In Situ Polymerized and Imidized Si@Polyimide Microcapsules with Flexible Solid‐Electrolyte Interphase and Enhanced Electrochemical Activity for Li‐Storage

Abstract A novel in situ polymerization and imidization method is adopted to synthesize Si‐based microcapsule materials with polyimide shell. As a mechanically stable polymer, polyimide microcapsule shell can effectively alleviate the volume effect of silicon nanoparticles during alloying/de‐alloying reactions, stabilize the electrode construction, suppress the serious side reactions of electrolyte components on silicon anode surface, and help to form a flexible, homogeneous and low‐resistance solid electrolyte interphase (SEI). In addition, the conjugated carbonyl groups of polyimide make it Li + ‐conductive and electrochemically active, thus increasing the electrochemical activity of silicon anode. The as‐prepared Si@polyimide microcapsules manifest high initial coulombic efficiency of 91.1 %, high initial discharge capacity of 2798.7 mA h g −1 at 210 mA g −1 (0.05 C), good rate behavior with a capacity of 1954 mA h g −1 at 10 C current rate, and considerably improved cycling performance preserving a capacity of 1239.9 mA h g −1 at 4.2 A g −1 (1 C) after 300 cycles.