R C Agrawal

Solid polymer electrolytes: materials designing and all-solid-state battery applications: an overview

Polymer electrolytes are promising materials for electrochemical device applications, namely, high energy density rechargeable batteries, fuel cells, supercapacitors, electrochromic displays, etc. The area of polymer electrolytes has gone through various developmental stages, i.e. from dry solid polymer electrolyte (SPE) systems to plasticized, gels, rubbery to micro/nano-composite polymer electrolytes. The polymer gel electrolytes, incorporating organic solvents, exhibit room temperature conductivity as high as ~10−3 S cm−1, while dry SPEs still suffer from poor ionic conductivity lower than 10−5 S cm−1. Several approaches have been adopted to enhance the room temperature conductivity in the vicinity of 10−4 S cm−1 as well as to improve the mechanical stability and interfacial activity of SPEs. In this review, the criteria of an ideal polymer electrolyte for electrochemical device applications have been discussed in brief along with presenting an overall glimpse of the progress made in polymer electrolyte materials designing, their broad classification and the recent advancements made in this branch of materials science. The characteristic advantages of employing polymer electrolyte membranes in all-solid-state battery applications have also been discussed.

Ion transport property studies on PEO–PVP blended solid polymer electrolyte membranes

The ion transport property studies on Ag+ ion conducting PEO–PVP blended solid polymer electrolyte (SPE) membranes, (1 − x)[90PEO : 10AgNO3] : xPVP, where x = 0, 1, 2, 3, 5, 7, 10 (wt%), are reported. SPE films were caste using a novel hot-press technique instead of the traditional solution cast method. The conventional solid polymeric electrolyte (SPE) film, (90PEO : 10AgNO3), also prepared by the hot-press method and identified as the highest conducting composition at room temperature on the basis of PEO–AgNO3-salt concentration dependent conductivity studies, was used as the first-phase polymer electrolyte host into which PVP were dispersed as second-phase dispersoid. A two-fold conductivity enhancement from that of the PEO host could be achieved at room temperature for PVP blended SPE film composition: 98(90PEO : 10AgNO3) : 2PVP. This has been referred to as optimum conducting composition (OCC). The formation of SPE membranes and material characterizations were done with the help of the XRD and DSC techniques. The ion transport mechanism in this SPE OCC has been characterized with the help of basic ionic parameters, namely ionic conductivity (σ), ionic mobility (μ), mobile ion concentration (n) and ionic transference number (tion). Solid-state polymeric batteries were fabricated using OCC as electrolyte and the cell-potential discharge characteristics were studied under different load conditions.

Solar energy conversion by photoelectrochemical cells using chemical-bath-deposited CdS films

A study of the direct conversion of solar energy into electricity by photoelectrochemical cells using chemical bath deposited CdS films on titanium and stainless steel substrates is reported.

Investigations on poly ethylene oxide based polymer electrolyte complexed with AgNO3

Abstract The polymer electrolyte PEO+AgNO3 has been investigated by IR, optical absorption, DTA, electrical conductivity, mobility, and transport number measurements. The material is a mixed (ionic + electronic) conductor. The ionic conductivity is due to Ag+ and anionic movement. The material properties change with time, mainly associated with an increased electronic conductivity due to reduction of Ag+ in PEO lattice. The maximum electrical conductivity has been found to be ∼3 × 10−7s cm−1 for the composition Ag + EO = 0.014 to 0.085.

Estimation of energies of Ag+ ion formation and migration using transient ionic current (TIC) technique

Abstract Transient ionic current (TIC) and impedance spectroscopy techniques were employed to measure the Ag+ ion mobility (ω) and conductivity (σ) respectively of AgI in both β- and α-phases. Subsequently, the mobile ion concentration (n) was calculated using σ and μ data. σ, μ and n show thermally activated type behaviour in both the regions of the phase transition. From the log μ versus 1/T and log n versus 1/T Arrhenius plots, the energies of migration and formation of mobile silver ion were estimated as 0.14 and 0.15 eV respectively in the β-phase and 0.05 and 0.006 eV respectively in the α-phase. The extremely low value of energy of formation in the α-phase suggested that a negligibly small number of mobile ions is thermally added to the large n already existing in this phase. On the basis of these experimental studies, it is concluded that the large increase of σ in αAgI is predominantly due to an abrupt increase of mobile ion concentration. The contribution of ionic mobility to the total conductivity is small.

Experimental investigations on a proton conducting nanocomposite polymer electrolyte

A new proton conducting nanocomposite polymer electrolyte (NCPE) comprising polyethylene oxide (PEO)-NH4HSO4 salt complex dispersed with nanosized SiO2 particles has been investigated. The NCPE films have been formed following the usual solution cast method. The results of various studies based on scanning electron microscopy, x-ray diffraction, differential scanning calorimetry, Fourier transform infra-red spectroscopy as well as some basic ionic transport parameters, namely conductivity, and ionic transference number, are presented and discussed. SiO2 concentration dependent conductivity measurements have been carried out on the NCPE films at room temperature. This study revealed the existence of two conductivity maxima at SiO2 concentrations ~3 and 12 wt% which have been attributed to two percolation thresholds in the composite polymer electrolyte phase. An optimum value of conductivity (σ ~ 6.2 × 10−5 S cm−1 at 27 °C) was achieved for the NCPE film with 3 wt% SiO2 dispersion. This has been referred to as optimum conducting composition. The temperature dependence of conductivity exhibited an Arrhenius-type thermally activated behaviour both below and above the semicrystalline–amorphous phase transition temperature of PEO.

Transport property and battery discharge characteristic studies on 1−x(0.75Agl∶0.25AgCl)∶ xAl2O3 composite electrolyte system

Various experimental studies on a new fast Ag+ ion-conducting composite electrolyte system: (1−x) (0.75Agl∶0.25AgCl)∶xAl2O3 are reported. Undried Al2O3 particles of size <10 Μm were used. The conventional matrix material Agl has been replaced by a new mixed 0.75Agl∶0.25AgCl quenched and/or annealed host compound. Conductivity enhancements ∼10 from the annealed host and ∼3 times from the quenched host obtained for the composition 0.7(0.75Agl∶0.25AgCl)∶0.3Al2O3, can be explained on the basis of the space charge interface mechanism. Direct measurements of ionic mobility Μ as σ function of temperature together with the conductivity σ were carried out for the best composition. Subsequently, the mobile ion concentration n values were calculated from Μ and a data. The value of heat of ion transport q* obtained from the plot of thermoelectric power θ versus 1/T supports Rice and Roths free ion theory for superionic conductors. Using the best composition as an electrolyte various solid state batteries were fabricated and studied at room temperature with different cathode preparations and load conditions.

[0.75AgI :0.25AgCl] quenched system: a better choice as host compound in place of AgI to prepare Ag+ ion conducting superionic glasses and composites

Abstract Various transport properties, namely, the electrical conductivity, σ, ionic transference number, tion, ionic mobility, μ, etc. were measured for the quenched [0.75AgI:0.25AgCl] system. The mobile ion concentration, n, was calculated using σ and μ data. The results were compared with the values for AgI. The quenched [0.75AgI:0.25AgCl] system exhibited a β → α like transition in the log σ versus 1/T plot at ∼ 135°C identical to AgI. The present investigations suggest that the quenched [0.75AgI:0.25AgCl] mixed system is a better choice as a host compound in place of AgI to prepare Ag+ ion conducting superionic glasses and composites. Using the quenched [0.75AgI:0.25AgCl] system as host, the following superionic solid systems were prepared and studied: (A) (1) x[0.75AgI:0.25AgCl] : (1 − x)[Ag2O · B2O3], (2) x[0.75AgI : 0.25AgCl] : (1 − x)[Ag2O · B2O3], (by the mellt-quenched method (glass systems)); (B) (1) (1 − x)[0.75AgI:0.25AgCl]: x Al2O3 (by dispersing second-phase particles of size (

Characterization of basic transport properties in a new fast Ag+ ion conducting composite electrolyte system : (1 - x)[0.75AgI :0.25AgCl] :xZrO2

Abstract Studies of some basic ionic transport properties of a new fast Ag+ ion conducting two-phase composite electrolyte system: (1−x)[0.75AgI:0.25AgCl]:xZrO2, where 0≤x≤0.5 (in molar weight fraction), are reported. A ‘quenched/annealed [0.75AgI:0.25AgCl] mixed system/solid solution’ has been used as a first phase host matrix salt as an alternative to the traditional host AgI, while particles (≤5 μm) of the insulating and inert ZrO2 were dispersed as second phase dispersoid. In order to find the ‘optimum conducting composition’ (OCC), different compositions of the two phases were mixed homogeneously adopting various routes of preparation. The phase identification studies revealed the coexistence of separate phases. The temperature-dependent transport property studies were carried out on OCC employing various techniques. The mechanism of ion transport has been explained on the basis of models proposed for two two-phase composite electrolyte systems.

Investigation on transport properties of the silver ion conducting composite electrolyte

We report here a conductivity enhancement (∼101) at room temperature in a new Ag+ ion conducting composite system. Two silver halides AgI and AgCl, in the mol.wt.(%) ratio 75:25 were taken as first phase host compound for the first time. Inert second phase Al2O3 particles of size<10 μm were dispersed in varying molar proportions in the first phase. The highest enhancement in the conductivity (∼9.2×10−4S/cm) was obtained for the ratio: 0.7[0.75AgI·0.25AgCl]·0.3Al2O3. The plot of electrical cond uctivity as a function of temperature for the best composition indicated the presence of characteristics β→α-like transition of AgI or host compound in the composite system with slightly decreased conductivity values from the host in the α-phase. The equations governing log σ versus 1/T for the composite system are represented by: σ=0.016 exp(−0.074/kT)→β-like phase; σ=0.041 exp(−0.024/kT)→α-like phase give the activation energies as 0.074 eV and 0.024 eV in β and α-like phases, respectively, as compared to the values 0.24 eV and 0.025 eV for the host material. The low activation energy value in the β-region suggest easy ion migration in the composite system. The ionic mobility μ∼(2.37±1)×10−2cm−2/Vs) was evaluated at room temperature for the best composition using the transient ionic current (TIC) technique, while the value of the transference number tions is close to unity as obtained by two different techniques, i.e. Wagners dc polarisation and electrochemical cell potential measurements. For the host material tion and μ(1.5±1)×10−2.