Theoretical study of a new porous 2D silicon-filled composite based on graphene and single-walled carbon nanotubes for lithium-ion batteries

Abstract

The incorporation of Si16 nanoclusters into the pores of pillared graphene on the base of single-walled carbon nanotubes (SWCNTs) significantly improved its properties as anode material of Li-ion batteries. Quantum-chemical calculation of the silicon-filled pillared graphene efficiency found (I) the optimal mass fraction of silicon (Si)providing maximum anode capacity; (II) the optimal Li: C and Li: Si ratios, when a smaller number of C and Si atoms captured more amount of Li ions; and (III) the conditions of the most energetically favorable delithiation process. For 2D-pillared graphene with a sheet spacing of 2-3 nm and SWCNTs distance of ~5 nm the best silicon concentration in pores was ~13-18 wt.%. In this case the value of achieved capacity exceeded the graphite anode one by 400%. Increasing of silicon mass fraction to 35-44% or more leads to a decrease in the anode capacity and to a risk of pillared graphene destruction. It is predicted that this study will provide useful information for the design of hybrid silicon-carbon anodes for efficient next-generation Li-ion batteries.