posted on 2020-03-18, 21:13authored byHong Chen, Yuruo Hua, Ningjing Luo, Xiaojie He, Yi Li, Yongfan Zhang, Wenkai Chen, Shuping Huang
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.