Miniature tool for characterization of supercapacitive charge storage

A new protocol to characterize supercapacitive charge storage parameters from discharge voltage measurement and using an electrical model is presented. A distribution of capacitances and resistances in three charge storing time domains (fast, medium, and slow) are derived through this protocol. The method relieson recording the self-discharge data (open circuit discharge) and using it along with the charge redistribution within the supercapacitor to obtain the parameters for the equivalent circuit model. The results are validated using the galvanostatic charge discharge cycling. The method proposed here uses comparatively lesser number of variables, thereby making it easier to compute and the validation shows a good match between the experimental and the simulated results

Transformation of supercapacitive charge storage behaviour in a multi elemental spinel CuMn2O4 nanofibers with alkaline and neutral electrolytes

Electrode material has been cited as one of the most important determining factors in classifying an energy storage system’s charge storage mechanism, i.e., as battery-type or supercapacitive-type. In this paper, we show that along with the electrode material, the electrolyte also plays a role in determining the charge storage behaviour of the system. For the purpose of our research, we chose multi-elemental spinal type CuMn2O4 metal oxide nanofibers to prove the hypothesis. The material is synthesized as nanofibers of diameter ~ 120 to 150 nm in large scales by a pilot scale electrospinning set up. It was then tested in three different electrolytes (1 M KOH, 1 M Na2SO4 and 1 M Li2SO4), two of which are neutral and the third is alkaline (KOH). The cyclic voltammograms and the galvanostatic charge–discharge of the electrode material in a three-electrode system measurement showed that it exhibit different charge storage mechanism in different electrolyte solutions. For the neutral electrolytes, a capacitive behaviour was observed whereas a battery-type behaviour was seen for the alkaline electrolyte. This leads us to conclude that the charge storage mechanism, along with the active material, also depends on the electrolyte used

Characterization of electrochemical double layer capacitor electrode using self-discharge measurements and modeling

A simple protocol to characterize the electrochemical double layer capacitors (EDLCs) using self-discharge (open circuit discharge) data and a three-branch electrical model is presented. The method relies on recording the self-discharge data of EDLCs and using it to estimate the parametric values of the variables in the model (time constants, maximum voltage, resistances, and capacitances). Porous carbon and metal oxide electrodes in three choice electrolytes are used for the experiments and the simulations are performed using MATLAB Simulink platform. The simulated and experimental self-discharge data are in close agreement for the EDLC storage mode but not for the battery type storage. The results are further validated by simulating the galvanostatic charge discharge (GCD) cycling data and fitting them to the experimental GCD of the assembled devices with high accuracies. The model presented here thus enables determination of charge storage parameters as well as whether a device is capacitive from a single self-discharge data, thereby providing an excellent tool to characterize EDLCs for both academia and industry

Self-rechargeable energizers for sustainability

Electrical energy generation and storage have always been complementary to each other but are often disconnected in practical electrical appliances. Recently, efforts to combine both energy generation and storage into self-powered energizers have demonstrated promising power sources for wearable and implantable electronics. In line with these efforts, achieving self-rechargeability in energy storage from ambient energy is envisioned as a tertiary energy storage (3rd-ES) phenomenon. This review examines a few of the possible 3rd-ES capable of harvesting ambient energy (photo-, thermo-, piezo-, tribo-, and bio-electrochemical energizers), focusing also on the devices' sustainability. The self-rechargeability mechanisms of these devices, which function through modifications of the energizers’ constituents, are analyzed, and designs for wearable electronics are also reviewed. The challenges for self-rechargeable energizers and avenues for further electrochemical performance enhancement are discussed. This article serves as a one-stop source of information on self-rechargeable energizers, which are anticipated to drive the revolution in 3rd-ES technologies

Pseudocapacitive charge storage in thin nanobelts

This article reports that extremely thin nanobelts (thickness ~ 10 nm) exhibit pseudocapacitive (PC) charge storage in the asymmetric supercapacitor (ASC) configuration, while show battery-type charge storage in their single electrodes. Two types of nanobelts, viz. NiO–Co3O4 hybrid and spinal-type NiCo2O4, developed by electrospinning technique are used in this work. The charge storage behaviour of the nanobelts is benchmarked against their binary metal oxide nanowires, i.e., NiO and Co3O4, as well as a hybrid of similar chemistry, CuO–Co3O4. The nanobelts have thickness of ~ 10 nm and width ~ 200 nm, whereas the nanowires have diameter of ~ 100 nm. Clear differences in charge storage behaviours are observed in NiO–Co3O4 hybrid nanobelts based ASCs compared to those fabricated using the other materials—the former showed capacitive behaviour whereas the others revealed battery-type discharge behaviour. Origin of pseudocapacitance in nanobelts based ASCs is shown to arise from their nanobelts morphology with thickness less than typical electron diffusion lengths (~ 20 nm). Among all the five type of devices fabricated, the NiO–Co3O4 hybrid ASCs exhibited the highest specific energy, specific power and cycling stability

Polymer versus cation of gel polymer electrolytes in the charge storage of asymmetric supercapacitors

Gel polymer electrolytes (GPEs) are promising candidates for highly efficient flexible electrochemical energy storage devices as they reduce leakage and size of the device as well as improving versatility with varied choice of solvents, polymers, and ions. However, the electrochemical mechanisms governing supercapacitive charge storage using a varied choice of polymers and cations (PVA, PEG, PEO-based Na + and K + ) are not systematically evaluated. In this work, the role of GPEs on the charge storage mechanism of a flexible solid-state asymmetric supercapacitor fabricated using porous carbon as the cathode and SnO 2 -TiO 2 composite flower as the anode with various GPEs, viz., poly(vinyl alcohol), poly(ethylene oxide), poly(ethylene glycol)-NaOH, and KOH, is reported. The composite electrode greatly improves the ion transportation, and the GPEs provide interconnected ion transport channels. The as-fabricated porous carbon/GPE/composite electrode as a flexible asymmetric supercapacitor displays an increased specific capacitance (C S up to ∼42.3 F g -1 ) compared to aqueous electrolytes (up to ∼14.1 F g -1 ). Among the studied GPEs, the poly(ethylene oxide)-NaOH-based GPE showed higher C S than poly(vinyl alcohol)-NaOH and poly(ethylene glycol)-NaOH, as the former offered a high cation response under the charge/discharge process

Quantitative sonoelastography of the uterine cervix in predicting successful outcome of induction of labour

Objectives: The aim of the study was to evaluate the stiffness of cervix and determine its significance in predicting successful outcome of induction of labour. The primary objective was to determine the differences in elastography indices of different areas of cervix between the outcome groups of successful and failed induction of labour. A secondary objective was to find out the correlation of these elastography indices with Bishop’s score and cervical length. Methods: This was a prospective, observational study conducted over a period of 6 months on pregnant women admitted in the labour room for induction of labour. Establishment of adequate regular uterine contractions – at least three contractions lasting 40–45 s in a 10-min period – was taken as end point for successful outcome of induction of labour. Even after 24 h of initiation of induction of labour, regular, adequate and painful uterine contractions were not established, then induction of labour was described as having failed. Prior to induction, cervical length measurement, Bishop’s scoring and elastographic evaluation of the cervix were done by stress–strain elastography. A colour map was produced from purple to red and a five-step scale – the elastography index – was used to describe the various parts of the cervix. The differences between elastography indices of different parts of cervix were estimated using Mann–Whitney U test. Correlation of the indices with cervical length and Bishop’s score was determined by Spearman’s correlation coefficient. Results: A total of 64 women were included in the study. A significant difference ( p  < 0.001) was found in the elastography index of internal os between the two outcome groups of success (1.76 ± 0.64) and failure (0.54 ± 0.18). However, the elastography index of central cervical canal, external os, anterior lip and posterior lips did not differ significantly across the outcome groups. A significant positive correlation was found between elastography index of internal os and cervical length (Spearman’s correlation coefficient, r  = 0.441, p  < 0.001) and between elastography index of external os and cervical length ( r  = 0.347, p  = 0.005), whereas a negative correlation was seen between elastography index of external os and Bishop’s score ( r  = −0.270, p  = 0.031). Conclusion: Elastography index of internal os can be used to predict outcome of induction of labour. Cervical elastography is a promising new technique for cervical consistency assessment. Further larger studies are required to determine some cut-off point for elastography index of internal os in prediction of outcome of induction of labour and to strongly establish the usefulness of cervical elastography for pregnancy management, preventing preterm delivery and establishment of cut-off points to determine successful induction