Lithiation Abilities of SiC Bulks and Surfaces: A First-Principles Study

Silicon carbide and its nanocomposites have recently emerged as a promising candidate for anodes in lithium-ion batteries. We systematically investigate the geometric structures and electronic structures of different types of silicon carbide compound (including bulk and surfaces), study the effects of changes in the compositions and structures on the lithiation abilities, and further explore the feasible approaches to enhance the lithiation capacities and rate capabilities of silicon carbide. Our calculations show that the lithiation in perfect bulk SiC is energetically not favorable, with the cubic SiC having the smallest lithiation energy, while the lithiations in bulk SiC with B doping or Si vacancy are possible. When the dimension of SiC is reduced from bulk to surfaces, the lithiation energy on the surfaces are thermodynamically feasible. The different packing sequences of silicon–carbon double-atomic layers have remarkable effects on lithiation energies and Li diffusion barriers at low Li concentration. The CM5 charge analysis show that the charge transfers from Li to C and Si (and to B for B-doped SiC) near Li in the bulk during lithiation, while the charge transfers mainly to Si (C) on Si (C) terminated surfaces. Our work is expected to provide reliable theoretical foundations and ideas to develop new anode materials with high performance.