Analysis of degradation
products in electrolyte for
rechargeable lithium-ion
battery through
high mass accuracy MSn and
multivariate statistical
technique
ASMS 2012
WP26-541
Hiroki Nakajima, Satoshi Yamaki, Tsutomu Nishine,
Masaru Furuta SHIMADZU CORPORATION, Kyoto, Japan
Analysis of degradation products in electrolyte for
rechargeable lithium-ion battery through high mass accuracy
MSn and multivariate statistical technique
Introduction
(a)
e-
negative and positive electrodes during the battery
charging process. As a result, various degradation products
are generated in the electrolyte and cause some problems
such as a decrease in the capacitance of battery (Fig. 1-(b)).
Here, we present the analysis method of degradation
products generated in electrolyte using high mass accuracy
MSn and multivariate statistical technique.
eM=Mn. Co, Ni
Li x C 6
Li -x MO2
Anode
Cathode
Li +
(b)
3
Capacity / mAh
Rechargeable lithium-ion batteries (LiB) are one of the
major power sources for portable electronic devices and
electric vehicles because of their high voltage and high
energy density (Fig. 1-(a)). The electrolyte of a LiB is
consisting of a lithium salt in an aprotic organic solvent.
The typical operational potential of a LiB is between 0 and
5 V. Therefore, solvent can be reduced or oxidized at the
2.5
Charge
Discharge
2
1.5
1
0.5
Electrolyte
Electrolyte
0
0
5
10
Separator
15 20 25
Cycle Number
30
35
Fig. 1 Rechargeable lithium-ion battery component of lithium-ion battery (a), a decrease in the capacitance of battery (b).
Experiment
The electrolyte was a mixture of ethylene carbonate (EC)
and diethyl carbonate (DEC) (EC : DEC = 1 : 1 vol%)
containing 1M lithium hexafluorophosphate (LiPF6). The
electrolyte A taken from unused lithium-ion battery and the
electrolyte B taken from lithium-ion battery repeated
charge and discharge cycles (60°C, 30 times) were used as
samples. Those samples were prepared 1/10 dilution with
methanol for LCMS-IT-TOF (Shimadzu Corporation)
measurement. Orthogonal Partial Least Squares
1. Acquisition of the high mass accuracy MSn data (LCMS-IT-TOF)
Discriminant Analysis (OPLS-DA) was performed using data
acquired by LCMS-IT-TOF measurement of electrolyte A
and electrolyte B (n=3) to find the compounds generated in
electrolyte B. Then, those compounds were identified
chemical formula using software “Formula Predictor”
(Shimadzu Corporation). SIMCA-P+ (Umetrics) and Profiling
Solution (Shimadzu Corporation) were used for OPLS-DA
(Scheme).
2. Peak alignment and generation of peak list (Profiling Solution)
Structual estimation
3. Searching of degradation products (SIMCA-P+)
4. Prediction of chemical formula
(Formula Predictor)
Scheme Work flow of the analysis of degradation product in electrolyte for LiB
2
Analysis of degradation products in electrolyte for
rechargeable lithium-ion battery through high mass accuracy
MSn and multivariate statistical technique
Results and discussion
Table 1 LCMS analytical conditions
MS data of electrolyte A and electrolyte B were acquired
using LCMS-IT-TOF under the analytical conditions shown
Table 1. On the score plot of OPLS-DA, the group of
electrolyte A and electrolyte B were located at left side and
right side, respectively (Figure 2-(a)). 15 unique ions of
electrolyte B were observed at right side on S-plot (Figure
2-(b)). And, those ions were not detected on the extracted
ion chromatogram (EIC) of electrolyte A (Fig. 3). These
results suggested that those ions were degradation
products generated in the electrolyte of lithium-ion battery
repeated charge and discharge 30 cycles.
20000
Column
Flow rate
Column temp.
Mobile phaseA
Mobile phaseB
Time prog.
Injection volume
Ionization mode
Probe voltage
CDL temperature
BH temperature
Nebulizing gas
Drying gas
Scan range
(x10,000,000)
(a)
7.0
15000
5000
Electrolyte A
5.0
b4
a1
(a)
6.0
Electrolyte B
Electrolyte A
10000
to[1]
: Shim-pack FC-ODS (2.0 mmI.D.x150 mm, 3 mm)
: water
: 0.2 mL/min
: 40°C
: methanol
: 5%B (0 min) → 55%B (30 min) → 5%B (30.01 min)
: 1 µL
: ESI(+)
: 4.5 kV
: 200°C
: 200°C
: 1.5 L/min
: 0.1 MPa
: m/z 80 - 1000
4.0
0
a2
a3
-5000
b5
b6
3.0
-10000
2.0
-15000
1.0
-20000
-40000
-30000
-20000
-10000
0
10000
t[1]
20000
30000
0.0
0.0
40000
2.5
5.0
7.5
10.0
12.5
15.0
17.5
20.0
22.5
25.0
27.5
30.0
min
30.0
min
R2X[1] = 0.674304
(x10,000,000)
1.0
0.8
7.0
(b)
Electrolyte B
(b)
8
6.0
3
0.6
2
6
7
1 9
4
12
5.0
0.4
5
15
4.0
p(corr)[1]
0.2
-0.0
10
3.0
11
14
-0.2
2.0
-0.4
-0.6
13
1.0
-0.8
0.0
0.0
-1.0
-0.10 -0.08 -0.06 -0.04 -0.02 0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0.20
0.22
0.24
0.26
2.5
5.0
7.5
10.0
12.5
15.0
17.5
20.0
22.5
25.0
27.5
0.28
w[1] R2X[1] = 0.674304
Fig. 3 EICs of ions detected in Electrolyte B (b)
These ions were not detected on EIC of electrolyte A (a).
Fig. 2 The result of OPLS-DA, score plot (a), S-plot (b)
Inten. (x10,000,000)
3.5
289.0529
(M+Na) +
3.0
21.9822
O
O
2.5
H3C
2.0
O
O
O
O
O
O
CH3
O
(M+NH 4) +
284.0982
1.5
1.0
(M+H) +
267.0707
0.5
(M+K) +
305.0251
17.0275
37.9544
0.0
255.0
260.0
265.0
270.0
275.0
280.0
285.0
290.0
295.0
300.0
305.0
310.0
315.0 m/z
Fig. 4 MS data and predicted structure of peak number 2 (m/z 284.0982) being one of 15 unique ions of electrolyte B
3
Analysis of degradation products in electrolyte for
rechargeable lithium-ion battery through high mass accuracy
MSn and multivariate statistical technique
of the ion (m/z 284.0982) also was measured to determine
the validity of the predicted chemical structure. Each
product ions and neutral loss in MS2 and MS3 data showed
that the predicted structure of C9H14O9 was correct.
The formula of peak number 2 (m/z 284.0982) being one
of 15 unique ions of electrolyte B was predicted as C9H14O9
(polycarbonate) using high mass accuracy MS data and
formula predictor. Indeed, the structure of C9H14O9 was
predicted as H3C-(OCO2-C2H4)2-OCO-CH3 referring to
some articles on degradation products in electrolyte. MSn
Inten.
(x10,000,000)
4.0
289.0534
3.0
MS
Precursor ion : m/z 284.0982
(C 9H 14O 9 +NH 4) +
2.0
284.0983
4.0
103.0067
O
O
H3C
O
1.0
0.0
NH 4+
O
O
200
300
267.0701
400
500
600
700
O
O
300
400
500
600
O
C 4H 7O 3+
700
NL: C 5H 8O 6
O
800
H3C
O
900
m/z
H3C
O
200
Fig. 5
MS 3
O
300
MSn
400
500
600
700
O
O
O
P
O
O
CH3
H+
O
O
1.0
100
O
C 4H 7O 3+
2.0
0.0
H+
CH3
H3C O
4.0
3.0
m/z
O
1.0
200
900
O
O
H3C
O
100
Inten. (x10,000)
800
MS 2
-NH 3
103.0374
CH3
O
C 9H 15O 9+
2.0
5.0
O
O
226.9505
100
Inten. (x100,000)
3.0
0.0
O
By the same method, formula of
peak number 13 (m/z 283.0336 )
was identified as C3H7O4P.
Structure of it was determined as
phosphate shown in Fig. 6.
O
CH3
O
800
900
m/z
Fig. 6 of Structure peak number 13
data of peak number 2 (m/z 284.0982) detected in electrolyte B
Conclusion
It was clear that the chemical species of degradation products generated in the electrolyte with increasing charge and
discharge cycles were carbonate and phosphate from result of this study.
The formulae of 15 degradation products detected in Electrolyte B were identified as below.
Peak No.
m/z
R.T.(min)
Ion species
M.W
Predicted formula
Mass accuracy (ppm)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
229.0678
284.0982
295.1032
177.0512
400.1458
295.056
262.0853
185.0577
251.1111
269.0162
350.1003
283.0336
381.0938
293.0777
245.0641
26.645
20.401
29.482
6.178
31.294
15.833
25.374
10.054
27.416
19.879
28.426
4.385
30.857
28.487
15.713
(M+Na)+
(M+NH4)+
(M+H)+
(M+Li)+
(M+NH4)+
(M+Na)+
(M+NH4)+
(M+H)+
(M+H)+
(M+H)+
(M+NH4)+
(2M+Li)+
(M+Na)+
(M+Na)+
(M+Na)+
206
294
170
382
272
244
184
250
268
332
138
358
270
222
266
C8H14O6
C9H18O9
C11H18O9
C4H11O5P
C14H22O12
C8H17O8P
C10H13O5P
C5H13O5P
C8H17O5F3
C7H7O2F6P
C8H17O7F4P
C3H7O4P
C12H23O10P
C9H19O7P
C8H14O7
-2.62
-0.35
+1.69
+2.92
+2.50
-1.36
+1.53
+4.32
+2.39
-2.60
+1.14
+4.32
-1.57
+1.36
-0.41
4
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