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

Abstract

Binder-free freestanding flexible Si nanoparticles-multi-walled carbon nanotubes (SiNPs-MWNTs) composite paper anodes have been prepared by the 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 the volume expansion of Si. Through control of Si/C weight ratio in the composite, we found out the SiNPs-MWNTs electrode with 3:2 Si/C ratio exhibits the optimal balance between the high capacity of SiNPs and the high electrical conductivity and structural stabilization quality of MWNTs, leading to high rate capability as well as cycle performance superior to the conventional slurry-cast SiNPs electrode using binder and Cu current collector. The reversible capacity can be recovered to 1790 mAh/g (based on the total composite weight, the same below) when the current rate returns to 100 mA/g. After 100 cycles, the electrode retains capacity of 1170 mAh/g at 100 mA/g and 750 mAh/g at 500 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. Figure 1