Defect-free, size-tunable graphene for high-performance lithium ion battery

The scalable preparation of graphene in control of its structure would significantly improve its commercial viability. Despite intense research in this area, the size control of defect-free graphene (df-G) without any trace of oxidation or structural damage remains a key challenge. Here, we propose a new scalable route for generating df-G with a controllable size of submicron to micron through sequential insertion of potassium and pyridine at low temperature. Structural and chemical analyses confirm that the df-G perfectly preserves the intrinsic properties of graphene. The Co₃O₄ (<50 nm) wrapped by ∼10.5 μm² df-G has unprecedented capacity, rate capability, and cycling stability with capacities as high as 1050 mAh g^-1 at 500 mA g^-1 and 900 mAh g^-1 at 1000 mA g^-1 even after 200 cycles, which suggests enticing potential for the use in high performance lithium ion batteries.