This project aims to study the redox mechanism of composite electrodes in solid-state chloride-ion batteries (CIBs) via tender x-ray absorption/emission spectroscopy. By using solid cells with composite electrodes as samples, the emission lines and the absorption spectra can be measured on Cl K-edge and the respective metal edges, allowing us to probe the redox-active species and their evolution at different charge states and cycles. In combination with other complementary techniques, we want to understand the fundamental mechanism of the conversion reactions for these metal chloride electrodes, and to identify the factors hindering the reversibility and stability in prolonged cycles. The findings will provide a valuable guidance on the selection of metal chloride cathodes, and help the rational design and optimization of CIBs for enhanced energy/power density and cycle life.