4

5

4

5

5

6

5

6

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, Japan2Elements Strategy Initiative for Catalysts and Batteries, Kyoto University, Katsura, Kyoto 615-8520, Japan

Studies on Electrode Materials for Rechargeable Na Batteries by Synchrotron Radiation

Structural Analysis on P2Structural Analysis on P2--Type NaType Na5/65/6[Li[Li1/41/4MnMn3/43/4]O]O22; X; X--Ray and Neutron Diffraction Ray and Neutron Diffraction

【【【【P2-Type Na5/6[Li1/4Mn3/4]O2 vs. Ion-Exchanged Li0.7[Li1/4Mn3/4]O2 】】】】 Na cell, P2-type Na5/6[Li1/4Mn3/4]O2 Li cell, O2-type Liz[Li1/4Mn3/4]O2

Charging to 4.8 V at 10 mA g-1

Sample Loading; 2.5 mg cm-2Charging to 4.4 V at 10 mA g-1

Sample Loading; 2.1 mg cm-2

【【【【Rietveld/MEM Analysis of P2-type Na5/6[Li1/4Mn3/4]O2】】】】

���� The results are indicative of self-

diffusion of Na ions at different sites.

Na at 2b and 2d sites

0.5 1.0 1.5 2.0 2.5 3.0

017

114

010

011

110

013

012

006

004

d / Å

obs. cal.

S.G. : P63/mmc; a = 2.8711(1) Å, c = 11.028(1) Å

Rwp = 8.12% RB = 5.07% RF = 6.15%

atom site g x y z B (Å2)

Naf 2b 0.320(1) 0 0 1/4 3.7(1)

Nae 2d 0.510(1) 1/3 2/3 3/4 2.3(1)

Li 2a 0.24 0 0 0 0.12(1)

Mn 2a 0.76 0 0 0 0.12(1)

O 4f 1.000(1) 1/3 2/3 0.094(1) 0.56(1)

Large B-values are also supported by ND.

[001]

A

B

B

A

A

B

B

A

Li, Mn

Na

edge-shared

Isosurface level; 0.7 (e-) Å-3

Na layer

[Li1/4Mn3/4] layer

Li-rich(2a site)

Mn-rich (2b sites)

face-shared

site g (Li) g (Mn)

2a 0.478 0.522

2b 0.121 0.879

2b 0.121 0.879

*using space group P63

���� in-plane “anti-site defects” (and / or stacking faults )

6 7 8 92θθθθ / deg. (λλλλ = 0.5 Å)

obs. cal.

The results are indicative of self-diffusion of Na ions at different sites.

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

a

b

Na layer with single Na-sites

6c (face)6c (edge)

Na layer with “splitting” Na-sites

P2-Na5/6[Li1/4Mn3/4]O2

S.G. : P63 ; a = 4.9672(3) Å, c = 11.039(1) Å

Rwp = 8.26% RB = 8.28% RF = 6.59%

atom site g x y z B (Å2)

Naf (1) 6c 0.104(1) 0.730(2) 0.397(2) 1/4 0.7

Naf (2) 6c 0.104(1) 0.064(2) 0.064(2) 1/4 0.7

Naf (3) 6c 0.104(1) 0.397(2) 0.730(2) 1/4 0.7

Nae (4) 6c 0.172(1) 0.606(1) 0.606(1) 1/4 0.7

Nae (5) 6c 0.172(1) 0.728(1) 2/3 1/4 0.7

Nae (6) 6c 0.172(1) 2/3 0.728(1) 1/4 0.7

5 10 15 20 25 30

2θθθθ / deg. (λλλλ = 0.5 Å)

obs. cal. (obs.) - (cal.) Bragg positionSPring-8, BL02B J-PARC, BL-21

iMATERIAHigh-resolution bank

(d = ~ 5 Å)

012

002

014

Na5/6[Li1/4Mn3/4]O2

P63/mmc

SPring-8, BL02B

5 10 15 20 25 302θθθθ / deg. (λλλλ = 0.5 Å)

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

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

0 50 100 150 2000

1

2

3

4

Voltage / V

Capacity / mAh g-1

0 50 100 150 2000

1

2

3

4

Voltage / V

Capacity / mAh g-1

0 50 100 150 200 2500

1

2

3

4

5

1st 2nd 10th 20th

Voltage / V vs. Li

Capacity / mAh g-1

0 50 100 150 200 2500

1

2

3

4

5

1st 2nd 10th 20th

Voltage / V vs. Na

Capacity / mAh g-1

2.0 – 4.8 V1.5 – 4.4 V

1/5 C1/2 C

1 C (275 mA g-1)

2 C

~1/28 C (10 mA g-1)1/10 C

Sample Loading; 2.1 mg cm

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

1/10 C

1/5 C1/2 C

1 C (236 mA g-1)

2 C

Na cell Li cell

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

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

5 10 15 20 25 30

112

110

015

013

012

011

004

1/3 1/3 1

008

112110

016

013

012011

010

004

1/3 1/3 0

002

2θθθθ / deg. (λλλλ = 0.5Å)

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

P63/mmc

a = 2.8677(2) Åc = 11.039(1) Å

P63mc

a = 2.8417 Åc = 9.7777 Å

ion-exchange

in molten salt

*The ratio of metals in the productwas determined by ICP-AES.

Reaction Mechanisms on P2Reaction Mechanisms on P2--NaNa2/32/3[Fe[Fe1/21/2MnMn1/21/2]O]O22; ; SXRD and XAS SXRD and XAS Studies on Surface of Phosphorus ElectrodesStudies on Surface of Phosphorus Electrodes

4 8 12 16 20 242θ / deg. (λ = 0.5 Å)

(107)

hex

(105) hex

(1010) hex

(110)

hex

(108) hex

(009) hex

(104) hex

(102) hex

(101) hex

(006) hex

(003) hex

(112)

(110)

(106)(104)

(103)(1

02)

(100)

(004)

(002) S.G. P6

3/mmc

a = 2.933(1) Å c = 11.223(1)Å

P2-Na2/3[Fe

1/2Mn

1/2]O

2

S.G. R-3ma = 2.958(1) Å c = 16.521(1)Å

O3-Na[Fe1/2Mn

1/2]O

2

a

c

AB

BA

AB

BA

b

MeO2 layer

NaPri.

AB

CA

BC

AB

ab

c

MeO2 layer

NaOct.

P2-Na2/3[Fe1/2Mn1/2]O2

O3-Na[Fe1/2Mn1/2]O2

P2-Na2/3[Fe1/2Mn1/2]O2 shows better electrode performance

0 50 100 150 2000

1

2

3

4

50

1

2

3

4

5

2nd5th 3rd

ca. 120 mAh/g

Capacity / mAhg-1

ca. 190 mAh/g

5th 2nd

Voltage / V

P2-Na2/3[Fe1/2Mn1/2]O2

O3-Na[Fe1/2Mn1/2]O2

Note; 1st cycle is not shown

1 mol dm-3 NaClO4 in PC：FEC=(98：2)

Charged to 4.2V

x = 0.12Clear change���� Phase transition

AB

BAC

(110)

(105)O2-type

【【【【Phase Transitions on Charge; SXRD】】】】

SPring-8, BL02B

SPring-8, BL02B

【【【【Crystal Structures and Electrode Performance】】】】N. Yabuuchi et al., Nature Mat., 11, 512 (2012)

S.G. P63/mmc

P + 3Na+ + 3e- ↔ Na3P

Na3P ab

c

P3-

Na+

Black Phosphorus is reversibly reduced with a three-electron reaction.

20 25 30 35 40 45 50

◆

*

*

Reduced to 0.38 V

Reduced to 0 V

Reduced to 0.17 V

2222θθθθ / deg. / deg. / deg. / deg.

As-prepared

* Al current collector◆ Na

3P

◆

Capacity /mAh g-1

0 500 1000 1500 2000 2500

Potential / (V vs. Na/Na+)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

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

Capacity /mAh g-10 50 100 150 200 250

Potential / (V vs. Na/Na+)

0.4

0.6

0.8

1.0

Hard X-ray absorption spectroscopy; HAXPES

TOF-SIMSAfter 1st cycle

-CH2-

NaO-C(=O)-O-R

Na2CO3

-C(=O)ONa P

NaxP

(H2PO2)-

PR2(OR’)(PO4)3-

NaxPFyOz

C1s P1s

SPring-8, BL46XU

【【【【Surface Analysis】】】】

【【【【Charge/Discharge Mechanisms】】】】Red phosphorus for Na cells; N. Yabuuchi et al.,

ChemElectroChem, in-press DOI: 10.1002/celc.201300149

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).

5 10 15 20 25

As-Prepared

Charged to 3.8V

(112)(110)

(106)

(104)

(103)

(102)

(100)

(004)

(002)

2θθθθ / deg. (λλλλ = 0.5 Å)

x = 2/3 (0.67)

x = 0.4

CA

AC

AB

AB

BA

AB

BA

NaPri.

(2/3,1/3,0)

(0,0,0)

P2 (as-prepared)

OP4 (charged)

Na+

extraction

Phase transition from P2 to OP4 phase during charge

5 10 15 20 25

(105)OP4

Observed

P2-type

OP4-type

O2-type

(107)OP4(106)OP4(103)OP4

2θθθθ / deg. (λλλλ = 0.5 Å)

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

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

6540 6550 6560 6570

Charged to 4.2 V

Charged to 3.8 V

As-Prepared

Norm

alized Absorbance

Energy / eV

Mn-K edge

���� Mn3+/Mn4+ Redox below 3.8V

Shift of XANES spectra during charge to 3.8 V,

but NOT from 3.8 to 4.2 V

7115 7125 7135 7145

As-Prepared

Charged to 3.8V

Charged to 4.2V

Norm

alized Absorbance

Energy / eV

0 2 4 6

5.0 Å-4

4.2 V Charge

3.8 V Charge

As-Prepared

F.T. Magnitude

R / Å

Fe-O Fe-Fe(Mn)

Fe-K edge

EXAFS

XANES

XANES

Change in the XAFS spectra and shortened Fe-O

interatomic distance above 3.8 V

1.99 Å for 3.8 V vs. 1.90 Å for 4.2 V

0 50 100 1501

2

3

4

5

Charge to 4.2 V

Charge to 3.8 V

As-Prepared

●

●

●

Voltage / V

Capacity / mAhg-1

【【【【Change in Electronic Structures; XAS】】】】

Fe3+/Fe4+ Redox at 4 V region.

99.2

99.6

100.0

-10 -5 0 5 10

97

98

99

100

Fe3+(s)

As-Prepared

Fe3+(d)

Fe3+(s)Fe

4+(d)

Fully Charged State

Relative Intensity / %

Velocity / mm s-1

Mössbauer spectroscopyX-ray absorption spectroscopy (XAS)

Photon Factory, BL-7C FEC and VC additives effectively stabilize the sufrace films formed on phosphorus and suppress

the continuous decomposition of electrolyte and deposition of decomposed products.

+ FEC (5%)

Inorganic

+ VC (1%)

Organic

After 20th cycle295 290 285 280

1 vol. % VC

5 vol.% FEC

Additive-free

As-prepared

sp2 C in A.B.hydrocarbon

Na2CO3NaxP

2152 2148 2144 2140

2152 2148 2144 2140

P

NaxP

(PO4)3-NaxPFyOz

FEC and VC additive effectively suppresses the loss of surface chemical species formed on the

black Phosphorus, resulting in the good cyclability as electrode materials.

295 290 285 280

1 vol. % VC

5 vol.% FEC

Additive-free

NaO-R

NaO-C(=O)-O-R

PR2(O-R’)

sp2 C in A.B.hydrocarbon

-CH2-

NaO-C(=O)-O-R

Na2CO3

-C(=O)ONa

C1sP1s

Capacity /mAh g-1

0 500 1000 1500 2000 2500

Potential / (V vs. N

a/Na+)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

1st30th 20th10th

Capacity /mAh g-1

0 500 1000 1500 2000 2500

Potential / (V vs. N

a/Na+)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

1st

25th20th

Capacity /mAh g-1

0 500 1000 1500 2000 2500

Potential / (V vs. N

a/Na+)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

1st

25th20th

EC/DEC/ 1M NaPF6 + FEC (5%) + VC (1% )

【【【【Cycle Performance】】】】