Browsing by Author "Sumathipala, H.H."

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Dual Composite Polymer Electrolytes for Lithium Rechargeable Batteries
(University of Kelaniya, 2008) Sumathipala, H.H.; Panero, S.; Scrosati, B.
Lithium-ion batteries have been drawn great attention due to their potential for use in high-performance electric vehicles. However, some drawbacks still remain to be solved for the optimization of some critical operational features such as safety, design flexibility etc. Replacing of the conventional liquid electrolytes currently being used by a polymer electrolyte is the most effective approach for reaching the goal. In this scenario, PEOLiX (X= CF3S03, Cl04, BF4, LiBOB), electrolytes have been widely studied for practical applications. Among the other drawbacks, low lithium ion transference number of PEO-LiX electrolytes, is more significant as it lowers the power capability of the battery. Focusing on this drawback, recently we have introduced new approach to improve the lithium ion transference number of PEO-based polymer electrolytes, still maintaining the overall high level of ionic conductivity. A composite polymer electrolyte, formed by dispersing dual additives, super acid zirconia (S-Zr02) acting as a conductivity promoter and calix(6)pyrrol acting as an anion trapper, into a PEO- LiCF3S03 has been tested as a separator in a new type of rechargeable lithium battery using lithium ion phosphate as the cathode. Promising results in terms of capacity delivery, rate capability and cycle life, have been obtained, demonstrating the effective practical relevance of the composite electrolyte membrane.
Investigating the thermal efficiency of commercially available thermo-foils in Sri Lanka
(Journal of Science of the University of Kelaniya Sri Lanka, 2011) Maduranga, A.D.; Sumathipala, H.H.; Jayatissa, N.W.K.
The thermo-foil is an insulation material which can be used to insulate roofs of residential buildings which causes less energy to accomplish a comfortable temperature inside the building. It?s becoming popular in Sri Lankan building construction sector. In this research, an investigation of the efficiency of the thermo-foils is done for commonly used brands. The important thermal properties are analyzed for thermo-foils with a thickness of 3mm, 5mm and 8mm and it is tested using a miniature building model for the further evaluation of the efficiency. It was observed that the aluminium layer of the thermo-foil could reflect most of the radiation back and the polyethylene foam layer could keep a temperature gradient of a few degrees. A temperature drop of 1.6 to 2.8 degrees was noted. The results obtained were discussed with an analysis of the thermal insulation properties. A heat transfer model for a residential building was also proposed.
Investigating the Thermal Efficiency of Thermo-foils as a Roof Insulation Material and Developing a New Roof Insulation Material Using Coir Fiber
(2011) Maduranga, A.D.; Jayatissa, N.W.K.; Sumathipala, H.H.
The thermo-foil is an insulation material which can be used to insulate roofs of residential buildings which causes less energy to accomplish a comfortable temperature inside the building. In this study, an investigation of the efficiency of the thermo-foils in building insulation is performed. The thermal insulation properties and structure of the thermo-foil were analyzed as well as how these properties affect the decrease of temperature inside the residential building. The thermo-foils were tested using miniature building models for a more general conclusion. A heat transfer mechanism for a residential building is also proposed. A new roof insulation material is designed using an efficient and low cost natural fiber, coconut fiber or coir. The insulation properties unique to the coir fiber are enhanced as an insulation material. The new foil which is called Coir-Foil is tested together with thermo-foil. The Coir-Foil could achieve considerable higher performance than the currently available thermo-foil. The performance analysis for new coir foil and existing thermo-foils was used to conclude how they affect the energy conservation of residential buildings, through reducing the cooling load.
Li-LiFePO4 rechargeable polymer battery using dual composite polymer electrolytes
(Journal of Applied Electrochemistry, 2008) Sumathipala, H.H.; Hassoun, J.; Panero, S.; Scrosati, B.
A composite polymer electrolyte, formed by dispersing into a poly(ethylene oxide)-lithium salt matrix two additives, i.e. calyx(6)pyrrole, (CP) acting as an anion trapper and superacid zirconia, S-ZrO2 acting as a conductivity promoter, has been tested as a separator in a new type of rechargeable lithium battery using lithium iron phosphate as the cathode. The choice of the electrolyte was motivated by its favourable transport properties both in terms of lithium ion transference number and of total ionic conductivity. The choice of the cathode was motivated by the value of its operating voltage which falls within the stability window of the electrolyte. The performance of the battery was determined by cycling tests carried out at various rates and at various temperatures. The results demonstrate the good rate capability of the battery which can operate at high charge-discharge efficiency even at 1 C rate and that it can be cycled at 90 �C with a satisfactory initial capacity of the order of 90 mAh g?1. These values outline the practical relevance of the composite electrolyte membrane and of its use as separator in a lithium battery.
New Li+-ion conductors, Li4 ? 2xTi1 ?xSxO4, based on the Li4TiO4 structure
(Journal of Materials Chemistry, 1994) Dissanayake, M.A.K.L.; Sumathipala, H.H.; West, A.R.
In the system Li4TiO4?Li2SO4, a wide range of solid solutions, Li4 ? 2xSxTi1 ?xO4(0 < x < 0.2) with Li4TiO4 structure is formed. The ionic conductivity increases with x and exhibits a maximum (bulk) value of 8.30 ? 10?6 S cm?1at 27 �C with an activation energy of 0.51 eV for x= 0.2. The enhancement in conductivity is associated with an increase in concentration of lithium-ion vacancies, created via the mechanism 2Li++ Ti4+ S6+, but is attributable specifically to a decrease in activation energy for conduction. This is the first report of high Li+-ion conductivity in the Li4TiO4structural family.
New solid electrolytes and mixed conductors: Li3 + xCr1 ? xMxO4: M = Ge, Ti
(Solid State Ionics, 1995) Dissanayake, M.A.K.L.; Gunawardane, R.P.; Sumathipala, H.H.; West, A.R.
New Li+ ion conducting solid solutions with ?-LISICON type structure have been found in the system Li3 + xCr1 ? xGexO4 for 0.35 < x < 0.92. Conductivity increases with x; at x = 0.90, ? (bulk) ? 1.4 ? 10?5 S cm?1 at 27 �C rising to 0.044 S cm?1 at 300 �C; Ea = 0.51 eV. Similar ? solid solutions form in the Ti system, Li3 + xCr1 ? xTixO4: 0.5 < x <0.8; however, these are mixed Li+ ion and electronic conductors. Both systems are unusual in containing Cr in the +V oxidation state.
Novel Li+ Ion Conductors and Mixed Conductors, Li3+xSixCr1-xO4 and a Simple Method for Estimating Li+/e- Transport Numbers.
(Chem Inform, 1995) Sumathipala, H.H.; Dissanayake, M.A.K.L.; West, A.R.
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Novel LISICON mixed conductors, Li4 ? 2xCoxGeO4
(Solid State Ionics, 1996) Sumathipala, H.H.; Dissanayake, M.A.K.L.; West, A.R.
A novel LISICON type ? solid solution range has been found in the system Li4 ? 2xCoxGeO4 for 0.15 ? x ? 0.8. The highest net conductivity, 8.4 ? 10?6Scm?1, was observed for x = 0.25 at 27 �C rising to 3.35 ? 10?3Scm?1 at 300 �C with an activation energy of 0.71 eV. A charge/discharge polarisation technique was used to investigate the transference number of these materials. Results corroborate those obtained by low frequency a.c. impedance measurements and show the occurrence of mixed Li+ ion and electronic conductivity. The relative amounts of each vary with composition; x = 0.25 has both the highest conductivity and the highest ionic transference number, 0.19.
Potential of using the Solar Chimney Dryer for Small Scale Industries in Sri Lanka
(Faculty of Graduate Studies, University of Kelaniya, 2015) Jayasinghe, J.U.K.; Sumathipala, H.H.
There have been many research work presenting various novel types of solar dryers that can be used for drying vegetables, fruits, and other agro-products etc. Solar chimney which consists of a large plate and a centered vertical chimney basically studied for electricity power generation using the draught through the chimney. In this study, it has been demonstrated by establishing a mini photo type chimney that the possibility of enhancing the drying process under the plate of a solar chimney. There is a great potential of using Solar Chimney dryer, drying for industrial, fishery and agro products or raw materials. The advantage is that drying can be done, with the similar efficiency of sun drying, under the rainy environment obviously with a law drying efficiency but without destroying quality and protecting them from environmental pollutants.
Synthesis and properties of a new ? polymorph of Li3CrO4
(Journal of Materials Chemistry, 1994) Dissanayake, M.A.K.L.; Garcia-Martin, S.; Saez-Puche, R.; Sumathipala, H.H.; West, A.R.
?-Li3CrO4, isostructural with ?-Li3PO4, has been synthesized by two routes. Reaction of Li2CO3 and Cr2O3 in a 5 : 1 mole ratio in flowing Ar at 800 �C yields ?-Li3CrO4, with a small amount of Li2O. The Li2CO3, seems to have two functions. It is an essential reactant and acts as a novel oxidant, promoting conversion of CrIII to CrV. Reaction of Li2CO3 and CrO3 in a 3 : 1 mole ratio in flowing Ar also gives phase-pure ?-Li3CrO4. Magnetic measurements show Curie?Weiss behaviour in the range 20?300 K with a magnetic moment of 1.70 �B consistent with CrV in tetrahedral coordination. Conductivity measurements show a modest level of electronic conduction.