Secondary batteries are crucial for eco-friendly systems, but existing technologies struggle with energy density and safety issues. This study aims to develop a next-generation battery utilizing quasi-solid electrolytes (QSE), which combine the advantages of both liquid and solid electrolytes. However, QSEs often lack the mechanical strength necessary to prevent lithium dendrite growth. To address this challenge, two strategies were proposed and experimentally validated. The first strategy involves creating a QSE-separator composite (QSE-PI) by integrating QSE with a polyimide (PI) separator. Among the various options, PI with a thickness greater than 20 μm and a pore size of 2-5 μm exhibited superior electrolyte absorption and dendrite suppression. This configuration allowed for rapid lithium plating/stripping, high ionic conductivity (1.7 × 10^-3 S cm^-1), and excellent Coulombic efficiency (99.94%).The second strategy incorporates silica (SiO₂) as a ceramic filler in the QSE-PI to enhance mechanical strength and ion transport. The addition of SiO₂ disrupted polymer crystallinity, increased the amorphous regions, and effectively suppressed dendrite formation. Notably, SiO₂ particles larger than 10 μm improved cycle stability, with the composite maintaining performance for over 50 cycles, compared to only 30 cycles for the version without filler.

A high temperature sintering process for solid electrolyte is the main cause of the increase in manufacturing costs of SOFCs. In this study, we developed a novel flash light sintering technique as an alternative sintering process of the conventional thermal sintering process. The YSZ electrolyte films were fabricated by conventional screen-printing method and the flash light sintering process and ESB sintering aid were applied to improve the flash light sinterability of the YSZ electrolyte. In the flash light sintering process, the effect of various pulse conditions such as energy density, and pulse interval were investigated and the microstructure, crystallinity, and sintering behavior of the sintered films were analyzed to demonstrate the effectiveness of the flash light sintering process. The flash light sintered YSZ electrolyte layer was used to fabricate the anode-supported SOFCs and its functionality is successfully demonstrated with the high open circuit voltage. The significance of this study includes minimization of the process time from tens of hours to just a few seconds, thus facilitating the commercialization of SOFCs.