Supporting Information
Lithium Transport at Silicon Thin Film:
Barrier for High-rate Capability Anode
Bo Peng, Fangyi Cheng, Zhanliang Tao, and Jun Chen*
Institute of New Energy Material Chemistry and Key Laboratory of Advanced
Micro/Nanomaterials and Batteries/Cells (Ministry of Education), Chemistry College,
Nankai University, Tianjin 300071, P.R. China
* To whom correspondence should be addressed. E-mail: [email protected]
This material contains Figure S1 , Figure S2, and Table S1.
Figure S1. (a) Cutoff energy test of Si bulk; (b) Lattice constant predicted by GGA
vs. experimental value (error < 1%); (c–e) k-points test of Si unit cell (c), 3×3×3 Si
supercell (d), and c(4×4) Si (100) (e).
Figure S2. Full Li transport path profile in B-doped case.
Table S1. Possible species that may exist at the surface of silicon anode and their
properties during the electrochemical process.
React with the organic solvent, lithium salt, organic additive
or impurities, which is one of the major reasons of initial
irreversible capacity loss.1
Less dense , decomposable, through which the electrolyte
can penetrate and break Si-Si network (cracking).2
With large bond energy (565 kJ mol-1) but high reactivity
due to a kinetics-driven surface chemistry,3 thus the
existence of Si-F at the surface is doubted.
Experimentally, to avoid these undesirable species, some
additives (e.g. carbon) are introduced to result in stable
solid-electrolyte-interface (SEI). For example, coating
Si-anode with carbon layer helps to enhance the electronic
conductivity and to keep the anode remaining integrated
after cycling.4 However, for a carbon-coated Si-anode with
the thickness of carbon layer less than the XPS penetration
depth (~10 nm), no obvious signal of interfacial Si-C bond
could either be observed from Si(2p3/2) or from C(1s) X-ray
photoelectron spectroscopy (XPS).4,5 Thus, Si-C is Less
possibly located on the surface of nanostructured silicon.
According to Ref. 4 and 6, Si-C exists with the form of
siloxane (C-Si-O), which may be soluble in the electrolyte
and subsequently diffuse through the SEI layer to deposit on
the top of carbon layer.
Reactive and can chemically reduce the electrolyte
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