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Supporting Information for:

Structural Evolution and Electrochemistry of the Mn-Rich P2- Na2/3Mn0.9Ti0.05Fe0.05O2

Positive Electrode Material.

Jennifer H. Stansby, a,b Wesley M. Dose, a Neeraj Sharma, *a Justin A. Kimpton, c Juan Miguel

López del Amo, d Elena Gonzalo, d and Teófilo Rojo *d,e

a. School of Chemistry, University of New South Wales, Sydney, New South Wales

2052, Australia

b. Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee

DC, New South Wales 2232, Australia

c. Australian Synchrotron, 800 Blackburn Road, Clayton, Victoria 3168, Australia

d. Centre for Cooperative Research on Alternative Energies (CIC energiGUNE), Basque

Research and Technology Alliance (BRTA), Alava Technology Park, Albert Einstein 48,

01510 Vitoria-Gasteiz, Spain.

e. Departamento de Química Inorganica, Universidad del País Vasco UPV/EHU, P. O.

Box. 644, 48080 Bilbao, Spain

Experimental:

For the in operando experiment an active material mass of 1.35 mg.cm-2 with the cell

charged to 4.2 V at 40 mA.g-1, discharged to 1.9 V at 40 mA.g-1, and charged back up to 4.2 V

at 60 mA.g-1. In order to reach the cut-off potential, the current rate was increased first to

50 mA.g-1 and subsequently to 60 mA.g-1 at 236 and 271 minutes into discharge,

respectively. XRD data were collected every 3.4 minutes (with detector position movement)

on the coin cell in transmission geometry. The cell produced a 1st charge capacity of 91

mAh.g-1, a 1st discharge capacity of 116 mAh.g-1 and 2nd charge capacity of 84 mAh.g-1.

Pristine sample:

Various single and two-phase models were trialled in order to fit the XRD data of the

pristine powder sample as shown below in Figures S1-3. Initially, a single-phase model was

used to fit the data. However, some of the reflections show signs of splitting (clearly seen for

the 004 reflection) and so a two-phase model was used to improve the fit to the data. As

shown in Figure S2, a good fit to the 004 reflection (yet poor overall fit) was obtained with

an artificial two-phase model which highlights the presences of two structurally similar

phases in the sample. Subsequently the starting two-phase model was optimised and gave

the fit shown in Figure S3. Statistically the optimised two-phase model produced a

significantly improved fit compared to the single phase model. Figures S1-3 highlight the 004

reflection because the peak splitting is much clearer than for the main reflection (002) of the

P2 structure.

Figure S1. Rietveld refined fit of the pristine P2- Na2/3Mn0.9Fe0.05Ti0.05O2. Observed, calculated

and difference are shown by a solid black line, a solid red line and a solid blue line

respectively. The green vertical reflection markers are for P2- Na2/3Mn0.9Fe0.05Ti0.05O2. The

broad feature at ~ 19° 2θ is caused by the Kapton film used to avoid atmospheric moisture

contact. The inset highlights the peak fit for the 004 reflection.

Table S1. Refined crystallographic parameters for P2- Na2/3Mn0.9Fe0.05Ti0.05O2, using a single-

phase model.

Atom Wyckoff x y z SOF a

Isotropic ADP a

(×100/Å2)

Na(1) 2 0 0 0.25 0.24(2) 7.8*

Na(2) 2 1/3 2/3 0.75 0.44(3) 15*

Mn 2 0 0 0 0.9 2.5*,#

Fe 2 0 0 0 0.05 2.5*,#

Ti 2 0 0 0 0.05 2.5*,#

O 4 1/3 2/3 0.0877(4) 1 0.79*a Atomic displacement parameter (ADP), site occupancy factor (SOF). * Refined alternatively

to SOFs, refined and fixed. # Constrained to be equal. Space group P63/mmc, χ2 = 2.6 Rp =

10.6%, wRp = 14.2%, a = 2.8939(1) Å, c =11.1742(4) Å.

Figure S2. Example fit of the pristine P2- Na2/3Mn0.9Fe0.05Ti0.05O2 XRD data which yields a

statistically poor overall fit to the data. The inset shows the 004 reflection which visually

highlights the presence of two structurally similar phases. Observed, calculated and

difference are shown by a solid black line, a solid red line and a solid blue line respectively.

The green and purple vertical reflection markers are for P2- Na2/3Mn0.9Fe0.05Ti0.05O2, Phase I

and P2- Na2/3Mn0.9Fe0.05Ti0.05O2, Phase II respectively. The broad feature at ~ 19° 2θ is caused

by the Kapton film used to avoid atmospheric moisture contact. The inset highlights the

peak fit for the 004 reflection.

Table S2. Crystallographic parameters for P2- Na2/3Mn0.9Fe0.05Ti0.05O2, Phase I


Isotropic ADP a

(×100/Å2)

Na(1 2 0 0 0.25 0.29(2)* 0.85*,#

30 31 32 33 34 35-1000

-500

0

500

1000

Inte

nsity

(arb

. uni

ts)

2θ (°)

004

)

Na(2) 2 1/3 2/3 0.75 0.34(2)* 0.85*,#

Mn 2 0 0 0 0.9 1.2*,#’

Fe 2 0 0 0 0.05 1.2*,#’

Ti 2 0 0 0 0.05 1.2*,#’

O 4 1/3 2/3 0.087(1)* 1 1.9*

a Atomic displacement parameter (ADP), site occupancy factor (SOF). * Refined

independently and fixed. #, #’ Constrained to be equal. Space group P63/mmc, χ2 = 10.22 Rp =

20.5%, wRp = 28.4%, a = 2.8888(1)* Å, c =11.1495(6)* Å.

Table S3. Crystallographic parameters for P2- Na2/3Mn0.9Fe0.05Ti0.05O2, Phase II


Isotropic ADP a

(×100/Å2)

Na(1) 2 0 0 0.25 0.29† 0.85†

Na(2) 2 1/3 2/3 0.75 0.34† 0.85†

Mn 2 0 0 0 0.9 1.2†

Fe 2 0 0 0 0.05 1.2†

Ti 2 0 0 0 0.05 1.2†

O 4 1/3 2/3 0.087† 1 1.9†

a Atomic displacement parameter (ADP), site occupancy factor (SOF). †Fixed to phase 1

values. Space group P63/mmc, χ2 = 10.22 Rp = 20.5%, wRp = 28.4%, a = 2.8999(2)* Å, c

=11.205(6)* Å. *Refined and fixed.

004

Figure S3. Rietveld refined fit of the pristine P2- Na2/3Mn0.9Fe0.05Ti0.05O2. Observed, calculated

and difference are shown by a solid black line, a solid red line and a solid blue line

respectively. The green and purple vertical reflection markers are for P2-

Na2/3Mn0.9Fe0.05Ti0.05O2, Phase I and P2- Na2/3Mn0.9Fe0.05Ti0.05O2, Phase II respectively. The broad

feature at ~ 19° 2θ is caused by the Kapton film used to avoid atmospheric moisture

contact. The inset highlights the peak fit for the 004 reflection.

Table S4. Refined crystallographic parameters for P2- Na2/3Mn0.9Fe0.05Ti0.05O2, Phase I


Isotropic ADP a

(×100/Å2)

Na(1) 2 0 0 0.25 0.27(1) 1.0*

Na(2) 2 1/3 2/3 0.75 0.30(1) 1.0*

Mn 2 0 0 0 0.9 1.1*,#

Fe 2 0 0 0 0.05 1.1*,#

Ti 2 0 0 0 0.05 1.1*,#


to SOFs, refined and fixed. # Constrained to be equal. Space group P63/mmc, 42 refinement

parameters, χ2 = 1.8 Rp = 8.4%, wRp = 11.8%, a = 2.8911(1) Å, c =11.1701(4) Å.

Table S5. Refined crystallographic parameters for P2- Na2/3Mn0.9Fe0.05Ti0.05O2, Phase II


Isotropic ADP a

(×100/Å2)

Na(1) 2 0 0 0.25 0.27† 1.0*

Na(2) 2 1/3 2/3 0.75 0.30† 1.0*

Mn 2 0 0 0 0.9 1.1*,#

Fe 2 0 0 0 0.05 1.1*,#

Ti 2 0 0 0 0.05 1.1*,#


to SOFs, refined and fixed. # Constrained to be equal. †Could not be refined reliably and

therefore fixed to phase 1 values. Space group P63/mmc, 42 refinement parameters, χ2 = 1.8

Rp = 8.4%, wRp = 11.8%, a = 2.9066(4) Å, c =11.224(2) Å.

Figure S4. SEM images of pristine P2- Na2/3Mn0.9Fe0.05Ti0.05O2 at different magnifications.

Electrochemistry:

Figure S5. Rate capabilities of P2- Na2/3Mn0.9Fe0.05Ti0.05O2 between 2.0 and 4.0 V at rates of

C/10, C/5, 1C, 5C, 10C and 50C with initial rates of a) 1C and b) C/10.

In situ cell:

Figure S6. Rietveld refined fit of the P2- Na2/3Mn0.9Fe0.05Ti0.05O2 electrode in the in situ cell

before cylcing. Observed, calculated and difference are shown by a solid black line, a solid

red line and a solid blue line respectively. The green, purple and orange vertical reflection

markers are for P2- Na2/3Mn0.9Fe0.05Ti0.05O2, Phase I, P2- Na2/3Mn0.9Fe0.05Ti0.05O2, Phase II and the

Al current collector respectively. Asterisks indicate unassigned reflections that remain

unchanged during cycling.

002102

***

Table S6. Refined crystallographic parameters for P2- Na2/3Mn0.9Fe0.05Ti0.05O2, Phase I in the in

situ cell.


Isotropic ADP a

(×100/Å2)

Na(1) 2 0 0 0.25 0.39(4) 7.1*

Na(2) 2 1/3 2/3 0.75 0.43(4) 5.5*

Mn 2 0 0 0 0.9 1.7*,#

Fe 2 0 0 0 0.05 1.7*,#

Ti 2 0 0 0 0.05 1.7*,#




Table S7. Refined crystallographic parameters for P2- Na2/3Mn0.9Fe0.05Ti0.05O2, Phase II in the

in situ cell.


Isotropic ADP a

(×100/Å2)

Na(1) 2 0 0 0.25 0.36(2) 8.1*

Na(2) 2 1/3 2/3 0.75 0.39(3) 7.9*

Mn 2 0 0 0 0.9 2.9*,#

Fe 2 0 0 0 0.05 2.9*,#

Ti 2 0 0 0 0.05 2.9*,#





during the 1st charge at 3.33 V or 51 minutes. Observed, calculated and difference are

shown by a solid black line, a solid red line and a solid blue line respectively. The green,

purple and orange vertical reflection markers are for P2- Na2/3Mn0.9Fe0.05Ti0.05O2, Phase I, P2-

Na2/3Mn0.9Fe0.05Ti0.05O2, Phase II and the Al current collector respectively. Asterisks indicate

unassigned reflections that remain unchanged during cycling.

002102

***


during 1st charge at 4.19 V or 136 minutes. Observed, calculated and difference are shown

by a solid black line, a solid red line and a solid blue line respectively. The green, purple and

orange vertical reflection markers are for P2- Na2/3Mn0.9Fe0.05Ti0.05O2, Phase I, P2-



102

002

***


during 1st discharge at 2.85 V or 204 minutes. Observed, calculated and difference are





102

002

***


during 1st discharge at 1.94 V or 289 minutes. Observed, calculated and difference are





102

002

***


during 2nd charge at 3.34 V or 340 minutes. Observed, calculated and difference are shown

by a solid black line, a solid red line and a solid blue line respectively. The green, purple and

orange vertical reflection markers are for P2- Na2/3Mn0.9Fe0.05Ti0.05O2, Phase I, P2-



002102

***

Figure S12. Peak fits of the the 002 and 102 reflections (P63/mmc space group) for selected

refinement plots during the charge-discharge process of P2- Na2/3Mn0.9Fe0.05Ti0.05O2.

Figure S13. Select regions of the P2- Na2/3Mn0.9Fe0.05Ti0.05O2 in situ cell XRD data, highlighting

evolution of the (a) 002 and (b)100, 102 reflections. The potential profile is shown in blue

and the red XRD patterns correspond to solid solution type behaviour (or where the

reflections of the two phases overlap). For clarity, data collected every 6.8 minutes is

plotted.

a

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