Synthesis, Materials and Chemistry of Alternative Solid State Electrolyte Films for Batteries
Authors: Rupp Jennifer L.M. 
Published: May 2020

Next generation of energy storage devices may largely benefit from fast and solid Li+ ceramic electrolyte conductors to allow for safe and efficient batteries and fast data calculation. For those applications, the ability of Li-oxides to be processed as thin film structures and with high control over Lithiation and phases at low temperature is of essence to control conductivity. In particular, Li-garnet structures are attractive due to their fast transfer properties and safe operation over a wide electrochemical stability range for batteries.
In the first part we focus on low temperature processing of Li-garnet thin films and nanostructures. Examining the structure-Li transport in solid state and asking the provocative question: How do Li-amorphous to crystalline structures conduct? How to alter processing of Li-oxide films to compensate for the challenge that most of Lithium phases lead to sluggish transport and hard phase stabilization? Bringing down battery solid electrolyte processing temperature and decreasing form factor opens new opportunities in battery design and new doors to give more functions for similar material classes for neuromorphic computing.
Through the talk, we focus on new processing opportunities to Lithiate thin film structures in crystalline state and to assure cubic and fast conduction on the example of Li-garnet for thin film form using some active Lithiation strategies at film deposition1-3. For this we will review the field of thin film processing and introduce to new processing routes based on vacuum and wet-chemical techniques to control various strategies of Lithiation and phase evolution. Excitingly, one has the opportunity for Li-garnet solid state conductors to not only synthesize crystalline structures, but also amorphous films in various frozen-in states4. Insights on degree of amorphous to crystalline Li-garnet thin films are presented based on model experiments, incl. JMAK and TTT-diagram analysis of Li-garnet structure types. Dependent on either a vacuum or wet-chemical based method chosen the phase evolution differs when synthesizing the glass states, with significant impact on condensation and Li-transport5-6. We find that the different amorphous structures that Li-garnets are no Zachariasen glasses as they violate several of Zachariasen rules by text book: These amorphous Li-garnets differ therefore significantly from LIPON but have a wider room to arrange the higher coordinated polyhedral, network former and builders. In amorphous garnets there is room for manipulation in densification and Li-transport and one may potentially profit from high stability window to design batteries with no grain boundaries at the Li electrolyte interface.
In the last part of the talk we will discuss novel low temperature synthesis strategies to define future solid state batteries for low costs and suitability to enter mass manufacturing from a ceramicists perspective.
Collectively, the insights on solid state energy storage provide evidence for the functionalities that those Li-materials can have in the future. The challenges are deeply connected to low temperature processing and design of structure-transport properties, however, solving those allows us to define novel solid state battery architectures.

References:

1. A Low Ride on Processing Temperature for a Fast Li Conduction in Garnet Solid State Battery Films
R Pfenninger, M. Struzik, I Garbayo, E Stilp , JLM Rupp, Nature Energy, 4, 475–4832019, 2019
2. Lithium-Containing Thin Films
JLM Rupp, R Pfenninger, M. Struzik, A Nenning, I Garbayo, US 62/718,838 (2018)
3. Methods of Fabricating Thin Films Comprising Lithium-Containing Materials
JLM Rupp, R Pfenninger, M. Struzik, A Nenning, I Garbayo, US 62/718,842 (2018)
4. Glass-Type Polyamorphism in Li-Garnet Thin Film Solid State Battery Conductors
I Garbayo, M Struzik, WJ Bowman, R Pfenninger, JLM Rupp, Advanced Energy Materials, 1702265 (2018)
5. Solid-state Electrolyte and Method of Manufacture Thereof.
ZD Hood, Y Zhu, L Miara, JLM Rupp. US 62/713,366 (2018)
6. Solution-Processed Solid-state Electrolyte and Method of Manufacture Thereof.
Y Zhu, ZD Hood, L Miara, JLM Rupp US 62/713,428 (2018)