Garnet Li7La3Zr2O12 (LLZO) is a potential solid electrolyte
for solid-state batteries
(SSBs) because of its high ionic conductivity, electrochemical stability,
and mechanical strength. However, large interface resistances arising
from deserted cathodes and rigid garnet/electrode interfaces block
its application. In order to deal with this issue, a gel polymer electrolyte
(GPE) was introduced into the cathode and both sides of LLZO to achieve
a solid-state battery. Especially, the provided GPE could be thermally
polymerized and solidified in situ, which would integrate LLZO with
both anode and cathode and dramatically simplify the battery manufacturing
process. Since the interface from rigid LLZO is improved by the flexible
GPE buffer, the inability of flexible GPE to inhibit lithium dendrites
is compensated by the rigid LLZO in return. As a result, the interface
resistances are reduced from 6880 to 473 Ω, the Li symmetric
cell exhibits a flat galvanostatic charge/discharge for 400 h without
lithium dendrites, and the solid-state Li|GPE@LLZO|LiCoO2 battery exerts a capacity retention of 82.6% after 100 cycles at
0.5 C at room temperature. Such an interfacial engineering approach
represents a promising strategy to address solid–solid interface
issues and provides a new design for SSBs with high performance.
Garnet
Li7La3Zr2O12 (LLZO) has
been a prospective solid electrolyte with high ionic
conductivity and a wide electrochemical window. Different from conventional
cold or hot isostatic pressing methods, a self-consolidation strategy
without any pressing assistance was proposed to prepare dense LLZO.
In this work, simultaneous substitution of Nb2O5 and Ta2O5 was attempted to further explore
the mechanism of self-consolidation sintering. The influence of the
Nb2O5 and Ta2O5 substitution
amount on the crystalline phase, morphology, and ionic conductivity
was investigated. Due to the different melting points and thermal
behaviors of Nb2O5 and Ta2O5, the endothermic peak corresponding to sintering became weaker,
which was associated with the self-consolidation process of LLZO.
Accordingly, larger grain sizes and fewer grain boundaries were observed
in LLZO when the amounts of Nb2O5 and Ta2O5 were both 0.25 mol. This indicates that the
simultaneous substitution of different cations plays a vital role
in self-consolidation sintering, which contributes to facilitating
the grain growth and reducing the amount of grain boundaries. This
work emphasizes the key role of the dopant melting point and thermal
behavior in sintering, suggesting an alternative way of substitution
for LLZO electrolyte preparation.
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