A Polyoxadiazole-Derived Porous N-doped Carbon Coated Silicon Anode for Superior Lithium-ion Storage

The substantial volume expansion and low conductivity of Silicon (Si) during charge-discharge cycles significantly hinder its commercial application. This study synthesizes polyoxadiazole (POD) via an in situ polymerization method to coat Si. Porous structures are introduced through non-solvent-induced phase separation, and the POD-coated Si is then carbonized to fabricate porous N-doped carbon-coated Si (Si@C) composites. Moreover, the graphitization degree of the prepared carbon is regulated by modifying the chemical composition using different ratios of the diacid monomers, terephthalic acid (TPA), and isophthalic acid (IPA) during the POD synthesis process. The rational design of a core–shell architecture helps mitigate the volume expansion of Si to maintain electrode structural integrity and enhance electrode conductivity. Compared to the Si coated with carbon derived from POD synthesized using TPA (Si@CTPOD), the sample using IPA (Si@CIPOD) exhibits a higher graphitization degree and increased graphite nitrogen content, facilitating electrons/ions migration. The result indicates that the cell with Si@CIPOD demonstrates lower charge transfer resistance, improved cycling stability, and enhanced rate performance. The Si@CIPOD electrode achieves a specific capacity of 1068.5 mAh g −1 even after 200 cycles at 1 A g −1 . This work provides novel insights into regulating the graphitization degree to synthesize superior porous N-doped Si@C anodes.