ORALS

SESSION: SISAMTuePM1-R2	Mizutani International Symposium (6th Intl. Symp. on Science of Intelligent & Sustainable Advanced Materials (SISAM))
Tue. 29 Nov. 2022 / Room: Ballroom A
Session Chairs: Shigeru Horii; Session Monitor: TBA

14:50: [SISAMTuePM107] OL Invited
Challenges for fluoride-ion conductors: Designing fluoride-ion conduction into layered materials
Tsuyoshi Takami¹ ; ¹Kyoto University, Kyoto, Japan;
Paper Id: 393 [Abstract]

The fluorine atom, the second smallest after the hydrogen atom, is characterized by its large electronegativity and small polarizability [1]. Thus, it has little effect on the crystal structure, even though it causes a large electron bias in materials. Because of these unique properties, the fluorine atom is called as ‘magic element’. Fluorine has brought tremendous benefits to our lives through heat-resistant plastics, pharmaceuticals, and pesticides. The oxidation reaction of fluoride ions with a high redox potential is also promising as fluoride-ion batteries. If a solid electrolyte with a sufficient high fluoride-ion conductivity is applied to all-solid-state FIBs, operation at room temperature would become possible. PbSnF₄ with a layered structure exhibits a superionic conductivity (> 10^-3 Scm^-1) at room temperature [2]. Besides it contains harmful lead in the crystal, however, it has a poor reduction resistance and there have been few reports of its incorporation into batteries. Recently, single crystals of fluorinated hexagonal BN were reported to exhibit a high in-plane fluoride-ion conductivity of 0.2 Scm^-1 at room temperature [3]. These reports propose that two-dimensional fluoride-ions diffusion is effective to enhance fluoride-ion conduction. In this lecture, we survey the core design principles that guide a high fluoride-ion conductivity. We conclude with a forward-looking discussion of the exciting link between fluoride-ions diffusion and layered structures in fluoride materials.

References:
[1] S. Dehnen, L. L. Schafer, T. Lectka, and A. Togni, Org. Lett. <b>23</b>, 9013 (2021).
[2] J. M. Reau, C. Lucat, J. Portier, P. Hagenmuller, L. Cot, and S. Vilminot, Mater. Res. Bull. <b>13</b>, 877 (1978).
[3] T. Takami, T. Saito, T. Kamiyama, K. Kawahara, T. Fukunaga, and T. Abe, Materials Today Physics <b>21</b>, 100523 (2021).

SESSION: SISAMTuePM2-R2	Mizutani International Symposium (6th Intl. Symp. on Science of Intelligent & Sustainable Advanced Materials (SISAM))
Tue. 29 Nov. 2022 / Room: Ballroom A
Session Chairs: Hiroshi Sakurai; Session Monitor: TBA

16:20: [SISAMTuePM210] OS Invited
Characterization of Battery Materials by X-ray Compton Scattering
Hiroshi Sakurai¹ ; Kosuke Suzuki¹ ; Tsuyoshi Takami² ; Yoshiharu Uchimoto² ; Naruki Tshuji³ ; Arun Bansil⁴ ; Bernardo Barbiellini⁵ ; Kazushi Hoshi¹ ; Yoshiharu Sakurai³ ; ¹Gunma University, Kiryu, Japan; ²Kyoto University, Kyoto, Japan; ³JASRI, Sayo, Japan; ⁴Northeastern University, Boston, United States; ⁵LUT University, Lappeenranta, Finland;
Paper Id: 401 [Abstract]

Compton-scattered X-ray spectra correspond to the electron momentum density in matter and reflect the wave function in the ground state [1]. Therefore, it is relatively easy to interpret the observed Compton-scattered X-ray spectrum by ab initio electronic structure calculations. The observed information is bulk-sensitive because prover X-rays have energies above 100 keV and are highly penetrating through materials. This research focuses on lithium-ion secondary battery materials. In green technologies such as electric vehicles, improvement of rechargeable battery materials is a key to enhance energy density and charge-discharge stability. In practical batteries, it is important to understand redox reactions and their spatial distribution. From a view point of redox reactions, we measured spinel LixMn2O4, a Li-ion battery cathode material. We found that the redox orbital in the lithium insertion and extraction process is mainly the oxygen 2p orbital [2], although the redox orbital has been considered to be manganese 3d states [3,4]. Furthermore, analysis of the shape of Compton-scattered X-ray spectra can be used as a new nondestructive testing (NDT) technique. We proposed S-parameter analysis to observe the spatial distribution of redox reactions in commercial batteries [5]. Our research shows that Compton scattering measurements can provide insight into the mechanism of lithium batteries and point the way to improved battery materials and new battery designs.

References:
references
[1] M. J. Cooper et al.,X-ray Compton Scattering (Oxford University Press, Oxford, 2004).
[2] K. Suzuki et al. Phys. Rev. Lett. 114, 087401 (2015).
[3] H. Berg et al., J. Mater. Chem. 9, 2813 (1999).
[4] G. E. Grechnev et al. Phys. Rev. B 65, 174408 (2002).
[5] K. Suzuki et al., J. Appl. Phys. 119, 025103 (2016).