Graphene has the characteristics of high conductivity, high specific surface area, two-dimensional continuous structure, etc., which can effectively improve the performance of a variety of electrochemical energy storage materials (such as silicon negative stage, lithium transition metal oxide cathode, sulfur cathode, lithium metal anode and Air cathode, etc.). However, there are still some problems when graphene is applied to the field of electrochemical energy storage. For example, the chemical vapor deposition method can effectively prepare low-defect single-layer graphene, but it is difficult to meet the needs of large-scale applications in the energy field in terms of material yield and cost control; while the chemical peeling method and mechanical peeling method are both in terms of yield and cost. It has certain advantages, but it is lacking in the quality of graphene, which limits the electrochemical performance of graphene-based electrode materials.

　　Therefore, it is necessary to develop a new strategy for low-cost mass production of high-quality graphene. To this end, the team of Professor Gao Chao from the Department of Polymer Science of Zhejiang University proposed a method for quantitatively producing high-quality graphene powder based on the key parameters in the design of high-quality graphene: "Defects, Stacking, and Lamellar Continuity": Using a commercial graphene oxide solution as a raw material, high-quality graphene microflowers can be prepared by a two-step method of spray drying and high temperature reduction. The use of commercialized graphene oxide as a raw material not only ensures its low cost and kilogram-level production capacity, but also ensures the continuity of graphene micro-flowers in the sub-micron size. High-temperature thermal reduction repairs the defects in the graphene atomic lattice and effectively improves the electrical conductivity of the material. The nano-scale folds in the graphene microflowers suppressed the effect of re-stacking of the sheets caused by high-temperature reduction, and finally formed an average of four layers of oligo-layer chaotic stacking graphene structure.

　　"Compared with the dense multilayer AB stacked graphite structure, this oligo-layer stacked structure is very conducive to electrolyte infiltration and uniform distribution of active materials. Compared with the heteroatom doping method commonly used to improve the performance of graphene-based electrodes, this defect-free graphene preparation method has more advantages in controllability and repeatability. In addition, as a powder material, this graphene microflower can be directly applied to the traditional commercial electrode coating process, which is conducive to large-scale battery assembly in the future. When applied to lithium-sulfur batteries, the electrochemical performance of high-quality graphene microflower-sulfur composites exceeds that of commonly used graphene-sulfur composites, reaching an area specific capacity of up to 5.2mAhcm-2. This is because the repair of the graphene lattice greatly increases the electrical conductivity of the material, thereby better exerting the capacity of the non-conductive active material sulfur. At the same time, the oligo-layer stacked graphene sheets in the graphene microflowers can effectively promote the uniform distribution of nano-scale sulfur particles on the graphene sheets; its unique wrinkled structure can inhibit the dissolution of polysulfide ions, thereby effectively improving the sulfur cathode Capacity and retention rate.

　　When used as the positive electrode of aluminum ion batteries, high-quality graphene microflower powder also exhibits excellent electrochemical performance, which exceeds that of similar graphite/graphene-based powders and bulk materials: at a current density of 0.1-20Ag-1 , The specific capacity of the positive electrode is stably maintained at about 100mAhg-1; it can be fully charged within 18 seconds, and there is no capacity loss after 5000 cycles. These excellent electrochemical properties are all due to the key parameters in the design of high-quality graphene: defect-free graphene lattice provides more active sites and higher conductivity, and the oligo-layer stacked graphene structure has It is conducive to electrolyte infiltration and ion transmission, and the sub-micron two-dimensional continuous graphene sheet reduces the electrode resistance. Related research work has been published on AdvancedEnergy Materials (DOI: 10.1002/aenm.201700051).