SPring-82009.6.18

La-Mg-Ni

2

Ni

OH

OH

NiOH

O

OH-H

H2Oe- e-

H+

H2O

OH-e-

H

e-

H+

3

AB5

La, Pr, Nd, etc.

Ni, Co, Mn, Al, etc.

NiNi + Ni

LaAB5Hx + xOH-

AB5 + xH2O + x e-

0.001

0.01

0.1

1

10

0 0.2 0.4 0.6 0.8 1Hydrogen storage capacity (H/M)

Equi

libriu

m H

ydro

gen

Pres

sure

(MPa

)

H/M

M

PaAB5

4

AA

Year

0

100

200

300

400

500

600

1996 1998 2000 2002 2004 2006

Ener

gy d

ensi

ty (W

h/l)

2008

AB5LaNi5372 mAh/g 85%

5

La-Mg-Ni

Kadir, Sakai1997

: AB3.0-AB4.0 (A:La, Mg, B:Ni)1-2 wt.%

ccc

La, MgNiNi + Ni

La

AB5 (CaCu5-)

c

A2B4 (Laves )

2:7H(AB3.5)

1:4R(AB4.0)

5:19R(AB3.8)

5:19H(AB3.8)

6

La-Mg-Ni

AB51.2

AB5

M. Kanemoto et al., ECS 208th Meeting, Abstract number 852, Los Angeles (2005).T. Ozaki, M. Kanemoto ,T. Kakeya, Y. Kitano, M. Kuzuhara, M. Watada, S. Tanase, and T. Sakai, J. Alloys Compds., 446-447, 620 (2007).

0.8

1.0

1.2

1.4

1.6

0 100 200 300 400

Discharge capacity (mAh/g)

Vo

ltag

e (

V)

MmNi5-based alloy(conventional)

La-Pr-Mg-Ni-based alloy

1.2

La-Mg-Ni

AB5

280

300

320

340

360

0 20 40 6

Cycle numberD

isch

arg

e c

ap

acit

y (

mA

h/g

)

Conventional AB5 alloy

La-Mg-Ni-based alloyLa-Mg-Ni

AB5

0

7

La-Mg-NiLaNi

La1-xMgxNiy (x = 0.150.2, y = 3.6-3.8)

Ce, Pr, Nd

Co, Mn, Al

X

8

(900-1000C)

X (SPring8 BL19B2 )

Rietveld : RIETAN-2000) XRD : 0.7 0.75)

XAFS )

EPMA

9

Mn,AlLa-Mg-Ni

La0.8Mg0.2Ni3.4-xCo0.3(MnAl)x

0% 20% 40% 60% 80% 100%

SY187

SY149

SY111

SY70

SY112

SY65

Mass fraction

2:7H

AB2

5:19R

5:19H

1:4R

AB5

x = 0

x = 0.1

x = 0.15

x = 0.2

x = 0.25

x = 0.4

0% 20% 40% 60% 80% 100%

SY187

SY149

SY111

SY70

SY112

SY65

Mass fraction

2:7H

AB2

5:19R

5:19H

1:4R

AB5

x = 0

x = 0.1

x = 0.15

x = 0.2

x = 0.25

x = 0.4

x = 0.15, 0.25:19H, 1:4R

10

Mn,AlLa-Mg-Ni

260

280

300

320

340

360

380

0 1 2 3 4 5 6 7 8 9 10

Cycle number

Dis

char

ge c

apac

ity (m

Ah/

g)

x=0x=0.15

x=0.4

x=0.25

5:19Hx = 0.15

La0.8Mg0.2Ni3.4-xCo0.3(MnAl)x

11

Mn,La,Ni,Co

A

0

5

10

15

20

25

0 1 2 3 4 5 6

MnKLaKN iKCoK

La K

Mn KCo K

Ni K

R

|FT|

La0.8Mg0.2Ni3.25Co0.3(MnAl)0.15

MnLaNiCoMnNiCo

12

La

La

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 1 2 3 4 5 6

La0.8Mg0.2Ni3.25Co0.3(MnAl)0.15

R

|FT|

13

Ni

A

0

2

4

6

8

10

12

14

0 1 2 3 4 5 6

La0.8Mg0.2Ni3.25Co0.3(MnAl)0.15

R

|FT|

14

XAFS

LaNiCoLa

La-Mg-NiLaNi5

NiLaLaNi5

LaNi

NiLa

15

La

-1

-0.9

-0.8

-0.7

-0.60 100 200 300 400

Capacity / mAh

Pote

ntia

l / V

(Hg/

HgO

)

AB5

RE': La

RE': Pr

RE': Nd

RE': Ce

, : 0.2 ItA

La0.64RE0.2Mg0.16Ni3.45Co0.2Al0.15

16

La

280

300

320

340

360

0 20 40 60

Cycle number

Dis

char

ge c

apac

ity (m

Ah/

g)

RE':Ce

RE':LaRE':Pr

RE':Nd

0.1 ItA, 15h0.2 ItA

cut off voltage-0.6V vs. Hg/HgO

La0.64RE0.2Mg0.16Ni3.45Co0.2Al0.15

Pr, Nd- : 5096%Ce-:

17

La

La0.64RE0.2Mg0.16Ni3.45Co0.2Al0.15

0% 20% 40% 60% 80% 100%

RE': La

RE': Ce

RE': Pr

RE': Nd

Phase abundancemass%

AB22:7H5:19R5:19H1:4RAB5

AB5

1:4R

5:19H

5:19R

2:7H

Pr, Nd : AB5, 2:7H .5:19H, 5:19R

18

Pr, NdAl

A2B4

A2B4

A2B4

AB5

AB5AB5

AB5AB5

AB5

18h1 siteM / Al = 0.89 / 0.1118h2 site M / Al = 0.95 / 0.05

5:19R phase

RERE, MgNi,Co,Mn,Al

AB5

AB5

AB5

AB5

RE = (La, Pr)M=(Ni,Co,Mn)

Ni

Ni

NiNi

La Ni

Ni Ni

Nd

Al

La: 1.877Nd: 1.821Ni: 1.246Al: 1.432

LaPr Ndc

AlNi

19

Pr, Nd

Pr, Nd

Al-rich

Al-poor

AB5

AlAB5

AlAB5

20

Pr, Nd

La-Mg-NiAB5

05

10152025303540

-10 0 10 20 30 40 50 60 70 80

Abundance of AB5 phase (%)

Part

icle

siz

e af

ter c

ycle

test

(um

)

Abundance of AB5 phase (%)

(m

)

Pr, Nd

AB5

21

CeCe-LIII XANES

La0.64Ce0.2Mg0.16Ni3.45Co0.2Al0.15

: CeO2 CeCl3 : Ce4+ Ce3+

0

0.2

0.4

0.6

0.8

1

5700 5720 5740 5760

Energy (eV)

Nor

mal

ized

abs

orpt

ion

CeCl3

Before hydriding

Ce metal

CeO2

After hydriding

22

La0.64RE0.2Mg0.16Ni3.45Co0.2Al0.15

0

5000

0000

5000

0000

10 20 302 (degree)

SPring8 BL19B2 :0.75

Inte

nsity

(a.u

.)

RE: Nd

RE: Ce

RE' Phases Volume increase

V /V (%)Ce AB5 14.4

1:4R 16.55:19H 18.25:19R 19.52:7H 21.6AB5 20.0

Pr 5:19H 20.35:19R 20.3AB5 17.5

Nd 5:19H 21.05:19R 20.9

23

La-Mg-NiHRTEM

A2B4

A2B4

A2B4

AB5 4

AB5 3

A2B4AB5 3

AB5 3

AB5 4

A2B4

A2B4

A2B4

AB5 4

AB5 3

A2B4AB5 3

AB5 3

AB5 4

A2B4

A2B4

A2B4

AB5 4

AB5 3

A2B4AB5 3

AB5 3

AB5 4

c5:19

1:4

c

24

Ce

Ce4+- Ce3+-

2:7H 2:7H2:7H 2:7H

5:19R5:19H

1:4R1:4R

AB5

5:19R5:19H

1:4R

Ce1:4R

AB5

25

La-Mg-NiNiMn,Al5:19H350 mAh/g

LaNiNiLa

LaPr,NdAB5CeCeCe(III)Ce(IV)XRDXAFS

26

XRDXAFSSPring8

TEM

La-Mg-NiAALa-Mg-NiLa-Mg-Ni Mn,AlLa-Mg-NiMn,AlLa-Mg-NiMn,La,Ni,CoLa NiXAFSLaLaLaPr, NdAlPr, NdPr, NdCeCe-LIII XANES La-Mg-NiHRTEMCe