Composite PEDOT:PSS-PEO Layers for Improving Lithium Batteries**

This work investigates the application of poly(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOT:PSS) with polyethylene oxide (PEO) in lithium batteries (LIBs). This composite film comprising PEDOT:PSS and PEO was 3D printed onto a carbon nanofiber (CNF) substrate to serve as a layer between the polypropylene (PP) separator and the lithium anode in LIBs. The resulting CNF-PEDOT:PSS-PEO film exhibited superior mechanical and thermal properties compared to conventional PP separators. Mechanical tests revealed a high Young's modulus and puncture strength for the composite film. Thermal stability tests indicated that the CNF-PEDOT:PSS-PEO film remained stable at higher temperatures compared to the commercial PP separator, and combustion tests confirmed its superior fire-resistance properties. In terms of conductivity, the composite film maintained comparable ionic conductivity to the commercial PP separator. Electrochemical tests demonstrated that LIBs incorporating the CNF-PEDOT:PSS-PEO film exhibited slight improvement in cycling performance, with a 7.9 % increase in long-term cycling capacity compared to LIBs using only the commercial PP separator. These findings indicate that the developed CNF-PEDOT:PSS-PEO composite film holds promise to improve safety, while maintaining the electrochemical performance of LIBs by reducing dendrite formation and enhancing thermal stability.