/Li cells, 10 mHz
to 2 MHz).
Voltage (V)
(Ω)
-Z ''
4.0
3.8
3.6
3.4
3.2
3.0
2.8
2.6
600
525
450
375
300
225
150
75
0
0 100 200 300 400 500 600 700 800 900
No filler
Al 2 O 3
SIO 2
BaTiO 3
Z ' (Ω)
2.4
0 20 40 60 80 100 120 140 160 180
Specific capacity (mAh/g)
No filler
Al 2 O 3
Fig. 8. Initial charge-discharge properties of
Li/NCPE/LiFePO4 cells with polymer electrolytes
based on electrospun P(VdF-HFP) membrane
containing 6% of ceramic fillers (25 °C, 0.1 C-rate,
2.5 to 4.0 V).
4. Conclusions
The nanocomposite PEs prepared by
elctrospinning of P(VdF-HFP) show well
interlaying of the fibers to generate a well
interconnected porous membranes. The presence
SiO 2
BaTiO 3
- 5 -
of the nano-scale ceramic fillers improves the
mechanical properties of the membranes. The
inclusion of fillers creates amorphous regions by
way of the interactions between the filler
surfaces and the polymer chains, which result in
the reduced crystallinity of the polymer. The
high electrolyte uptake by the NCPEs is
attributed to the well interconnected pore
structures and interactions of the fillers with the
polymers as well as with the electrolyte. The
nanocomposite PEs show minimum electrolyte
leakage despite very high electrolyte uptake.
Among the fillers BaTiO3 has been observed to
exhibit the highest electrolyte uptake, ionic
conductivity, electrochemical stability and better
compatibility with lithium metal. It also shows
the maximum charge and discharge capacities.
The reason for higher mechanical strength,
electrolyte uptake and electrochemical
performance of BaTiO3 is attributed to the
effective dispersion of its nanoparticles in the
composite membranes during the electrospinning
process that results in better interactions both
with the polymer and the electrolyte.
Acknowledgements
This research was supported by Ministry of Knowledge
Economy, Korea, under the Information Technology Research
Center (ITRC) support program supervised by the Institute of
Information Technology Assessment (IITA).
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