A highly plastic Li+ ion conductor based on the KI-KBH4 solid solvent system
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In the present work, the dominant Li+ conduction in 6 mol% LiI-doped KI-KBH4 solid solvent was verified by electrochemical measurement and time-of-flight secondary ion mass spectrometry (TOF-SIMS). After the potentiostatic reduction of the cell Li | KI-KBH4-LiI | Mo at − 0.5 V vs Li+/Li, the deposition of Li metal on the surface of Mo electrode was confirmed by TOF-SIMS measurement. A pair of reduction and oxidation currents are clearly observed at 0 V vs Li+/Li in a cyclic voltammogram of the cell Li | KI-KBH4-LiI | Mo, which is a direct indication for Li+ ion conduction in the KI-KBH4 solid solvent system. From the results of AC impedance measurement of KI-KBH4-LiI, the bulk resistance was mainly observed while the solid electrolyte was pelletized only by uniaxial pressing. The dense microstructure of the pellet supports the results of impedance measurement where the contribution of grain boundary resistance was not observed. The extreme plastic property of the Li+ ion conductor based on KI-KBH4 will allow the interfaces between the solid electrolytes and electrode active materials to be adhered closely.
KeywordsSolid electrolyte Lithium ion conductor Li-free compounds Solid solvent KI LiI
R. M. expresses his great thanks for the financial support from Iketani Science and Technology Foundation and the Ministry of Education, Culture, Sports, Science and Technology, through a Grant-in-Aid for Scientific Research (C), 2015, No. 15 K06463.
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