What advantage does lithium battery negative electrode material use Silylene have?

Lithium-ion batteries are the most commonly used energy storage devices. They are widely used in smart phones, laptops, and electric vehicles due to their portability, environmental friendliness, and high energy density. The most commonly used negative electrode material is graphite, and the Fan de Waals force between the layers ensures the stability of the material during charging and discharging and the recycling service life. However, due to the small lattice constant, which limits the position of lithium ions that can be interpolated, the capacity value is low. Finding a material with high capacity and cyclic stability is a hot topic in lithium-ion battery research.

Silylene is a layered silicon material having a honeycomb structure and can be prepared by molecular beam epitaxy and solid phase reaction. Since the bond length between the silicon atoms in the silylene is much larger than the bond length between the carbon atoms in the graphene, the inter-layer atom arrangement in the silylene has a warped arrangement. Compared with the silicon material of the traditional diamond structure, the interlayer coupling effect of silylene is Fan de Waals force, and a space for lithium ion insertion is provided between the layers to ensure that the structure of the silylene is not destroyed during charging and discharging. Thereby, the problem of the expansion of the electrode volume of the conventional silicon electrode material during charging and discharging is avoided. The stability and cycle number of the negative electrode material made of silylene can be greatly improved. Compared with graphite, The polycrystalline silylene has a larger lattice constant and a theoretical capacity of about three times that of graphite.

Recently, the Du Fu group of the University of Wollongong, Australia, prepared single-layer/multi-layer silylene samples by molecular beam epitaxy, and studied the atomic and electronic structures of silylene in detail by scanning tunneling microscopy. The results clearly show the ABA structure of silylene. The Dirac fermion characteristics of silylene were determined by angular resolution photoelectron spectroscopy. This study shows that the electrons in silylene have extremely fast transmission speed and solve the problem of poor conductivity in traditional silicon materials. In addition, studies have shown that the stability of silylene in the atmosphere is much higher than that of traditional silicon materials, and its structure and electronic properties are maintained. This achievement was recently published in Advanced Materials [1] and ACS Central Science [2]. The first author of the article is Dr. Zhuang Jincheng and Dr. Li Zhi from the University of Wollongong.

In addition, the silicon atoms and the calcium atoms in the silylene prepared by the solid phase method are alternately arranged to form a layered structure, and the calcium is removed by a local chemical intercalation method, thereby obtaining a substrate-free silylene. The silylene prepared by the chemical method is used as the cathode of the lithium battery, and has the advantages of high capacity of the silicon-based material and good cycle characteristics of the graphite material, and becomes a very potential anode material for the lithium ion battery.

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