Effect of electrode structure on performance of Si anode in Li-ion batteries: Si particle size and conductive additive

The effects of Si particle size and the amount of carbon-based conductive additive (CA) on the performance of a Si anode in a Li-ion battery are investigated by adopting combinations of two different Si particle sizes (20 and 3 μm on average) and CA contents (15 and 30 wt.%), respectively. The CA contains graphitic flakes and nano-sized carbon black. Cyclic voltammetry, charge-discharge tests, scanning electron microscopy and X-ray diffraction establish that the CA content has a profound effect on the cycle-life and irreversible capacity of the Si anode. The former increases, while the latter decreases significantly with increasing CA content. Reducing the particle size of Si, on the other hand, facilitates the alloying/de-alloying kinetics. For instance a cycle-life of over 50 cycles with >96% capacity retention at a charge capacity of 600 mAh per g-Si has been demonstrated by adopting of 30 wt.% CA and 3 μm Si particles.