All-Solid-State Li-ion Batteries Based on Garnet-Type Fast Li

All-Solid-State Li-ion Batteries Based on Garnet-Type Fast Li
All-Solid-State Li-ion Batteries Based on
Garnet-Type Fast Li-ion Conductor Li7La3Zr2O12
Jan van den Broek
Solid oxide electrolytes for Li-ion batteries offer many advantages in comparison to their liquid
electrolyte battery counterparts, such as a higher safety, a much higher electrochemical and
thermal stability window, and higher chemical stability with a variety of different electrode
materials. They have therefore the potential to enable higher energy densities of Li-ion
batteries in the future. The Li-stuffed garnet-type oxide Li7La3Zr2O12 (LLZO) is the most
promising solid oxide electrolyte at the moment because it offers high Li-ion conductivity and
a large electrochemical stability window over a wide potential range. LLZO is mostly
synthesized by standard solid-state reactions, requiring relatively high temperatures. Here a
novel modified sol-gel combustion method is presented that greatly simplifies processing and
lowers processing temperatures of LLZO powder with composition Li6.25Al0.25La3Zr2O12.
Electrolyte pellets pressed from this powder show high relative densities and ionic
conductivities after sintering. All-solid-state batteries based on LLZO were so far only tested
with cathode materials, and reasonable electrochemical activities were only obtained for
cathodes deposited by thin film deposition. Here, the anode material Li4Ti5O12 is deposited
directly on sintered electrolyte pellets using drop casting of a composite electrode slurry. The
important role of the solid electrolyte–electrode interface is investigated, and it is shown how
to decrease resistance values and to improve charge–discharge capacities by interfacemodification. It is revealed how a more intimate embedding of the electrode into the electrolyte
by means of a porous interface enhances delivered capacities and cycling properties of allsolid-state Li-ion batteries based on garnet-type LLZO electrolytes.
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