Details

Autor(en) / Beteiligte

• Santhosha, A. L.
• Medenbach, Lukas
• Buchheim, Johannes R.
• Adelhelm, Philipp

Titel

The Indium−Lithium Electrode in Solid‐State Lithium‐Ion Batteries: Phase Formation, Redox Potentials, and Interface Stability

Ist Teil von

• Batteries & supercaps, 2019-06, Vol.2 (6), p.524-529

Erscheinungsjahr

2019

Quelle

Wiley Blackwell Single Titles

Beschreibungen/Notizen

• Lithium solid‐state batteries (Li‐SSBs) require electrodes that provide a sufficiently stable interface with the solid electrolyte. Due to the often limited stability window of solid electrolytes, researchers frequently favor an In−Li alloy instead of lithium metal as counter electrode for two‐electrode measurements. Maintaining a stable potential at the counter electrode is especially important because three‐electrode measurements are hard to realize in solid‐state cells. Although a constant potential of about 0.6 V vs. Li+/Li is commonly accepted for the In−Li electrode, only little is known about the behavior of this electrode. Moreover, the In−Li phase diagram is complex containing several intermetallic phases/compounds such as the InLi phase, or line compounds such as In4Li5 or In2Li3. This means that the redox potential of the In−Li electrode depends on the alloy composition, i. e. the In/Li ratio. Here, we study the behavior of In−Li electrodes in cells with liquid electrolyte to determine their phase evolution and several equilibrium potentials vs. Li+/Li. The room temperature equilibrium redox potential of the In−Li electrode with the favored composition (or more precisely the Li+/(In−InLi) electrode) is 0.62 V vs. Li+/Li. We then discuss the use of In−Li electrodes in solid state cells using Li3PS4 as solid electrolyte and give examples on the importance of the right In/Li ratio of the electrode. While the right In/Li ratio enables stable lithium insertion/deinsertion in symmetrical cells for at least 100 cycles, too much lithium in the electrode leads to a drop in redox potential combined with a rapid build‐up of interface resistance. The combination of indium and lithium provides an electrode that is popular in the field of solid‐state lithium‐ion battery research. The authors study the phase behavior of this electrode and determine the corresponding equilibrium redox potentials versus Li+/Li. They also discuss the stability of different InLi‐intermetallic phases in contact with the solid electrolyte Li3PS4 using symmetrical cells. The results clearly demonstrate the importance of assembling InLi‐electrodes with the right stoichiometry to obtain sufficient interface stability.