Deposition SnO₂/nitrogen-doped graphene nanocomposites on the separator: A new type of flexible electrode for energy storage devices

It is currently very urgent to develop flexible energy storage devices because of the growing academic interest in and strong technical demand of flexible electronics. Exploration of high-performance electrode materials and a corresponding assembly method for fabrication of flexible energy storage devices plays a critical role in fulfilling this demand. Here, we have developed a facile, economic, and green hydrothermal process to synthesize ultrasmall SnO₂ nanocrystallites/nitrogen-doped graphene nanocomposites (USNGs) as a high-performance electrode material for Li-ion batteries (LIBs). Furthermore, using the glass microfiber filters (GMFs) as supporting substrate, the novel flexible USNG-GMF bilayered films have been prepared by depositing the as-prepared USNG on GMF through a simple vacuum filtration. Significantly, for the first time, the flexible USNG-GMF bilayered films have directly been used for assembling LIBs, where the GMF further functions as a separator. The obtained highly robust, binder-free, conducting agent-free, and current collector-free new type of flexible electrodes show excellent LIB performance.