Alkali-ion batteries have revolutionized modern life through enabling the widespread application of portable electronic devices. The call for adapting renewable energy in many applications will also see an increase in the demand of alkali-ion batteries, specially to account for the intermittent nature of the renewable energy sources. However, the advancement of such technologies will require innovation on the forefront of materials development as well as fundamental understanding on the physical and chemical processes from atomic to device length scales. Herein, we focus on advancing energy storage devices such as alkali-ion batteries through cathode materials development and discovery as well as fundamental understanding through multiscale advanced synchrotron spectroscopic and microscopic characterizations. Multiscale electrochemical properties of cathode materials are unraveled through complementary characterizations and design principles are developed for stable cathode materials for alkali-ion batteries.
In Chapter 1, we provide a comprehensive background on alkali-ion batteries and cathode materials. The future prospect of Li-ion and beyond Li-ion batteries are summarized. Surface to bulk chemistry of alkali-ion cathode materials is introduced. The prospect of combined cationic and anionic redox processes to enhance the energy density of cathode materials is discussed. Structural and chemical complexities in cathode materials during electrochemical cycling as well as due to anionic redox are summarized.
In Chapter 2, we explain an inaugural effort on tuning the 3D nano/mesoscale elemental distribution of cathode materials to positively impact the electrochemical performance of cathode materials. We show that engineering the elemental distribution can take advantage of depth dependent redox reactions and curtail harmful side reactions at cathode-electrolyte interface which can stabilize the electrochemical performance.
In Chapter 3, we show that the surface to bulk chemistry of cathode particles is distinct under applied electrochemical potential. We show that the severe surface degradation at the beginning stages of cycling can impact the long-term cycling performance of cathode materials in alkali-ion batteries.
In Chapter 4, we utilize the structural and chemical complexities of sodium layered oxide materials to synthesize stable cathode materials for half cell and full cell sodium-ion batteries. Meanwhile, challenges with enabling long term cycling (more than 1000 cycles) are deciphered to be transition metal dissolution and local and global structural transformations.
In Chapter 5, we utilize anionic redox in conjunction with conventional cationic redox of cathode materials for alkali-ion batteries to enhance the energy density. We show that the stability of anionic redox is closely related to the local transition metal environment. We also show that a reversible evolution of local transition metal environment during cycling can lead to stable anionic redox.
In Chapter 6, we provide design principles for cathode materials for advanced alkali-ion batteries for application under extreme environments (e.g., outer space and nuclear power industries). For the first time, we systematically study the microstructural evolution of cathode materials under extreme irradiation and temperature to unravel the key factors affecting the stability of battery cathodes. Our experimental and computational studies show that a cathode material with smaller cationic antisite defect formation energy than another is more resilient under extreme environments. / Doctor of Philosophy / Alkali-ion batteries are finding many applications in our life, ranging from portable electronic devices, electric vehicles, grid energy storage, space exploration and so on. Cathode materials play a crucial role in the overall performance of alkali-ion batteries. Reliable application of alkali-ion batteries requires stable and high-energy cathode materials. Hence, design principles must be developed for high-performance cathode materials. Such design principles can be benefited from advanced characterizations that can reveal the surface-to-bulk properties of cathode materials. Herein, we focus on formulating design principles for cathode materials for alkali-ion batteries. Aided by advanced synchrotron characterizations, we reveal the surface-to-bulk properties of cathodes and their role on the long-term stability of alkali-ion batteries. We present tuning structural and chemical complexities as a method of designing advanced cathode materials. We show that energy density of cathode materials can be enhanced by taking advantage of a combined cationic and anionic redox. Lastly, we show design principles for stable cathode materials under extreme conditions in outer space and nuclear power industries (under extreme irradiation and temperature). Our study shows that structurally resilient cathode materials under extreme irradiation and temperature can be designed if the size of positively charged cations in cathode materials are almost similar. Our study provides valuable insights on the development of advanced cathode materials for alkali-ion batteries which can aid the future development of energy storage devices.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/103600 |
| Date | 03 June 2021 |
| Creators | Rahman, Muhammad Mominur |
| Contributors | Chemistry, Lin, Feng, Madsen, Louis A., Li, Zheng, Morris, Amanda J. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf, application/x-zip-compressed |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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