This paper seeks to develop safe, low-cost, and long-life all-solid-state Li-ion batteries (LIBs) using Doped Prussian Blue Analogs (PBAs) thin-film cathode materials. SmCuFe(CN)₆ and other PBAs were synthesized and characterized. Coin batteries were prepared with the synthesized SmCuFe(CN)₆ and electrochemical measurements were performed. Overall, the SmCuFe(CN)₆ coin batteries show a good cyclic performance after 10 cycles, retaining a discharge capacity of around 50 mAh/g. However, the electrochemical performance of our cathodes is poor. Further research is in progress to identify the cause of the low capacity and find the possible remedies to improve it. DFT-based calculations were performed to better understand the structure and electronic properties of the PBAs. The preliminary results show that doping CuFeCN with Sm can distort the local structure of CuFeCN.