Materials Science Forum Vol. 846

Abstract: Single phase LiMn_0.3Co_0.3Ni_0.3Ti_0.1O₂ materials are prepared using a self-propagating combustion method. The structure and morphology of the materials were characterized using X-Ray powder diffraction (XRPD) and Field Emission Scanning Electron Microscopy (FESEM). The electrochemical performances of the materials were characterized by means of galvanostatic charge-discharge test on the fabricated cells. XRD results showed that the materials are impurity-free and single phase with well ordered hexaganol structure of Rm space group. The compound was annealed at 700 °C and 800 °C for 24 h. The discharge capacities obtained was 143 mAhg^-1 in the first cycle for both materials. The voltage range was between 2.5 to 4.2 V. The 30^th cycle, however, revealed that the material annealed at 700 °C shows the better performance. The capacity fading is only about 14% compared to 17% for the 800 °C sample. This implies that LiMn_0.3Co_0.3Ni_0.3Ti_0.1O₂ material is sensitive to annealing temperature. They exhibited good specific capacity values and looked promising for Li-ion battery application.

Abstract: Energy and power capability of a supercapacitor is important because of its function to provide backup power or pulse current in electronic/electric products or systems. The choice of its electrode materials, typically such as carbon, metal oxide or conducting polymer determines the mechanism of its energy storage process. This short review focuses on the supercapacitors using porous carbon electrode prepared, respectively, from fibers of oil palm empty fruit bunches. The specific energy and specific power of these supercapacitors were analyzed to observe their trend of change with respect to the electrode preparation parameters affecting the porosity, structure, surface chemistry and electrical conductivity of electrodes, and thence influence the energy and power capability of a supercapacitor. This review found that the trend of change in specific energy and specific power was not in favor of the expectation that both the specific energy and specific power should be in increasing trend with a significant progress.

Abstract: The current solid electrolytes suffer from low ionic conductivity and interfacial instability. To improve the performance of the electrolyte, the addition of additives to the solid electrolyte is being extensively investigated. A Na–ion conducting solid electrolyte system was prepared via solid state reaction technique. NaI and Na₃PO₄ were mixed in varied compositions and the optimum composition obtained with the highest conductivity at room temperature was used to study the effect of polymer additive by using Poly (L–Leucine)–1,3–diamino propane. A small amount of Poly (L–Leucine)–1,3–diamino propane in the range of 2–10 weight percent was added to the optimum composition of the binary compound with a composition of 0.5 NaI and 0.5 Na₃PO₄. The effect of Poly (L–Leucine)–1,3–diamino propane on the electrical conductivity of the binary compound was investigated by Electrical Impedance Spectroscopy (EIS) technique. Results from EIS have proven this compound to be superionic with maximum conductivity in the range of 10⁻³ S cm^–1. Fourier Transform Infrared Spectroscopy (FTIR) analysis revealed the band of C=O at 1650 cm^–1 experienced shifting indicates some interaction has occurred. The ionic transference number was found to be ≈ 1 for the optimum composition with maximum conductivity which suggests that the sample is ionic in nature.

Abstract: Solid polymer electrolyte (SPE) can be viewed as an alternative of conventional liquid electrolyte since it is easier to handle. Previous Solid polymer electrolyte (SPE) can be viewed as an alternative of conventional liquid electrolyte since it is easier to handle. In the present work, starch/chitosan-ammonium nitrate (NH₄NO3) SPE has been prepared by solution casting technique. Different amount of 1-ethyl-3-methylimidazolium nitrate ([EMIM][NO₃]) was added to the sample. Ionic conductivity analysis was conducted over a wide range of frequency between 50 Hz-1 MHz using impedance spectroscopy to evaluate the dielectric properties and conductivity of the sample. Sample with 15 wt% of [EMIM][NO₃] has shown the highest conductivity of 7.36 x 10^-5 S cm^-1 at room temperature. Complex permittivity for real (ε_r), imaginary (ε_i) and electrical modulus for real (M_r) and imaginary (M_i) part was determined and plotted.

Abstract: Low ionic conductivity and easily attacked by air are among the common issues of lithium salts in lithium based solid electrolytes. Toward this end, our efforts have been focused on the development of a new lithium based electrolyte system which exhibits a good stability against atmosphere and posses high electrical conductivity. Normally, lithium carbonate (Li₂CO₃) alone shows a low electrical conductivity (2×10^-5 Scm^-1). However, the corporation of lithium iodide (LiI) has made a significant impact on the electrical conductivity of the system (4.63×10^-3 Scm^-1). The xLi₂CO₃-yLiI (x = 95-70, y = 5-30 wt.%) solid electrolyte were prepared by mechanical milling technique. The electrical and structural properties of the electrolyte systems were characterized by Electrical Impedance Spectroscopy (EIS) and Fourier Transform Infrared (FTIR) respectively. The highest electrical conductivity (4.6×10^-3 Scm^-1) of the electrolyte system was obtained from the sample containing 20 wt.% of lithium iodide (LiI). The carbonate groups play a role to provide sites for the interaction between interconnected pathways and lithium ions for the fast lithium ion migration.

Abstract: Gel polymer electrolyte films based on cellulose acetate (CA) complexed with ammonium iodide (NH₄I), and ethylene carbonate (EC) was prepared by the solution cast technique. The conductivity increases to 10^-4 Scm^-1 upon the addition of salt. The incorporation of EC and to the salted polymer enhances the conductivity significantly 10^-3 Scm^-1. The complexation of doping materials with polymer was confirmed by X-ray diffraction and infrared studies. The present of ethylene carbonate (EC) as plasticizer did not disturbed the complexation between polymer and salt that has been confirm by FTIR. XRD studies further confirmed that all sample prepared are crystalline. This result affirmed that there were no complexations occur between plasticizer in the CA-NH₄I polymer system.

Abstract: Previously, the addition of silicon dioxide (SiO₂) improved the homogeneity of polymethyl methacrylate/50 % epoxidised natural rubber (PMMA/ENR 50) blend. However, the presence of SiO₂ agglomerates limits its overall performance. The formation of these agglomerates was due to the hydrogen bonding interaction that form between the oxygen atoms in silanol groups (Si-OH) and hydrogen atoms from the surrounding moisture. Therefore, in this study, SiO₂ were modified with dodecanoic acid (DOA) to reduce the number of Si-OH on the SiO₂ surface using esterification technique. Interestingly, it was found that the addition of DOA modified SiO₂ (D-SiO₂) improves the homogeneity of PMMA/ENR 50 blend. However, the amount of DOA used in the modification affect the capability of forming hydrogen bonding with the neighbouring of polymer chain. Different amounts of DOA were used upon the surface modification of SiO₂ filler and then were added into PMMA/ENR 50 blends doped with lithium tetrafluoroborate (LiBF₄)_. The films were prepared by solvent casting technique. CHNS analysis proven the increases of percentage of carbon atoms in D-SiO₂. The attachment of DOA on SiO₂ surface was confirmed using Fourier transform infrared spectroscopy (FTIR) and ionic conductivity of PMMA/ENR 50/LiBF₄ filled D-SiO₂ films was measured by electrochemical impedance spectroscopy (EIS). The result shows the blend properties and ionic conductivity of PMMA/ENR 50 filled D-SiO₂ films was improved due to surface modification of SiO₂ filler.

Abstract: In this study, gel polymer electrolytes (GPEs) system is prepared by the solution cast technique. The system consists of cellulose acetate (CA) as a host polymer, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as a dopant salt and diethylene glycol dibutylether (BDG) from glyme based family as a plasticizer. GPEs (65 wt. % CA–25 wt. % LiTFSI–10 wt. % BDG) sample is the highest conductivity of 2.88×10^-3 S.cm⁻¹ at room temperature. The lithium-electrolyte interfaced stability is established and the highest ionic conducting electrolyte is able to withstand up to 3.8V vs Li/Li⁺.

Abstract: This article presents the discovery on biopolymer electrolytes comprising of ammonium nitrate, NH₄NO₃ with dual-blend biopolymer materials, carboxymethyl cellulose/chitosan which were prepared via solution-casting technique. The biopolymer blend based electrolyte films were characterized by Fourier Transform Infrared spectroscopy to investigate the formation of the dual-blend biopolymer based complexes. X-Ray Diffraction result showed that all dual-blend samples were predominantly amorphous. Electrochemical impedance spectroscopy was conducted to obtain their ionic conductivities. The highest conductivity at ambient temperature of 1.03 × 10^–5 S cm^–1 was obtained for the electrolyte film containing 40 wt% of NH₄NO₃. These results indicated that the dual-blend biopolymer based electrolyte has potential for application of electrochemical devices.

Abstract: Self-adhesive carbon grains (SACG) and lignin were prepared from fibres of oil palm empty fruit bunches by a low carbonization temperature and chemical treatment methods, respectively. Green monoliths were prepared from the KOH-treated SACG mixed with the organosolv-treated lignin with their weight percentages of 0%, 5%, 10%, 15% and 20%, respectively. The green monoliths were carbonized and activated into highly porous activated carbon monoliths (ACMs) electrodes for supercapacitor applications. The electrochemical characterization using galvanostatic charge-discharge (GCD) technique was carried out on the supercapacitor cell fabricated using these electrodes. The results show that the addition of 5 wt.% lignin was optimum, corresponding to the higher values of the specific capacitance (137 Fg^-1), specific energy (4.13 Wh kg^-1), specific power (192 W Kg^-1), and a satisfactory value of equivalent series resistance (0.467 Ω) of the supercapacitor.