Won-Sub Yoon1,*, Kyung-Wan Nam2, Kyung Yoon Chung3, Mahalingam

Balasubramanian4, Dong-Hyuk Jang1, Joengbae Yoon1, Jonathan Hanson2, Xiao-Qing

Yang2 , James McBreen2

1Department of Energy Science, Sungkyunkwan University, Suwon 440-746, South Korea

2 Chemistry department, Brookhaven National Laboratory, Upton, NY 11973, USA 3Korea Institute of Science and Technology (KIST), Seoul 136-791, South Korea

4Advanced Photon Source, Argonne National Lab. Argonne, IL 60439, USA

* email: wsyoon@skku.edu

Thermal Behavior of Charged Cathode Materials

Studied by Synchrotron-Based X-ray Techniques

0 100 200 300 4000

50

100

150

200

250

Gra

vim

etr

ic E

nerg

y D

ensity (

Wh/k

h)

Specific Volumetric Energy Density (Wh/l)

Lead Acid

Battery

Ni/Cd

Battery

Ni/MH

Battery

Rechargeable

Lithium

Battery

Smaller

Lig

hte

r

Comparison of the gravimetric and volumetric energy densities of

rechargeable lithium batteries with those of other systems.

Comparison of rechargeable batteries

A laptop explodes at a conference in Japan

Safety First !!

Introduction

▣ Safety of Li rechargeable batteries

▶ a major technical barrier for more demanding applications such as EV and HEV

▶ related to the exothermic reactions in charged batteries at elevated temperatures

that results in thermal runaway and catastrophic failure of the battery

▶ thermal runaway: reactions between the charged electrodes and the electrolyte

▣ Improving the thermal stability of the electrode materials

▶ many approaches: doping, surface coating, particle size, and so on

▶ better understanding of thermal behavior of the charged electrode

Literature review Thermal behavior of cathode materials

LiMn2O4 is generally considered a safer compound than either LiCoO2 and LiNiO2. It is

reported that the oxygen release from -MnO2 starts at about 400℃. The reaction process is

shown below as

The layered Li0.5NiO2 converts to the spinel LiNi2O4 when heated near 200℃. The

transformation is accompanied by no weight loss or heat generation. In contrast at higher

degrees of deintercalation than x = 0.5, the conversion to spinel is apparently accompanied

by significant oxygen evolution and heat generation. Above 400℃, all of Lix-yNi2-xO2

undergo the following reaction:

Highly deintercalated LixCoO2 is decomposed to layered LiCoO2 and electrochemically

inactive Co3O4 at about 250℃. The reaction process is shown below as

Lix<0.4CoO2 → [(1-x)/3]Co3O4 + xLiCoO2 + [(1-x)/3]O2

λ-MnO2 → (1/2)Mn2O3 + (1/4)O2

Lix-yNi2-xO2 → Lix-yNi2-xO2-y + (y/2)O2

Dahn et al, Solid State Ionics, 265 (1994)

Literature review Temperature-induced structural changes in nickel-based cathodes

Li1-xNiO2 → (2-x)Li(1-x)/(2-x)Ni1/(2-x)O (Fm3m) + x/2 O2 at ~ 200℃ Arai et al, Solid State Ionics, 295 (1998)

Li1-xNiO2 → (1-2x)LiNiO2 (R-3m) + xLiNi2O4 (Fd3m) (x<0.5)

→ [Li1-xNi(2x-1)/3][Ni(4-2x)/3]O(8-4x)/3 (Fd3m) + (2x-1)/3 O2 (x>0.5) Lee et al, J. Electrochem. Soc., A716 (2001)

LiNi1-xMxO2 (M = Mn, Co, and Al)

The decomposition occurs in two steps:

1st transition – layered to spinel-type phase

2nd transition – pseudo-spinel phase to NiO-type phase

through a highly disordered R-3m phase Guilmard et al, Chem. Mater., 4484 (2003)

Most temperature dependent diffraction studies of the structure of the charged

electrodes have been performed in the absence of electrolyte/solvents.

Need to investigate the structural changes of the charged cathode materials in

the presence of electrolyte using in situ x-ray diffraction

10 15 20 25 30 35 40

10 15 20 25 30 35 40

In-situ XRD data: Electrolyte effect

Li0.67Ni0.8Co0.15Al0.05O2 with/without electrolyte (50%SOC)

25C

240C

450C

003

101

110 108

102

104

105

107

113

R-3m

002

Graphite

111 200 220

Fm3m Li2CO3 phase

without electrolyte with electrolyte

Yoon et al., ESSL, 2005

Electrolytes accelerate the thermal decomposition and change the decomposition path !!

TR-XRD study on thermal stability of Li0.33NiO2 with electrolyte (as a reference)

20 30 40 50 60 70

2 ( =1.54 )

(113)

(110)

(108)

(107)

(105)

(104)

(102)

(101)

(003)

R-3m

Fd3m

Fm3m

(111)

(200)

(220)

Metallic Ni

210oC

25oC

450oC

Heating up to 450oC

- Li0.33NiO2

A good road map for the structural

changes of nickel-based cathode

materials during heating.

Layered structure

Disordered spinel structure

Rock salt structure

Metallic nickel

Li0.33NiO2 goes through a whole series of phase

transitions (i.e., thermal decomposition) when heated up to 450 oC.

In situ time-resolved (TR) XRD of charged

cathode materials during heating

Samples in

capillary

Samples in

capillary Heating

Average structural

information (long

range order) during

heating

Thermal stability of charged Li0.33Ni0.8Co0.15Al0.05O2 (NCA) with electrolyte

20 30 40 50 60 70

200oC

2 ( =1.54 )

260oC

240oC

Fd3m

Fm3m

R-3m(1

13)

(110)

(108)

(107)

(105)

(104)

(102)

(101)graphite

(003)

(220)

(200)

(111)

25oC

450oC

10 20 30 40

At ~265°C

(220) spinel (440)

layered

Disordered spinel

Rocksalt

Much better thermal stability than Li0.33NiO2.

Narrow temperature range (~20 oC) for the disordered spinel

region. (boxed region)

Heating up to 450 oC

LiM2O4 type

8a tetrahedral site : Mostly lithium

Thermal stability of charged Li0.33Ni1/3Co1/3Mn1/3O2 (NCM) with electrolyte

20 30 40 50 60 70

(a)

(220)

(200)

(111)

Fm3m

600oC

(113)

(110)

(108)

(107)

(105)

(104)

(102)

(101)

R-3m

236oC

Fd3m

441oC

304oC

2 ( =1.54 )

graphite

25oC(0

03)

metalic phase

Much wider temperature range (~140 oC) for the disordered spinel region

(boxed region) due to the stabilization of two different spinel-type structures.

much better thermal stability!!

Heating up to 600 oC

K. W. Nam et al, Journal of Power Sources, 189 (2009) 515 pp.

layered

2 types of disordered spinel

Rocksalt

8a tetrahedral site : Mostly lithium

8a tetrahedral site

: Mostly transition metal

M3O4 type

LiM2O4 type

Comparison of thermal stability of charged layered cathodes with electrolyte

20 30 40 50 60 70

2 ( =1.54 )

(11

3)

(11

0)

(10

8)

(10

7)

(10

5)

(10

4)

(10

2)

(10

1)

(00

3)

R-3m

Fd3m

Fm3m

(111

)

(20

0)

(220

)

Metallic Ni

210oC

25oC

450oC

20 30 40 50 60 70

2 ( =1.54 )

260oC

Fd3m

Fm3m

R-3m(1

13

)(1

10

)(1

08

)

(10

7)

(10

5)

(10

4)

(10

2)

(10

1)

(00

3)

(22

0)

(20

0)

(11

1)

25oC

450oC

20 30 40 50 60 70

(220)

(200)

(111)

Fm3m

600oC

(113)

(110)

(108)

(107)

(105)

(104)

(102)

(101)

R-3m

236oC

Fd3m

441oC

304oC

2 ( =1.54 )

25oC(0

03)

metalic phase

Li0.33NiO2 Li0.33Ni0.8Co0.15Al0.05O2 Li0.33Ni1/3Co1/3Mn1/3O2

NCM cathode shows the best thermal stability due to the large spinel stabilized temperature region.

why? Need better understanding of role of each elements during thermal decomposition.

Excellent thermal stability of Mn4+ ions in the charged Li0.33Ni1/3Co1/3Mn1/3O2 cathode.

likely due to the high preference of octahedral coordination of Mn4+ ions.

Mn K-edge XANES and EXAFS of charged Li0.33Ni1/3Co1/3Mn1/3O2 (NCM) during heating

6540 6550 6560 6570

0.0

0.4

0.8

1.2

1.6

6535 6540 6545 6550

Norm

aliz

ed inte

nsity (

a. u.)

Energy ( eV )

25oC

100oC

150oC

200oC

250oC

300oC

350oC

400oC

450oC

500oC

NCM (Li1-x

Ni1/3

Co1/3

Mn1/3

O2)

0

5

10

15

20

25

30

35

40

45

1 2 3 4 5 6

0

10

20

30F

T m

agnitude (

a. u. )

NCM

500 oC

450 oC

400 oC

300 oC

200 oC

25 oC

Before charge

NiO

CoO

Co3O

4

Interatomic distance ( A )

XANES : Oxidation state

EXAFS : local atomic structure

Mn-O Mn-M

No reduction of Mn ions

during heating.

In depth analysis of better thermal stability of NCM cathode using XAS

Preserving

local structure

around Mn during

heating.

10 15 20 25 30 35 40

Spinel 220

240 oC

450 oC

25 oC

Graphite 002

11

01

13

10

8

10

7

10

4

10

5

10

21

01

R-3m

00

3

10 15 20 25 30 35 40

Ni2O

3

Fm3m

200 220 111

240 oC

450 oC

25 oC

Graphite 002

11

01

13

10

8

10

7

10

4

10

5

10

21

01

R-3m

00

3

In-situ XRD data Comparison of Li0.33Ni1-xCoxO2 with MgO-coated Li0.33Ni1-xCoxO2

Much slower decomposition !!

Uncoated Li0.33Ni1-xCoxO2 MgO-coated Li0.33Ni1-xCoxO2

In-situ XRD data: first charging curve Li1.2Ni0.133Co0.133Mn0.533O2 after first charge activation

0 50 100 150 200 250 300 350

3.0

3.2

3.4

3.6

3.8

4.0

4.2

4.4

4.6

4.8

: 312 mAh/g

Capacity (mAh/g)

Vo

lta

ge

(V

)

- C-rate C/C = C/16 C/V = C/80 - Cut off : 4.7V -A.M / Current Activation : 3.7014 mg C/C = 0.0854 mA C/V = 0.0168 mA

Li1.2Ni0.133Co0.133Mn0.533O2 = 0.5Li2MnO3-0.5LiNi0.333Co0.333Mn0.333O2

20 30 40 50 60 70

(53

1)

(33

1)

(44

0)

(51

1)

(42

2)(4

00

)

(22

2)

(31

1)

(22

0)

(11

1)

Fd3m

Inte

nsity (

arb

. u

nit)

2 (=1.54)

466C

379C

600C

(10

8)

(11

0)

(11

3)

(10

7)

(10

5)

(10

4)

(10

2)

(10

1)(0

03

)

R-3m

20 30 40 50 60 70

(44

0)

(51

1)

600C

393C

207C

Fm3m

R-3m

Inte

nsity (

arb

. u

nit)

2 (=1.54)

Fd3m

(01

8)

(11

0)

(11

3)

(10

7)

(01

5)

(10

4)

(01

2)

(10

1)

(00

3) Beam dump

(31

1)

(20

0)

(11

1)

(22

0)

Metallic

(31

1)

(42

2)

(11

1)

(22

2)

(22

0)

(40

0)

In-situ XRD data Li1.2Ni0.133Co0.133Mn0.533O2 after first charge activation

with electrolyte no electrolyte

Li-rich layered cathode shows more complicating decomposition reaction with electrolyte.

16 18 20 22 24 26 28 30 32 34 36

LMP pure (100% charge:without electrolyte)

(3 0

1)

(3 0

1)

(3 1

1)

(0 2

0)

(2 1

1)

(1 1

1) (

1 1

1)

(2 1

0)

(0 1

1)

(1 0

1)

(2 0

0)

Inte

nsity (

arb

. u

nit)

2 (=1.54)

595C

505C

400C

295C

205C

100C

25C

(2 0

0)

(2 1

1)

(0 2

0)

16 18 20 22 24 26 28 30 32 34 36

Inte

nsity (

arb

. u

nit)

2 (=1.54)

(3 0

1)

(3 0

1)

(3 1

1)

(0 2

0)

(2 1

1)

(1 1

1) (

1 1

1)

(2 1

0)

(0 0

1)

(1 0

1)

(2 0

0)

(2 0

0)

(2 1

1)

(0 2

0)

595C

505C

400C

295C

205C

100C

25C

LMP pure (100% charge:with electrolyte)

Thermal Abuse: In situ XRD Olivine cathode (LiMnPO4) : electrolyte effect

2MnPO4→ Mn2P2O7 +0.5O2

ICSD # :047137 : Mn2P2O7

Olivine cathode shows less sensitivity with electrolyte.

16 18 20 22 24 26 28 30 32 34 36

Inte

nsity (

arb

. u

nit)

2 (=1.54)

(3 0

1)

(3 0

1)

(3 1

1)

(0 2

0)

(2 1

1)

(1 1

1) (

1 1

1)

(2 1

0)

(0 0

1)

(1 0

1)

(2 0

0)

(2 0

0)

(2 1

1)

(0 2

0)

595C

505C

400C

295C

205C

100C

25C

LMP pure (100% charge:with electrolyte)

16 18 20 22 24 26 28 30 32 34 36

Inte

nsity (

arb

. u

nit)

2 (=1.54)

(3 0

1)

(0 2

0)

(2 1

1)

(1 1

1)

(0 1

1)

(1 0

1)

(2 0

0)

595C

505C

400C

295C

205C

100C

25C

LMP doping (100% charge:with electrolyte)

Thermal Abuse: In situ XRD Olivine cathode (LiMn0.88Mg0.1Zr0.02PO4) : doping effect

2MnPO4→ Mn2P2O7 +0.5O2

ICSD # :047137 : Mn2P2O7

Doped olivine cathode shows better thermal stability with electrolyte.

Summaries

- Synchrotron based X-ray results clearly elucidate the thermal decomposition

mechanism of charged cathode materials in the presence of electrolyte.

- The electrolyte accelerates the thermal decomposition of the charged cathode

materials

- The presence of electrolyte alters the paths of the structural changes and lowers

the onset temperatures of the reactions.

- The electrolyte induced thermal decomposition of nickel containing layered

cathode can be successfully suppressed by MgO surface coating.

- Li-rich layered compounds show more complicating decomposition reaction

compared to other nickel containing layered compounds.

- Olivine cathode materials show less sensitivity in the presence of electrolyte.

- The thermal XRD study helps design thermally stable and safer cathode materials.

Thank you !!!