Binder-Free Freestanding Flexible Si Nanoparticles-Multi-Walled Carbon Nanotubes Composite Anodes for Li-Ion Batteries

Binder-free freestanding flexible Si nanoparticles-multi-walled carbon nanotubes (SiNPs-MWNTs) composite paper anodes have been prepared by simple, inexpensive, and scalable approach of ultra-sonication and pressure filtration. The 3D network of MWNTs forms a continuous conductive pathway within the composite structure, which ensures sufficient electrical conductivity, holds the particles together, and alleviates volume expansion of Si. Through control of Si/C weight ratio, we found out the SiNPs-MWNTs electrode with 3: 2 Si/C ratio exhibits the optimal balance between high capacity of SiNPs and high conductivity and structural stabilization quality of MWNTs, leading to high rate capability as well as specific capacity and cycle performance superior to conventional slurry-cast SiNPs anode using binder and Cu current collector. After 100 cycles, the electrode retains capacity of 1170 mAh/g at 100 mA/g. The freestanding feature of our electrode eliminates the non-active mass, which is promising for enhanced capacity and energy density of Li-ion cells.