Lithium-ion batteries are the most commonly used energy storage devices and are widely used in smartphones, laptops and electric vehicles for their portability, environmental friendliness and high energy density. The most commonly used negative electrode material is graphite. The van der Waals forces between layers ensure the material's stability and cycle life during charging and discharging. However, due to the smaller lattice constant lithium-ion can limit the position of the intercalation, low capacity value. Looking for a material with high capacity and cycling stability is a hot spot in current lithium ion battery research.
Silicone is a layered silicon material with a honeycomb structure, which can be prepared by molecular beam epitaxy and solid phase reaction. As in the silylene, the bond length between the silicon atoms than the carbon atoms in graphene much longer, so the arrangement of the intermetallic atoms in the silazane has Alice structure. Compared with the conventional diamond structure of silicon material, the interlayer coupling effect of silylene is Van der Waal's force, and the space between the layers provides a space for insertion of lithium ions to ensure that the structure of the silylene is not damaged during charging and discharging, Thus avoiding the problem that the volume expansion of the electrode in the process of charging and discharging the traditional silicon electrode material. The stability and the number of cycles of the negative electrode material made of the silylene can be greatly improved. Compared with the graphite, the multi-layer silylene has a larger lattice constant, and the theoretical capacity can reach about three times of the graphite.
Recently, Du Yi, a group of researchers at the University of Wollongong, Australia, prepared single-layer / multi-layer samples of silicones by molecular beam epitaxy. The atomic and electronic structures of silylenes were studied in detail using scanning tunneling microscopy. The results clearly show the ABA? Structure of the silylene. The Dirac fermions of silylene were identified by angle-resolved photoelectron spectroscopy. This study shows that electrons in silylene have an extremely fast transfer rate and solve the problem of poor conductivity in conventional silicon materials. In addition, the study also showed that the stability of silanes in the atmosphere is much higher than the traditional silicon materials, the structure and electronic properties are maintained. This result was recently published in Advanced Materials [1] and ACS Central Science [2]. The first authors are Dr. John Chuang and Dr. Lee Chi of Wollongong University.
Silicone honeycomb ABA? Atomic structure
In addition, the silicon atoms and the calcium atoms in the silanol prepared by the solid phase method are alternately arranged to form a layered structure, and the calcium is removed by a local chemical intercalation to obtain an independent substrateless silylene. Silicone made by this chemical method, as the cathode of lithium battery, has the advantages of high capacity of silicon-based material and good cycling characteristics of graphite material, and becomes a very promising anode material for lithium ion batteries.
Preparation of silylene by solid state reaction method and chemical method
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