The lithium diffusion pathway in the LGPS structure visualized through MEM analysis assisted in elucidating the conductivity pathway changes with temperature.

All solid-state batteries are of key importance in the development of next-generation energy storage devices with high energy density. Herein, we report the fabrication and operation of bulk-type 5 V-class all solid-state batteries consisting of LiNi 0.5 Mn 1.5 O 4 cathode, Li 10 GeP 2 S 12 solid-electrolyte, and Li metal anode. The 1st discharge capacity is about 80 mAh g −1 with an average voltage of 4.3 V. The discharge capacity gradually decreases during the subsequent cycles. Xray diffraction and electrochemical impedance spectroscopy measurements reveal that the capacity fading results from the growth of a resistive interfacial layer on the cathode composite. The development of suitable conductive additive and sulfide solid electrolyte materials is essential for the development of high-voltage all solid-state batteries.

Understanding Li-ion conduction in superionic conductors accelerates the development of new solid electrolytes to enhance the charge− discharge performances of all-solid-state batteries. We performed a quasi-elastic neutron scattering study on a model superionic conductor (Li 10+x Ge 1+x P 2−x S 12 , LGPS), to reveal its ion dynamics on an angstrom-scale spatial range and a pico-tonanosecond temporal range. The observation of spectra at 298 K confirmed the high lithium diffusivity. The obtained diffusion coefficient was in the order of 10 −6 cm 2 s −1 at temperatures >338 K and was higher than the reported diffusion coefficient over a longer time scale, as determined by the pulse-field gradient nuclear magnetic resonance method. This difference indicates that there are impediments to ionic motion over a longer time scale. The dynamic behavior of the Li ions was compared with that observed for the Li 9 P 3 S 9 O 3 phase, which possesses the same crystal structure type, but a lower ionic conductivity. The LGPS phase possessed a high lithium mobility over a distance of ∼10 Å, as well as a larger fraction of mobile Li ions, thereby indicating that these features enhance lithium conduction over a longer spatial scale, which is important in all-solidstate batteries.

LiNbO 3 -coated LiNi 0.5 Mn 1.5 O 4 powders were synthesized by a sol-gel method, and their intercalation property as a cathode material was investigated using all-solidstate batteries with Li 10 GeP 2 S 12 solid electrolyte and In-Li metal anode. The LiNbO 3 coating delivered reversible lithium intercalation of LiNi 0.5 Mn 1.5 O 4 through an electrochemical interface with the Li 10 GeP 2 S 12 . Oxygen-deficient LiNi 0.5 Mn 1.5 O 4-δ with a higher electronic conductivity than LiNi 0.5 Mn 1.5 O 4 improved the intercalation © 2016. This manuscript version is made available under the Elsevier user license http://www.elsevier.com/open-access/userlicense/1.0/ 2activity. An all-solid-state battery consisting of 3 wt.%-LiNbO 3 -coated LiNi 0.5 Mn 1.5 O 4δ /Li 10 GeP 2 S 12 /In-Li exhibited a discharge capacity of 80 mAh g -1 at the first cycle with an average discharge voltage of 4.1 V (vs. In-Li), which demonstrates the possibility of 5 V class all-solid-state batteries with a high voltage spinel cathode.

Fast ionic conduction in solid electrolytes plays a key role in feasibility of the all-solid-state battery system. Among the lithium ion conductors, the Li10GeP2S12 (LGPS) system shows the conductivity comparable to organic liquid electrolytes [1]. The recent study focused on the synthesis of solid solutions of this material, which might introduce either lithium vacancy or interstitial lithium ions and might affect its ionic conductivity and electrochemical stability. The crystal structures of the solid solution were studied using neutron diffraction technique. Their conduction pathway was estimated using Maximum Entropy Method (MEM) based on the structure information. These results indicate the lithium conduction pathway in LGPS is one-dimensional pathway along c axis at room temperature, and three-dimensional one at higher temperature [2]. However, the results of MEM provided only the space area of possible lithium ion conduction. Then, the study of lithium diffusive behaviors is necessary to understand lithium ionic conductivity in more details. The dynamics of lithium ion diffusions can be obtained directly by using the Quasielastic Neutron Scattering (QENS) technique because the quasielastic scattering spectrum is a broadening of elastic peak caused by the diffusion of atoms or ions within a material. When ions cause diffusion motions on a fixed sublattice, the quasielastic scattering spectra can exhibit a Q-dependence, which provides information on the dynamical structure of the ions diffusion. In this study, the QENS measurements were performed using the high-resolution Si crystal analyzer TOF type near-backscattering spectrometer, DNA, at MLF/J-PARC, Tokai, Ibaraki, Japan, at the energy resolution of 3.6 µeV [3]. S(Q,ω) spectra from 150 to 640 K were collected. After the analyzed those using jump-diffuse model [4,5], self-diffusion constants, jump length and mean residence time of conduction lithium ions in LGPS system were determined. The jump length was 1.73 Å at 473K and 2.72 Å at 640 K respectively. The jump length at 473 K was consistent with conduction along caxis. The jump length at 640 K also corresponded to the three dimensional conduction model. In this presentation, the mechanism of lithium ion diffusion in LGPS system will be discussed. References [1] N. Kamaya, K. Homma, Y. Yamakawa, M. Hirayama, R. Kanno, M. Yonemura, T. Kamiyama, Y. Kato, S. Hama, K. Kawamoto and A. Mitsui, Nature Materials, 10, 5 (2011). [2] O. Kwon, M. Hirayama, K. Suzuki, Y. Kato, T. Saito, M. Yonemura, T. Kamiyama and R. Kanno, J. Mater. Chem. A, 3, 9 (2014). [3] K. Shibata, N. Takahashi, Y. Kawakita, M. Matsuura, T. Yamada, T. Tominaga, W. Kambara, M. Kobayashi, Y. Inamura, T. Nakatani, K. Nakajima, and M. Arai, JPS Conf. Proc. 8, 036022 (2015). [4] C.T. Chudley and R.J. Elliott, Proc. Phys. Soc. 77, 353 (1967) [5] P.A. Egelstaff, B.C. Haywood and F.J. Webb, Proc. Phys. Soc. 90, 681 (1967)