In Batteria Electrochemical Polymerization to Form a Protective Conducting Layer on Se/C Cathodes for High-Performance Li–Se Batteries

The lithium–selenium (Li–Se) battery is a promising energy storage system for portable devices owing to its high energy density (2528 Wh L⁻¹) and electrical conductivity (10⁻³ S m⁻¹). The main issue with Li–Se batteries is their poor stability originating from the dissolution of Se-containing compounds. Hence, many studies have focused on the immobilization of Se using protective layers prepared via ex situ or in situ approaches. However, these strategies are too complicated and costly for practical use. Herein, a facile in batteria electrochemical treatment to form a protective conductive layer on a Se-based cathode is introduced. Specifically, aniline monomers added to an assembled Li–Se cell are polymerized into electrically conductive polyaniline. The treated Li–Se cell exhibits 40% higher capacity retention compared to untreated one. Moreover, at a high rate (4 C), the treated cell maintains a capacity of 1538 mAh cm⁻³, whereas the untreated cell exhibits no capacity. The enhanced cyclic stability and rate capability are attributed to the electrochemical formation of a uniform, ultrathin (≤10 nm) polyaniline layer, to confine lithium polyselenides with its C−N bonds, and improve ionic conductivity by self-doping with lithium salts to form delocalized polaron lattice in the polyaniline.