Elasticity-related periodical Li storage behavior delivered by porous graphene
Porous carbon materials have been widely used as active materials, additives or substrates in the energy storage devices using Li+ as charge carrier. Fluctuations in the cycling performance have been widely observed for the Li storage by porous carbon materials, but the reason for such phenomena has not been clearly revealed. In this work, periodic variations of capacities and coulombic efficiencies are observed in the lithium insertion/extraction cycles of fibre-like graphene 3D networks. Volume expansion of the nanopores in graphene networks aroused by Li+ accumulation and their elastic compression that leads to Li+ release are considered as the key reasons for the periodic behavior. For the flexible few-layered graphene, the increase of the pore volume is remained, thus leading to a continuous increase of the Li storage capacity. Our results reveal a clear relationship between the elasticity of a porous carbon material and its Li storage performance.