Large-scale production of graphene encapsulated silicon nanospheres as flexible anodes for lithium ion batteries

Silicon (Si) is regarded as the most promising anode candidate for the next high energy density lithium ion batteries (LIBs) owing to its highest theoretical specific capacity and low lithiation potential. However, the practical application of Si-based materials is severely limited due to their enormous volume expansion, which leads to the breakdown of the electrode structure and shortens the cycle life. Herein, we successfully fabricated a free-standing graphene encapsulated silicon nanospheres (Si/rGO) film through homogenizing nano-Si in the lyotropic liquid crystallinity of graphene oxide (GO), followed by coating on the PET substrate and hot pressing technology. For the first time during the preparation process, the dispersion of nano-Si in deionized water was quantitatively characterized through real-time measurements of zeta potential and average particle size. Benefiting from the highly ordered layer-to-layer stacking and dense framework, the as-prepared Si/rGO film shows a high initial discharge capacity of 1727.2 mAh/g at 200 mA/g and superior cycling stability (1024.2 mAh/g over 200 cycles). This straightforward and easy-to-implement method can be used for industrial-scale production through continuous feeding.