Multidimensional, Superflexible, and Binder-free CNT-rGO/Si Buckypaper as Anodes for Lithium-Ion Batteries and Electrochemical Performance

It is a challenge to prepare self-supporting electrodes with superflexibility and excellent electrochemical properties for lithium-ion batteries (LIBs) using a simple method. The utilization of Si in LIB anodes is widespread due to its high specific capacity. However, the significant volume expansion during charge-discharge cycles hinders its large-scale application, and the Si-carbon anodes are mostly in powder form. Herein, a simple and low-cost method for synthesizing self-supporting superflexible Si-carbon electrodes via ultrasonic self-assembly, followed by directional pressure filtration technology, is proposed. Ultrasonic self-assembly was realized during the formation of a homogeneous and stable suspension of Si, carbon nanotubes (CNTs), and reduced graphene oxide (rGO), which was followed by a directional pressure filtration technique, leading to binder-free, self-supported, and superflexible buckypaper (BP). For the BP, CNTs were inserted into the exfoliated rGO nanosheets to avoid restacking and agglomeration, while the Si micro- and nanoparticles were uniformly filled between the CNTs and the rGO nanosheets, forming a three-dimensional network structure. The superflexible carbon skeleton not only provided cushioning and support for the volume changes of Si but also provided multiple conductive pathways. The BP with 50 nm Si (CNT-rGO/Si-0.05) had a residual capacity of 540 mAh/g after 200 cycles at 820 mA/g, which is 91% of that at the fourth cycle. Its structure had almost no damage after 1500 successive cycles of 180° bending-straightening.