The growth of modern technical prospects and our viable society as a whole has been greatly aided by the development of energy storage systems (ESSs). Like other technologies, the ESSs have undergone several major developments since its first conceptual proposal to ubiquitous commercialization and adaptation into our contemporary lifestyle. Lithium-ion batteries (LIBs) have emerged as prime candidates within the available ESS. LIBs are universal in our modern digital life. LIBs boast moderate energy density and long cycle life. However, traditional Li-ion liquid electrolyte batteries' limited energy density and safety concerns have propelled the expansion of other technologies, e.g., solid electrolyte batteries (SSBs).

Solid electrolytes offer significantly higher energy density with the employment of lithium metal as an anode and fewer safety concerns than liquid electrolytes. In addition, the durability and longevity of the SSBs are also promising prospects. With the advancement of modern materials knowledge, many candidates, such as the garnet type (Li7La3Zr2O12, LLZO), NASICON type (Li1.3Al0.3Ti1.7(PO4)3, LATP), have been identified for SSBs. Nonetheless, as this emerging technology, many significant challenges still need to be ameliorated. The manufacturing process of solid electrolytes is not yet industrialized and profitable for the assembly community. Existing solid-state electrolyte synthesis technologies can produce the quality of material required for state-of-the-art SSBs. However, there is no denying the time constraints, the volume aspect, and, most importantly, the cost associated with the manufacturing process, which still needs further development.

In this thesis, the Spray-flame synthesis (SFS) technique has been adapted to produce LLZO, LATP, and LYZP [Y-doped LiZr2(PO4)3] solid electrolytes. SFS is easily scalable and can tune the synthesized material's size/shape/ stoichiometry. The as-synthesized samples were characterized through various techniques to understand the effect of precursor solution doping. The crystalline phase of the as-synthesized samples was LZO (La2Zr2O7), anatase-TiO2, and ZrO2 for LLZO, LATP, and LYZP, respectively. The rest of the elements Li (in the case of LLZO), Li, Al, phosphate (in the case of LATP), and Li, Y, phosphate (in the case of LYZP) were present on the surface of the crystalline particles as an amorphous phase. Subsequent calcination steps up to 1000 °C for LLZO, 1300 °C for LYZP, and 750 °C for LATP were required to form the intended phase. Excess of Li precursor (25 % extra) was added in all the SFS reactions to compensate for Li loss during the calcination step. Moreover, due to the homogeneous mixing and presence of neighboring elemental sources in the as-synthesized samples, a short (1h) under the O2 atmosphere calcination step was sufficient to obtain a high ionic conductive phase.