posted on 2022-03-17, 21:03authored byMarius Müller, Johannes Schmieg, Sebastian Dierickx, Jochen Joos, André Weber, Dagmar Gerthsen, Ellen Ivers-Tiffée
Garnet-type Li7La3Zr2O12 (LLZO) is a potential
electrolyte material for all-solid-state Li-ion
batteries mainly because of its reported excellent chemical stability
in contact with Li metal. But good wettability of LLZO and 100% surface
coverage of lithium are still a challenge. This study elucidated the
suitability of magnetron-sputtered indium in Li(In)/LLZO/Li(In) symmetrical
model cells as one of the promising interfacial modifications reported
in the literature. Importance was given to the impact of preparation
parameters on the surface coverage of Li(In)/LLZO interfaces and the
consequences of impedance, cycling stability, and critical current
density. SEM and EDXS analyses of In layers of thickness 100 nm to
1 μm revealed complete dissolution of indium in the lithium
anode after annealing; 300 nm In layers annealed at 220 °C/10
h provided a surface coverage of >80%, best reproducibility, and
a
supreme interface resistance Rint of 12.4
Ω·cm2. Presuming a surface coverage of 100%,
an ultimate interface resistance close to 1 Ω·cm2 can be expected. The critical current density was determined as
200–500 μA/cm2 at a charge of 100–250
μAh, whereas 500 μA/cm2 and above affected
cell stability. The increasing voltage plateau was assigned to the
increase of the interface resistance Rint and the electrolyte resistance RG+GB. SEM, EDXS, and X-ray microtomography analyses after voltage breakdown
confirmed Li-dendrite growth along grain boundaries into LLZO, often
curved parallel to the interface, indicating short-circuiting of the
solid electrolyte. Grain boundary characteristics are supposed to
be decisive for lithium deposition in and failure of garnet-type solid
electrolytes after cycling.