Introducing electrolytic electrochemical polymerization for constructing protective layers on Ni‐rich cathodes of Li‐ion batteries

Abstract LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) is the most promising cathode for high‐energy Li‐ion batteries, despite its poor cycling stability that originates from the reactions that occur with the electrolyte. Herein, to solve this interfacial issue, a facile electrolytic electrochemical polymerization process was introduced in this paper, and a uniform conductive electrolyte interface (polyaniline) was successfully constructed on the surface of the NCM811 porous electrode (PANI‐NCM), which facilitated the charge transfer during charge/discharge. The side reactions at the interface between the cathode and the electrolyte are suppressed, and thereby, the cycling performance and rate capability are considerably improved. PANI‐NCM delivers an initial capacity of 157.2 mAh·g −1 as well as excellent cyclability (capacity retention of 88% after 500 cycles at 2C), whereas the capacity of the bare NCM811 has dropped to 31.3 mAh·g −1 . In addition, polypyrrole and polythiophene also can be formed through electrolytic electrochemical polymerization process, which provides a practicable tactic to modify the interfacial stability of cathodes for high‐energy Li‐ion batteries.