Scalable Fabrication of LiMn₂O₄/Polythiophene with Improved Electrochemical Performance for Lithium-Ion Batteries

Abstract

Surface modification with conductive polymers has been widely used to improve the electrochemical performance of cathode materials for lithium-ion batteries. However, the conductive polymer-modified cathodes universally employ a solution-based oxidation polymerization method, making suspicious Li+ leaching of the cathodes during the modification process. In this paper, we report on a simple method for scalable fabrication of polythiophene-coated LiMn2O4 (LMO/PTh) through a room-temperature-and-pressure chemical vapor deposition approach. Thiophene can be oxidized by surface Mn4+ ions of LMO, yielding in situ PTh formation upon LMO. The resulting LMO/PTh composites are characterized with XRD, SEM, TEM, ICP–OES, XPS, and AES techniques. A thin layer of PTh with an average thickness of ca. 1.5 nm can be coated onto the LMO particles, using 300 μL of thiophene relative to 10 g of LMO powders. The LMO/PTh-300 composite manifests improved aging resistance and electrochemical performance at both room temperature and 55 °C, compared with pristine LMO. The improved properties are attributed to the PTh coating, which not only functions as a moisture-buffering layer but also serves as an absorber to eliminate HF in the electrolyte.