Self-Assembled Porous-Silica within N-Doped Carbon Nanofibers as Ultra-flexible Anodes for Soft Lithium Batteries

Silica is an attractive anode material for soft lithium batteries owing to its high specific capacity, but it suffers severe problems of large volume change and unstable solid-electrolyte interface. Moreover, it is a challenge to fabricate flexible silica anodes. Here, we report a low-cost and scalable strategy to create flexible anodes of N-doped carbon nanofiber-confined porous silica (p-SiO2@iN-CNF) by developing a sol-gel electrospinning process followed by carbonization. This approach causes the p-SiO2 nanoparticles (NPs) to be self-assembled within the N-CNFs, which act like elastomer and electrolyte barrier to accommodate volume changes and to enhance the stability of SiO2, whereas the NPs act as soft plasticizer providing strength to the CNF skeletons. Benefiting from the hierarchical structures, the anodes with high p-SiO2 loadings (>1.6 mg/cm(2)) exhibit exceptional cycling performance (>1,000 cycles) in terms of bending, current rate, and capacity. Moreover, the batteries remain stable when discharging at 0.5 C and charging at 2 C.