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