Yohei Onodera

Real-time observations of lithium battery reactions—operando neutron diffraction analysis during practical operation

Among the energy storage devices for applications in electric vehicles and stationary uses, lithium batteries typically deliver high performance. However, there is still a missing link between the engineering developments for large-scale batteries and the fundamental science of each battery component. Elucidating reaction mechanisms under practical operation is crucial for future battery technology. Here, we report an operando diffraction technique that uses high-intensity neutrons to detect reactions in non-equilibrium states driven by high-current operation in commercial 18650 cells. The experimental system comprising a time-of-flight diffractometer with automated Rietveld analysis was developed to collect and analyse diffraction data produced by sequential charge and discharge processes. Furthermore, observations under high current drain revealed inhomogeneous reactions, a structural relaxation after discharge, and a shift in the lithium concentration ranges with cycling in the electrode matrix. The technique provides valuable information required for the development of advanced batteries.

Development of SPICA, New Dedicated Neutron Powder Diffractometer for Battery Studies

SPICA, a new special environment powder neutron diffractometer was built at BL09 in the Material and Life science Facility (MLF) of the Japan Proton Accelerator Research Complex (J-PARC). This is the first instrument dedicated solely to the study of next-generation batteries in J-PARC and is optimized for in situ measurements to clarify structural changes of materials in batteries. The basic design and instrumentation of SPICA have been completed. The highest Δd/d resolution achieved at the commissioning stage was 0.09% at the back scattering bank of SPICA. The reliability of the diffraction data has achieved a sufficiently high level for the structural analysis of materials using the Rietveld method. The air scattering banks with the blades made of B4C for in situ measurements also function very well.

Structural and electronic features of binary Li(2)S-P(2)S(5) glasses.

The atomic and electronic structures of binary Li2S-P2S5 glasses used as solid electrolytes are modeled by a combination of density functional theory (DFT) and reverse Monte Carlo (RMC) simulation using synchrotron X-ray diffraction, neutron diffraction, and Raman spectroscopy data. The ratio of PSx polyhedral anions based on the Raman spectroscopic results is reflected in the glassy structures of the 67Li2S-33P2S5, 70Li2S-30P2S5, and 75Li2S-25P2S5 glasses, and the plausible structures represent the lithium ion distributions around them. It is found that the edge sharing between PSx and LiSy polyhedra increases at a high Li2S content, and the free volume around PSx polyhedra decreases. It is conjectured that Li+ ions around the face of PSx polyhedra are clearly affected by the polarization of anions. The electronic structure of the DFT/RMC model suggests that the electron transfer between the P ion and the bridging sulfur (BS) ion weakens the positive charge of the P ion in the P2S7 anions. The P2S7 anions of the weak electrostatic repulsion would causes it to more strongly attract Li+ ions than the PS4 and P2S6 anions, and suppress the lithium ionic conduction. Thus, the control of the edge sharing between PSx and LiSy polyhedra without the electron transfer between the P ion and the BS ion is expected to facilitate lithium ionic conduction in the above solid electrolytes.

Crystal Structure of Li7P3S11 Studied by Neutron and Synchrotron X-ray Powder Diffraction

Time-of-flight neutron powder diffraction (TOF-NPD) and synchrotron X-ray powder diffraction (SXPD) experiments were carried out to study the crystal structure of 7 Li isotope enriched 7 Li 7 P 3 S 11 glass ceramics, which is a lithium superionic conductor. Combined X-ray/neutron Rietveld refinement informed us precise atomic coordinates, especially lithium. Furthermore, a network of neighboring Li + cations was visualized in the crystal structure of Li 7 P 3 S 11 with the triclinic system (space group: P 1 ) in order to predict the diffusion pathway of Li + cations.

Structural Evidence for High Ionic Conductivity of Li7P3S11 Metastable Crystal

Electrical conductivity, time-of-flight neutron diffraction (TOF-ND), and synchrotron X-ray diffraction (SXRD) measurements were carried out for 7 Li 7 P 3 S 11 metastable crystal and ( 7 Li 2 S) 70 (P 2 S 5 ) 30 glass. Reverse Monte Carlo modeling based on the TOF-ND and SXRD data showed three-dimensional structures of 7 Li 7 P 3 S 11 metastable crystal and ( 7 Li 2 S) 70 (P 2 S 5 ) 30 glass. A detailed polyhedral analysis of the three-dimensional atomic configuration yielded the spatial distribution of [LiS 4 ] tetrahedra ([LiS 4 ] units) and S 4 tetrahedra (without Li + ion; [S 4 ] units) in 7 Li 7 P 3 S 11 metastable crystal and ( 7 Li 2 S) 70 (P 2 S 5 ) 30 glass. When an a c -[S 4 ] unit is recognized as a fully acceptable unit of the Li + ion, the coordination number of a c -[S 4 ] units around a [LiS 4 ] unit for 7 Li 7 P 3 S 11 metastable crystal was estimated to be 3.9 on average, whereas it was 1.9 for ( 7 Li 2 S) 70 (P 2 S 5 ) 30 glass. Such structural characteristics in 7 Li 7 P 3 S 11 metasta...

Structural origin of ionic conductivity for Li7P3S11 metastable crystal by neutron and X-ray diffraction

Reverse Monte Carlo modeling was carried out for Li7P3S11 metastable crystal and (Li2S)70(P2S5)30 glass based on time-of-flight neutron and synchrotron X-ray diffraction data. Polyhedral analysis of three-dimensional structures for Li7P3S11 metastable crystal and (Li2S)70(P2S5)30 glass were gave us not only structural characteristics but also structural origins related to their high ionic conductivity.

Neutron scattering studies of Ti-Cr-V bcc alloy with the residual hydrogen and deuterium

Hydrogen and deuterium pressure-composition (P-C) isotherm measurements were carried out for Ti0.31Cr0.49V0.20 bcc alloy. As a result, the residual hydrogen-to-metal ratio (H/M)res was almost the same as the residual deuterium-to-metal one (D/M)res; the (H/M)res and (D/M)res were approximately 0.5. Furthermore, the neutron scattering experiments were conducted with Ti0.31Cr0.49V0.20 alloys including the residual hydrogen and/or deuterium. It was found that H atoms absorbed in the first absorption cycle up to H/M = 0.5 are hardly bound in the desorption cycle as the residual hydrogen, whereas D atoms are mainly bound in Ti0.31Cr0.49V0.20 bcc alloy as the residual deuterium when D2 gas is partially used in the H absorption reaction.

Ionic conductivity and structural properties of lithium lanthanum titanate quenched into liquid nitrogen studied by neutron powder diffraction

For 7 Li-enriched La 2/3- x 7 Li 3 x TiO 3 samples quenched into liquid nitrogen and cooled in the furnace, impedance measurements and time-of-flight neutron powder diffraction (TOF-NPD) experiments were carried out in order to study the effect of the quenched-into-liquid-nitrogen treatment for the ionic conduction and the structural properties. It was found that the quenched-into-liquid-nitrogen treatment enhances the lithium ionic conductivity in the 7 Li-content range between 3 x ∼0.25 and 0.45. Furthermore, the local structure within 6 A did not change, according to the atomic pair density function (PDF) analysis.

Reverse Monte Carlo modeling of Li2S-P2S5 superionic conductors

Synchrotron X-ray and neutron diffraction measurements were carried out for (7Li2S)x(P2S5)100?x glasses and a 7Li7P3Sn11 metastable crystal. The Reverse Monte Carlo (RMC) modeling provided us the three-dimensional structures of (7Li2S)x(P2S5)100?x and 7Li7P3S11, particularly the distribution of Li+ cations.

Microstructure of hydrogenated Mg2Ni studied by SANS

X-ray powder diffraction (XRD) and small-angle neutron scattering (SANS) experiments were carried out for the hydrogenated and duterated Mg2Ni, respectively. According to the results of XRD experiments, both of them coexisted with unhydrogenated (or undeuterated) Mg2Ni in the hydrogen absorbing cycle. Furthermore, in the SANS experiments, a slope of SANS curve, I(Q), was roughly evaluated by using the following power law: I(Q) ∝ Q−m, where Q is the magnitude of the scattering vector, and m can be equated with a fractal dimensionality, DS (= 6 − m). In conclusion, the hydrogenated and duterated Mg2Ni showed DS~ 3 and ~ 2, respectively. The significant difference between DSs can be understood by considering the scattering length densities, ρ, of Mg2Ni, Mg2NiH4, and Mg2NiD4.