Author: Wang, Huizhong
Title: CoP@C nanocomposite and its application as anode materials for Li (Na)-ion battery
Advisors: Zhou, Limin (ME)
Degree: M.Sc.
Year: 2018
Subject: Hong Kong Polytechnic University -- Dissertations
Lithium ion batteries
Storage batteries -- Materials
Department: Faculty of Engineering
Pages: xi, 113 pages : color illustrations
Language: English
Abstract: Due to gradually increasing consumption of fossil fuel based energy and the carbon emission standard, sustainable energy alternatives (renewable energy) have attracted highest attention in recent times, such as wind energy, solar energy, tidal energy, biomass energy, geothermal energy. The application of the renewable energy also causes the increasing demand for energy storage devices. Lithium (sodium)-ion battery has the application potential of electric vehicles and hybrid electric vehicles as power supplier, for its higher power density and energy density. The anode materials in recent research could not satisfy the requirements of the future commercial market, due to the poor rate performance, low capacity and other problems. It is urgently demanded to develop a new anode material with an extraordinary electrochemical performance for a secondary battery. Recently, the transition metal phosphides have attracted considerable interests in research community, due to their rich natural reserves and high theoretical capacity of lithium (sodium) storage ability. However, the commercial battery and electrochemical devices not only demand high energy density but also require the long cycle life and excellent power density. During the charge/discharge process, the transition metal phosphides transform to new crystallographic phases which may result in volume expansion. That may lead to smashing and agglomeration of active material. These hinders the battery to achieve good rate performance or excellent cycle performance. The metal-organic frameworks (MOFs) are crystalline compounds, which consists of metal ions and organic ligands forming one-, two-, or three-dimensional structures. As a novel porous organic material, it is proposed as a promising candidate for rechargeable batteries due to its large specific surface area, stable structure and excellent electrochemical properties. The controllable porous nanostructure makes the MOFs a potential candidate for application in energy storage and electrochemical conversion reaction. Besides, the derivatives obtained from MOFs are also can be utilized in diverse energy fields. In this study, the zeolite imidazole framework (ZIF-67) is used as a template and a precursor to synthesize the amorphous carbon coated cobalt phosphide composite material (CoP@C), followed by the characterization of component and morphology. The result shows that the structure of CoP@C is a polyhedron with uniform size. As the anode material of lithium-ion battery (LIB), the first discharge specific capacity is 1401.9 mAh·g⁻¹, the charge specific capacity is 851.6 mAh·g⁻¹. At the current density of 100 mA·g⁻¹, the specific capacity remains 507.4 mAh·g⁻¹ after 100 charge/discharge cycles. At a current density of 1000 mA·g⁻¹, the specific capacity remains 494.9 mAh·g⁻¹ after 1200 cycles, which exhibits the excellent ability of lithium storage. As the anode material of sodium-ion battery (SIB), the specific capacity remains 251.6 mAh·g⁻¹, after 100 cycles at a current density of 100 mA·g⁻¹. After 1000 cycles at a current density of 1000 mA·g-1, the specific capacity is 155.8 mAh·g⁻¹. These represent excellent sodium strorage ability.
Rights: All rights reserved
Access: restricted access

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