G.P. Pandey

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 ~10−3u2009Su2009cm−1, while dry SPEs still suffer from poor ionic conductivity lower than 10−5u2009Su2009cm−1. Several approaches have been adopted to enhance the room temperature conductivity in the vicinity of 10−4u2009Su2009cm−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.

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.

Electrical and electrochemical properties of magnesium ion conducting composite gel polymer electrolytes

The effect of micro- and nano-sized MgO and nano-sized SiO2 dispersion on the electrical and electrochemical properties of poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) based Mg2+ ion conducting gel polymer electrolyte has been investigated. The gel electrolytes have been characterized using electrical conductivity, cationic transport number (t+) measurements and cyclic voltammetry. A two-maxima feature has been observed in the conductivity versus composition curve at ~3 wt% and 10–15 wt% of the filler contents. The highest conductivity has been obtained for the SiO2 dispersed gel electrolyte of ~1 × 10−2 S cm−1 for 3 wt% and ~9 × 10−3 S cm−1 at 15 wt% content. The value of t+ is found to be enhanced substantially with increasing amount of MgO (both micro- and nanoparticles), whereas in the case of SiO2 dispersion the value does not increase substantially. The highest t+ value of ~0.44 has been obtained for the addition of 10 wt% MgO nanoparticles. The enhancement in t+ is explained on the basis of the formation of space-charge regions due to the presence of MgO : Mg2+-like species, which supports Mg2+ ion motion. A substantial increase in the amount of anodic and cathodic peak currents is observed due to the addition of nano-sized MgO particles in the gel polymer electrolyte, whereas in the cases of micrometre-sized MgO and nano-sized SiO2 the enhancement is not significant. The enhancement in conductivity in SiO2 dispersed nanocomposite gel electrolyte is predominantly due to anionic motion.