Reactions at the electrode/electrolyte interface of all-solid-state lithium batteries incorporating Li–M (M=Sn, Si) alloy electrodes and sulfide-based solid electrolytes

• Published in: Solid state ionics Vol. 285; pp. 101 - 105
• Main Authors: Sakuma, Masamitsu, Suzuki, Kota, Hirayama, Masaaki, Kanno, Ryoji
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.02.2016
• Subjects: Electrode potentials; Electrodes; Electrolyte decomposition; Electrolytes; Formations; Interface resistance; Lithium batteries; Solid electrolytes; Sulfide-based solid electrolyte; Tin base alloys; X-rays; Electrolyte decomposition; Interface resistance; Sulfide-based solid electrolyte
• ISSN: 0167-2738; 1872-7689
• DOI: 10.1016/j.ssi.2015.07.010

Reactions at the electrode/electrolyte interface of all-solid-state lithium batteries were studied for combinations of sulfide-based solid electrolytes with various Li4-xGe1-xPxS4 and Liy-M (M=Sn, Si) alloys as the negative electrodes, using ac impedance, X-ray diffraction and energy-dispersive X-ray spectroscopy. The solid electrolyte at the interfacial region was found to decompose with the application of a current through the cells, resulting in the formation of a solid electrolyte interphase (SEI) layer. Resistivity changes at the interface varied depending on the electrolyte composition and the redox potential (vs. Li/Li+) of the negative electrode material. Lower resistances were observed with lower Ge contents in the solid electrolyte and the use of a Li–M alloy with a higher redox potential due to the formation of an electrochemically stable SEI layer during battery operation. In contrast, a combination of higher Ge content and an alloy with a lower redox potential led to a rapid increase in the SEI resistance and increase in its thickness. The presence of a Li–P–S compound with low ionic conductivity in the interfacial region was found to be related with the increase of interfacial resistance, leading to poor cycling characteristics. The formation of a suitable SEI layer is an important factor in the future development of all-solid-state batteries and this study serves to clarify the relationships between the formation of the SEI phase, the redox potential of the electrode and the sulfide-based solid electrolyte composition. •Interfacial resistances in all-solid-state lithium batteries were investigated.•AC impedance method clarified the changes of the resistance during battery operation.•Sulfide solid electrolytes were decomposed at lower voltage region (vs. Li/Li+).•Lower resistances were observed with lower Ge proportion in the Li4-xGe1-xPxS4.