Three-Dimensional Silicon Carbide from Siligraphene\nas a High Capacity Lithium Ion Battery Anode Material

Abstract

We\nreport density functional theory calculations for two siligraphene\nmembranes, SiC₃ and SiC₇, to assess their suitability\nas lithium ion anode materials. We find high capacities of 627.09\nand 955.84 mA h g^–1 for the SiC₃ and\nSiC₇ monolayers, respectively. Both membranes also facilitate\nexcellent lithium mobility with barriers of less than 0.5 eV. We find\nvan der Waals stacked bilayer configurations for both siligraphenes.\nThe volume expansion in the bilayer for SiC₃ on lithiation\nis 28%, whereas the expansion for SiC₇ is much higher at\n62%. Both bilayers remain stable under high lithium loading. For the\nfirst time for siligraphene materials, we report bulk configurations\nfor SiC₃ and SiC₇. Here we find that the siligraphenes\nform three-dimensional structures with cavities and channels. The\nlayers are not held together by van der Waals forces, but rather by\nsingle silicon–silicon and single silicon–carbon bonds.\nSurprisingly, these three-dimensional siligraphene bulk structures\nhave a larger average interlayer distance than the van der Waals structures\nwhich yields an expansion due to lithiation of 20% for SiC₃ and a very small expansion of 4% for SiC₇.