Complex Impedance Spectroscopic Studies of PMMA(80,70,60,50) : PC(10,20,30,40): PVP(10): LiClO4(5) Polymer Solid Electrolyte Systems

Polymer solid electrolytes PMMA(80,70,60,50): PC(10,20,30,40):PVP(10):LiClO4(5) were synthesized according to stoichiometric ratios using solution cast method. FTIR study confirms the good complexation among the constituent materials in the polymers matrix. Complex impedance and electric modulus studies are carried out and explained. From cole-cole plots, maximum decrement of resistance is observed at a threshold ratio 70 Wt% PMMA: 20 Wt% PC: 10 Wt% PVP: 5 Wt% LiClO4 and this could be due to the high mobility of the Li + ion in the polymer network due to the plasticizer. The plasticizer plays an important role in decreasing the viscosity of the system, which in turn favors the mobility of segmental motion of polymer network and fast ion motion in the polymer. Real and Imaginary electric modulus spectra show the presence of relaxation peaks and confirm that the polymer solid electrolyte is an ionic conductor. Material Science Research India www.materialsciencejournal.org ISSN: 0973-3469, Vol.17, No.(3) 2020, Pg. 276-280 CONTACT R. Swarnalatha swarnalatha424@gmail.com Department of Physics, University College of Engineering (A), Osmania University, Hyderabad, Telangana, India. © 2020 The Author(s). Published by Oriental Scientific Publishing Company This is an Open Access article licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License Doi: http://dx.doi.org10.13005/msri/170310 Article History Received: 2 November 2020 Accepted: 23 December 2020


Results And Discussion Complex Impedance Plots
Complex impedance spectroscopy studies are carried out for different polymer solid electrolytes. Figure 1 shows the cole-cole plots at different temperatures for PPSE1, PPSE2, and PPSE3 solid polymer systems, respectively. The intercepts of the semicircle on the real axis give the bulk resistance (R b ) of the sample when a plot is drawn between Z' and Z" at a given temperature. The conductivity of the sample is evaluated at a given temperature by using Where 't' is the thickness and 'A' is the area of the cross-section of the sample. From Cole-Cole plots, it has been observed that the magnitude of the bulk resistance (R b ) decreases with an increase in temperature in all these three polymer matrices 6,9 .
The maximum decrement of resistance is observed at a threshold ratio 70 Wt% PMMA: 20 Wt% PC: 10 Wt% PVP: 5 Wt% LiClO 4 (PPSE2) and this could be due to the high mobility of the Li + ion in the polymer network.

Electric Modulus
The real (M΄) and imaginary (M΄΄) electric modulus spectra as a function of temperature at different frequencies for PPSE2 have been shown in figures 2 and 3, respectively. Real electric modulus spectra show that there is dispersion at the highfrequency region and a long tail with '0' magnitude at low frequency, indicating the presence of large capacitance associated with the electrode. Imaginary modulus spectra in figure 3 show the peak at different temperatures. The left and right side of the peak gives information about the conduction process(long-range mobility of charge carriers) and the relaxation process of the conducting ions(shortrange mobility of charge carriers) 12,14 . There is a shift in the asymmetric peaks, which can be understood that there exists a correlation between the mobility of different charge carriers. The presence of relaxation peaks confirms that the polymer solid electrolyte is an ionic conductor 13,14 .  Figure 4 depicts the FTIR spectra of four polymer electrolyte systems; in pure LiClO 4 , a peak is located at 1630 cm -1 is related to vibration mode has been shifted to 1645 cm -1 , 1660 cm -1 , 1641 cm -1 , and 1643 cm -1 with peak broadening and decrease in the intensity in all the polymer matrices. This can be understood by the miscibility of the salt with the polymer matrix has properly taken place.
A peak associated with PMMA corresponding to C=O stretching with wave no. 1737 cm -1 shifts from its original position in the PPSE1, PPSE2, PPSE3 and PPSE4 at 1734 cm -1 , 1726 cm -1 , 1732 cm -1 , 1730 cm -1 respectively. The C=O stretching at 1698 cm -1 is present in pure PC has been shifted to 1789 cm -1 in PPSE1, 1805 cm -1 in PPSE2, 1815 cm -1 in PPSE3 and 1817 cm -1 in PPSE4. The peak corresponding to 3441 in PPSE1 shifts to 3448 cm -1 with peak boarding. In pure PVP a peak at 1348 cm -1 related to C-H stretching shifts to 1440 cm -1 , 1448 cm -1 , 1450 cm -1 and 1451 cm -1 in respective polymer electrolytes. Overall results conclude that the good complexation has been taken place in the polymer matrix 12,6 .

Conclusions
FTIR spectra of solid Polymer electrolytes of PMMA (80,70,60,50) : PC (10,20,30,40) : PVP (10) : LiClO 4(5) confirms the good miscibility of all the constituent chemicals with the shifting of position in each solid electrolyte. Cole-Cole plots show the decrease in the value of R b with an increase in temperature could be due to the existence of more number of free volumes present around the polymer chain and fast Li + ion mobility in the polymer network favored by PC. Electric modulus studies confirm the electrolyte is an ionic conductor. Frequency-dependent Electric Modulus spectra at different temperatures show the value of M΄ is '0' at lower frequencies and this could be due to the large value of capacitance associated with the electrode-electrolyte interface. The values of M΄ increases with respect to frequency this can be explained due to the short-range mobility of charge carriers and M΄΄ (imaginary) spectra explains the conduction and relaxation of conducting ions.