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

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.

Automated summary

In this study, Si-based microcapsule materials with polyimide shell were synthesized using a novel in situ polymerization and imidization method. The polyimide shell, as a mechanically stable polymer, effectively alleviates the volume effect of silicon nanoparticles, stabilizes the electrode construction, suppresses side reactions, and helps to form a flexible, homogeneous, and low-resistance solid electrolyte interphase (SEI). Furthermore, the polyimide shell has Li+ conductivity and electrochemical activity, which increases the electrochemical activity of the silicon anode.