Since the lithium-ion secondary batteries (LIBs) based on the LiCoO₂ cathode materials, carbon based anode materials and organic liquid electrolyte have been commercialized, LIBs have been applied as power source for electric or hybrid vehicles beyond small IT applications. [1,2] As used in the large-scale energy storage devices, the safety of LIBs has given rise to more important issue. Therefore, the all-solid-state-batteries (ASSBs) with non-flammable inorganic solid electrolyte are one of the promising candidates.[3,4] Among the solid electrolyte materials, the sulfide-based solid electrolytes are widely used due to higher Li-ion conductivity and their soft property. Nevertheless, the ASSBs have been yet difficult to operate with the long cycle life and high current density despite the use of high Li-ion conducting solid electrolyte owing to the interfacial resistance and insufficient electrochemically active area. [5,6] Therefore, it is important to understand the interfacial characterization of solid-solid interface, especially the cathode and solid electrolyte in the composite cathode of ASSBs. Generally, the cathode materials and sulfide-based solid electrolytes have shown the large interfacial resistance from the space-charge layer and thus, as an effective approach to improve the electrochemical performance of ASSBs, the interfacial modifications for the cathode material by coating of LiNbO₃, Li₄Ti₅O₁₂, LiTaO₃, and Li₂O-SiO₂ have been reported in previous studies. [5-7]

Herein, the detailed microscopic observation and structural analysis for the interface between Li(Ni_0.6Co_0.2Mn_0.2)O₂ (NCM622) layered cathode materials and sulfide-based solid electrolyte are carried out and the comparison with pristine NCM622 and LiNbO₃-coated NCM622 is also depicted. For this study, transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS) analysis have been mainly used. For further investigations, the electrochemical impedance spectroscopy and charge-discharge performance of the all-solid-state batteries using pristine and LiNbO₃-coated NCM622 were demonstrated.

References

[1] J.B. GoodenoughAuthor Vitae, K.S. ParkAuthor VitaeAuthor VitaeAuthor VitaeAuthor Vitae, J. Am. Chem. Soc., 4 (2013) 1167-1176.

[2] J.-Y. Hwang, S.-T. Myung, Y. K. Sun, Chem. Soc. Rev, 46 (2017) 3529−3614.

[3] Y. Ito, M. Otoyama, A. Hayashi, T. Ohtomo, M. Tatsumisago, Journal of Power Sources, 360 (2017) 328-335.

[4] N. Kamaya, K.Homma, Y.Yamakawa, M.Hirayama, R. Kanno. M. Yonemura, T. Kamiyama, Y. Kato, S. Hama, K. Kawamoto, A. Mitsui, Nat. Mater., 10 (2011), 628−686.

[5] N. Ohta, K. Takada, I. Sakaguchi, L. Zhang, R. Ma, k. Fukuda, M. Osada, T. Sasaki, Electrochem. Commun., 9 (2007), 1486-1490.

[6] Y. Seino, T. Ota, K. Takada, Journal of Power Sources, 196 (2011) 6488-6492.

[7] A. Sakuda, H. Kitaura, A. Hayashi, K. Tadanaga, M. Tatsumisago, Electrochem. Solid-state Lett. 11 (2007) A1-A3