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

We report density functional theory calculations for two siligraphene membranes, SiC₃ and SiC₇, to assess their suitability as lithium ion anode materials. We find high capacities of 627.09 and 955.84 mA h g^-1 for the SiC₃ and SiC₇ monolayers, respectively. Both membranes also facilitate excellent lithium mobility with barriers of less than 0.5 eV. We find van der Waals stacked bilayer configurations for both siligraphenes. The volume expansion in the bilayer for SiC₃ on lithiation is 28%, whereas the expansion for SiC₇ is much higher at 62%. Both bilayers remain stable under high lithium loading. For the first time for siligraphene materials, we report bulk configurations for SiC₃ and SiC₇. Here we find that the siligraphenes form three-dimensional structures with cavities and channels. The layers are not held together by van der Waals forces, but rather by single silicon-silicon and single silicon-carbon bonds. Surprisingly, these three-dimensional siligraphene bulk structures have a larger average interlayer distance than the van der Waals structures which yields an expansion due to lithiation of 20% for SiC₃ and a very small expansion of 4% for SiC₇.