http://support.spring8.or.jp/Report_JSR/PDF_JSR_2019B/2019B1818.pdf
http://support.spring8.or.jp/Report_JSR/PDF_JSR_2019B/2019B1818.pdf

2019B1818

BL08W

Operando observation of lithiation state in commercial 18650-type
lithium-ion cell using Compton scattering imaging
Kosuke Suzukia, Daisuke Hiramotoa, Naruki Tsujib, Mika Kanninenc, Yoshiharu Sakuraib,
Hiroshi Sakuraia and Bernardo Barbiellinid,eaGunma University, bJASRI. cAkkurate Oy, dLUT University, eNortheastern University

In this study, Compton scattering imaging was applied to commercial 18650-type lithium ion battery cellto observe the change of lithiation state in operando condition. By analysing line-shape of Compton scattered
X-ray energy spectrum (S-parameter analysis), S-parameter distributions of charged and discharged state
were visualized. From these results, the cathode and anode positions shift regarding volume expansion orcontraction of the electrodes were observed. Moreover, the change of S-parameter corresponding to charge
and discharge was observed in both the cathode and anode in operando condition.
Keywords:

18650-type cell, Lithiation state, Compton scattering, Non-destructive measurement

Background and Objective:
Although lithium-ion batteries are already used widely in our daily life, demand for them is rapidlyincreasing, because the development of electric vehicles is attracting much attention all over the world. To
farther expand the use of electric vehicles, battery cells are required not only high capacities but also highsafety and long life time. Moreover, it is needed fast charging batteries. However, previous neutron diffraction
study using cylindrical-type cell has revealed inhomogeneous reactions of the carbon anode on a high-rate[1].
These inhomogeneous reactions are related to the degradation of cell performance. Although the neutron
diffraction technique is a powerful tool for non-destructive measurement, it reveals the reaction mechanism
through the change of the lattice parameter in the electrode materials. In order to deeply understand themechanism of the lithium reaction, it is important to monitor lithiation state and lithium reactions directly inthe cells under in operando condition.
Gunma University group has been developed direct monitoring method of the lithiation state from
Compton scattered X-ray energy spectrum which obtained Compton scattering experiment[2]. This method
has been mainly applied to commercial coin-type cells[3, 4]. Most recently, we have adapted to commercial
cylindrical-type cell and successfully observed lithiation state on the full charged and discharged state [5].
Moreover, the difference of lithiation states between the fresh and aged cells has been revealed. Purpose ofthis study measure the change of lithiation state in operando condition and show dependency of chargedischarge speed in lithiation state.
Experiments:(b) Experimental setupThe schematic image of the sample (a) Sample
18 mm
and the experimental setup ofDetector
Compton scattering imaging is shownin figure 1. The sample is commercial
Scattered X-ray
18650 formats cylindrical lithium-ion
65 mm
Collimator
Slitbattery cell (MH1) made by LG
X-ray camera
SampleIncident X-ray
Chem, Ltd. as shown in Fig. 1(a).
Collector
115.56 keV(Al)This cell mainly composed of
Anode
CathodeLiNi1−x−yMnxCoyO2 cathode (0.15(Graphite)
x-, z-stage(NMC)
mm in thickness), graphite anodeCollector(Cu)Separator
Cycler device(0.187 mm in thickness), andseparator (0.015 mm in thickness).
The experimental setup of Compton
Fig. 1. Schematic image of the sample and experimental setup.
scattering imaging is shown in Fig.
1(b). The incident X-ray energy is115.56 keV and the scattering angle was fixed at 90 degrees. The Compton scattered X-ray energy spectrum
was measured by nine-segments of a pure Ge solid-state detector. The proving volume in the cell isdetermined by an incident slit and a collimator slit which arranged between the sample and the detector. Thesize of the incident and collimator slits in this study was 0.015 mm in height, 0.75 mm in width and 0.5 mm
in diameter. The cell was set on a movable stage along x, y and z-directions and scanned incident X-rays
along z direction which correspond to the stacking direction of the electrodes to measure Compton scattering
X-ray energy spectra. The Compton scattered X-ray energy spectra were measured with changing the stateof charge of the cell.
Results and Discussion:
Figure 2(a) and (b) are Compton scattered X-ray intensity and S-parameter obtained by scanning X-raysalong z direction of the cell, respectively. Here, Compton scattered X-ray intensity mainly proportional toelectron density of the matter[6] and S-parameter digitalizes line-shape of Compton scattered X-ray energy
spectrum[2]. The blue, grey, yellow and green background colours in these figures show the region of outercase, collector, anode and cathode, respectively. There is separator between the cathode and anode and thisis shown by weak Compton scattered X-ray intensity in Fig. 2(a). Fig. 2 clearly show inner structure of the18650-type cell non-destructively.

Fig. 2. (a) Compton scattered X-ray intensity and S-parameter
Then, Compton scattered X-ray energy spectra were measured during charge and discharge. The state ofcharge of the cell was changed by constant current (7 hours) and constant voltage (3 hours) mode. The
constant current mode corresponds to 0.14C rate. S-parameter distribution are shown in Fig. 3. Fig.3 (a) andIn charge state(a) Anode(b) Cathode(c) Anode(d) Cathode

Cell structure image

In Discharge state
Cell structure image

Fig. 3. (a) and (b) are S-parameter distribution of anode and cathode in charge state. (c) and (d) are Sparameter distribution of anode and cathode in discharge state.

(b) are S-parameter distribution of the anode and cathode during charge and Fig. 3 (c) and (d) are S-parameter
distribution of the anode and cathode during discharge, respectively. The colour in these figures is Sparameter intensity. In order to see the change of the S-parameters, the colour scale was optimized. Bychanging the state of charge of the cell, the cathode and anode positions shifts since volume expansion orcontraction of the electrodes. Moreover, as shown in Fig. 3 (a) and (b), S-parameter increased in anode withcharging the cell and S-parameter decreased in the cathode with discharging. On the other hand, S-parameter
distributions in discharged state show opposite trend to charge state. Actually, amount of change of Sparameters at each electrode layers is summarised in Table 1. In Table 1, 0th layer is anode which do not havecounter cathode. Hence the amount of change of S-parameter is almost constant. This change of S-parameters
corresponds to the lithiation state from our previous study [3, 5] therefore we could observe the change oflithiation state in operando condition in each electrode layer of the 18650-type cell.

0th layer
1st layer
2nd layer
3rd layer
4th layer

Table 1. Amount of change of S-parameter
Anode
CathodeChargeDischarge
ChargeDischarge
0.0004−0.0001
0.0026−0.0027−0.0035
0.00360.0041−0.0021−0.00430.00360.0018−0.0028−0.0035
0.00340.0017−0.0035−0.0027
0.0036

Next Steps:
We reveal lithiation state along thickness direction in one electrode layer by analysing experimental dataobtained from high spatial resolution. Moreover, cycle rate dependency of lithiation state will be shown by
analysing experimental data obtained from another charge-discharge rate.
References:[1] S. Taminato et al., Sci. Rep., 6, 28843 (2016).
[2] K. Suzuki et al., J. Appl. Phys., 119, 025103 (2016).
[3] K. Suzuki et al., J. Synchrotron Rad., 24, 1006-1011 (2017).
[4] K. Suzuki et al., Condens. Matter., 3, 27 (2018).
[5] K. Suzuki et al., Condens. Matter., 4, 66 (2019).
[6] M. Itou et al., J. Synchrotron Rad., 22, 161-164 (2015).