Transformation of Supercapacitive Charge Storage Behaviour in a Multi elemental Spinel CuMn_(2)O_(4) 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 CuMn_(2)O_(4) 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 Na_(2)SO_(4) and 1 M Li_(2)SO_(4)),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 sys-tem 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.

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-Co_(3)O_(4) hybrid and spinal-type NiCo_(2)O_(4),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 Co_(3)O_(4),as well as a hybrid of similar chemistry,CuO-Co_(3)O_(4).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-Co_(3)O_(4) hybrid nanobelts based ASCs compared to those fabricated using the other materials-the former showed capacitive behav-iour 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-Co_(3)O_(4) hybrid ASCs exhibited the highest specific energy,specific power and cycling stability.

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.