Room-temperature Operation of All-solid-state Chloride-ion Battery with Perovskite-type CsSn_0.95Mn_0.05Cl₃ as a Solid Electrolyte

Abstract

Perovskite-type CsSnCl₃ is an attractive candidate for use as a solid electrolyte in all-solid-state chloride-ion batteries because it exhibits high ionic conductivity. However, perovskite-type CsSnCl₃ is metastable at room temperature and easily undergoes a phase transition to a stable phase. Here, we prepared perovskite-type CsSn_0.95Mn_0.05Cl₃, in which the Sn²⁺ in CsSnCl₃ is partly substituted with Mn²⁺, via a mechanical milling method. Differential scanning calorimetry showed that the perovskite-type CsSn_0.95Mn_0.05Cl₃ is stable to −15 °C. Moreover, it exhibits a high chloride ionic conductivity of 2.0 × 10⁻⁴ S cm⁻¹ at 25 °C. We demonstrated the room-temperature operation of an all-solid-state chloride-ion battery with a BiCl₃ cathode, an Sn anode, and CsSn_0.95Mn_0.05Cl₃ as the electrolyte. The first discharge capacity of the all-solid-state cell at room temperature was 169 mAh g⁻¹ based on the weight of BiCl₃. X-ray diffraction and X-ray photoelectron spectroscopic analyses confirmed that the reaction mechanism of the cell is derived from the redox reaction of BiCl₃ and Sn.

1. Introduction

Halogenide-ion batteries that transfer halogenide ions such as F⁻, Cl⁻, or Br⁻ as a charge carrier are attractive battery systems because they possess theoretical energy densities beyond those of conventional lithium-ion batteries.^1–3 Chloride-ion batteries, which transfer Cl⁻ ions, have a high theoretical energy density comparable to that of Li–S batteries. In addition, the Cl⁻ salts used as the electrode and electrolyte in chloride-ion batteries are abundant and available worldwide.

Metal chlorides, metal oxychlorides, layered double hydroxides, and polymers have been used as electrode active materials in chloride-ion batteries.^4–11 Among these, metal chlorides are expected to be high-capacity active materials because they undergo multielectron reactions. However, in general, metal chlorides exhibit poor cycle performance because they exhibit high solubility in polar solvents. One approach to overcoming the solubility problem of active materials is to use a solid electrolyte. Chen et al. found that polymer electrolytes based on poly(ethylene oxide) exhibit a high conductivity of 1.2 × 10⁻⁵ S cm⁻¹ at 25 °C.¹² They used this electrolyte, an FeOCl cathode, and a Li anode to construct the first all-solid-state chloride-ion battery. Because the authors used an insoluble oxychloride as the cathode material, they did not discuss the cyclability of metal chlorides. SrCl₂, BaCl₂, PbCl₂, SnCl₂, and LaOCl have been investigated as inorganic solid electrolytes.^13–17 The ionic conductivities of these materials can be increased by doping with an alkali-metal chloride or an alkaline-earth-metal chloride, which increases the concentration of Cl⁻-ion vacancies in the crystal structure. Our group demonstrated an all-solid-state chloride-ion battery with a BiCl₃ cathode, Pb anode, and KCl-doped PbCl₂ solid electrolyte.¹⁸ We showed that the all-solid-state cell exhibits better cycle performance than a similar nonaqueous cell because dissolution of the active material was suppressed. However, the charge–discharge tests of the all-solid-state cell were performed at 160 °C because the KCl-doped PbCl₂ solid electrolyte exhibits a low conductivity of ∼10⁻⁷ S cm⁻¹ at room temperature.

Cubic perovskite-type CsSnCl₃ is an attractive solid electrolyte candidate because of its high conductivity of ∼10⁻⁴ S cm⁻¹ near room temperature.¹⁹ However, perovskite-type CsSnCl₃ is a metastable phase at room temperature and easily undergoes a phase transition to a stable phase that exhibits low conductivity. To stabilize the perovskite structure of CsSnCl₃ at room temperature, Wu et al. manipulated the tolerance factor of CsSnCl₃.²⁰ The tolerance factor calculated from the ionic radii of Cs⁺, Sn²⁺, and Cl⁻ is 0.87. Either a cation larger than Cs⁺ or a cation smaller than Sn²⁺ would increase the tolerance factor. They showed that CsSn_0.9Mn_0.1Cl₃ and CsSn_0.9In_0.067Cl₃, which were respectively prepared by substitution of Mn²⁺ and In³⁺, whose ionic radii are smaller than the ionic radius of Sn²⁺, possess perovskite-type structures at room temperature. These compounds maintain their perovskite-type structure to approximately −80 °C. Recently, Xia et al. proposed synthesizing CsSnCl₃ using a mechanical milling method to stabilize its perovskite structure.²¹ The perovskite-type CsSnCl₃ prepared in two steps of mechanical milling and heat treatment exhibited a high conductivity of 3.6 × 10⁻⁴ S cm⁻¹ at 25 °C. Moreover, they conducted cyclic voltammetry measurements of SnCl₂//CsSnCl₃//Sn and BiCl₃//CsSnCl₃//Bi cells to confirm that Cl⁻-ion transfer occurs in CsSnCl₃. However, room-temperature operation of an all-solid-state cell with CsSnCl₃ as the electrolyte has not been reported.

In the present study, we synthesized perovskite-type CsSnCl₃ doped with Mn²⁺ in a single step by mechanical milling and investigated its phase transition behavior and electrochemical properties. Moreover, room-temperature operation of an all-solid-state chloride-ion battery with Mn²⁺-doped CsSnCl₃ as the electrolyte, BiCl₃ as the cathode material, and Sn as the anode material was demonstrated.

2. Experimental

CsSn_1−xMn_xCl₃ with compositions of x = 0, 0.05, and 0.1 were prepared by ball-milling. Anhydrous MnCl₂ as an ingredient was obtained by heating MnCl₂·4H₂O (99 %, Wako) at 300 °C for 3 h under flowing Ar. CsCl (99.9 %, Sigma-Aldrich), SnCl₂ (98 %, Sigma-Aldrich), and anhydrous MnCl₂ were mixed in stoichiometric amounts using a mortar in an Ar-filled glove box. Grinding vessels (volume: 80 mL) were filled with the mixture (total mass: 1 g) and 60 g of zirconia balls (diameter: 3 mm). The resultant mixtures were mechanically rotated for 12 h at a speed of 600 rpm using a planetary ball-mill apparatus (Fritsch P-7 premium line). To avoid interaction with O₂ and moisture, the grinding vessels were filled and emptied in a glovebox with a dry Ar atmosphere. CsSnCl₃ was synthesized by the liquid-phase method reported previously.²⁰

The prepared samples were characterized at room temperature by powder X-ray diffraction (XRD) using a MiniFlex600 (Rigaku) equipped with a CuKα radiation source. Rietveld analysis of the obtained XRD patterns was performed using the RIETAN-FP program.²² Differential scanning calorimetry (DSC, DSC 200 F3 Maia, NETZSCH-Gerätebau) curves for CsSnCl₃ and CsSn_0.95Mn_0.05Cl₃ were recorded at a heating and cooling rate of 5 °C min⁻¹ with the sample under a N₂ atmosphere.

Electrochemical impedance spectroscopy (EIS) measurements were carried out using a potentiostat (SP300, Biologic) in the frequency range from 7 MHz to 100 mHz. The spectra of the CsSn_1−xMn_xCl₃ electrolytes were collected at various temperatures. EIS measurements were performed on pellets (10 mm in diameter and ∼0.8 mm thick) compacted under a pressure of 510 MPa and then sputtered with Pt on both sides to form ion-blocking electrodes. The obtained pellets were sealed in a HS cell (Hohsen) in an Ar-filled glovebox.

To investigate the electrochemical stability window of CsSn_0.95Mn_0.05Cl₃, linear sweep voltammetry (LSV) was carried out. The counter-electrode composite used in LSV measurements was prepared as follows. Sn and SnCl₂ were ground in a molar ratio of 1 : 1, and the resultant mixture was combined with acetylene black (AB; Denka) in a weight ratio of 4 : 1 by ball-milling for 12 h at 600 rpm. The counter-electrode composite was obtained by grinding the mixture and CsSn_0.95Mn_0.05Cl₃ in a weight ratio of 5 : 5 using a mortar. The prepared counter-electrode composite (40 mg) and CsSn_0.95Mn_0.05Cl₃ (100 mg) were pressed at 510 MPa using a jig with an inner diameter of 10 mm. A thin Pt layer was applied to the CsSn_0.95Mn_0.05Cl₃ side of the two-layer pellet via sputtering. The obtained pellet was sealed into a HS cell in Ar-filled glovebox. LSV measurements were carried out using a potentiostat at a scan rate of 0.1 mV s⁻¹ at room temperature. To investigate the electronic conductivity of CsSn_0.95Mn_0.05Cl₃, chronoamperometry measurements were performed using the CsSn_0.95Mn_0.05Cl₃ electrolyte pellets with sputtered Pt on both sides in a HS cell at a constant voltage of 0.2 V.

The BiCl₃ composite used as the cathode was prepared in two steps: First, carbon-coated BiCl₃ was obtained by ball-milling BiCl₃ (99.9 %, Sigma-Aldrich) and AB for 1 h at 400 rpm. In the second step, the carbon-coated BiCl₃ and CsSn_0.95Mn_0.05Cl₃ were mixed using a mortar in an appropriate weight ratio (BiCl₃ : CsSn_0.95Mn_0.05Cl₃ : AB = 4 : 5 : 1). The Sn composite used as the anode was prepared by mixing Sn powder (99.5 %, Wako), CsSn_0.95Mn_0.05Cl₃, and AB in a weight ratio of 4 : 5 : 1 using a mortar. To prepare the all-solid-state chloride-ion battery cell, the CsSn_0.95Mn_0.05Cl₃ electrolyte (100 mg) was pressed at 128 MPa using a polyetheretherketone sleeve (EQ-PSC, AA Portable Power) having an inside diameter of 10 mm. The CsSn_0.95Mn_0.05Cl₃ was sandwiched between the BiCl₃ cathode composite (25 mg) and the Sn anode composite (25 mg) and pressed at 510 MPa. Galvanostatic charge–discharge tests of the cell were conducted at room temperature using a battery cycler (HJ1020mSD8, Hokuto Denko) at a current density of 20 µA cm⁻² (∼1.6 mA g⁻¹) with the cell in an Ar-filled glovebox. XRD patterns of the BiCl₃ cathode and Sn anode were acquired at the initial and discharged states of the cell. Also, XPS measurements using a JPS-9010MC/IV (JEOL) with a monochromatic MgK_α radiation source (1253.6 eV) were carried out on the initial BiCl₃ cathodes and Sn anodes as well as on the discharged electrodes after 30 cycles.

3. Results & Discussion

Figure 1 shows the XRD patterns for the obtained CsSnCl₃ and CsSn_0.95Mn_0.05Cl₃. The XRD patterns of CsSnCl₃ prepared by the liquid-phase method and the mechanical milling method were indexed as monoclinic CsSnCl₃ with space group P2₁/c. However, CsSn_0.95Mn_0.05Cl₃ prepared by the mechanical milling method was indexed as a cubic perovskite structure with space group Pm-3m. We carried out Rietveld analysis of the obtained XRD patterns to further characterize the structure of CsSn_0.95Mn_0.05Cl₃. The results of the Rietveld analysis are shown in Fig. S1 and Table S1. The lattice parameter is a = 5.504 Å (= 0.5504 nm), which is slightly smaller than that of perovskite-structured CsSnCl₃ (a = 5.604 Å).¹⁹ This smaller lattice parameter is attributed to the partial substitution of the Sn²⁺ site in CsSnCl₃ by Mn²⁺ with a smaller ionic radius. We prepared CsSn_0.9Mn_0.1Cl₃ with increased Mn²⁺ substitution by the mechanical milling method, and CsMnCl₃ was detected in the XRD pattern of the product. Therefore, the amount of Mn²⁺ in solid solution at the Sn²⁺ site in CsSnCl₃ prepared by mechanical milling is less than 10 mol%. On the other hand, it has been reported that CsSn_0.9Mn_0.1Cl₃ could be prepared by slowly cooling the melt of a stoichiometric mixture of the chlorides,²⁰ thus the solid solubility limit of Mn²⁺ may differ depending on the synthesis method.

Figure 1.

XRD patterns for CsSnCl₃ prepared by a liquid-phase method and a mechanical milling method, along with the patterns of CsSn_0.95Mn_0.05Cl₃ and CsSn_0.9Mn_0.1Cl₃.

DSC measurements were performed to investigate the temperature range in which perovskite-type CsSn_0.95Mn_0.05Cl₃ is stable. Figures 2a and 2b show DSC curves of CsSnCl₃ prepared by the liquid-phase method and CsSn_0.95Mn_0.05Cl₃ prepared by mechanical milling, respectively. In the heating scan from room temperature to 200 °C, CsSnCl₃ shows a sharp endothermic peak at ∼115 °C, which corresponds to the phase transition from monoclinic (phase II) to cubic perovskite (phase I).¹⁹ By contrast, a very weak peak is observed in the heating scan of CsSn_0.95Mn_0.05Cl₃. The cooling scans of CsSnCl₃ and CsSn_0.95Mn_0.05Cl₃ from 200 to −150 °C each show a single endothermic peak at approximately 15 °C and −15 °C, respectively. These peaks represent the phase transition from phase I to phase I*. Phase I* is considered to be disordered compared to the perovskite Phase I.²⁰ Because the phase-transition temperature of CsSn_0.95Mn_0.05Cl₃ is lower than that of CsSnCl₃, the Mn²⁺ doping clearly enhanced the stability of the perovskite structure at low temperatures. CsSnCl₃ doped with 10 mol% Mn²⁺ undergoes a phase transition at −80 °C,²⁰ which is likely attributable to the difference in stability of the perovskite-type structure depending on the concentration of Mn²⁺.

Figure 2.

DSC curves for (a) CsSnCl₃ prepared by a liquid-phase method and (b) CsSn_0.95Mn_0.05Cl₃; both curves were recorded at a heating and cooling rate of 5 °C min⁻¹.

The conductivities of CsSnCl₃ and CsSn_0.95Mn_0.05Cl₃ were investigated by EIS. Their EIS spectra were recorded as the temperature was raised and then lowered in the range from −30 to 150 °C. Figures S2 and S3 show Nyquist plots of CsSnCl₃ and CsSn_0.95Mn_0.05Cl₃, respectively. A semicircle at high frequencies and a straight line at low frequencies are observed in the Nyquist plots. The semicircle was ascribed to the resistances of the bulk and grain boundaries of the electrolytes, while the straight line was ascribed to the contribution by the blocking electrodes. Figure 3 shows the conductivity of CsSnCl₃ and CsSn_0.95Mn_0.05Cl₃ at several temperatures. During the heating process of CsSnCl₃, the conductivity drastically increased at 120 °C, near the temperature of the phase transition to the cubic perovskite structure. In the cooling process, CsSnCl₃ exhibited a conductivity on the order of 10⁻⁴ S cm⁻¹ when the temperature was lowered to 40 °C; however, the conductivity remarkably decreased at 25 °C. This result is consistent with the DSC results. By contrast, the Arrhenius plots of CsSn_0.95Mn_0.05Cl₃ showed no drastic conductivity change during the heating and cooling processes in the temperature range from 25 to 150 °C. The results indicate that the phase transition was not occurred in this temperature range, which is consistent with the DSC results. CsSn_0.95Mn_0.05Cl₃ exhibits a high conductivity of 2.0 × 10⁻⁴ S cm⁻¹ at 25 °C because it possesses a perovskite-type structure.

Figure 3.

Arrhenius plots for CsSnCl₃ prepared by a liquid-phase method and for CsSn_0.95Mn_0.05Cl₃.

Because perovskite-type CsSnCl₃ is known to exhibit semiconducting behavior,^19,20 CsSn_0.95Mn_0.05Cl₃ might exhibit electronic conductivity. We investigated the electronic conductivity of CsSn_0.95Mn_0.05Cl₃ via chronoamperometry measurements using a Pt/CsSn_0.95Mn_0.05Cl₃/Pt cell. Figure 4a shows the chronoamperogram obtained for CsSn_0.95Mn_0.05Cl₃ under an applied constant potential of 0.2 V at 25 °C. A large current was observed immediately after the voltage was applied; however, the current decreased as time progressed and reached equilibrium after 5000 s. The current value at this time was attributed to electron transfer. A current of 39 nA was observed, and the electronic conductivity of CsSn_0.95Mn_0.05Cl₃ was calculated to be 1.5 × 10⁻⁸ S cm⁻¹. This value is four orders of magnitude smaller than the conductivity calculated from the impedance measurement, suggesting that the high conductivity of CaSn_0.95Mn_0.05Cl₃ is mostly due to ionic conduction.

Figure 4.

(a) Chronoamperogram for CsSn_0.95Mn_0.05Cl₃ at a voltage of 0.2 V. (b) LSV curve for CsSn_0.95Mn_0.05Cl₃ at a scan rate of 0.1 mV s⁻¹.

LSV measurements were performed to investigate the electrochemical stability window of CsSn_0.95Mn_0.05Cl₃. Figure 4b shows LSV curves of CsSn_0.95Mn_0.05Cl₃ with Pt as the working electrode and a Sn/SnCl₂ composite electrode as the counter electrode, recorded at a scan rate of 0.1 mV s⁻¹. A small reduction peak was observed below approximately −0.35 V vs. Sn/SnCl₂, and a large reduction peak was observed near −1 V vs. Sn/SnCl₂. By contrast, no oxidation peak was observed in the potential range to 2.5 V vs. Sn/SnCl₂. These results indicate that the electrochemical stability window for CsSn_0.95Mn_0.05Cl₃ is above 2.85 V.

Figure 5a shows the charge–discharge curves of the all-solid-state cell with a BiCl₃ cathode, Sn anode, and CsSn_0.95Mn_0.05Cl₃ solid electrolyte at room temperature at a current density of 20 µA cm⁻². The capacities presented here correspond to the weight of BiCl₃ in the cathode. The first discharge capacity of the BiCl₃ cathode was 169 mAh g⁻¹ at an average of 0.3 V vs. Sn/SnCl₂, which represents 66 % of the theoretical capacity of BiCl₃ (255 mAh g⁻¹). The first charge curve shows a capacity of 134 mAh g⁻¹, which corresponds to 79 % of the first discharge capacity. The cycle performance of the Sn/CsSn_0.95Mn_0.05Cl₃/BiCl₃ cell operated at room temperature is presented in Fig. 5b and Fig. S4. The initial reversible capacity of 134 mAh g⁻¹ decreased to 30 mAh g⁻¹ after 10 cycles. The capacity decay may be ascribed to an increase of the electrode-electrolyte interfacial resistance by the large volume change of the BiCl₃.

Figure 5.

(a) Charge–discharge profiles and (b) cycle performance of the Sn/CsSn_0.95Mn_0.05Cl₃/BiCl₃ cell at room temperature.

To investigate the reaction mechanism, we recorded ex situ XRD patterns for three-layer pellets before and after discharge. Figure 6a shows the XRD patterns of the BiCl₃ cathode before and after discharge. Before discharge, the peaks derived from BiCl₃ and CsSn_0.95Mn_0.05Cl₃ were observed. After discharge, the intensity of the BiCl₃ peak decreased and a peak of Bi metal appeared at ∼27°, suggesting that BiCl₃ was reduced to Bi metal during the discharge process. Figure 6b shows the XRD patterns of the Sn anode at the initial and discharged states. In the pattern acquired before discharge, diffraction peaks of Sn metal and CsSn_0.95Mn_0.05Cl₃ were observed. After discharge, new peaks assigned to SnCl₂ resulting from the oxidation of Sn metal during the discharge process were observed. No substantial change in the peak intensity of Sn was observed even after discharge because of the excess amount of anode material used. These results confirmed that the redox reaction of BiCl₃ and Sn occurred as a result of Cl⁻-ion shuttle via the CsSn_0.95Mn_0.05Cl₃ electrolyte.

Figure 6.

XRD patterns for the (a) BiCl₃ cathode and (b) Sn anode of the Sn/CsSn_0.95Mn_0.05Cl₃/BiCl₃ cell before and after discharge.

This redox reaction mechanism of BiCl₃ and Sn is supported by the XPS analysis results. Figure 7 shows the XPS spectra of the initial BiCl₃ cathode and the Sn anode powders, along with the spectra of the corresponding discharged samples after 30 cycles. In the spectra of the BiCl₃ cathode before cycling, two dominant peaks were observed at binding energies of 159.7 and 165.0 eV, corresponding to Bi 4f_7/2 and 4f_5/2, respectively. According to our XPS measurement results for pure BiCl₃ powder and the reference data for BiF₃ (160.8 eV for Bi 4f_7/2) and BiI₃ (159.3 eV for Bi 4f_7/2) from the National Institute of Standards and Technology (NIST) XPS database, these two peaks are attributable to BiCl₃. After cycling, the shoulder peak of Bi 4f_7/2 centered at 157.0 eV was observed, corresponding to Bi metal;^23,24 thus, the reduction of Bi³⁺ to Bi⁰ during cycling was confirmed. In the spectra of the Sn anode, dominant peaks of Sn 3d_5/2 at 486.6 eV and 3d_3/2 at 495.0 eV are attributed to the large amount of CsSn_0.95Mn_0.05Cl₃ in the anode.²⁵ According to the NIST XPS database, the spectrum of SnCl₂ includes a 3d_5/2 signal at 486.6–486.7 eV; thus, the oxidation product SnCl₂ can be detected directly. In addition to the two dominant peaks, the two shoulder peaks at 484.6 eV of Sn 3d_5/2 and 495.0 eV of 3d_3/2 also appeared, corresponding to Sn⁰ metallic species in the anode.²⁶ We observed that the peak intensity ratio of Sn⁰ to Sn²⁺ decreased slightly after cycling, indicating an oxidation consumption of Sn⁰. These results are consistent with the conclusions obtained from the XRD analysis.

Figure 7.

XPS spectra for the Bi 4f and Sn 3d regions of the BiCl₃ cathode and Sn anode (a) before and (b) after cycling for 30 cycles (discharged state).

4. Conclusion

We showed that the perovskite-type CsSn_0.95Mn_0.05Cl₃ synthesized by a mechanical milling method is stable at room temperature. It exhibits a high ionic conductivity of 2.0 × 10⁻⁴ S cm⁻¹ at 25 °C. LSV experiments showed that CsSn_0.95Mn_0.05Cl₃ is stable in the potential range above −0.35 V vs. Sn/SnCl₂ and exhibits an electrochemical window of at least 2.85 V. An all-solid-state chloride-ion battery with CsSn_0.95Mn_0.05Cl₃ as a solid electrolyte, BiCl₃ as a cathode, and Sn metal as an anode exhibited an initial discharge capacity of 169 mAh g⁻¹ at room temperature. XRD and XPS analyses before and after discharge indicated that Cl⁻ ions migrate between the cathode and anode during the discharge process.

Acknowledgments

This work was supported by “Crossover Alliance” Grant Number 2022Y008.

Data Availability Statement

The data that support the findings of this study are openly available under the terms of the designated Creative Commons License in J-STAGE Data at https://doi.org/10.50892/data.electrochemistry.23304770.

• 1) Perovskite-type CsSnCl₃ is an attractive candidate for use as a solid electrolyte in all-solid-state chloride-ion batteries because it exhibits high ionic conductivity. However, perovskite-type CsSnCl₃ is metastable at room temperature and easily undergoes a phase transition to a stable phase. Here, we prepared perovskite-type CsSn_0.95Mn_0.05Cl₃, in which the Sn²⁺ in CsSnCl₃ is partly substituted with Mn²⁺, via a mechanical milling method. Differential scanning calorimetry showed that the perovskite-type CsSn_0.95Mn_0.05Cl₃ is stable to −15 °C. Moreover, it exhibits a high chloride ionic conductivity of 2.0 × 10⁻⁴ S cm⁻¹ at 25 °C. We demonstrated the room-temperature operation of an all-solid-state chloride-ion battery with a BiCl₃ cathode, an Sn anode, and CsSn_0.95Mn_0.05Cl₃ as the electrolyte. The first discharge capacity of the all-solid-state cell at room temperature was 169 mAh g⁻¹ based on the weight of BiCl₃. X-ray diffraction and X-ray photoelectron spectroscopic analyses confirmed that the reaction mechanism of the cell is derived from the redox reaction of BiCl₃ and Sn.

CRediT Authorship Contribution Statement

Ryo Sakamoto: Conceptualization (Lead), Data curation (Equal), Formal analysis (Equal), Writing – original draft (Lead)

Nobuaki Shirai: Formal analysis (Supporting)

Liwei Zhao: Formal analysis (Supporting), Writing – original draft (Supporting)

Atsushi Inoishi: Data curation (Equal), Funding acquisition (Lead), Project administration (Lead), Writing – review & editing (Equal)

Hikari Sakaebe: Writing – review & editing (Equal)

Shigeto Okada: Writing – review & editing (Equal)

Conflict of Interest

The authors declare no conflict of interest in the manuscript.

Funding

Crossover Alliance: 2022Y008

Footnotes

R. Sakamoto and A. Inoishi: ECSJ Active Members

H. Sakaebe and S. Okada: ECSJ Fellows

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