1

Review

Ni Mn

1

LiCoO2

Structural Aspects of Materials for Lithium Battery Electrodes

*

Ryoji Kanno

Department of Electronic Chemistry, Tokyo Institute of Technology G1-1, Nagatsuta, Midori, Yokohama, 226-8502 Japan

Tel/Fax : +81-45-924-5401, e-mail : kanno@echem.titech.ac.jp

Electrode materials for lithium batteries are reviewed from the viewpoint of their structures. The materials for the next generation are expected to have high lithium storage capacity and high power density with high thermal stability beyond these limitation values so far. The materials design concepts are important subject to achieve these high characteristics and will be discussed based on the reaction mechanisms using nano-space, na-no-particles, and low crystallinity, for example. The new experimental methods by X-ray and neutron scattering techniques for determining a wide range of structures are also reviewed for these electrode materials. Further-more, the importance of the interfacial structures will be discussed together with their characterization methods.

Key words : Electrode material ; Lithium battery ; Structural analysis ; X-ray scattering ; Neutron scattering

Abstract

*

2006 GS Yuasa Corporation, All rights reserved.

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2

2.1 4 V

2Tarascon 1)Fig. 1 LiCoO2 150 mAh/g 370 mAh/g

NiCo NiCoMn NiMn 270 mAh/g LiMn2O4 LiFePO4 150 mAh/g 12.2 2)Fig. 2 Fig. 3

40003800

5

4

3

2

1

0

Pote

ntia

l vs.

Li /

Li+

10008006004002000Capacity / mAh g-1

LiMn0.5M0.5O4 spinel

LiMn2O4 spinelLiCoO2 layered rocksaltLiNiO2 layered rocksalt

LiFePO4 olivine and related compoundsMnO2 and related compounds

GraphiteCarbons

SnO glasses CoO, Co3O4 nano particle

Li2.6Co0.4N nitridesSi alloy

Li metal

Cr3O8

Mo6S8 Chevrel phase

V2O5 and related compounds

Electronically conducting materials

Electronically insulating materials

Fig. 1Relationship between potential and capacity for electrode materials.

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3.1XX

Rietveld 3.2Fig. 4 Fig. 5 0.5 10 d d

(a) (b)

(d) (e)

( f )

(h)

(g)

(c)

Fig. 2Structures of intercalation electrodes. (a) NaCl, (b) -LiFeO2, (c) -NaFeO2LiCoO2, LiNiO2, Li(Ni0.5Mn0.5)O2, Li(Ni1/3Mn1/3Co1/3)O2 (d) -NaMnO2(LiMnO2), (e) Spinel(LiMn2O4), (f) Holandite(LiFeO2, MnO2), (g) Olivine(LiFePO4), and (h) Ramsdellite(MnO2).

Fig. 3 Electrode reaction mechanism of lithium batteries. Various types of new battery reactions are proposed for the future lithium battery systems. In the IMLB 2006 meeting in Biarritz, there were many new proposals for new systems using nano-particles, meso-porous materials, and nano-wire materials.

PresentIntercalationLiCoO2/organic solvent/carbon

FutureNano porous (lithium cluster)Meso porous

Nano particle(lithium intercalation and lithium adsorption)Nano wire

Conventional mechanism(layer, spinel, olivine, alloy, etc)

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3.3TEM

3.4XPS

X in-situ

4

4.1 4.1.1

-NaFeO2 Fig. 2 (c) LiCoO2 LiNi0.8Co0.2O2 LiCoO2 X

Particle boundary

Surface

Local structure

+R

-R-R

-R

-R-R

+R

+R+R

+R

cb

Crystal structure fluctuationStacking faults

Crystal structure

Crystal structurefluctuationLong-rangeordering

Fig. 4Schematic drawing of the structures for electrode materials. Several levels of structures composed of battery materials are indicated : surface, grain-boundary, crystal structures, local structures, and long-range structures. All these structures affect the battery properties.

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LiNi1/3Co1/3Mn1/3O2

LiNi0.5Mn0.5O2 3,4)LiNiO2 Ni

Co, Mn, Ni LiNi0.5Mn0.5O2 LiNi1/3Mn1/3Co1/3O2 (i) LiCoOLiNiO2-NaFeO2Li

(ii) 2.5- 4.2 V 110- 150 mAh/g LiCoO2

(iii) Ni2+ Mn4+ XPS Ni3+/Mn3+ Ni2+/Mn4+ Ni2+ Mn4+

LiCoO2LiNiO2 Ni2+/Ni4+

(iv) 4.2 V Li0.5 (Ni0.5Mn0.5) O2

(v) 4.3- 4.7 V 280 mAh/g

5MnLiNi0.5Mn0.5O2 6)LiNi0.5Mn0.5O2 Li2MnO3 LiCoO2 3+ 4+ 2+ 4+ 4.1.2 4 V LiMn2O45 V LiMn1.5Ni0.5O4 LiMn2O4 Fd3m 8a Li16d Mn16c Fig. 2 (e)XMn Li 4.1.3 LiFePO4 3.5 V 150 mAh/g PO4 Li Fe 6 P 4 Fig. 2 (g)

0.01

0.1

1

10

0.1 1 10 100r /

121086420

SANS WANS VEGA HIT

SANS

WANSVEGA

HIT

Local structure

Crystal structure Nano

structure

Surface structure

Fig. 5 Neutron scattering patterns using various diffractometers, powder diffractometer (VEGA), total scattering (HIT), small angle scattering (SANS), and wide angle scattering (WANS). Each diffractometer measures different d-ranges which provide different structure area of the materials, from local to long range structures.

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Nb 7) Fe2P 6 8)LiFePO4FePO4 9) 10) 11) 4.2 4.2.1

12)HEV , 1200 VEGASANS HIT(i) X (Diffax) a c

(ii) Fig. 6

(iii) 3

(iv) Fig. 7 Franklin Conard wave wave

4.2.2 MnO2 -MnO2 Pannetier 13)XMnO2 14) MnO2 15)Mn

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10

100

1000

Inte

nsity

0.01 0.1 1Q / -1

C-LiC10.4largeLiC10.4-LiC5constant

Debye-Buescheparametercorresponds to the size of the scatter(length correlation)

C-LiC10.4constantLiC10.4-LiC5large

Peak corresponding to the Bragg reflection

C LiC10.4 LiC5

Fig. 6Small angle scattering patterns of the hard carbon. The patterns are composed of Bragg reflections and a scattering from the nano-voids.

24Lithium intercalationbetween graphite layer

Lithium insertion into voids

c = 7.192Lc = 13.8 QO = 1.747 -1

= 3.19P = 4.00

c = 7.480QO = 1.680 -1

= 3.04P = 3.62

c = 7.656QO = 1.641 -1

= 3.26P = 3.18

La = 23.8 First neighbor (C-C)rC-C= 1.418 CNC-C= 3.0Second neighbor (C-C)rC-C= 2.456

First neighbor (C-C)rC-C= 1.418 CNC-C= 3.0Second neighbor (C-C)rC-C = 2.456

First neighbor (C-C)rC-C= 1.426 CNC-C= 3.1Second neighbor (C-C)rC-C= 2.469

First neighbor (C-C)rC-C= 1.433 CNC-C= 2.8Second neighbor (C-C)rC-C= 2.480

Fig. 7Electrode structure and reaction mechanism of the hard carbon determined by various neutron scatter-ing techniques.

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MnO2 2 1 1 1 Mn3+ 2Mn3+ MnO2Fig. 8 MnO6 1 1 2 111Mn3+ 4.2.3

4.3 4.3.1

(i) 4.3.3

(ii)

(iii) (ii)(iii)

(iv) 4.3.2

4.3.2MO 16)CoO, NiO, CuO, FeO 1-5 nm 2CoO + Li Li2O + 2Co 700 mAh/g 4.3.3-Fe2O3Fe(CO)5 -Fe2O3 17)1 m-Fe2O3 50 mAh/g 7 nm 230 mAh/g -Fe2O3 Fe3O4 7 nm -Fe2O3

Mn

Mn Mn

Mn Mn

Mn Mn

Mn Mn

Mn

Mn Mn

Mn

Mn MnH

H H

HMn

Mn Mn

Mn Mn Mn Mn

Mn

Mn Mn

Mn Mn

Mn Mn

Mn Mn Mn Mn

Mn

Mn

Mn Mn

Mn

Mn Mn

Mn

Mn Mn

Mn

Mn Mn

Mn Mn

Mn

Mn Mn

Mn Mn

HHHH

HHHH

HHHH

(c, d)

(b)

(a)

Fig. 8 Schematic drawing of the MnO2 structure. The stacking faults composed of 11 and 12 tun-nels provide nano-scall voids where two-types of proton exist.

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4.4

V2O5, Cr3O818

) V2O5 P2O5 19) 19) -MnO2

MnO2 1.6 mol Li 440 mAh/g 20)1MO2 270 mAh/g 1 21)LiMnO2 Li1.5Na0.5MnO2.85I0.12 1.5 4.2 V Mn 1 Li 1.3 LiMnO2 260 mAh/g 22)4.5 TEM 4.5.1

LiCoO2 LiNiO2 Li 0.5 LiCoO2 TEMLiNiO2

LiNi0.5Mn0.5O2 TEM Li Li, Ni, Mn

P3112 3ahex 3ahex chex 23

)Ni2+

Mn4+ Li+ Mn4+ LixCoO2 12 Li2MnO3 Li (Li1/9Ni1/3Mn5/9) O2TEMXISIS 24)TEM4.5.2 LiFePO4 LiFePO4 FePO4 2 Li0.5FePO4 TEMLiFePO4 FePO4 100 nm 11) bc b ac 3 ac

5

25)

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Fig. 9XPSTEMXFig. 105.1XPS

SEI SEI SEI XPS

4 nmLiNi0.8Co0.2O2 26) XPS ArEdstrom XPS LiMn2O4 LiNi0.8Co0.2O2LiFePO4 SEI 27)LiMn2O4 LiNi0.8Co0.2O2 LiFePO4 XPS SEI SEI 5.2 TEM LiNi0.8Co0.2O2 TEMLixNi1-xO 2-5 nm 28) 35 nm

LiNiO2 Li1-x Ni3+/4+ O2 (delithiation)

Li1-xNi3+/2+O2- (oxygen loss)

5.3 in-situX 29)Ex-situ in-situ

Current collector

Li+ElectrolyteElectrode

Electrochemicaldouble layere-

Current

Fig. 9Electrochemical reactions at the interface between electrode and electrolyte. The electrode re-action at the electrochemical double layer is a rate determining step for the total battery reactions.

Electrode surface

Electrolyte

SEI layer

Surface analysis methods: XPS and so on

Surface observation methods:

AFM,STM and so on

Surface analysis methods:

TEM, Surface reflection

A few-several tens nm

A few nm

A few mInside of electrode:Crystal structure,Local structure analysis

Fig. 10Schematic drawing of the electrode sur-face and its characterization methods.

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