One of the main challenges in rechargeable energy sources is providing high safety, high energy and power density with reliable cycling performance and operational stability. Rechargeable Lithium ion batteries (rLiBs) are one of the most frequent types of cells employed in portable electronics due to their superior specific power and energy. Typical rLiBs make use of liquid electrolytes. However, these devices have several disadvantages, like the need of separators that limits their downscaling and the high risk of fire and explosion due to leakage. Thus, suitable solid electrolytes are needed to overcome these drawbacks. Inorganic glass-based electrolytes are very promising materials due their ease of preparation and can be easily downscalable which can provide an advantage due to short Li+ diffusion lengths. The demand for flexible and lighter batteries with large energy densities and power output is continuously increasing. The growth in thin film technology and miniaturization applications (i.e. IoT) gave a significant boost to this field. The use of all solid-state batteries (ASSB) could surmount the limitations of commonly used Li-ion batteries employing liquid electrolytes. Also, ASSB can explore other routes for battery integration that typical liquid electrolyte batteries cannot, such as form factor, scalability and material property control. The introduction of these type of new devices will be helpful to fulfill the needs of miniaturized power sources for modern society. The main purpose of HS-Glass+ion is to find ways of obtaining highly stable glass-based (HSG) electrolytes that can enhance thermal stability, ion conduction and improve interfacial effects, integrate them in thin film ASSB and systematically study its effects on device performance. In this project, thin film solid state electrolytes are grown to study the deposition temperature dependence on ionic conductivity, battery performance and stability. The structural changes in these materials due to process conditions will definitely modify their performance and affect the overall performance on a complete thin film battery device in a way that has not yet been explored so far in the field of thin film ASSB. To test these possible effects, several fully working thin film batteries were fabricated in HS-Glass+ion. The battery devices were based on Li4Ti5O12 (LTO) cathode material electrode, Lithium Phosporous Oxinitride (LiPON) solid electrolyte layers with different properties and Lithium metal as anode electrode. These batteries give an open circuit potential of 1.5 V. These thin film ASSB were characterized in order to determine their performance and dependence on LiPON properties. The reported outcome is interpreted as the result of a change in the local structure of the glassy network of LiPON which makes Li diffusion through vacancies and interstitials tougher to occur. This is related to the creation of a HSG LiPON layer with a closed-packed structure which is attained at deposition temperatures close to the glass transition temperature (Tg) of the material.
