1

Supporting Information

Structural evolution and redox processes involved in the electrochemical cycling of P2-

Na0.67[Mn0.66Fe0.20Cu0.14]O2

Elahe Talaie,a Se-Young Kim, a Ning Chen,b and Linda F. Nazara*

aDepartment of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, 200

University Ave W, Waterloo, Ontario N2L 3G1, Canada

bCanadian Light Source, 44 Innovation Blvd, Saskatoon, Saskatchewan S7N 2V3, Canada

Figure S1. Schematic representation of the coin cell used for operando XAS study.

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Figure S2. The XRD patterns of Z-Nax[Mn0.66Fe0.2Cu0.14]O2 obtained from the

electrochemically oxidized electrode in the operando cell (a) and the chemically oxidized

powder sample (b). The two patterns show different background shape because of different

X-ray windows (glassy carbon vs. Kapton film, respectively).

3

Figure S3. Comparison of the PDF curves (a) and schematic representation of bilayers (b) in Z-Na0.1[Mn0.5Fe0.5]O2, Z-Na0.1[Mn0.66Fe0.2Cu0.14]O2, and Z-Na0.1[Mn0.65Fe0.2Ni0.15]O2.

4

0 10 20 30 40 50 60 70

200

300

400

500

600

Sp

ecif

ic E

nerg

y (

Wh

.kg

-1)

Cycle Number

Na0.67

[Mn0.66

Fe0.20

Cu0.14

]O2

Na0.67

[Mn0.65

Fe0.20

Ni0.15

]O2

Na0.67

[Mn0.5

Fe0.5

]O2

1.5 - 4.3 V,

C/20

P2 stability window,

C/10 rate

Figure S4. Specific energy of Na0.67[Mn0.66Fe0.2Cu0.14]O2 (red), Na0.67[Mn0.65Fe0.20Ni0.15]O2 (blue), Na0.67[Mn0.5Fe0.5]O2 (green) cycled within 1.5 - 4.3 V at a C/20 rate (filled circles) and over P2-stability window at a C/10 rate (hollow circles). The data form Na0.67[Mn0.65Fe0.20Ni0.15]O2 and Na0.67[Mn0.5Fe0.5]O2 are adapted from Ref. Error! Bookmark not defined..

0.2 0.4 0.6 0.8

2

3

4

Vo

ltag

e (

V )

x in Nax[Mn0.66Fe0.20Cu0.14]O2

0.2 0.4 0.6 0.8

2

3

4

(b)

Vo

ltag

e (

V )

(a)

Figure S5. First two galvanostatic charge/discharge cycles of Nax[Mn0.66Fe0.20Cu0.14]O2 vs. Na metal collected from an standard coin cell (a) and a coin cell modified for operando XAS study (b).

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Figure S6. The voltage profile of a Nax[Mn0.66Fe0.20Cu0.14]O2 electrode (vs. Na metal) from which the X-ray

absorption spectra at the Mn K-edge were collected (a). The marks on the graph show the points at

which data collection was started. Normalized XANES spectra of Nax[Mn0.66Fe0.20Cu0.14]O2 at the Mn K-

edge (b).

6

0 2 4 6 8 10 12 14 16 18

1.5

2.0

2.5

3.0

3.5

4.0

4.5

6540 6545 6550 6555 6560

6540 6545 6550 6555 6560 6540 6545 6550 6555 6560

6540 6545 6550 6555 6560 6540 6545 6550 6555 6560

a)

M1

Vo

ltag

e (

V)

Time (h)

M17

M16

M15

M14

M13

M12

M11M10M9M8

M7M6

M5

M4M3

M2

e)

Discharge 1

M1

M2

M3

M4

M5

d/d

E

Energy (eV)

b)

Charge 1

c)

Charge 1

d)

Charge 1 M5

M6

M7

M8

M9

M10

d/d

E

Energy (eV)

M11

M12

M13

d/d

E

Energy (eV)

M13

M14

M15

M16

M17

d/d

E

Energy (eV)

M1

M17f)

d/d

E

Energy (eV)

Figure S7. The voltage profile of a Nax[Mn0.66Fe0.20Cu0.14]O2 electrode (vs. Na metal) from which the X-ray absorption spectra at the Mn K-edge were collected (a). The marks on the graph show the points at which data collection was started. Normalized first derivative of XANES spectra of Nax[Mn0.66Fe0.20Cu0.14]O2 at the Mn K-edge during the first charge (b,c), first discharge (d,e), and the comparison of the initial state and the end of discharge (f).

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Figure S8. The voltage profile of a Nax[Mn0.66Fe0.20Cu0.14]O2 electrode (vs. Na metal) from which the X-ray absorption spectra at the Cu K-edge were collected (a). The marks on the graph show the points at which data collection was started. Normalized XANES spectra of Nax[Mn0.66Fe0.20Cu0.14]O2 at the Cu K-edge (b).

8

0 2 4 6 8 10 12 14 16

1.5

2.0

2.5

3.0

3.5

4.0

4.5

8975 8980 8985 8990 8995 9000

8975 8980 8985 8990 8995 9000 8975 8980 8985 8990 8995 9000

8975 8980 8985 8990 8995 9000 8975 8980 8985 8990 8995 9000

a)

Vo

ltag

e (

V)

Time (h)

C15

C14

C13

C12

C11

C10

C9C8C7

C6

C5

C4

C3

C2

C1

d/d

E

Energy (eV)

C1

C2

C3

C4

C5

b)

Charge 1

d/d

E

Energy (eV)

C5

C6

C7

c)

Charge 1

d/d

E

Energy (eV)

C7

C8

C9

C10

d)

Charge 1

d/d

E

Energy (eV)

C10

C11

C12

C13

C14

C15

d)Discharge 1

f)

d/d

E

Energy (eV)

C1

C16

Figure S9. The voltage profile of a Nax[Mn0.66Fe0.20Cu0.14]O2 electrode (vs. Na metal) from which the X-ray absorption spectra at the Cu K-edge were collected (a). The marks on the graph show the points at which data collection was started. Normalized first derivative of XANES spectra of Nax[Mn0.66Fe0.20Cu0.14]O2 at the Cu K-edge during the first charge (b-d), first discharge (e), and the comparison of the initial state and the end of discharge (f).

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Figure S10. Pre-edge of the normalized XANES spectra of Nax[Mn0.66Fe0.20Cu0.14]O2 electrode during the first charge (a) and the first discharge (b) collected at the Cu K-edge. The insets show the voltage profile and the points at which each scan was started.

Figure S11. The voltage profile of a Nax[Mn0.66Fe0.20Cu0.14]O2 electrode (vs. Na metal) from which the X-ray absorption spectra at the Fe K-edge were collected (a). The marks on the graph show the points at which data collection was started. Normalized XANES spectra of Nax[Mn0.66Fe0.20Cu0.14]O2 at the Fe K-edge (b).

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0 2 4 6 8 10 12 14 16

1.5

2.0

2.5

3.0

3.5

4.0

4.5

7115 7120 7125 7130 7135

7115 7120 7125 7130 7135 7115 7120 7125 7130 7135

7115 7120 7125 7130 7135 7115 7120 7125 7130 7135

Vo

ltag

e (

V)

Time (h)

F13

F12F11

F10F9F8F7

F6

F5

F4

F3

F2F1

a)

d/d

E

Energy (eV)

b)

F1

F2

F3

F4

F5

F6

Charge 1

c)

Charge 1d)

Charge 1

e)

Discharge 1

F6

F7

d/d

E

Energy (eV)

F7

F8

F9

F10

d/d

E

Energy (eV)

F10

F11

F12

F13

d/d

E

Energy (eV)

d/d

E

Energy (eV)

f) F1

F13

Figure S12. The voltage profile of a Nax[Mn0.66Fe0.20Cu0.14]O2 electrode (vs. Na metal) from which the X-ray absorption spectra at the Fe K-edge were collected (a). The marks on the graph show the points at which data collection was started. Normalized first derivative of XANES spectra of Nax[Mn0.66Fe0.20Cu0.14]O2 at the Fe K-edge during the first charge (b-d), first discharge (e), and the comparison of the initial state and the end of discharge (f).