Use of Natural Graphite for an Energy Storage Device

Ever growing high concerns over use of safe and low cost devices have provided a substantial attention on natural materials. As such natural graphite which has been deeply integrated into numerous applications is being received a consideration to be used for electrochemical devices. The main objective of this study is to explore the suitability of Sri Lankan natural graphite to serve in electrochemical double layer capacitors (EDLCs). In order to uplift the safety of the device, a gel polymer electrolyte was used instead of a liquid electrolyte. Two identical electrodes were consisted with Sri Lankan natural graphite as the active material and polyvinylidenefluoride as the binder. To prepare the electrolyte, polyvinylidenefluoride co hexafluoropropylene and magnesium perchlorate were used as the polymer and the salt respectively. Cyclic voltammetry test results show that single electrode specific capacitance is depending on the potential window. The percentage reduction of capacitance with continuous cycling was about 28%. Nyquist plot of EDLC further confirm the capacitive nature at low frequency

Healable Cellulose Iontronic Hydrogel Stickers for Sustainable Electronics on Paper

The authors acknowledge the support from FCT - Portuguese Foundation for Science and Technology through the Ph.D. scholarships SFRH/BD/126409/2016 (I.C.) and SFRH/BD/122286/2016 (J.M.). The authors would like to acknowledge the European Commission under project NewFun (ERC-StG-2014, GA 640598) and project SYNERGY (H2020-WIDESPREAD-2020-5, CSA, proposal no 952169). This work was also supported by the FEDER funds through the COMPETE 2020 Program and the National Funds through the FCT - Portuguese Foundation for Science and Technology under the Project No. POCI-01-0145-FEDER-007688, reference UID/CTM/50025, project CHIHC, reference PTDC/NAN-MAT/32558/2017. The authors would also like to thank their colleagues Daniela Gomes and Ana Pimentel from CENIMAT/i3N for the SEM and DSC-TGA measurements, respectively.Novel nature-based engineered functional materials combined with sustainable and economically efficient processes are among the great challenges for the future of mankind. In this context, this work presents a new generation of versatile flexible and highly conformable regenerated cellulose hydrogel electrolytes with high ionic conductivity and self-healing ability, capable of being (re)used in electrical and electrochemical devices. They can be provided in the form of stickers and easily applied as gate dielectric onto flexible indium–gallium–zinc oxide transistors, decreasing the manufacturing complexity. Flexible and low-voltage (<2.5 V) circuits can be handwritten on-demand on paper transistors for patterning of conductive/resistive lines. This user-friendly and simplified manufacturing approach holds potential for fast production of low-cost, portable, disposable/recyclable, and low-power ion-controlled electronics on paper, making it attractive for application in sensors and concepts such as the “Internet-on-Things.”.publishersversionpublishe

Ionic conductivity enhancement in PEO:CuSCN solid polymer electrolyte by the incorporation of nickel-chloride

\ua9 2015 Elsevier B.V. All rights reserved. Copper-ion based solid polymer electrolytes exhibit interesting electrochemical properties, environmental stability and lower fabrication cost compared to lithium ion based systems. Although, poly(ethylene oxide)(PEO)-based solid polymer electrolytes have been extensively studied, those incorporating copper salts have not been explored much. One major drawback in these electrolytes is the low ionic conductivity at room temperature. In this work, we attempted to enhance the ionic conductivity of PEO9CuSCN polymer electrolyte by the incorporation of NiCl2. Incorporation of 10 wt% NiCl2 showed the highest conductivity enhancement with almost two orders of magnitude increase. The ionic conductivity value at 30 \ub0C increased from 3.1 7 10- 9 S cm- 1 for the NiCl2-free electrolyte to 1.8 7 10- 7 S cm- 1 for the 10 wt% NiCl2 incorporated electrolyte. This was associated with a significant reduction in Tg by about 30 \ub0C from - 53 \ub0C for PEO9 CuSCN to - 83 \ub0C for PEO9 CuSCN + 10 wt% NiCl2, indicating an increased segmental flexibility of the polymer chains for NiCl2 added electrolyte

Effect of TiO2 nano-filler and EC plasticizer on electrical and thermal properties of poly(ethylene oxide) (PEO) based solid polymer electrolytes

Ionic conductivity of poly(ethylene oxide)-lithium trifluoromethanesulfonate (LiCF3SO3 or LiTf) based polymer electrolyte has been increased by incorporating TiO2 nano-filler. Incorporation of 10 wt.% TiO2 exhibited the highest conductivity enhancement with a value of 4.9 x 10(-5) S cm(-1) at 30 degrees C. A further enhancement in conductivity to a value of 1.6 x 10(-4)S cm(-1) at 30 degrees C has been obtained by the incorporation of 50 wt.% ethylene carbonate (EC) plasticizer. Both additives cause a reduction of the PEO crystalline phase content and an increased segmental flexibility leading to conductivity enhancement

Rigidity transitions in glasses driven by changes in network dimensionality and structural groupings

Calorimetric, Raman and electrical conductivity properties of alkali borates ${(100-x)}\text{B}_2\text{O}_3\text{-}x\text{M}_2\text{O}$ ($\text{M}=\text{Li}$ , Na) are studied as a function of composition $(x)$ and these show the presence of stiffness transitions and an intermediate phase which are driven by a combination of network dimensionality change and usual topological constraint changes. This picture is confirmed by a detailed Raman analysis showing that specific modes of molecular structural groupings dominate the network structure in the intermediate phase. Their evolution shows a one-to-one correspondance with the observed non-reversing heat flow at the glass transition, and are correlated with thresholds in ionic conductivity that allows identifying a flexible phase at high alkali content, whereas the mildly stressed-rigid $\text{B}_2\text{O}_3$ -rich glasses are driven by the conversion of planar 2D boroxol ring structures into the 3D structural groupings. These findings deeply modify the usual picture of these archetypal glasses, and reveal the very first example of the onset of rigidity tuned by network dimensional conversion

The Voltammetric Hysteresis Behavior and Potential Scan Rate Dependence of a Dye Sensitized Solar Cells

The voltammetric hysteresis visible in current density versus solar cell potential (J-V) curves is a serious concern because it is known that the performance of Dye-sensitized Solar Cells (DSCs) depends on the direction of the potential and the rate of scan. J-V characteristics of gel electrolyte based DSCs were obtained by varying the scan rate from 0.01 to 0.1 V s-1 and the direction from forward bias to reverse bias and reverse bias to forward bias. Three electrolytes were tested, two of them were 100% single salt electrolytes of KI and Hex4NI, and the other was a mixed salt electrolyte containing KI (75%) and Hex4NI (25%). DSC containing mixed salts electrolyte exhibited higher efficiency than single salt electrolytes. The energy conversion efficiency with mixed salts increased from 5.9 to 6.4% with the increase of the scan rate from 0.01 to 0.1 V s-1, when the scanning was conducted from forward bias to reverse bias direction. However, when the scanning was carried out with revised polarity a drop of the efficiency was observed with increasing rate of potential scan. Present work emphasizes the importance of reporting the rate and direction of potential scan along with solar cell performance parameters

Polyethyleneoxide (PEO)-based, anion conducting solid polymer electrolyte for PEC solar cells

Solid polymer electrolyte membranes were prepared by complexing tetrapropylammoniumiodide (Pr4N+I-) salt with polyethylene oxide (PEO) plasticized with ethylene carbonate (EC), and these were used in photoelectrochemical (PEC) solar cells fabricated with the configuration glass/FTO/TiO2/dye/electrolyte/Pt/FTO/glass. The PEO/Pr4N+I-+I-2=9:1 ratio gave the best room temperature conductivity for the electrolyte. For this composition, the plasticizer EC was added to increase the conductivity, and a further conductivity enhancement of four orders of magnitude was observed. An abrupt increase in conductivity occurs around 60-70 wt% EC; the room temperature conductivity was 5.4 x 10(-7) S cm(-1) for 60 wt% EC and 4.9 x 10(-5) S cm(-1) for the 70 wt% EC. For solar cells with electrolytes containing PEO/Pr4N+I-+I-2=9:1 and EC, IV curves and photocurrent action spectra were obtained. The photocurrent also increased with increasing amounts of EC, up to three orders of magnitude. However, the energy conversion efficiency of this cell was rather low

Polyethyleneoxide (PEO)-based, anion conducting solid polymer electrolyte for PEC solar cells

Solid polymer electrolyte membranes were prepared by complexing tetrapropylammoniumiodide (Pr4N+I-) salt with polyethylene oxide (PEO) plasticized with ethylene carbonate (EC), and these were used in photoelectrochemical (PEC) solar cells fabricated with the configuration glass/FTO/TiO2/dye/electrolyte/Pt/FTO/glass. The PEO/Pr4N+I-+I-2=9:1 ratio gave the best room temperature conductivity for the electrolyte. For this composition, the plasticizer EC was added to increase the conductivity, and a further conductivity enhancement of four orders of magnitude was observed. An abrupt increase in conductivity occurs around 60-70 wt% EC; the room temperature conductivity was 5.4 x 10(-7) S cm(-1) for 60 wt% EC and 4.9 x 10(-5) S cm(-1) for the 70 wt% EC. For solar cells with electrolytes containing PEO/Pr4N+I-+I-2=9:1 and EC, IV curves and photocurrent action spectra were obtained. The photocurrent also increased with increasing amounts of EC, up to three orders of magnitude. However, the energy conversion efficiency of this cell was rather low

Current trends and future challenges of electrolytes for sodium-ion batteries

Research and development efforts on sodium-ion batteries are gaining momentum due to their potential to accommodate high energy density coupled with relatively lower cost in comparison with lithium-ion batteries. In order for the sodium-ion batteries to be commercially viable, high performance electrolytes with acceptable ambient temperature ionic conductivity and wider electrochemical stability windows are being developed. A bibliometric analysis of the publications on various types of Na+ ion conducting electrolytes since 1990 shows a total of 200 + publications and reveals an exponential growth in the last few years, due to reasons that the sodium-ion systems promise great potential as the future large scale power sources for variety of applications. This review consolidates the status of liquid (non-aqueous, aqueous and ionic), polymer gel and solid (ceramics, glasses, and solid polymers) electrolytes and discusses their ionic conductivity, thermal characteristics, electrochemical stability and viscosity towards applications in sodium-ion batteries. Among various types available, the non-aqueous solvent based electrolyte is the most promising one in terms of ionic conductivity even though it is flammable