Studies on Electrode Materials for Rechargeable Na Batteries by Synchrotron Radiation
Naoaki Yabuuchi1,2, Kei Kubota1, Mouad Dahbi1, and Shinichi Komaba1,2
1Department of Applied Chemistry, Tokyo University of Science, 1-3 Kagurazaka, Tokyo 162-8601, Japan
2Elements Strategy Initiative for Catalysts and Batteries, Kyoto University, Katsura, Kyoto 615-8520, Japan

Structural Analysis on P2P2-Type Na5/6[Li1/4Mn3/4]O2; X
X--Ray and Neutron Diffraction【Rietveld/MEM Analysis of P2-type Na5/6[Li1/4Mn3/4]O2】
Li, Mn013

2a, 2b (face)
6c (edge)NaB012

A004

011

006

114017
110

obs.
cal.

obs.
cal.
(obs.) - (cal.)
Bragg positionedge-sharedbNa layer

AaB

Na layer with single Na-sites

Mn-rich (2b sites)

B
20

25

0.5

30

1.0

1.5

2.0

2.5

obs.
cal.

site

site

gxyz

B (Å2)

2a0.478

0.522

Naf

2b0.320(1)

00

1/4

3.7(1)

2b0.121

0.879

Nae

2d0.510(1)

1/3

2/3

3/4

2.3(1)

Li

2a0.240000.12(1)Mn

2a0.760000.12(1)O4f

1.000(1)

1/3

2/3

0.094(1)0.56(1)6782b9014008

112

Voltage / V vs. Na

013
010004011

110

Li0.70[Li1/4Mn3/4]O2
112015013

gxyz

B (Å2)

6c0.104(1)0.730(2)0.397(2)1/4

0.7

6c0.104(1)0.064(2)0.064(2)

1/4

0.7

6c

0.104(1)0.397(2)0.730(2)1/4

0.7

Na e (4)6c0.172(1)0.606(1)0.606(1)1/4

0.7

Na e (5)6c0.172(1)0.728(1)

2/3

1/4

0.7

Na e (6)6c0.172(1)2/30.728(1)1/40.7

Li cell, O2-type Liz[Li1/4Mn3/4]O255Charging to 4.4 V at 10 mA g-1
Sample Loading; 2.1 mg cm-2

44
1st
2nd
10th20th3
2

1/10 C ~1/24 C(10 mA g-1)

3
2
1

1002C

1/2 C 1/5 C
1 C (236 mA g-1)

Na cell
050

100

150

200025050100150

65544
1st
2nd
10th
20th

32Charging to 4.8 V at 10 mA g-1
Sample Loading; 2.5 mg cm-2
~1/28 C
1/10 C (10 mA g-1)

3
2
1/2 C 1/5 C110200-102CLi cell

2.0 – 4.8 V

05010015020050100150200-1

Capacity / mAh g

Capacity / mAh g

P2-type Na5/6[Li1/4Mn3/4]O2 in the Na cell shows better ratecapability compared with the O2-type phase in the Li cell.

1 C (275 mA g-1)

0250-1

Capacity / mAh g-1

Capacity / mAh g

P63mc
a = 2.8417 Å30 c = 9.7777 Å25site

Na f (3)The results are indicative of self-diffusion of Na ions at different sites.

Na cell, P2-type Na5/6[Li1/4Mn3/4]O2

1.5 – 4.4 V*The ratio of metals in the productwas determined by ICP-AES.

20

Na layer with “splitting” Na-sites

0.879

6P63/mmc
a = 2.8677(2) Åc = 11.039(1) Å016
110012002
1/3 1/3 1004011012

15

atom

Na f (2)Crystal structures of new layered oxides are resolved by synchrotron XRD and ND, N. Yabuuchi et al., submitted

Na5/6[Li1/4Mn3/4]O2002
1/3 1/3 010*using space group P63

 in-plane “anti-site defects” (and / or stacking faults )【P2-Type Na5/6[Li1/4Mn3/4]O2 vs. Ion-Exchanged Li0.7[Li1/4Mn3/4]O2 】

530

2θ / deg. (λ = 0.5 Å)

Large B-values are also supported by ND.

SPring-8, BL02B

0.121[Li1/4Mn3/4] layer

[001]

25

Na f (1)g (Mn)

atom

 The results are indicative of selfdiffusion of Na ions at different sites.

ion-exchange
in molten saltg (Li)

20

S.G. : P63 ; a = 4.9672(3) Å, c = 11.039(1) ÅRwp = 8.26% RB = 8.28% RF = 6.59%

6c (edge)

Isosurface level; 0.7 (e-) Å-3

S.G. : P63/mmc; a = 2.8711(1) Å, c = 11.028(1) Å
Rwp = 8.12% RB = 5.07% RF = 6.15%

15

P2-Na5/6[Li 1/4 Mn3/4]O 26c (face)

3.0d/Å

Voltage / V vs. Li

152θ / deg. (λ = 0.5 Å)

Voltage / V

10102θ / deg. (λ = 0.5 Å)

A55Li-rich(2a site)

Voltage / V

obs.
cal.
(obs.) - (cal.)
Bragg position

Na at 2b and 2d sites

face-sharedAB

J-PARC, BL-21
iMATERIA
High-resolution bank(d = ~ 5 Å)010

SPring-8, BL02B

 Facilitated diffusion of Na ions in the P2-type phase with aopen two-dimensional path.

2θ / deg. (λ = 0.5Å)Studies on Surface of Phosphorus Electrodes

Reaction Mechanisms on P2P2-Na2/3[Fe1/2Mn1/2]O2; SXRD and XAS

Red phosphorus for Na cells; N. Yabuuchi et al.,【Crystal Structures and Electrode Performance】
】

83

B
A
A
B

(112)

(106)(110)(104)

NaPri.
(103)

(102)

A
B

1216

20

24b2θ / deg. (λ = 0.5 Å)

15thNote; 1st cycle is not shown

2nd05O3-Na[Fe1/2Mn1/2]O2431ca. 120 mAh/g5th03rd050100150

Capacity / mAhg

x = 0.12(106)OP4(107)OP410(106) (110)(104)

15(112)050
100 150 200
Capacity /mAh g-1c

Reduced to 0.17 V

Na3P

Reduced to 0 V

500

1000

1500

2000

2500

202530354045502θ / deg.

Capacity /mAh g-1

Black Phosphorus is reversibly reduced with a three-electron reaction.
Hard X-ray absorption spectroscopy; HAXPES【Surface Analysis】】

SPring-8, BL46XU

After 1st cycle

TOF-SIMSPR2(OR’)(H2PO2)-

P1s-C(=O)ONa

NaO-C(=O)-O-R(PO4)3NaxPFyOz-CH2-C1sPNaxP

Na2CO3
sp2 C in A.B.
hydrocarbon

1 vol. % VC
5 vol.% FEC+ FEC (5%)
Additive-free

10152θ / deg.

20AB25(λ = 0.5 Å)

295

After 20th cycle

B
A

NaPri.

AB

Phase transition from P2 to OP4 phase during charge-C(=O)ONa

285

280

2152

2148

NaxPFyOz

2144

2140

(PO4)3-P1s

NaO-R

C1s

P-CH2NaO-C(=O)-O-R
Na2CO3P2 (as-prepared)

Z. Lu and J.R. Dahn, J. Electrochem. Soc. 148, A1225A1229 (2001).

290
PR2(O-R’)

NaO-C(=O)-O-R

BA

Note: P2-O2 phase transition for Nax[Ni1/3Mn2/3]O2

2θ / deg. (λ = 0.5 Å)

Inorganic(0,0,0)(2/3,1/3,0)As-preparedx = 2/3 (0.67)

NaxP
sp2 C in A.B.
hydrocarbon

1 vol. % VC

【Change in Electronic Structures; XAS】】
X-ray absorption spectroscopy (XAS)+ VC (1%)

Organic

5 vol.% FEC

Additive-freeXANES

Mössbauer spectroscopy
295

Fe-K edge
7115

Charged to 3.8 V

7125

7135

7145

Energy / eV

EXAFS

6540

6560

6570

Energy / eV

 Mn3+/Mn4+ Redox below 3.8V3+Fe (d)5.0 Å-4【Cycle Performance】】

As-Prepared
3.0

100
9998
4+3+Fe (s)Fully Charged State-10

As-Prepared

3+Fe (s)99.2

Fe (d)

Fe-Fe(Mn)

Fe-O-505-1
Velocity / mm s

103.0

EC/DEC/ 1M NaPF6

2.530thth20 10th

1

st

2.0
1.5
1.0
0.5
0.0

3.8 V Charge

Change in the XAFS spectra and shortened Fe-O

3.0+ FEC (5%)

2.5th20 1
2.025

stth

1.5
1.0
0.5
0.00500

1000

1500

Capacity /mAh g-1

2000

2500+ VC (1% )

2.5

20th
2.025

th

1st1.51.00.50.00500

1000

1500

Capacity /mAh g-1

2000

2500

0500

1000

1500

2000

2500

Capacity /mAh g-1

interatomic distance above 3.8 V
1.99 Å for 3.8 V vs. 1.90 Å for 4.2 V

4.2 V Charge

Shift of XANES spectra during charge to 3.8 V,
but NOT from 3.8 to 4.2 V

99.6

97

Charged to 4.2 V

6550

2140+

Charged to 4.2V

XANES

As-Prepared

2144

Potential / (V vs. Na/Na )Capacity / mAhg

150-1

2148+

1002152280

Potential / (V vs. Na/Na )50+0As-Prepared

Potential / (V vs. Na/Na )1As-Prepared285

FEC and VC additives effectively stabilize the sufrace films formed on phosphorus and suppress
the continuous decomposition of electrolyte and deposition of decomposed products.

100.0

Relative Intensity / %Voltage / V●

F.T. Magnitude

Normalized Absorbance●Charge to 3.8 V

32

Mn-K edge●

Normalized AbsorbanceCharge to 4.2 V
4290

Charged to 3.8V

5Photon Factory, BL-7C

aS.G. P63/mmc

AB

Na+extraction

525

Reduced to 0.38 V

250

OP4 (charged)

As-Prepared

200.4

P2-typeObserved(102)
(103)

(004)
(100)

(002)

5As-prepared◆◆AB
BACAAC

Charged to 3.8V

x = 0.4

P3Na+*

0.5-1(105)OP4(103)OP4◆ Na3P

0.60(110)

OP4-type

Additive-free+ FEC (5%)+ VC (1%)

0.8** Al current collector

1.0200P2-Na2/3[Fe1/2Mn1/2]O2 shows better electrode performanceO2-type

1.5

1.0

0.0

Charged to 4.2V

Clear change Phase transition

2.0

1 mol dm-3 NaClO4 in PC：FEC=(98：2)

2nda【Phase Transitions on Charge; SXRD】】
SPring-8, BL02B

ca. 190 mAh/g

2BA

2.5+22c44aP2-Na2/3[Fe1/2Mn1/2]O2

3.0

P2-Na2/3[Fe1/2Mn1/2]O2
Potential / (V vs. Na/Na )(110)hex(1010)hex(108)hex(107)hex

cb

P + 3Na+ + 3e- ↔ Na3P

5P2-Na2/3[Fe1/2Mn1/2]O2 MeO layer

(100)

(004)

(002)

S.G. P63/mmc
a = 2.933(1) Åc = 11.223(1)Å

A
B
CA
B
CA
B

NaOct.

Voltage / V

O3-Na[Fe Mn ]O2

1/2
O3-Na[Fe1/2Mn1/2]O1/2
2

Potential / (V vs. Na/Na+)

MeO2 layer(104)hex(101)hex(102)hex(006)hex

S.G. R-3m
a = 2.958(1) Åc = 16.521(1)Å

(105)hex(009)hex(003)hex

SPring-8, BL02B【Charge/Discharge Mechanisms】】 ChemElectroChem, in-press DOI: 10.1002/celc.201300149

N. Yabuuchi et al., Nature Mat., 11, 512 (2012)02R/Å

46Fe3+/Fe4+ Redox at 4 V region.

FEC and VC additive effectively suppresses the loss of surface chemical species formed on theblack Phosphorus, resulting in the good cyclability as electrode materials.
Acknowledgements; these studies were in part granted by JSPS through the “Funding for NEXT Program,”and MEXT program "Elements Strategy Initiative to Form Core Research Center" (since 2012).

b