Flame made nanoparticles permit processing of dense, flexible, Li⁺ conducting ceramic electrolyte thin films of cubic-Li₇La₃Zr₂O₁₂ (c-LLZO)

Abstract

Conventional casting–sintering of flame made nanoparticles result in high density and ionic conductivity c-LLZO flexible thin film membranes.

Review—Practical Challenges Hindering the Development of Solid State Li Ion Batteries

“…Defects can be loosely defined as any non-uniformity at the macroscopic level, including large-scale porosity or cracks, or at the microscopic level, such as pore channels at multi-grain junctions, grain boundaries, impurity precipitates, or even local non-stoichiometry. SSE materials, shown in Figure 2, displaying translucency can be considered simple examples of low macroscopic defect density, 33,[36][37][38][39] exhibiting low levels of optical scattering defects. However, it is not clear that even such materials are sufficiently defect-free as to avoid Li metal penetration.…”

“…53 Control of the starting particle size and morphology is important for developing a high final sintered density in ceramic systems, and methodologies to create tight particle size distributions of nanoparticles such as flame spray pyrolysis have been shown to be largely successful in this regard. 38 Like previously well-studied high performance ceramic systems that contain a volatile cation, such as Pb(Zr x Ti 1-x )O 3 (PZT), 57 the stoichiometry of sintered surfaces will likely be deficient in volatile species, namely Li, for LLZO type materials. Removal of this nonstoichiometric surface via plasma cleaning, ablation, or polishing of the sintered bodies may help improve chemical homogeneity and engineer surface roughness, both of which are critical for high quality interfacial contact.…”

“…38,40,60,66 Like the bulk powder process described above, cast films require elevated temperature steps to remove binder and sinter to full density. As alluded to previously, free standing films require attention to surface compositional changes, physical shrinkage, warpage, sticking, and breakage at thin length scales.…”

“…Typical batching of 20-50% excess have been reported by teams developing highly dense samples. 33,38,56 Like many other ceramics, the gaseous environment; i.e. oxygen partial pressure, must also be optimized for a given stoichiometry.…”

Reducing the Interfacial Resistance in All‐Solid‐State Lithium Batteries Based on Oxide Ceramic Electrolytes

“…Compared to LiPON, a thin‐film OCE with a thickness of 100 μm also has a comparative specific resistance due to its superior ionic conductivity . Notably, the mechanical strength is a critical factor with respect to the feasibility of assembly and battery safety in thin‐film OCEs . The high elasticity modulus of OCEs can impede the permeation of Li dendrite but may also result in poor interfacial contact between the electrolyte and electrode accompanied by large interfacial resistance.…”