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008			240726t20242024my a|||fr|||| 000 0 eng d
020			_aTHE0009894 (Local) _qHardback
040			_aUMPSA _beng _cUMP _erda
090			_aFIM .L56 2024 r Thesis
100	0		_aLing Jin Kiong, _eauthor.
245	0	0	_aMorphological control of ternary composite innickel-cobalt-manganese system and enhancing surface of porous carbon using sunlight for energy storage application / _cLing Jin Kiong
264		1	_aKuantan, Pahang : _bUMPSA, _c2024
264		4	_c© 2024
300			_axxiv, 240 pages : _billustrations ; _c30 cm.
336			_2rdacontent _atext
337			_2rdamedia _aunmediated
338			_2rdacarrier _avolume
347			_2rda _atext file _bPDF
500			_aFaculty of Industrial Management
502			_aThesis (Doctor of Philosophy) -- Universiti Malaysia Pahang – 2023
504			_aIncludes bibliographical references
520	3		_aEnergy storage devices under lithium-ion battery and electrochemical capacitor storage modes are currently commercial; however, increasing their performance indicators such as specific energy and power as well as the charge-discharge cycle lifetime is an ongoing research topic. Often composite materials containing two or more components are required to serve a device functionality; and in the case of energy storage devices, composites of two ternary metal oxide have never been examined as an anode. Besides, the volume changes (isotropic/anisotropic) of transition metal oxide composite anode could significantly impact the cycling stability and need to be investigated. For the porous carbon cathode, capability of enhancing the surface of carbon through surface modification technique that does not depend on high temperature annealing and toxic chemical is equally important. Electrolyte modification for wider electrochemical potential window and inducing redox reaction (either bulk or surface-limited) is equally important to achieve improved specific energy and power. Herein, ternary metal oxide system consisting of nickel, cobalt, and manganese with two different morphologies (one-dimensional fiber and three-dimensional octahedron) were synthesized, characterized, and compared. For the first time, the formation of octahedron was achieved through electrospinning technique during this study. The nickel-cobaltmanganese system (regardless of the morphology) could offer specific capacity >1000 mAh/g at a current density of 100 mA/g. During charge-discharge cycling, the quasianisotropic volume changes of octahedrons significantly maintained the crystal structure of the nickel-cobalt-manganese system, leading to a superior capacity retention of 72.1%, compared to 24.1% capacity retention in fibers. On the other hand, the surface of the porous carbon was treated with 20 seconds of focused sunlight under mild vacuum conditions. Trapped moisture was released under illumination as steam, creating an environment identical to the physical activation process, etching the surface and enhanced porosity. The treated porous carbon leads to 50% enhancement on its electrochemical performance. Using this solar activation process, a procedure to regain 95% of the electrochemical properties of degraded carbon electrode was also established. Regarding the electrolyte modification, a carbon symmetric supercapacitor with 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid as the electrolyte offered a 4-fold improvement in specific energy as compared to the aqueous electrolyte (2M potassium hydroxide), owing to its exceptional high operating voltage of 3V. Addition of lithium perchlorate at a concentration of 0.5M doubled the specific energy of the symmetric device. Addition of lithium salts also induced surface redox reaction on the metal oxide electrode, enhancing its specific energy by an order of magnitude. Thus, this study presents advanced electrochemical energy storage devices with improved performance indicators by appropriately tailoring the materials properties of anode, cathode, and electrolyte.
610	2	0	_aFaculty of Industrial Management _xDissertations
650		0	_aUniversities and colleges _xDissertations
650		0	_aTheses _xDissertations
942			_2lcc _cTHESIS