Oxide ceramic electrolytes for all-solid-state lithium batteries – cost-cutting cell design and environmental impact

All-solid-state batteries are a hot research topic due to the prospect of high energy density and higher intrinsic safety, compared to conventional lithium-ion batteries. Of the wide variety of solid-state electrolytes currently researched, oxide ceramic lithium-ion conductors are considered the most difficult to implement in industrial cells. Although their high lithium-ion conductivity combined with a high chemical and thermal stability make them a very attractive class of materials, cost-cutting synthesis and scalable processing into full batteries remain to be demonstrated. Additionally, they are Fluorine-free and can be processed in air but require one or more high temperature treatment steps during processing counteracting their ecological benefits. Thus, a viable cell design and corresponding assessment of its ecological impact is still missing. To close this gap, we define a target cell combining the advantages of the two most promising oxidic electrolytes, lithium lanthanum zirconium oxide (LLZO) and lithium aluminium titanium phosphate (LATP). Even though it has not been demonstrated so far, the individual components are feasible to produce with state-of-the-art industrial manufacturing processes. This model cell then allows us to assess the environmental impact of the ceramic electrolyte synthesis and cell component manufacturing not just on an abstract level (per kg of material) but also with respect to their contributions to the final cell. The in-depth life cycle assessment (LCA) analysis revealed surprising similarities between oxide-based all-solid-state batteries and conventional Li-ion batteries. The overall LCA inventory on the material level is still dominated by the cathode active material, while the fabrication through ceramic manufacturing processes is a major contributor to the energy uptake. A clear path that identifies relevant research and development directions in terms of economic benefits and environmental sustainability could thus be developed to promote the competitiveness of oxide based all-solid-state batteries in the market

Laser-sintered thin films of doped SiGe nanoparticles

We present a study of the morphology and the thermoelectric properties of short-pulse laser-sintered (LS) nanoparticle (NP) thin films, consisting of SiGe alloy NPs or composites of Si and Ge NPs. Laser-sintering of spin-coated NP films in vacuum results in a macroporous percolating network with a typical thickness of 300 nm. The Seebeck coefficient is independent of the sintering process and typical for degenerate doping. The electrical conductivity of LS films rises with increasing temperature, best described by a power-law and influenced by two-dimensional percolation effects.Comment: 4 pages, 4 figure

Stabilization of mid-sized silicon nanoparticles by functionalization with acrylic acid

We present an enhanced method to form stable dispersions of medium-sized silicon nanoparticles for solar cell applications by thermally induced grafting of acrylic acid to the nanoparticle surface. In order to confirm their covalent attachment on the silicon nanoparticles and to assess the quality of the functionalization, X-ray photoelectron spectroscopy and diffuse reflectance infrared Fourier spectroscopy measurements were carried out. The stability of the dispersion was elucidated by dynamic light scattering and Zeta-potential measurements, showing no sign of degradation for months

Spray Flame Synthesis (SFS) of Lithium Lanthanum Zirconate (LLZO) Solid Electrolyte

A spray-flame reaction step followed by a short 1-h sintering step under O2 atmosphere was used to synthesize nanocrystalline cubic Al-doped Li7La3Zr2O12 (LLZO). The as-synthesized nanoparticles from spray-flame synthesis consisted of the crystalline La2Zr2O7 (LZO) pyrochlore phase while Li was present on the nanoparticles’ surface as amorphous carbonate. However, a short annealing step was sufficient to obtain phase pure cubic LLZO. To investigate whether the initial mixing of all cations is mandatory for synthesizing nanoparticulate cubic LLZO, we also synthesized Li free LZO and subsequently added different solid Li precursors before the annealing step. The resulting materials were all tetragonal LLZO (I41/acd) instead of the intended cubic phase, suggesting that an intimate intermixing of the Li precursor during the spray-flame synthesis is mandatory to form a nanoscale product. Based on these results, we propose a model to describe the spray-flame based synthesis process, considering the precipitation of LZO and the subsequent condensation of lithium carbonate on the particles’ surface

Towards a Framework for Evaluating and Reporting Hansen Solubility Parameters: Applications to Nano and Micron Scale Particle Dispersions

A thorough understanding of complex interactions within particulate systems is a key for knowledge-based formulations. Hansen solubility parameters (HSP) are widely used to assess the compatibility of the dispersed phase with the continuous phase. At present, the determination of HSP is often based on a liquid ranking list obtained by evaluating a pertinent dispersion parameter using only one pre-selected characterization method. Furthermore, one cannot rule out the possibility of subjective judgment especially for liquids for which it is difficult to decipher the compatibility or underlying interactions. As a result, the end value of HSP might be of little or no information. To overcome these issues, we introduce a generalized technology-agnostic combinatorics-based approach. We discuss the principles of the approach and the implications of evaluating and reporting particle HSP values. We demonstrate the approach by using SiNx particles synthesized in the gas phase. We leverage the analytical centrifugation data to evaluate stability trajectories of SiNx dispersions in various liquids to deduce particle-liquid compatibility. </p

Multiscale Simulation of the Formation of Platinum-Particles on Alumina Nanoparticles in a Spray Flame Experiment

Platinum decorated alumina particles have the potential of being a highly (cost-)effective catalyst. The particles are synthesized from platinum(II) acetylacetonate dissolved in a mixture of isopropanol and acetic acid with dispersed alumina carriers. The process is simulated by means of large eddy simulation with reaction kinetics and aerosol dynamics modeling. A two mixture fraction approach for tabulated chemistry with a thickened flame model is used to consider the complex reaction kinetics of the solvent spray combustion. Diffusion is described followings Ficks law with a unity Lewis number for the gas phase species, whereas the particle diffusion coefficients are calculated according to the kinetic theory. An extended model for aerosol dynamics, capable of predicting deposition rate and surface particle growth, is derived from the classical sectional technique. The simulations are compared and validated with product particle characteristics obtained from the experimental observations. Distributions for different locations within the simulation domain show the evolution of particle sizes deposited on the alumina particle surface, and transmission electron microscopy (TEM) images of the composite particles are shown in comparison to 3D particles ballistically reconstructed from simulation data. The ratio of deposited platinum on the alumina carrier particles and the mean diameters of the deposited particles are in good agreement with the experimental observation. Overall, the new method has demonstrated to be suitable for simulating the particle decoration process

Validation of the silicon nanoparticle production on the pilot plant scale via long-term gas-phase synthesis using a microwave plasma reactor

The formation of crystalline silicon nanoparticles by homogeneous gas-phase reactions as a direct way to produce high-purity raw material is applied. For this purpose, a microwave-assisted plasma reactor is used. Goal of this paper is to show the scalability of our process technology from laboratory scale to pilot plant scale while maintaining the particle characteristics. This is demonstrated by producing and analyzing silicon nanoparticles during long-term synthesis in a pilot-scale microwave plasma reactor over a period of six hours. The focus is on a high production rate in conjunction with consistent particle characteristics. A continuous production of the mostly spherical crystalline silicon particles with a count median diameter (CMD) of 23.4 nm and a geometric standard deviation of 1.5 is shown using TEM analysis. The stability of the synthesis process is monitored by means of regular sampling and analyzing batch samples extracted from the process every 30 min. Here it is shown that the CMD varies statistically between 21 and 26 nm. Moreover, the decomposition rate of the precursor was determined to be 99%, while the energy supply remained constant. A constant production rate of about 200 g∙h−1 is shown