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Polyhedral oligomeric silsesquioxane (POSS)-derived Si@C anode material is prepared by the copolymerization of octavinyl-polyhedral oligomeric silsesquioxane (octavinyl-POSS) and styrene. Octavinyl-polyhedral oligomeric silsesquioxane has an inorganic core (-Si8O12) and an organic vinyl shell. Carbonization of the core-shell structured organic-inorganic hybrid precursor results in the formation of carbon protected Si-based anode material applicable for lithium ion battery. The initial discharge capacity of the battery based on the as-obtained Si@C material Si reaches 1500 mAh g−1. After 550 charge-discharge cycles, a high capacity of 1430 mAh g−1 was maintained. A combined XRD, XPS and TEM analysis was performed to investigate the variation of the discharge performance during the cycling experiments. The results show that the decrease in discharge capacity in the first few cycles is related to the formation of solid electrolyte interphase (SEI). The subsequent rise in the capacity can be ascribed to the gradual morphology evolution of the anode material and the loss of capacity after long-term cycles is due to the structural pulverization of silicon within the electrode. Our results not only show the high potential of the novel electrode material but also provide insight into the dynamic features of the material during battery cycling, which is useful for the future design of high-performance electrode material.

The ionic conductivity of the separator is the essential parameter for performance of lithium ion batteries. Herein, we synthesize a new composite separator through coating of the mixture of poly (methyl methacrylate) and alpha alumina on the surface of commercial polyethylene separator. Benefiting from the excellent electrolyte wettability and high ionic conductivity of the poly (methyl methacrylate), the synthesized separator exhibits promising electrochemical properties. The lithium ion diffusion coefficient of the synthesized separator is 1.48 × 10 À 15 cm 2 s -1 , higher than that of the pristine polyethylene separator (0.808 × 10 À 15 cm 2 s -1 ). Furthermore, the introduced alumina can prevent the blockage of the ion transport channels from the electrolyte absorption-induced swelling of poly (methyl methacrylate), which in turn can improve the cycle performance of the thus-assembled cells. it means that the cell assembled form the synthesized composite separator shows high charge-discharge cyclability, i. e. the cell assembled from the synthesized composite separator maintains 93.9% of initial discharge capacity after 200 charge-discharge cycles under the rate of 1 C.