of 10
Supplemental Materials for
Controlling
Covalency and Anion Redox Potentials through
Anion Substitution in Li-rich Chalcogenides
Andrew J. Martinolich,
,
Joshua J. Zak,
,
David N. Agyeman-Budu,
Seong Shik Kim,
Nicholas H. Bashian,
Ahamed Irshad,
§
Sri R. Narayan,
§
Brent C. Melot,
Johanna Nelson Weker,
and Kimberly A. See
,
Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena,
California 91125, United States
Stanford Synchrotron Radiation Light Source, SLAC National Accelerator Laboratory, Menlo
Park, CA 94025, United States
Department of Chemistry, University of Southern California, Los Angeles, California 90089,
United States
§
Department of Chemistry and Loker Hydrocarbon Research Institute, University of Southern
California, Los Angeles, California 90089-1661, United States
These authors contributed equally to this work
E-mail: ksee@caltech.edu
Rietveld Refinement Details
Rietveld refinements of powder X-ray diffraction data were executed to gain quantitative structural
data regarding the solid solution Li
2
FeS
2–y
Se
y
. The occupancies of the metals on the mixed Li/Fe
site were constrained to 0.5 for both Li and Fe, and the mixed constrained to the input stoichiometry
S1
for the mix ed S/Se site. Positions of the mixed Li/Fe and S/Se sites were allowed to refine and the
position of both the Li and the Fe or the S and the Se were forced to remain equivalent. Structural
parameters and goodness of fit (reduced
χ
2
) values are listed in Table S1.
y
in Li
2
FeS
2-y
Se
y
a
(Å)
c
(Å)
reduced
χ
2
Li
a
coordinates
(
x, y, z
)
Li
b
/Fe coordinates
(
x, y, z
)
S/Se position
(
x, y, z
)
0.2
3.917(1)
6.3248(5)
2.0736
0, 0, 0
1/3, 2/3, 0.337(2)
2/3, 1/3, 0.26(2)
0.6
3.925(2)
6.3949(7)
3.8025
0, 0, 0
1/3, 2/3, 0.35(8)
2/3, 1/3, 0.255(4)
1
3.997(2)
6.4625(5)
3.0625
0, 0, 0
1/3, 2/3, 0.408(6)
2/3, 1/3, 0.224(1)
1.4
4.018(2)
6.5205(5)
4.1616
0, 0, 0
1/3, 2/3, 0.407(3)
2/3, 1/3, 0.234(2)
1.8
4.056(4)
6.5762(5)
7.0756
0, 0, 0
1/3, 2/3, 0.409(1)
2/3, 1/3, 0.227(5)
2
4.058(2)
6.5892(5)
2.5281
0, 0, 0
1/3, 2/3, 0.380(2)
2/3, 1/3, 0.255(1)
Supplemental Figures
30
40
50
60
70
2
θ
(°,
λ
= CuK
α
)
counts (arb. units)
data
Li
2
FeS
2
fit
difference
Figure S1: PXRD data and quantitative Rietveld refinement of Li
2
FeS
2
.
S2
30
40
50
60
70
2
θ
(°,
λ
= CuK
α
)
counts (arb. units)
data
Li
2
FeS
1.8
Se
0.2
fit
difference
Figure S2: PXRD data and quantitative Rietveld refinement of Li
2
FeS
1.8
Se
0.2
.
30
40
50
60
70
2
θ
(°,
λ
= CuK
α
)
counts (arb. units)
data
Li
2
FeS
1.4
Se
0.6
fit
difference
Figure S3: PXRD data and quantitative Rietveld refinement of Li
2
FeS
1.4
Se
0.6
.
S3
30
40
50
60
70
2
θ
(°,
λ
= CuK
α
)
counts (arb. units)
data
Li
2
FeSSe fit
difference
Figure S4: PXRD data and quantitative Rietveld refinement of Li
2
FeSSe.
30
40
50
60
70
2
θ
(°,
λ
= CuK
α
)
counts (arb. units)
data
Li
2
FeS
0.6
Se
1.4
fit
difference
Figure S5: PXRD data and quantitative Rietveld refinement of Li
2
FeS
0.6
Se
1.4
.
S4
30
40
50
60
70
2
θ
(°,
λ
= CuK
α
)
counts (arb. units)
data
Li
2
FeS
0.2
Se
1.8
fit
difference
Figure S6: PXRD data and quantitative Rietveld refinement of Li
2
FeS
0.2
Se
1.8
.
30
40
50
60
70
2
θ
(°,
λ
= CuK
α
)
counts (arb. units)
data
Li
2
FeSe
2
fit
difference
Figure S7: PXRD data and quantitative Rietveld refinement of Li
2
FeSe
2
.
S5
0
50
100
150
200
250
300
350
capacity (mAh g
1
)
1.75
2
2.25
2.5
2.75
3
V
(vs. Li/Li
+
)
y
= 0
y
= 0.2
y
= 0.6
y
= 1
y
= 1.4
y
= 1.8
y
= 2
Figure S8: Galvanostatic charge/discharge curves for the solid solution Li
2
FeS
2-y
Se
y
.
0
50
100
150
200
capacity (mAh g
1
)
1.8
1.9
2
2.1
2.2
2.3
2.4
2.5
V
(vs. Li/Li
+
)
cycle 1
cycle 2
cycle 10
cycle 25
cycle 50
Figure S9: The 1
st
, 2
nd
, 10
th
, 25
th
, and 50
th
galvanostatic cycles of Li
2
FeSe
2
. The first cycle
exhibits multiple inflections below 2.25 V, which are not observed upon further cycling.
Significant capacity fade occurs in the first 10 cycles.
S6
0
50
100
150
200
250
300
capacity (mAh g
1
)
1.75
2
2.25
2.5
2.75
3
V
(vs. Li/Li
+
)
cycle 1
cycle 2
cycle 5
cycle 10
cycle 24
Figure S10: The 1
st
, 2
nd
, 5
th
, 10
th
, and 24
th
galvanostatic cycles of Li
2
FeSSe. The first cy-
cle exhibits multiple inflections below 2.38 V, which are not observed upon further cycling.
Capacity fade becomes evident after the first 10 cycles.
1.8
2.1
2.4
2.7
3
V
(vs. Li/Li
+
)
-100
-50
0
50
dQ/dV
(mAh g
1
V
1
, constant offset)
y
= 0
y
= 0.2
y
= 0.6
y
= 1
y
= 1.4
y
= 1.8
y
= 2
0
0.5
1
1.5
2
y
in Li
2
FeS
2
y
Se
y
1.8
2
2.2
2.4
2.6
peak position
Figure S11: dQ/dV plots of the solid solution Li
2
FeS
2-y
Se
y
. The inset tracks the various
oxidation processes as a function of chalcogen content.
S7