Computational investigation of a promising Si-Cu anode material

摘要

The lack of suitable anode materials is a limiting factor in the creation of a new generation of lithium-ion batteries. We use the molecular dynamics method to explore the processes of intercalation and deintercalation of lithium in the anode element, represented by two sheets of silicene, on a copper substrate. It is shown that the presence of vacancy-type defects in silicene increases the electrode capacitance, which becomes especially significant with bivacancies. However, the enlargement of defect sizes reduces the strength of the silicene channel during cycling and in the presence of hexavacancies it suffers a strong deformation and becomes impassable for Li+ ions during intercalation. The presence of a copper substrate greatly changes the electronic properties of silicene. The calculated DOS spectrum shows that silicon on a copper substrate acquires metallic properties. To analyze the structure we used the statistical geometry method. Lithium atoms in the channel are predominantly irregularly packed. However, part of the Li atoms are located above the hexagonal Si cells. The average stresses in silicene, calculated with limiting filling of the channel with lithium, are usually small. However, in the case of silicene with monovacancies, the tensile stress reaches 12.5% of the ultimate tensile stress. Evaluation of the dynamic stress observed in silicene during cycling shows that its value is less than 5% of the ultimate tensile stress.