A new effective surface poly(1-vinyl-2-pyrrolidone) (PVP) grafted layer protected selective etching strategy has been used for preparing vinyl functionalized porous silica nanospheres (V-PSNSs). The main reaction mechanism was relied on the vinyl groups distributed on the surface of
outer vinyl silica nanospheres (V-SiO2) which can be polymerized with another vinyl monomer, such as 1-vinyl-2-pyrrolidone (VP), in the presence of initiator. It was observed from the research results that only grafting PVP on the surface of outer vinyl silica nanospheres (V-SiO2)
can V-PSNSs be obtained, because grafting PVP was able to protect outer V-SiO2 from being etched prior to inner pure silica (sSiO2). In addition, effect of the amounts of sSiO2@V-SiO2 as another monomer substrate on the formation of PVP grafted sSiO2@V-SiO2
(sSiO2@V-SiO2/PVP) was discussed. The results showed that the less of the sSiO2@V-SiO2 amounts, the thinner of the PVP grafted layer on the surface of sSiO2@V-SiO2, the poorer protection ability of the surface. In the present
study, V-PSNSs with 29 m2g−1 of BET surface areas and 0.1 cm3g−1 pore volumes were successfully synthesized by grafting 0.3 g of VP on the surface of 0.3 g of sSiO2@V-SiO2 and subsequent etching.
The application of the SiO 2 anodes for flexible and free-standing lithium-ion batteries (LIBs) is restricted by the weaknesses of SiO 2 nanoparticles , such as agglomeration, huge volume expansion and rapid capacity fading during charge/discharge cycles. Herein, the PVP-grafted-silica@carbon nanofibers (PVP-g-SiO 2 @CNF) flexible free-standing anode with high capacity and long cycle stability is successfully fabricated by PVP-grafted-SiO 2 , electrospinning and subsequent heat treatment . PVP modifies the interface between SiO 2 nanoparticles and electrospinning solution to prevent the nanoparticles from aggregation, which makes them are uniformly encapsulated in nanofibers. The uniform structure is beneficial to enhance the interface contact between SiO 2 and Li + , and alleviate volume expansion during lithiation . Furthermore, PVP introduces mesoporous into carbon nanofibers , facilitating the transports of ions and electrons to attain high-rate performance. As a flexible free-standing anode material for LIBs, PVP-g-SiO 2 @CNF achieves high reversible capacity, high-rate capacity and superior cycle stability (440 mAh g −1 at 0.1 A g −1 after 200 cycles), especially 89% capacity retention after 180° bending deformation . Consequently, enhanced capacity and cycle stability for flexible free-standing anode are available through PVP-grafted interface modification and electrospinning.
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