Pristine graphene for advanced electrochemical energy applications

The research on preparation and application of defect-free pristine graphene (PG) is a hot topic. However, large-scale non-destructive exfoliation of graphite into single-layered PG still remains a challenge. The common method of exfoliating graphite is based on the oxidation-exfoliation-reduction strategy. Nevertheless, there are many structural defects for the graphene produced by this approach due to the excessive oxidation and incomplete reduction processes, which significantly deteriorate the intrinsic properties of graphene. Therefore, researchers attempt to develop non-oxidative chemical/physical methods to directly exfoliate graphite into PG layers without damaging the sp2 carbon lattice, and utilize PG-based materials and structures for various applications. Herein, we review recent development on the direct exfoliation of graphite into PG via non-oxidative chemical methods. Firstly, we outline the various exfoliation systems based on different acting forces as well as liquid media, which are two key factors determining the ultimate exfoliation effect. Then the structural qualities of the PG sheets are discussed. Finally, we summarize in detail the diverse electrochemical energy applications of PG materials, and provide some perspectives for the future developments of PG materials towards commercialization.