Lithium-ion battery (LIB) is an indispensable energy storage device in portable electronics, and its applications in electric vehicles and grid-level energy storage are increasing dramatically in recent years due to high demands. To meet energy demands and address fire hazards, next generation batteries with better safety, higher energy density, and longer cycle life have been actively investigated. In this thesis, works on polymer and ceramic solid electrolytes to improve safety and energy density of rechargeable solid-state batteries are discussed. In the first section, a flexible composite solid electrolyte is presented. Since ceramic electrolytes have high conductivities but are fragile, and polymer electrolytes are easy to process but have low conductivities, we propose a composite structure that combines these advantages. A vertically aligned and connected ceramic electrolyte is realized through the ice-templating method to improve the ionic conduction. Then a polyether-based polymer electrolyte is added to make the composite electrolyte flexible. Specifically, vertically aligned and connected LATP and LAGP nanoparticles (NPs) in the polyethylene oxide (PEO) matrix are made. The conductivity reaches 0.52 × 10-4 S/cm for LATP/PEO, and 1.67 × 10-4 S/cm for aligned LAGP/PEO composite electrolytes, which are several times higher than that with randomly dispersed LATP/LAGP NPs in PEO. Compared to the pure PEO electrolyte, the mechanical and thermal stabilities of the composite solid electrolyte are higher. The LFP-LAGP/PEO-Li cell with 148.7 mAh/g during the first discharge at 0.3C has over 95% capacity retention after 200 cycles. This method opens a new approach to optimize ion conduction in composite solid electrolytes for solid-state batteries. In the next section, polyether-based polymer electrolytes such as PEO and PEG are studied. Polyether-based electrolytes are electrochemically unstable above 4 V, restricting their use with high voltage cathodes such as NMC for high energy density. A technique involving atomic layer deposition (ALD) of Al2O3 to stabilize the polyether-based electrolyte with 4 V class cathodes is described. With a 2 nm Al2O3 coating, the capacity retention stays at 84.7% after 80 cycles and 70.3% after 180 cycles for the polyether-based electrolyte. Without the coating, the capacity drops more than 50% after only 20 cycles. This study opens new opportunity to develop safe electrolytes for lithium batteries with high energy density. In the final section, we propose a new polymer electrolyte, a poly(vinylidene fluoride) (PVDF) polymer electrolyte with organic plasticizer dimethylformamide (DMF), which possesses compatibility with 4V cathode for high energy density and high ionic conductivity (1.2×10-4 S/cm) at room temperature. This polymer electrolyte can be used as a supplement for the polyether-based electrolytes we discussed in the first two sections. In this polymer electrolyte, palygorskite ((Mg,Al)2Si4O10(OH)) nanowires are introduced to form composite solid electrolytes (CPE) to enhance both stiffness and toughness of PVDF/DMF-based polymer electrolyte. With 5 wt % of palygorskite nanowires, the elastic modulus of the PVDF-DMF CPE increases from 9.0 MPa to 96 MPa, and its yield stress increases by 200%. We further demonstrate that full cells composed of Li(Ni1/3Mn1/3Co1/3)O2 (NMC 111) cathode, PVDF-DMF/palygorskite CPE, and lithium metal anode, can be cycled over 200 times at 0.3 C, with 97% capacity retention. Moreover, the PVDF-DMF electrolyte is nonflammable, making it a safer alternative to the conventional liquid electrolyte. Our work illustrates that the PVDF-DMF/palygorskite CPE is a promising electrolyte for solid state batteries with better safety and cycling performance. Collectively, we study the polyether-based polymer electrolyte and ceramic electrolyte to combine their advantages through the ice-templating method in a battery, use ALD technique to stabilize polyether-based electrolyte for high energy density, and propose an alternative PVDF/DMF-based polymer electrolyte with nanowire additives for high energy density and stable cycling, contributing to the rechargeable solid-state batteries, with better safety, higher energy density and better cycling stability.

Thesis (Ph. D.)--University of Hong Kong, 2002. / Includes bibliographical references.

The world faces two major energy-related challenges: reducing greenhouse-gas emissions and improving energy security. Wind-electricity, a clean and environmentally sustainable energy source, appears promising. However, its intermittency is problematic when used as a supply for on-demand electricity. Wind-electricity can be used for space heating when combined with thermal-storage systems; although its intermittency can result in periods of excess electricity. To reduce the excess, this thesis proposes using wind-electricity for thermal-storage and electric-vehicles. Four charging procedures are designed and developed. Data from an eastern Canadian wind-farm is used to demonstrate the procedures. The results are compared and discussed in terms of the supply of wind-electricity and its ability to meet the energy requirements of these services. Depending on the procedure, wind-electricity displaced between 20 and 26 GWh of energy previously required for space-heating and transportation, demonstrating that wind-electricity, with intermittently-chargeable loads using storage, is a solution to the intermittency problem.

No description available.

Thesis (M.S.)--Rochester Institute of Technology, 1992. / Typescript. Includes bibliographical references (leaf 41).

Thesis (M.Phil.)--University of Hong Kong, 2003. / Includes bibliographical references. Also available in print.

This thesis reports exploratory studies on the synthesis and characterisation of new compounds as cathode materials for second generation sodium batteries, with a particular emphasis on preparing new iron-phosphite and molybdenum oxyfluoride cathode materials. Seven different compounds are hereby reported: the sodium iron fluoro-phosphite of formula NaFe₃(HPO₃)₂[(H,F)PO₂OH)₆], the iron-phosphite Fe₂(HPO₃)₃, the sodium iron-phosphite NaFe(H₂PO₃)₄, the sodium iron phosphate NaFe(HPO₄)(H₂PO₄)₂·H₂O and three molybdenum oxyfluoride compounds of formula Na₂MoO₂F₄, KNaMoO₂F₄ and KMoO₂F₃. The synthesis of these compounds was performed by hydrothermal and solvothermal methods at temperatures ranging from 100 °C to 160 °C. The compounds were then fully characterised using the following techniques: single crystal X-ray diffraction (SXD), powder X-ray diffraction (PXRD), energy-dispersive X-ray spectroscopy (EDX), elemental analysis (EA), infrared spectroscopy (IR), thermogravimetric analysis (TGA) and electrochemical testing. Magnetic properties have also been studied where appropriate.

By replacing the intercalation electrode with a porous electrode and allowing lithium to react directly with O₂ from the air, the new rechargeable Li/O₂ battery system was studied. The porous cathode is comprised of carbon, catalyst and binder. The effect of every component was investigated. The catalyst was believed to play an important role in the performance of the electrode. A number of potential materials have been examined as the catalyst for the O₂ electrode. It suggests that the nature of the catalyst is a key factor controlling the performance of the O₂ electrode. Several catalysts based on first row transition metal oxides each with three different morphologies, bulk, nanoparticulate and mesoporous were studied. The influence of the morphology on the discharge and charge voltage, discharge capacity and cyclability were examined. Among all the catalysts studied, α-MnO₂ nanowires was found to be the best candidate. The reversible capacities of 3000 mAhg⁻¹(normalised by the mass of carbon) or 505 mAhg⁻¹ (based on the total mass of cathode + O₂ ) was obtained. Some of other factors, such as type of carbon, type of binder, type of electrolyte, the construction of cathode and the modification of the catalyst were also investigated, even just in the early stage. Capacity fading during cycling is the main problem in all the cases. A number of experiments were carried out to understand and attempt to avoid the fading problem. After successful synthesis of mesoporous α-Fe₂O₃ with unique properties (by Jiao et al.), the application of these materials in conventional Li battery was studied. Mesoporous α-Fe₂O₃ with ordered walls, mesoporous α-Fe₂O₃ with disordered walls and Fe₂O₃ nanoparticles were examined. It was also applied to examine the different factors that influence the rate of conversion electrodes, i.e., Li⁺ and e⁻ transport to and within the particles, as well as the rate of the two-phase reaction, demonstrating that for this conversion reaction electron transport to and within the particles is paramount.

A vehicular battery must consist of a large number of cells to provide the necessary energy and power. Management only at the level of the battery pack causes out-of-investigation cells and lack of cell equalization ability. Therefore, in the smart module concept, cells are first grouped into modules, which are then connected to the battery pack. Each module is an independent unit with a controller to investigate and control cells. Based on this concept, the work in this thesis redistributes tasks among module controllers and a central controller, applies a self-power design to enhance module independence, and selects the newly developed automotive ICs and sensors. Finally, a prototype of the BMS has been developed and successfully applied in a series of HEVs. / Cell equalization is a crucial technique to balance the cells inside a battery pack, with the ability to maximize pack capacity and protect cells from damage. For the bi-directional Cuk equalizing circuit, we propose a SoC based, instead of voltage based, fuzzy controller to intelligently determine the equalizing current, with the aim of reducing equalizing duration, enhancing equalizing efficiency, and protecting cells. The inputs to the controller are specially designed as the difference in SoC, the average SoC, and the total internal resistance. Because of the lack of theoretical analysis on equalizing current in the electrochemistry field, we utilize a fuzzy controller to incorporate the experience and knowledge of experts. Simulations and experiments verify its availability and efficacy. Especially for a LiFePO4 battery, a large SoC difference may lead to only a small difference in voltage and cause the failure of a traditional voltage based equalizer. The SoC based method successfully avoids this problem and obtains good performance in equalizing LiFePO4 cells. / Fast charge is intended to charge a battery as fast as possible, without any damage and with high energy efficiency, thus helping to reduce vehicle out-of-service time and promote the commercialization of EVs. Battery safety and charging efficiency are partially reflected by the increase in temperature during the charging process. Therefore, the aims of this thesis were to accelerate charging speed and reduce the temperature increase. We introduce a model predictive control framework to control the charging process. An RC model and the modified enhanced self-correcting model are employed to predict the future SoC in simulations and experiments respectively. A single-node lumped-parameter thermal model and a neural network trained by real experimental data are also applied respectively. In addition, a genetic algorithm is applied to optimize the charging current under multiple objectives and constraints. Simulation and experimental results strongly demonstrate that the Pareto front of the proposed algorithm dominates that of the popular constant current constant voltage charge method. / State of charge (SoC) is a battery state indicating its residual capacity. It is the fundamental state of the battery and is the basis for other battery operations. However, SoC is not a directly measurable state and has to be obtained by estimation techniques. Aiming to enhance the anti-noise ability of SoC estimation in a real vehicle environment, we propose a SoC estimation framework consisting of an adaptive nonlinear diffusion filter to reduce the noise of current measurement, a self-learning mechanism to remove its zero-drift, an open loop coulomb counting estimator and a model based closed loop filter to estimate SoC, and a data fusion unit to reach the final estimation result. In a simulation study, the closed loop filter is implemented based on an RC model and Hinfinity filter. In experiments and application, we modify the enhanced self-correcting model to model a type of LiFePO4 battery and apply an extended Kalman filter to estimate SoC. The framework has been demonstrated to improve accuracy and anti-noise ability, and achieves the technique upgrading goal recently published by the Chinese government. / The automotive industry has experienced a significant boom in recent years, accelerating the problems of energy shortage and environmental disruption around the world. To solve the two problems, electric vehicles (EVs), including battery electric vehicles (BEV), hybrid electric vehicles (HEV), and fuel-cell electric vehicles (FEV), have been proposed and studied in recent years. Despite the efforts devoted to the development of EVs by both the scientific research and industrial communities, there are still many obstacles hindering the mass commercialization of EVs. Among these obstacles, the battery system, the new energy storage component in EVs, is one of the most important yet most difficult parts of EV design, and the battery management system (BMS) is recognized as the single most important technical issue in the successful commercialization of EVs. / Yan Jingyu. / Adviser: Xu Yangsheng. / Source: Dissertation Abstracts International, Volume: 73-03, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 166-182). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Abstract not available