Carbon materials play an important role in improving the critical properties of high energy density silicon anodes. Recently, the research team of Li Yuliang, a researcher of the Institute of Chemistry of the Chinese Academy of Sciences, combined with the natural low temperature growth of graphene, realized the in-situ growth of ultra-thin two-dimensional all-carbon graphene protective layer on the silicon anode at room temperature. This way of constructing a protective layer of all-carbon material in situ on a silicon negative electrode is not realized by other carbon materials, and has important foundation and application value. The researchers built a three-dimensional graphene all-carbon network with excellent mechanical properties and electrical conductivity directly on the silicon negative electrode, and a solid all-carbon interface contact was formed between the electrode assemblies. The method effectively suppresses the destruction of the conductive network and the electrode interface caused by the huge volume change of the silicon negative electrode during the cycle, and fully exerts the high specific capacity advantage of the silicon negative electrode, and the specific capacity reaches 4122 mAh at 0.2 A g-1. G-1, area specific capacity up to 4.72 mAh cm-2. At 2 A g-1, after 1450 cycles, the specific capacity was still able to maintain 1503 mAh g-1. In addition, this strategy shows great potential for application when solving the problems of other high energy density anodes. Fig. 1 Characterization and synthesis of GDY on Si negative electrode (a) a schematic diagram of a process for in-situ woven ultra-thin graphene alkene nanosheet conductive network on a Si negative electrode; (b) Schematic diagram of the interaction between ultrathin graphene, SiNPs and CuNWs; (c) XRD spectrum of graphene; (d) a Raman spectrum of the graphene alkyne; (e) XPS spectrum of graphene. Figure 2 SEM comparison of in situ preparation of reticular graphene (a, b) SEM image of FPCuSi woven graphene; (c,d) SEM image of FPCuSi woven graphene; (e, f) SEM image of a cross section of FPCuSi woven graphene. Figure 3 Structural characterization between graphene alkene nanosheets and SiNP (a) a TEM image of graphene-supported Si; (b) High resolution TEM images of ultrathin graphene alkene nanosheets; (c) a seamless coating TEM image on SiNP; (d) a high resolution TEM image of the junction of the graphene alkene nanosheet and the SiNP; (e) high resolution TEM images at the two SiNP interfaces; (f) a high resolution TEM image of the junction of the graphene alkene nanosheet and the CuNWs; (g) is (a) an element distribution map in the image. Figure 4 Electrochemical characterization of SiNPs (a) The first 4 turns of CV plots of SiNPs at 0.3 mVs-1; (b) charge and discharge curves of SiNPs at different current densities; (c) Magnification performance map of SiNPs; (d) Cycle life map of SiNPs at 2 A g-1; (e) Cycle life map of SiNPs at 5 A g-1; (f) Cycle life map of SiNPs at 1 A g-1 and 4 A g-1; (g) an impedance map before and after 200 laps of 2 A g-1; (h) Comparison of performance of different Si negative electrodes. Figure 5 Structural evolution of SiNPs before and after CV testing (a) SEM image of the surface of SiNPs at 100 A cycles at 2 A g-1; (b) a cross-sectional SEM image of SiNPs at 100 A cycles at 2 A g-1; (c) SEM image of SiNPs after removal of SEI film at 2 A g-1 for 100 cycles; (d) SEM image of SiNPs after removing the SEI film by 1450 cycles; (e) TEM image of SiNPs after removing the SEI film by 1450 cycles; (f) High resolution TEM image of SiNPs after 1450 cycles of removal of SEI film; (g) is the elemental distribution map in (e); (h-j) Schematic diagram of the mechanism of graphene-modified Si anode. Figure 6 Schematic diagram of the connection between GDY nanosheets and SiNPs (a) an optimized map of adsorption energy changes and geometric units of graphene nanosheets and Si polymers; (b) a top view of Si and graphene; (c) Left view of Si and graphene. In this paper, a three-dimensional graphene conductive network structure was constructed on the Si negative electrode by in-situ and ultra-low temperature methods. The interfacial contact and volume change of the silicon negative electrode during the cycle were studied. The graphene network improves the mechanical properties and electrical conductivity of the Si negative electrode. At 0.2 A g-1, its specific capacity is as high as 4122 mAh g-1. At 2 A g-1, 1503 mAh g-1 was maintained after 1450 cycles, showing excellent reversibility in the cycle. This strategy has a high reference for improving the energy density of tin, antimony and oxidation. Floor Standing Display,Signage Advertising Display,Advertising Lcd Screen,Standing Digital Signage APIO ELECTRONIC CO.,LTD , https://www.displayapio.com
Discussion on Improvement of Lithium Ion Storage Performance of Silicon Negative Electrode by Low Temperature Growth of All Carbon Graphene
The Si anode material is one of the lithium ion anode materials with a high theoretical lithium storage capacity in a lithium ion battery, and its theoretical capacity can reach 4000 mAh g-1 or more. However, when lithium is stored in the negative electrode material, volume expansion is likely to occur, resulting in electrode pulverization and a sharp drop in battery capacity. At present, the problem of reducing the volume expansion of the Si negative electrode on the electrode material, increasing the void volume in the Si negative electrode composite material, alleviating the sharp decrease in capacity, and improving the cycle life of the Si negative electrode battery are major problems to be solved in this field.