Comments welcome via email:
natalie@wfu.edu.
Li4SnS4 and Li4SnSe4:
Simulations of Their Structure and Electrolyte Properties
Ahmad Al-Qawasmeh, Jason Howard, and
N.A.W. Holzwarth
J. Electrochem. Soc.
164 A6386-A6394 (2017)
Local copy
Recent experimental literature reports the solid state electrolyte
properties of Li4SnS4 and Li4SnSe4,
identifying interesting questions
regarding their structural details and motivating our first principles
simulations. Together with Li4GeS4, these
materials are all
characterized by the orthorhombic space group Pnma and are found to be
isostructural. They have a ground state crystal structure (denoted
Li4SnS04) having interstitial sites
in void channels along the c-axis.
They also have a meta-stable structure (denoted
Li4SnS*4) which is
formed by moving one fourth of the Li ions from their central sites to
the interstitial positions, resulting in a 0.5 Å contraction of the a
lattice parameter. Relative to their ground states, the meta-stable
structures are found to have energies 0.25 eV, 0.02 eV, and 0.07 eV for
Li4GeS*4,
Li4SnS*4, and
Li4SnSe*4,
respectively. Consistent with these
simulation results, the ground state forms for
Li4GeS04,
Li4SnS04, and
Li4SnSe04,
and the meta-stable form for Li4SnS*4
have been reported in
the experimental literature. In addition, simulations of Li ion
migration in these materials are also investigated.