At the moment, there is a significant push towards environmentally friendly energy production and gasoline-free transportation technologies. As a result, there is a renewed interest in energy storage devices such as lithium-ion batteries which will play a key role in providing energy storage capability for these applications. However, the current battery technology is reaching its limits and may not meet future energy storage demands. The increased demand and the limited lithium reserves in geographically remote areas of the earth will lead to higher cost of Li. The alternative battery technologies, such as sodium-ion batteries, are promising due to their low cost, abundance, and low toxic electrode materials. The electrodes such as silicon (Si), germanium (Ge), tin (Sn), and their alloys have been studied as Li battery anode. These anode materials are known to expand significantly upon reacting with Li and a similar, or more severe, behavior can be expected when they react with Na as the cationic radius of Na is larger than that of Li. Consequently, the anode materials will experience a significant amount of stresses which, if not managed properly, will degrade the electrodes rapidly. The stresses are responsible for cracking, pulverization, and ultimate failure of the electrode, and they also affect the transport phenomena.
A large body of literature exists on electrochemical characterizations of various high capacity lithium and sodium-ion battery electrodes such as Si, Ge, and Sn electrodes. However, real-time chemo-mechanical characterization has not been well explored much on those battery electrodes because of complicated experimental setup and data acquisition method.
Thin film Ge, Sn, and SiO2 electrodes are fabricated using various thin film deposition techniques. The fabricated electrodes are electrochemically cycled against Li and Na while recording the variation of electrochemical, mechanical, and transport properties to understand the key factors influencing the performance of the batteries. The real-time stresses during electrochemical cycling are recorded with the help of a multi-beam optical sensor (MOS) setup. A high magnitude of stress is recorded in both Li and Na-ion batteries, which is detrimental to the chemical and mechanical stability of the electrodes. Cycled electrodes are characterized by SEM and AFM to understand the morphological changes of the thin film electrode upon cycling.
Thin film Ge, Sn, and SiO2 electrodes are fabricated using various thin film deposition techniques. The fabricated electrodes are electrochemically cycled against Li and Na while recording the variation of electrochemical, mechanical, and transport properties to understand the key factors influencing the performance of the batteries. The real-time stresses during electrochemical cycling are recorded with the help of a multi-beam optical sensor (MOS) setup. A high magnitude of stress is recorded in both Li and Na-ion batteries, which is detrimental to the chemical and mechanical stability of the electrodes. Cycled electrodes are characterized by SEM and AFM to understand the morphological changes of the thin film electrode upon cycling.
The observed mechanics and the electrochemical response of Na-ion battery electrodes are compared to the existing literature on Li-ion battery materials. The data and observations presented in the thesis will be helpful in developing and designing future damage tolerant electrode architecture for future application.
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