Free‐Standing Graphene‐Encapsulated Silicon Nanoparticle Aerogel as an Anode for Lithium Ion Batteries

Silicon is a remarkable candidate for lithium‐ion battery anodes, due to the highest theoretical specific capacity, low working potential, and abundance on earth. However, the volume of Si changes ≈300 % during the lithiation–delithiation cycling, leading to pulverization and poor electrical contact between Si and the current collector, resulting in fast fading capacity. To overcome these problems, we develop a novel free‐standing anode by encapsulating Si nanoparticles into a lightweight, flexible, and conductive graphene network by utilizing a facile freeze‐drying strategy. The Si nanoparticles are tightly anchored on the ultrathin and flexible graphene sheets, which can serve as mechanical support, electrical network, and buffer layer for Si. This free‐standing aerogel exhibits superior electrochemical performance, and the specific capacity is 617 mA h g −1 after 50 cycles at a current density of 0.8 A g −1 , 4 times that of a traditional Si electrode on Cu foil fabricated by a typical slurry method.