Reaction ball milling self-assembly derived micro/nano-Si flakes as the high tap density Si source for high-performance Si@C anode materials

Micro/nano-Si flakes were obtained by a facile approach of reaction ball milling self-assembly, and then, a Si@C anode material with a carbon content of 17.7wt% was synthesized by combining the Si flakes with phenol formaldehyde resin. It was revealed that the micro/nano-Si flakes inherited the advantages of both nano-Si and bulk Si, showing not only a considerable surface area of 65.6 m 2 g −1 but also a high tap density of 0.66 g cm −3 . The Si@C anode showed outstanding electrochemical performance, particularly its high volumetric capacity, due to the formation of dual-layer SiO x /C film on the micro/nano-Si. The Si@C anode delivered a gravimetric/volumetric capacity as high as 1721.9 mAh g −1 /1239.8 mAh cm −3 at 0.05 A g −1 and preserved a large gravimetric/volumetric capacity of 1028.7 mAh g −1 /740.7 mAh cm −3 at 2.0 A g −1 . It retained 92.0% of its initial capacity after 200 cycles at 0.5 A g −1 .