Atomic-Scale Control of Silicon Expansion Space as Ultrastable Battery Anodes.

Development of electrode materials with high capability and long cycle life are central issues for lithium-ion batteries (LIBs). Here, we report an architecture of three-dimensional (3D) flexible silicon and graphene/carbon nanofibers (FSiGCNFs) with atomic-scale control of the expansion space as the binder-free anode for flexible LIBs. The FSiGCNFs with Si nanoparticles surrounded by accurate and controllable void spaces ensure excellent mechanical strength and afford sufficient space to overcome the damage caused by the volume expansion of Si nanoparticles during charge and discharge processes. This 3D porous structure possessing built-in void space between the Si and graphene/carbon matrix not only limits most solid-electrolyte interphase formation to the outer surface, instead of on the surface of individual NPs, and increases its stability but also achieves highly efficient channels for the fast transport of both electrons and lithium ions during cycling, thus offering outstanding electrochemical performance (2002 mAh g(-1) at a current density of 700 mA g(-1) over 1050 cycles corresponding to 3840 mAh g(-1) for silicon alone and 582 mAh g(-1) at the highest current density of 28 000 mA g(-1)).