In this present study, nano composite polymer films are prepared based on PVA and Magnesium Bromide (MgBr2) with doping of additive plasticizers (Al2O3) with different ratios using Solution cast technique. XRD pattern confirms the semi crystalline nature of the polymer films. The ionic conductivity of the prepared films is measured by using AC impedance spectroscopy and it is found to be at 10− 2 S/cm. The electrical conductivity studies are carried out by DC ionic conductivity set up and for the composition 85 (PVP):15(MgBr2):0.1(Al2O3), the high ionic conductivity is found to be at \(1.25\times {10}^{-2} \text{S}/\text{c}\text{m}\) at room temperature. The conductivity is found to rise with an increase in temperature. The temperature dependent conductivity of the polymer electrolyte follows the Arrhenius relationship which shows hopping of ion mechanism in the polymer matrix. The transference numbers are calculated using Wagner DC Polarization technique and the majority of charge carrier’s are found to be ions rather than electrons. The charge distribution is studied at electrode–electrolyte interface by dielectric properties. Finally a solid state battery has been fabricated with the combination of Mg/(PVP + MgBr2:Al2O3)/(I2 + C + electrolyte) and discharge characteristics of the cell measured is up to 180 Hrs.
Research Article
Structural and Ionic conductivity studies of aluminium doped PVP-MgBr 2 Nano composite films
https://doi.org/10.21203/rs.3.rs-3132253/v1
This work is licensed under a CC BY 4.0 License
Version 1
posted
You are reading this latest preprint version
NCP’s
Solution Casting Technique
XRD
Ionic conductivity
Impedance spectroscopy and discharge characteristics
From the past few decades, researchers and scientists drags their attention towards the advancement of nano composite polymer electrolytes (NCPE) and widely studied for many applications like sensors, solid state batteries and fuel cells [1, 2]. Ongoing investigations have found that NCPE particle directing frameworks for their possible use in strong state batteries with the high cell voltages and energy densities that are normal for rechargeable batteries. A great deal of exploratory examination has been made on monovalent salt frameworks like Magnesium salts [3]; little consideration has been given to the polymer electrolytes in which multivalent cations are the portable species. Magnesium metal has various qualities that make it appealing as a negative cathode material for battery-powered batteries, including its minimal expense, relative plenitude, high conductivity, non toxic which takes into account metropolitan garbage removal [4]. Considering insignificant perils and upgraded wellbeing, examines of battery-powered magnesium batteries are relied upon to have a wide extension in the future [5–8]. There have been a few examinations on the strong polymer electrolytes dependent on magnesium salts [9, 10]. An option in contrast to the utilization of monomer cations is to utilize polycations to make another Al+ particle leading strong polymer electrolyte framework. This adjustment might prompt improved material properties like adaptability, grip, and thermally stable in an ionically conductive polymer sheet. The core mechanism of conductivity lies behind, as far the doping of additive nano filler to the host matrix the transport of ions increases abruptly. Therefore, some of the investigations have been performed with other metal particle directing polymers like Aluminium oxide and just a set number of aluminium particles leading polymer electrolyte frameworks have been contemplated [11, 12]. The NCPs display high conductivities up to 10− 2 S/cm at 373 K [13].
Polymer salt complex with high ionic conductivity has been widely explored in the course of recent a long time because of their likely applications as electrolyte material in high-energy-thickness strong state batteries [14]. The polymer battery enjoys the benefit of having high-energy thickness, dissolvable free condition, non rust condition and light weight. Polyvinylpyrrolidone (PVP) has drawn an extraordinary consideration among the formed polymers due to its great ecological stability.PVP is a potential material having a good charge storage capacity, electrical and optical properties. Artificially PVP will undoubtedly be latent, nontoxic and it shows a solid propensity for complex development with a wide assortment of nano particles.
In the current examination, magnesium bromide complexed with PVP polymer electrolytes with additive plasticizers of Al2O3 films are prepared and contemplated.
2.1 Preparation of Polymer Films
PVP with average molecular weight (M.W: 36,000) and Magnesium bromide (MgBr2) with 98% pure and Al2O3 Nano filler 99% pure were purchased from Sigma Aldrich chemicals, India. The samples were prepared by properly measured the different wt% ratios and distilled water was used as a solvent in this process. The above mentioned chemicals were allowed to continuous stirring for 24 Hrs in a conical flask for complete dissolution. After the obtained homogenous solution was casted in polypropylene petri-dishes and kept in a hot air oven at 60 0C for 48 hrs to evaporate the solvent. A set of nano composite PVP-MgBr2- Al2O3 polymer electrolyte films were prepared at different wt% ratios (95:5:0.1), (90:10:0.1) and (85:15:0.1). Finally the obtained films were kept in desiccators until further characterization.
2.2 Characterization
X-ray diffraction studies were performed by using a Philips analytical X’pert diffractometer in the diffraction 2θ angular range 10–90o with nickel filtered CuKα radiation (λ = 1.5403 Å). The Dielectric and impedance measurements of the prepared films were carried out in the frequency between 5000 and 50000 Hz on HIOKI 3532-50 LCR Heister. The ionic and electronic transport numbers (tion and tele) were calculated by means of Wagner’s polarization technique, under a DC bias at 1.5V. Electrochemical measurements were performed on 600E series electrochemical analyzer work station by fabricating the Sodium battery with the prepared combination Mg/(PVP + MgBr2 + Al2O3)/(I2 + C + electrolyte).
3.1 XRD Analysis
X-ray diffraction design is fundamental to get the crystalline structural information on the given material. Under the investigation if the sample seems to be crystalline then it tends to be well defined peaks. While non-crystalline or amorphous systems show a broad peaks rather than well defined peaks [15, 16]. The X-ray diffraction sample of pure PVP and PVP complexed with MgBr2 with the addition of nano filler Al2O3 are displayed in Fig. 1. In the figure, the Pure PVP shows sharp peaks at an angle of 2θ = 21.8, 26.23, 30.33, 31.11, 33.630 this indicates the sample processes the semi crystalline nature [17]. The intensity of these peaks step by step diminishes with the increment of MgBr2 along with additive nano filler Al2O3. This can be because of the interruption of the PVP glass like structure by MgBr2. From the figure it is observed that the XRD peaks for the compositional ratios of (PVP + MgBr2:Al2O3) (95:5:0.1, 90:10:0.1) are found to be at 2θ = 21.34, 25.47, 27.05, 33,190. This shows a diminishing in the level of crystallanity of polymer after the expansion of salt. It is observed that; at high compositional ration (85:15:0.1) the intensity of the peaks are quietly decreases. No other sharp peaks are noticed for higher groupings, this indicates the complete dissolution of salt within the host polymer the additional peaks which are observed at 33.190 and 33.630 may be due to the addition of nano filler in the host polymer. This recommending the dominant presence of amorphous phase.
3.2. Complex impedance examination
AC impedance spectroscopy is a powerful technique which is used to measure the electrical properties of the material. The impedance (Cole–Cole) plots of PVP doped MgBr2 for the different compositions of the films with additive nano filler 0.1(Al2O3) fixations are displayed in Fig. 2. The plot comprises of a high frequency semicircle which might be because of the mass impact of the electrode-electrolyte interfaces. The block of the half circle or spike with the genuine impedance (Z') pivot gives the mass electrical obstruction (Rb) of the polymer electrolytes.
The ionic conductivity (σ) of the polymer electrolytes has been determined by using
Where “Rb” is the bulk resistance, “t” is the thickness of the film and ‘A’ is the cross sectional area of the electrolytes individually.
The ionic conductivity esteems for the various compositions of PVP doped MgBr2 with an additive fillers Al2O3 at various temperatures are introduced. More amount of salt added into the polymer matrix leads to increase in the viscosity of the polymer electrolyte films [18]. Consequently, the mobility of the charge carriers has been decreased due to free space and the ion transportation is reduced. Hence, the conductivity is decreased for higher compositions. The most elevated ionic conductivity at surrounding temperature has been viewed as \(2.64 \times {10}^{-6} to 1.25\times {10}^{-2} \text{S}/\text{c}\text{m}\) for 85 (PVP):15(MgBr2):0.1(Al2O3) NCP’s. Figure 3 addresses the intricate impedance plot of the greatest conductivity test at surrounding temperatures. The higher dielectric consistent is attributed due to the addition of nano filler in the polymer matrix which brings a more expansion in charge carriers and consequently conductivity [19]. The major role of a plasticizer in a host polymer is to diminish thickness of the electrolyte and aid the separation of the salt; this results in expanding the quantity of charge transporters. The decline in conductivity has been observed at higher grouping, this might be because of the segregation of the ions.
3.3 Dielectric properties:
The variation of dielectric constant with logerthermic frequency of polymer films for different wt% ratios of PVP doped MgBr2 with additive fillers Al2O3 at room temperature is shown in Figure.3. It is observed from the figure; as increasing the logerthermic frequency, the dielectric constant values are gradually decreased and found to be high for the sample prepared with 85 (PVP):15(MgBr2):0.1(Al2O3), this concludes that the drifting of ions is high giving raise to conductivity phenomenon. It is observed that the dielectric steady and dielectric misfortune increment with increment of logarithmic frequency. This increment builds due to the level of salt separation and dissociation of the particle bringing about the increment in the quantity of free particles or charge transporter thickness [20].
This reveals that the salt is completely dissolute in the polymer chains giving raise to mobile ions whereas dispersion of nano fillers enhance the charge carriers results in increase of an ionic conductivity. The upsides of ε" are extremely high at low frequencies and somewhat steady at higher frequencies. Such high worth of ε" might be because of the interfacial impacts inside the greater part of the sample Due to the formation of space charge region at the electrode and electrolyte interfaces a variation is observed in between dielectric constant of ε". The loss spectra characterized by peak appearing at a characteristic frequency for polymer samples suggest the presence of relaxing dipoles in the samples and also with electrical relaxation process or inability of dipoles [21]. It is evident that the peak is shifted towards higher frequency side thereby reducing the relaxation time. This tends in the improvement in charge transporter thickness in the space charge area.
3.4 DC ionic conductivity:
Conductivity estimations have been made for different wt% ratios of PVP doped MgBr2 with additive fillers Al2O3 at room temperature which is shown in Figure. 4. The determined conductivity from the qualities; it is tracked down that the conductivity increments with expanded temperature just as convergence of salts and the nano fillers [22]. It is observed that; the ionic conductivity of the 85 (PVP):15(MgBr2):0.1(Al2O3), proportion is more prominent than on account of other wt% ratios. From Figure.5i.e., log (σT) versus 1000/T plot, all blends are straightly fluctuating with temperature. At room temperature, the conductivity of Pure PVP is measured up to 1.93 x 10− 6 S/cm and its value increases abruptly up to 2.21x 10− 4 S/cm upon increasing the temp at 373K.
The Ionic conductivity and the temperature shows an Arrhenius sort of thermally initiated process. In these areas, the conductivity is measured by
Where i is the current, t is the thickness of the film, V is the applied voltage and A is the area of the cross section of the film.
Among all the compositional ratios the high ionic conductivity was found up to 1.23 x10− 2 S/cm for the 85 (PVP):15(MgBr2):0.1(Al2O3) and other compositional ratios and its ionic conductivity values are listed in Tabel.1. From the figure it is observed clearly; the conductivity values increases sharply as increase in the temperature [23]. Whereas the dispersion of the nano filler in the electrolyte films enhance the ionic conductivity. But further addition of nanocomposites the conductivity may be decreased at a higher concentration, because of segregations of ions which decreases overall mobility [24]. The increase in conductivity with respect to temperature is explained by Arrhenius plots; as the temperature increased the conductivity of the electrolyte films also increased. This favours hopping mechanism between coordinating sides, local structure relaxation and segmental motion of the polymer.
3.5 Wt% composition studies:
The variation in logarithmic conductivity sigma as a function for different wt% ratios of PVP + MgBr2:Al2O3 is shown in Fig. 5. From the graph it is observed that as increasing the salt concentration the conductivity value also increases up to an order of 10− 6 to 10− 2 S/cm. The conductivity of pure PVP is 10− 6 S/cm at room temperature and its value increases sharply to 10− 4 S/cm at higher temperature. By adding the different compositional ratios to the polymer the ionic conductivity was increased the order of 10− 2 S/cm. further up on adding of salt and nano filler in a host matrix the conductivity becomes slower. This decrement in the ionic conductivity, due to the segregation of ions and formation of charge multipliers in the polymer matrix
3.6 Transference number measurement:
To check the predominant leading species in the current electrolyte framework, Transference number estimations were done utilizing Wagners polarization technique [25]. In this strategy, the dc current was observed as a component of time on use of a decent dc voltage of 1.5 V across the cell Mg/(PVP + MgBr2:Al2O3)/(I2 + C + electrolyte). The current versus time plot of (PVP + MgBr2:Al2O3) is displayed in Fig. 6. From the figure, the transaction numbers (tion and tele) have been assessed utilizing the equation and the transference number values are presented in Table 2.
Table. 2: Transference number of PVP+ MgBr2:Al2O3 nanocomposite polymer films
The total conductivity is given by σT = \(\frac{{{\sigma }}_{ion}+{{\sigma }}_{ele}}{{{\sigma }}_{hole}}\) ---------------------- (3)
The ionic transference number is given by
\({ t}_{ion}= \frac{{{\sigma }}_{ion}}{{{\sigma }}_{T}}\) ---------------------- (4)
and the electronic transference number is given by
\({ t}_{ele}= \frac{{{\sigma }}_{ele}}{{{\sigma }}_{T}}\) ---------------------------- (5)
Where it is the initial current and iele is the final residual current for all ratios of PVP + MgBr2:Al2O3 polymer electrolyte systems. From the figure it is clearly observed that; Initially polarization, the current (it) rises up and immediately a decay of current has been observed a steady state after a long time of polarization takes place. For every one of the creations of the (PVP + MgBr2:Al2O3) electrolyte framework, the upsides of the ionic transaction number are near solidarity. This recommends that the charge transport in these polymer electrolyte films is transcendently to ions instead of electrons
3.6 Battery discharge characteristics:
The solid state battery has been fabricated with the combination of Mg/(PVP + MgBr2:Al2O3)/(I2 + C + electrolyte) at a surrounding temperature for a consistent load of 100 kω. The discharge characteristics are assessed for every one of the batteries and are displayed in Fig. 7. The underlying sharp abatement in the voltage and current in these cells might be because of polarization as well as the development of a thin layer of potassium at the terminal - electrolyte interface. Among these cells, the cell comprised of (PVP + MgBr2:Al2O3) (85:15:0.1) electrolyte is viewed as more steady than the other two cells.. From the table obviously, cell with the composition 85(PVP):15(MgBr2):0.1(Al2O3) shows preferable execution up to 180 Hrs. These outcomes are in well examination and shows longer durability with the current reports [26].
The XRD design uncovers the expansion in indistinct nature of the film with the expansion of salt. The XRD peaks for the compositional ratios are found to be at 2θ = 21.8, 26.23, 30.33, 31.11, 33.630 This shows a diminishing in the level of crystallanity of polymer after the expansion of salt. From the impedance plot and DC ionic conductivity values it is observed that; the most elevated ionic conductivity at surrounding temperature has been viewed as \(2.64 \times {10}^{-6} to 1.25\times {10}^{-2} \text{S}/\text{c}\text{m}\) for 85 (PVP):15(MgBr2):0.1(Al2O3) NCP’s at room temperature. The dielectric steady and dielectric misfortune increases with an increment of logarithmic frequency. Initially polarization, the current (it) rises up and immediately a decay of current has been observed a steady state after a long time of polarization takes place. This increment builds due to the level of salt separation and dissociation of the particles which brings about the increment in the quantity of free particles or charge transporter thickness. Finally a solid state battery has been fabricated with the combination of Mg/(PVP + MgBr2 + Al2O3)/(I2 + C + electrolyte) and their discharge characteristic of the cell measured is found up to 180 Hrs. Finally the prepared solid state battery has executed long durability which can bring a new revolution in battery technology.
Ethical Approval: I have read and understand the journal policies and submit this manuscript in accordance with the policy
Competing interests: The authors declare that there is no conflict of interests regarding the publication of this paper.
Authors' contributions: The main manuscript text was prepared by the J.Srinivas Rao, figures are prepared by the Sk.Shahenoorbasha and all authors reviewed the manuscript.
Funding: There are no funding sources for this article work.
Availability of data and materials: All the data like impedance plot, conductivity, transport properties and discharge characteristics are available.
- Gray FM, (1991) Solid Polymer Electrolytes: Fundamentals and Technological Applications, VCH, New York.
- Geller S (1977) Topics in Applied Physics, Solid Electrolytes, Springer Verlag, New York.
- Maccallum R, Vincent CA (1987) Polymer electrolytes Reviews, Elsevier, Amsterdam.
- Eliasson H, Albinsson I, Mellander BE (1998) Dielectric and conductivity studies of a silver ion conducting polymer electrolyte. Electrochim. Acta 43:1459–1463. https://doi.org/10.1016/S0013-4686(97)10084-6.
- SRao S, Rao KVS, Shareefuddin Md, Rao UVS, Chandra S (1994) Ionic conductivity and battery characteristic studies on PEO+ AgNO3 polymer electrolyte. Solid State Ionics 67:331–334. DOI:10.1016/0167-2738(94)90026-4.
- Shahenoorbasha Sk, Sunita Sundari G, Vijaya Kumar K, Rao MC (2017) Spectroscopic Studies of PVP Based Composite Polymer Electrolyte. Thin Films. J. Inorg. Organomet Poly, 27(2) :455-466. DOI:10.1007/s10904-016-0487-3.
- Rajeswari N, Selvasekarapandian S, Sanjeeviraja C, Kawamura J, Bahadur SA (2014) A study on polymer blend electrolyte based on PVA/PVP with proton salt. Polym. Bull. 71:1061. DOI:10.1007/s00289-014-1111-8.
- Cherng J.Y, Munshi MZA, Owens BB, Smyrl WH (1988) Applications of Multivalent Ionic Conductors to Polymeric Electrolyte Batteries. Solid State Ionics. 28:857-861, 1988. http://dx.doi.org/10.1016/S0167-2738(88)80159-0.
- Hema M, Selvasekarapandian S, Hirankumar G, Sakunthala A, Arunkumar D, Nithya H (2010) Laser Raman and ac impedance spectroscopic studies of PVA: NH4NO3 polymer electrolyte. Spectrochim. Acta A Mol. Biomol, 75(1):474-478.
- S. Chandra, S. A. Hashmi and G. Prasad, “Studies on ammonium perchlorate doped polyethylene oxide polymer electrolyte,” Solid State Ionics, vol. 40-41, no. 2 pp. 651-654, 1990.
- M. Kumar and S. S. Sekhon, “Ionic conductance behavior of plasticized polymer electrolytes containing different plasticizers,” Ionics, vol. 8, no. 3-4, pp. 223-233, 2002.
- Chandra S, Hashmi SA, Saleem M, Agrawal RC (1993) Investigations on poly ethylene oxide based polymer electrolyte complexed with AgNO3. Solid State Ionics 67:1-7. https://doi.org/10.1016/0167-2738(93)90301-I
- Kaplan ML, Reitman EA, Cava RJ (1989) Solid polymer electrolytes: attempts to improve conductivity. Polymer 30:504–508. https://doi.org/10.1016/0032 3861(89)90021-9
- Fabry P, Montero-Ocampo C, Armand M (1988) Polymer electrolyte as internal ionic bridge for ion solid-state sensors. Sens. Actuators 15:1–9. DOI:10.1016/0250-6874(88)85012-1
- Abrantes TMA, Alcacer L J, Sequeira CAC (1986) Thin film solid state polymer electrolytes containing silver, copper and zinc ions as charge carriers. Solid State Ionics 18– 19: 315– 320. DOI:10.1016/0167-2738(86)90133-5
- Owens BB, Tobias CW (Eds.), (1971) Solid Electrolyte Batteries, Advances in Electrochemistry and Electrochemical Engineering, Wiley-Interscience, New York, pp-1
- Vaidyanathan S, Nicholas N, Seebauer E G, Mark A, Shannon R, Masel I (2008) Synthesis and Characterization of Polyvinyl pyrrolidine Assisted Tantalum Pentoxide Films Thin Solid Films 516 15 4784-4792. DOI:10.1016/j.tsf.2007.08.138
- Naveen R, Shahenoor Basha Sk,Rao M C, (2018) Effect of TiO2 Nanofiller on Optical and Ionic Conductivity Studies of (1-X) PVP: X (CH3COOK) Polymer Electrolyte Films Rasyan J Chem 11 195-202. http://dx.doi.org/10.7324/RJC.2018.1112016.
- Benedict TJ, Banumathi S, Veluchamy A, Gangadharan R, Ahamad AZ, Rajendran S (1998) Characterization of plasticized solid polymer electrolyte by XRD and AC impedance methods. J Power Sources 75(1):171–174. https://doi.org/10.1016/S0378-7753(98)00063-9
- S. S. Gasaymeh, S. Radiman, L. Y. Heng and E. G. H. M. Saion, “Synthesis and Characterization of Silver/Poly- vi- nilpirrolidone (Ag/PVP) Nanoparticles Using Gamma Ir-radiation Techniques,” American Journaences, Vol. 7, No. 7, 2010, pp. 892-901 https://doi.org/10.3844/ajassp.2010.892.901
- Armstrong RD, Dickinson T,Wills PM (1974) The A.C. impedance of powdered and sintered solid ionic conductors J. electroanal. chem. 53(3): 389-405.DOI:10.1016/S0022-0728(74)80077-X
- Dieterich W, Maass P (2002) Non-Debye relaxations in disordered ionic solids,” Chem Phys 284: 439-467. DOI:10.1016/S0301-0104(02)00673-0
- Pandey GP,Hashmi SA (2013) Performance of solid-state supercapacitors with ionic liquid 1-ethyl-3-methylimidazolium tris(pentafluoroethyl) trifluorophosphate based gel polymer electrolyte and modified MWCNT electrodes. Electrochem Acta 105:333-341. DOI:10.1016/j.jpowsour.2013.05.183
- Subba Reddy Ch.V, Sharma Ak, NarasimhaRao VVR (2003) Conductivity and discharge characteristics of polyblend (PVP + PVA + KIO3) electrolyte, J. Power Sources.114(2):338-345. DOI:10.1016/S0378-7753(02)00582-7
- Qiao J, Fu J, Lin R, Ma J,Liu J (2010) Alkaline solid polymer electrolyte membranes based on structurally modified PVA/PVP with improved alkali stability. Polymer 51, (21):4850–4859. DOI:10.1016/j.polymer.2010.08.018.
- Arof AK, Amirudin S, Yusof SZ, Noor IM (2014) A method based on impedance spectroscopy to determine transport properties of polymer electrolytes. Phys Chem Chem Phys 16(5):1856–1867. https://doi.org/10.1039/C3CP53830C
No competing interests reported.