ae9b02401_si_001.pdf (1.41 MB)
Discovering the Influence of Lithium Loss on Garnet Li7La3Zr2O12 Electrolyte Phase Stability
journal contribution
posted on 2020-03-05, 22:43 authored by Andrea Paolella, Wen Zhu, Giovanni Bertoni, Sylvio Savoie, Zimin Feng, Hendrix Demers, Vincent Gariepy, Gabriel Girard, Etienne Rivard, Nicolas Delaporte, Abdelbast Guerfi, Henning Lorrmann, Chandramohan George, Karim ZaghibGarnet-type
lithium lanthanum zirconate (Li7La3Zr2O12, LLZO)-based ceramic electrolyte has
potential for further development of all-solid-state energy storage
technologies including Li metal batteries as well as Li–S and
Li–O2 chemistries. The essential prerequisites such
as LLZO’s compactness, stability, and ionic conductivity for
this development are nearly achievable via the solid-state reaction
route (SSR) at high temperatures, but it involves a trade-off between
LLZO’s caveats because of Li loss via volatilization. For example,
SSR between lithium carbonate, lanthanum oxide, and zirconium oxide
is typically supplemented by dopants (e.g., gallium or aluminum) to
yield the stabilized cubic phase (c-LLZO) that is characterized by
ionic conductivity an order of magnitude higher than the other polymorphs
of LLZO. While the addition of dopants as phase stabilizing agent
and supplying extra Li precursor for compensating Li loss at high
temperatures become common practice in the solid-state process of
LLZO, the exact role of dopants and stabilization pathway is still
poorly understood, which leads to several manufacturing issues. By
following LLZO’s chemical phase evolution in relation to Li
loss at high temperatures, we here show that stabilized c-LLZO can
directly be achieved by an in situ control of lithium
loss during SSR and without needing dopants. In light of this, we
demonstrate that dopants in the conventional SSR route also play a
similar role, i.e., making more accessible Li to the formation and
phase stabilization of c-LLZO, as revealed by our in situ X-ray diffraction analysis. Further microscopic (STEM, EDXS, and
EELS) analysis of the samples obtained under various SSR conditions
provides insights into LLZO phase behavior. Our study can contribute
to the development of more reliable solid-state manufacturing routes
to Garnet-type ceramic electrolytes in preferred polymorphs exhibiting
high ionic conductivity and stability for all-solid-state energy storage.