Compared with traditional graphite anode materials (372 mAh/g), silicon anode materials have a very high theoretical specific capacity (3580 mAh/g), which is the preferred anode material for high-energy density power lithium ion batteries in the future. However, there are volume changes (up to 3 times or more) in the charging and discharging cycle of the silicon anode material, which results in the pulverization of the silicon particles. As a result, the SEI film is regenerated repeatedly with low coulomb efficiency, and the polarization of electrical contact variation increases, resulting in poor cycle life and multiplier performance of the actual silicon anode material.
Since 2011, the research and development of silicon-based anode materials has been carried out in the power lithium battery engineering laboratory of ningbo institute of materials technology and engineering, Chinese academy of sciences. In 2012, a 3d porous nano-silicon/graphene composite anode material was reported. Recently, a new type of 2D nano-si /SiO2 composite anode material (2D nano-si /SiO2) has been reported. The work CaSi2 topology changes with layered structure, chemical stripping Ca atoms in acidic solution, leaving a single atomic layer fold shape silicon material, due to the Si atoms exist only sp3 hybridization, unstable, silicon oxide in aqueous solution for metastable two-dimensional silica, two-dimensional silica material after proper heat treatment conditions are dehydrated disproportionation two-dimensional nano silicon/silicon dioxide composite cathode materials nano - Si/SiO2 (2 d), the dispersion of silica nanoparticles on the amorphous silicon oxide. The two-dimensional structure can effectively reduce the migration distance of lithium ions, and nano-silicon and silicon oxide can effectively reduce the volume expansion rate, so the 2D nano-si/sio2@c prepared by this method shows excellent cycle stability and magnification performance. The research was published on Nano Energy with the title of "two-dimensional silicon suboxides nanostructures with Si nanodomains insensitive in amorphous SiO2 derived from siloxene as high performance anode for li-ion batteries".
Schematic diagram and performance characterization
(a) schematic diagram of siloxene stripping process.
(b) schematic diagram of the molecular structure of siloxene.
(c) microstructure diagram of carbon coated two-dimensional nano-silicon/silica composite nano-anode materials.
Cyclic stability of two-dimensional nano-silicon/silicon dioxide composite anode materials
The electrochemical performance test showed that at the condition of 0.15a /g, the initial discharge capacity was greater than 950mah /g, and at the high current density of 7.5a /g, the discharge capacity was up to 360mah /g, which was significantly superior to the reported silicon or silicon oxide materials in the literature. At high current densities of 1.5, 3.0, and 7.5 A/g, the volume retention rates for 300 cycles were 73%, 73%, and 92%, respectively. The new 2D nano-si/sio2@c anode material is expected to be used in electric vehicles with long battery life.