a transparent plastic varnish with nanoparticulate magnetic additives

For the purpose of preparing TCCs (= transparent and electrical conducting coatings), metallic and ferromagnetic nano-additives were dispersed into a transparent varnish and the obtained dispersions were coated on transparent plastic substrates. During hardening of the dispersion the magnetic nano- additives were aligned by a magnetic field. The resulting coatings have electrical pathways along lines of nano-additive chains and are highly transparent in the areas between the lines. Therefore, the electrical conductivity is anisotropic, and it depends on the alignment of the nano- additives (i.e. on the distance between the nano-additives within the chains and the length of the lines) as well as on the thickness of an oxide and/or solvent shell around the nano-additives. The transparency depends also on the alignment and here especially on the thickness and the distance between the formed lines. The quality of the alignment in turn, depends on the magnetic properties and on the size of the particles. We used commercial plastic varnishes, which form electrically isolating (≥ 10− 12 S/m) and transparent (about 90% transparency) coatings, and the following magnetic additives: Co-, Fe-, CoPt3, CoPt3@Au- and Fe@Au-nanoparticles as well as CoNi-nanowires. Coatings with Fe@Au-nanoparticles show the best results in terms of the electrical conductivity (10− 5 S/m–10− 6 S/m) at transparencies above 70%. Furthermore, in addition to the magnetic nano-additives, transparent additives (Al2O3-particles) and non-magnetic, but better conducting additives (carbon- nanotubes) were added to the varnish to increase the transparency and the electrical conductivity, respectively

Working principle of an ionic liquid interlayer during pressureless lithium stripping on Li6.25Al0.25La3Zr2O12 (LLZO) garnet-type solid electrolyte

Solid-state-batteries employing lithium metal anodes promise high theoretical energy and power densities. However, morphological instability occurring at the lithium/solid–electrolyte interface when stripping and plating lithium during cell cycling needs to be mitigated. Vacancy diffusion in lithium metal is not sufficiently fast to prevent pore formation at the interface above a certain current density during stripping. Applied pressure of several MPa can prevent pore formation, but this is not conducive to practical application. This work investigates the concept of ionic liquids as “self-adjusting” interlayers to compensate morphological changes of the lithium anode while avoiding the use of external pressure. A clear improvement of the lithium dissolution process is observed as it is possible to continuously strip more than 70 μm lithium (i. e., 15 mAh cm−2 charge) without the need for external pressure during assembly and electrochemical testing of the system. The impedance of the investigated electrodes is analyzed in detail, and contributions of the different interfaces are evaluated. The conclusions are corroborated with morphology studies using cryo-FIB-SEM and chemical analysis using XPS. This improves the understanding of the impedance response and lithium stripping in electrodes employing liquid interlayers, acting as a stepping-stone for future optimization. © 2021 The Authors. Batteries & Supercaps published by Wiley-VCH Gmb

On the Additive Microstructure in Composite Cathodes and Alumina-Coated Carbon Microwires for Improved All-Solid-State Batteries

All-solid-state batteries promise to enable lithium metal anodes and outperform state-of-the-art lithium-ion battery technology. To achieve high battery capacity, utilization of the active material in the cathode must be maximized. Carbon-based conductive additives are known to improve the capacity and rate performance of electrode composites. However, their influence on cathode composites in all-solid-state batteries is yet not fully understood. Here, we study the influence of several carbon additives with different morphologies and surface areas on the performance of an all-solid-state battery cell Li|β-Li3PS4|Li(Ni0.6Co0.2Mn0.2)O2/β-Li3PS4/carbon. Cycling tests and microstructure-resolved simulations show that higher utilization of the cathode active material can be achieved using fiber-shaped vapor-grown carbon additives, whereas particle-shaped carbons show a minor influence. Unfortunately, carbon additives generally lead to an accelerated capacity loss during cycling and an enhanced formation of solid electrolyte decomposition products. The latter was studied in more detail using cyclic voltammetry, X-ray photoelectron spectroscopy, and cycling experiments. The results show that carbon additives with a small surface area and a fiber-like morphology result in the lowest degree of decomposition. To completely overcome electrolyte degradation caused by the use of carbon additives, a protection concept is developed. A thin alumina coating with a few nanometers thickness was deposited on the carbon fibers by atomic layer deposition, which successfully prevents decomposition reactions, reduces long-term capacity fading, and leads to an enhanced overall all-solid-state battery performance