Role of Filler Content and Morphology in LLZO/PEO Membranes

Abstract

Polymer electrolytes containing Li-ion conducting fillers are among the extensively investigated materials for the development of solid-state Li metal batteries. The practical realization of these electrolytes is, however, impeded by their low Li-ion conductivity, which is related to the filler and the interplay between the filler and the polymer. Therefore, we performed an in-depth analysis on the influence of the filler content (0, 10, and 20 wt%) and filler morphology (particles and nanowires) on the electrical and electrochemical properties of the PEO-based composite electrolyte using a wide spectrum of characterization techniques, such as 3D micro-X-ray computed tomography, cross-sectional scanning electron microscopy, X-ray diffraction, and differential scanning calorimetry, impedance spectroscopy, and galvanostatic cycling. The studies reveal that the filler materials are well distributed within the membranes, without any indications for the formation of agglomerates. For 10 wt% filler, a decrease in the crystallinity compared to PEO was observed, in contrast to 20 wt% filler showing an increase in crystallinity. Impedance spectroscopic studies on the Li-ion conductivity of the membranes have shown that the change in the Li-ion conductivity is solely related to the change in the crystallinity, rather than to the participation of LLZO as an active transport mediator. The PEO membranes containing 10 wt% LLZO have been tested in terms of their rate capability in symmetrical Li cells by galvanostatic cycling. A critical current density of up to 1 mA cm−2 at 60°C was observed.

Understanding the Influence of Li7La3Zr2O12 Nanofibers on Critical Current Density and Coulombic Efficiency in Composite Polymer Electrolytes

“…Figure a shows the conductivity of 0 wt % LLZO and 50 wt % LLZO composite electrolytes at various temperatures. At all temperatures, the electrolytes with 50 wt % nanofibers have lower conductivity than PEO-LiTFSI alone; this is in line with previous reports demonstrating a maximum plasticizing effect of ceramic content around 10–20 wt % before a drop in conductivity is seen. , Below 30 °C, there are slight deviations in conductivity and activation energy trends between 0 and 50 wt % LLZO. These differences may be related to the Li + and TFSI – transport along the fiber surface or PEO plasticization, both of which can be impacted by the fiber surface’s Lewis acidity or basicity. − Above 30 °C, all samples exhibit the same activation energies, indicating that the polymer phase dominates ion transport at the temperatures used in our cycling.…”

Overview and perspectives of solid electrolytes for sodium batteries

“…The Li‐ion transport in this system is mainly attributed to the amorphous polymer. Additionally, the cause of the lower ionic conductivity of composite than LLZO ceramic seems to be an extension in the conduction pathway with the formation of an interfacial barrier 158 . The ionic conductivity of NZSP ceramic powder is higher than the NZSP‐doped PVDF–HFP powder studied by Kim et al 148 .…”

“…Additionally, the cause of the lower ionic conductivity of composite than LLZO ceramic seems to be an extension in the conduction pathway with the formation of an interfacial barrier. 158 The ionic conductivity of NZSP ceramic powder is higher than the NZSP-doped PVDF-HFP powder studied by Kim et al 148 In this case, the active filler allows more Na-ion transport than polymer; accordingly, the polymerceramic interfacial layer function as a high-energy barrier to conducting Na-ions. Another example of polymer in ceramic-type composite electrolyte NZSP/PEO was studied by Wang et al and a decrease in ionic conduction from 1.4 × 10 −4 to .83 × 10 −4 S/cm was observed with an increased volume fraction from 10% to 25% of polymer filler in the ceramic matrix.…”

Materials Towards the Development of Li Rechargeable Thin Film Battery

“…Thus, numerous efforts are made by researchers to improve Li ionic conductivity of LLZO SSE (Lv et al, 2021). Some of these efforts are made by forming composites (Huang et al, 2019;Li et al, 2019), designing specialised morphology (Wu et al, 2020;Din et al, 2021;Kravchyk et al, 2022) and by changing method of synthesis (Sakamoto et al, 2013;Yang et al, 2020). Among these, doping remains one of the major efforts (Adhyatma et al, 2022;Wang et al, 2022).…”