Quantitative oxidation state analysis of transition metals in a lithium-ion battery
With high energy resolution AES
A. Tanaka1,*, K.Tsutsumi1, H.Onodera1 and T. Tazawa1
1JEOL
Ltd., 3-1-2 Musashino, Akishima, Tokyo, 196-8558, Japan
Introduction
Difference of chemical state analysis between XPS and AES
For an effective development of a lithium-ion battery・・・
NIST XPS Database
Electron transition of XPS
To control the oxidation number of a transition-metal in a
cathode active material
Valence shell
estimation by the peak position
depending on the oxidation number
XPS is well-known as an instrument to study a chemical state
but・・・it is difficult to detect the oxidation number difference of transition-metals
Atomic
core
This study
Chemical state analysis for
manganese oxides by AES
Electron optical column
3nm SEI resolution
d N(E) /dE (arbitrary unit)
Sn(metal)
AES standard spectra
Valence shell
Chemical state analysis by AES
Atomic
core
Sn (SnO2)
440
Electron energy (eV)
40000
40000
20000
Measurement condition
10kV,196.0nA,E/E=0.1%
5000
0
C
0
20
40
60
80
100
120
140
Intensity
Mn0(metal)
70
Mn2+(MnO)
Mn4+(MnO2)
60
2+
0
160
-4000
-8000
Mn (MnO)
Deconvolution
10000
Mn
4+
5000 Mn (MnO )
MnO
2
C
MnO2
0
Ar etch.(500eV,40sec/cycle)
--->rate : 3.0nm/min as SiO2
0
20000
15000
Mn
10000
25000
20
40
4000
60
80
100
120
140
160
Electron energy (eV)
Etching time (min)
Measured spectrum
Convolution curve
Residual curve
-4000
-8000
540
Quantitative chemical state depth profile
The atomic concentration calculation of Mn2+
560
580
600
620
640
O
50
2+
40
Mn (MnO)
2000
0
0
-2000
-4000
10kV,196.0nA
-6000
Mn (MnO2)
-12000
520
C
0
20
40
60
80
100
120
140
160
Etching time (min)
The errors of total atomic% at each cycle were less than 5%
Standard
atomic %
Istd(Mn2+)
-5000
-10000
0
Istd(Mn )
19,102 count
-15000
0
540
560
580
600
620
-30000
520
540
640
= 37.7 %
560
580
600
620
640
Electron energy (eV)
Electron energy (eV)
50.0
Ｘ I (Mn2+) =
×6,219
8,247
Mn (metal) standard
0
Mn (metal) measured in depth
-25000
2+
20
0
-20000
Mn (MnO) standard
2+
Mn (MnO) measured in depth
-10000
4+
I(Mn )
4,173 counts
5000
2+
Istd(Mn )
8,247 count
-8000
30
0
I(Mn )
6,219 counts
Intensity (dN(E)/dE)
70
60
2+
4000
80
10
The atomic concentration calculation of Mn0
10000
Intensity (dN(E)/dE)
Atomic concentration (%)
90
50
2-
40
O (MnO2)
2+
Mn (MnO)
30
(Mn2+)
Standard
atomic %
Istd(Mn0)
Ｘ I (Mn0) =
Ar sput.( 300eV, 15s/cycle)
rate: 1.2 nm/min as SiO2
2-
O (MnO2)
40
30
4+
Mn (MnO2)
2-
O (MnO)
20
2+
Mn (MnO)
Li O(-Li)
Li
2-
O (MnO)
10
10
4+
Mn (MnO2)
O(-Li)
5
10
15
20
25
30
0
35
0
5
10
15
20
25
30
35
Etching time (min)
Summary
6000
Mn (metal)
50
Etching time (min)
15000
0
Ar sput.( 300eV, 15s/cycle)
rate: 1.2 nm/min as SiO2
0
Quantitative analysis with an absolute intensity method
100
60
0
Electron energy (eV)
110
Probe condition (10 keV, 10 nA)
Probe condition (10 keV, 10 nA)
20
520
Total atomic % (non-normalized)
70
0
Peak deconvolution calculation was applied spectra measured at each cycle
650
Powder particles
that do not contain lithium internally
Powder particles
containing lithium
Atomic %
A manganese plate after
heated in the atmosphere
at 573K for 1 hour
25000
15000
O
30000
Intensity
Intensity
30000
Measured spectrum
Mn (metal)
Intensity
O
600
Quantitative chemical state depth profile for a
particle of active material in a cathode of LIB
4000
35000
550
Electron energy (eV)
0
Mn
35000
※ three nines purity
It is easy to detect oxidation number difference of manganese by AES
Peak deconvolution
Chemical state depth profile
Mn(MnO)
Mn(MnO2)
Observed clearly
Quantitative oxidation state analysis for manganese by AES
Elemental depth profile
Mn
MnO2
Peak shape difference between
MnO and MnO2
→ complex and broader
than XPS
460
MnO
※ three nines purity
Auger peaks consisting of electrons
of which transition usually involves
a few valence shells
4+
420
Energy resolution : 0.1%
estimation by the peak shape
depending on the oxidation number
(x0.5)
Sn (SnO)
400
It is difficult to detect oxidation number difference of manganese by XPS
Mn LMM
2+
380
(http://srdata.nist.gov/xps/elm_Spectra_query.aspx?Elm1=Mn&LD1=2
p1%2f2&Elm2=&LD2=&Elm3=&LD3=&Elm4=&LD4=&sType=PE)
Electron transition of AES
(E/E=0.1%)
Eucentric 5-axies Stage
JAMP-9510F
Insulator analysis is realized by tilting
sample more than 75 deg.
only 0.4 ～ 0.5eV
→ sharper than AES
Differentiated spectra
Ionization Gun
Sputtering and
neutralization
The peak position difference between
MnO and MnO2
XPS peaks consisting of electrons
coming from a inner shell than a
valence shell
Hemi-spherical Analyzer
Variable energy resolution
0.05% ~ 0.6%
Auger instrument
・Manganese oxide
Atomic %
Our passed study
It was possible to detect the oxidation
number difference of tin with using the
standard spectra by AES
・Manganese metal
Chemical state analysis by XPS
100.0
×9,616
12,753
= 21.8% (Mno)
Each atomic concentration could be calculated by comparison with the intensity between
the deconvoluted spectrum and the standard one measured in the same condition
Auger spectra measured with energy resolution of 0.1 %
can be applied for chemical state analysis, which is a
different way from XPS to estimate peak deconvolution
calculation.
According to standard spectra of MnO and MnO2, Mn LMM
peak has a unique shape due to it’s chemical state. We
found that Mn LMM peaks are available for chemical state
analysis for a manganese oxide sample in AES.
The peak intensity of each chemical component spectrum
can be converted to atomic concentration by absolute peak
intensity ratio. In the case of the depth profile of the
manganese oxide sample, the quantitative error of this
method is estimated less than 5 atomic%.
In the result of the chemical state depth profile for two
different types of cathode particles, the manganese
oxidation number was depending on the atomic
concentration of lithium.
An advanced quantitative analysis of Li in LIB with AES
Preparation for a clean cross section with the Cross Section Polisher
A. Tanaka1,*, K.Tsutsumi1, H.Onodera1 and T. Tazawa1
1JEOL
Ltd., 3-1-2 Musashino, Akishima, Tokyo, 196-8558, Japan
Pretreatment techniques for a lithium ion battery
Motivation
electrode (Al)
To study a lithium ion battery
electrode (Cu)
 Establishing the pretreatment method
separator
active materials
LiMn2O4
LiFePO4
LiCoO2 etc
cathode
anode
separator
electrolyte
Shield
plate
 Detection the lithium distribution with
higher spatial resolution
active materials
graphite
Si or SiO2 etc
cathode
Cross section polisher
Sample
 Quantification and chemical state
analysis of lithium
AES can be the most suitable instrument
but…applications by AES seem less.
anode
The second difficulty to detect lithium with AES
~overlapping with some peaks of other elements~
The first difficulty to detect lithium with AES
~escape depth difference~
Glove box
The kinetic energy of Li
KVV : 50 eV
Electron
Kinetic energy(eV)
LiKVV Li1s
50
1437
2000
Li
0
Mn Fe
Escape detpth (nm)
2 nm
0.5
1.5
1.5
4.5
MnO2
Li2O
-4000
NiO
40
50
60
Electron energy (eV)
-8000
70
30
40
50
60
70
Electron energy (eV)
Auger spectra of transition metals
Auger spectra of lithium
Lithium peaks are often difficult to be identified under
overlapping with some peaks of transition metals
Lithium detection by AES is disturbed easily
by such a slight contamination of 1.5nm
Auger maps at a cross section of LIB
Quantitative analysis with the absolute intensity method
electrode(Al)
LiCoO2
particles
2000
[LiCoO2]
1500 Conditions
Polymer
1500
Intensity
1000
[LiCoO2]
Intensity
Conditions
1000 10kV,10nA,M5(0.5%)
x20000
1 m
-500
-2000
0
-500
-2000
0
-1500
ICo
Co Co
Co
Co
-1500
500
-1000
10kV,10nA,M5(0.5%)
500
-1000
Li
ILi
200
CoCo Co
IO
Co
Li
Ii
RSFi
Intensity of an element i
for quantification
O
400
600
800
1000
RSFLi = 0.446
RSFO = 0.365
RSFCo = 0.473
elements
Li
O
Co
Sum
Atomic
concentration (%)
9.9
79.1
11.1
100.0
Stoichiometric
value (%)
25.0
50.0
25.0
100.0
Normalized
Electron energy [eV]
Conclusion
 Quantitative analysis
with the absolute intensity method
 Quantitative analysis
with the relative sensitivity factor method
2000
The latest Auger microprobe (JAMP-9510F) with the
hemi-spherical analyzer, which has a quick selectable
energy resolution system to obtain high-speed Auger
maps and unique various chemical state analyses
Peak deconvolution technique is necessary for
identification and quantification of lithium !!
Pretreatment technique is important to make a
clean surface with less contamination !!
Step1
the peak deconvolution calculation was
carried out with standard spectra if it overlaps
with some peaks of another elements
Step2
atomic concentration could be calculated by
comparison with the intensity between the
deconvoluted spectrum and the standard one
Co
Li
O
step2
step1
100 200 300 400 500 600 700 800 900 1000
LiCoO2
1000
0
Co Co
Co
-1000
-2000
Co
Li
-3000
O
200
400
600
800
1000
Li2O
Practical spectrum is
deconvoluted into spectra
of Li2O, CoO and Co3O4.
The intensity of lithium in
a practical spectrum is
underestimated caused
by the peak overlapping
of Co oxides.
Co3O4
-500
CoO
Practical
spectrum of
LiCoO2
-1000
-1500
Co peak
Li peak
-2000
Electron energy (eV)
30
40
50
practical spec.
Li2O
CoO
Co3O4
60
70
80
component spectrum of Li2O
0
Intensity
10kV,10nA,M5(E/E:0.5%)
Diff. point: 9
Intensity [dN(E)/dE]
O
C
2000
Intensity [dN(E)/dE]
SE images and a spectrum at LiCoO2 in a cross section
of a LIB cathode prepared by CP
0
●For Lithium ion battery analysis,
AES is a useful tool to detect lithium
sensitively with high spatial
resolution. However, it needs some
technique to make a pretreated
sample without contamination, and
the peak deconvolution calculation
should be carried out in order to
indentify it under overlapping with
some elements of other elements
10kV,10nA,M5(E/E:0.5%), Diff. point: 9
10kV,10nA,M5(E/E:0.5%)
Electron energy [eV]
Li
Air lock chamber
-6000
30
100
1000
Electron energy (eV)
The transfer vessel can bring
the sample from the glove box
to the AES chamber under
keeping the argon atmosphere.
Li2CoO3
Fe2O3
The kinetic energy of Li1s
excited by Al Kα : 1437 eV
0.5 nm
10
Ni
Co
-2000
Mean free path (nm)
1
Intensity [dN(E)/dE]
10
Ag
Be
Fe
C
Intensity [dN(E)/dE]
Mean free path (nm)
Au
Mo
Ni
W
P
Cross-section made by CP
Transfer vessel
A Glove box helps to
transfer the sample to
an AES holder from the
CP holder under an
inert atmosphere.
4000
Crosssection
Cross section polisher (CP), which is one of pretreatment
instruments, can make a clean cross section of a LIB sample
using a low incident-angled beam of Ar+ without water.
IB-09010CP
why?
configuration of a Li-ion battery (LIB)
~ 50 μm
in the spectrum of LiCoO2
1078
counts
the standard spectrum of Li2O
-1000
measured with
the same condition
-2000
3127
counts
-3000
30
40
50
Standard
atomic % Ｘ I (Li O)
2
Istd(Li2O)
66.66
×1078
3127
= 23.0 % (Li+ )
=
60
70
80
90 100
Electron energy (eV)
●The cross-section polisher (CP) is
an important pretreatment method to
reveal a fresh cross-section of a
lithium ion battery without any
damage nor any contamination.
Electron energy (eV)
x20000
F
1 m
x20000
1 m
x20000
10kV,10nA,M5(E/E:0.5%), Diff. point: 9
Co
P
Practical spectrum
O(Co3O4)
2000
The deconvolution result of
1500 oxygen peak (O KLL)
Intensity
1000
500
O(Lithium)
1721
counts
O(Li2O)
total convolution
O(Cobalt)
2075
counts
0
-500
-1000
-1500
-2000
1 m
x20000
1 m
x20000
1 m
Auger maps (probe condition:30kV, 10nA)
x20000
440
460
480
500
520
Electron energy (eV)
540
560
Standard
atomic % Ｘ I (Co O )
3 4
Istd(Co3O4)
= 57.14 ×2075
2843
= 41.7 % (O2- cobalt)
Standard
atomic %
Istd(Li2O) Ｘ I (Li2O)
= 33.33 ×1721
4741
= 12.1 % (O2- lithium)
800
600
Component of Co3O4
10kV,10nA
M5(E/E:0.5%)
Diff. point: 9
in the spectrum of LiCoO2
1217 counts
400
696
counts
200
Intensity
1 m
step2
step2
0
Standard
atomic % Ｘ I (Co O )
3 4
Istd(Co3O4)
-200
-400
42.86
= 1217 ×696
-600
-800 Standard spectrum of Co3O4
-1000
measured with the same condition
600
650
700
750
800
Electron energy (eV)
850
elements
Li
O
Co
Sum
Atomic
concentration (%)
23.0
53.8
24.5
101.3
Stoichiometric
value (%)
25.0
50.0
25.0
100.0
= 24.5 % (Co2+, Co3+ )
Non-normalized
●The quantitative analysis with the
absolute intensity method is more
trustable than the traditional RSF
method. Because it can provide
the absolute error value without any
normalizing procedure.