Lightweight polymer-carbon composite current collector for lithium-ion batteries

A hermetic dense polymer-carbon composite-based current collector foil (PCCF) for lithium-ion battery applications was developed and evaluated in comparison to state-of-the-art aluminum (Al) foil collector. Water-processed LiNi0.5Mn1.5O4 (LMNO) cathode and Li4Ti5O12 (LTO) anode coatings with the integration of a thin carbon primer at the interface to the collector were prepared. Despite the fact that the laboratory manufactured PCCF shows a much higher film thickness of 55 µm compared to Al foil of 19 µm, the electrode resistance was measured to be by a factor of 5 lower compared to the Al collector, which was attributed to the low contact resistance between PCCF, carbon primer and electrode microstructure. The PCCF-C-primer collector shows a sufficient voltage stability up to 5 V vs. Li/Li+ and a negligible Li-intercalation loss into the carbon primer. Electrochemical cell tests demonstrate the applicability of the developed PCCF for LMNO and LTO electrodes, with no disadvantage compared to state-of-the-art Al collector. Due to a 50% lower material density, the lightweight and hermetic dense PCCF polymer collector offers the possibility to significantly decrease the mass loading of the collector in battery cells, which can be of special interest for bipolar battery architectures. © 2020 by the authors. Licensee MDPI, Basel, Switzerland

Deprivation of dietary fiber in specific-pathogen-free mice promotes susceptibility to the intestinal mucosal pathogen Citrobacter rodentium.

peer reviewedThe change of dietary habits in Western societies, including reduced consumption of fiber, is linked to alterations in gut microbial ecology. Nevertheless, mechanistic connections between diet-induced microbiota changes that affect colonization resistance and enteric pathogen susceptibility are still emerging. We sought to investigate how a diet devoid of soluble plant fibers impacts the structure and function of a conventional gut microbiota in specific-pathogen-free (SPF) mice and how such changes alter susceptibility to a rodent enteric pathogen. We show that absence of dietary fiber intake leads to shifts in the abundances of specific taxa, microbiome-mediated erosion of the colonic mucus barrier, a reduction of intestinal barrier-promoting short-chain fatty acids, and increases in markers of mucosal barrier integrity disruption. Importantly, our results highlight that these low-fiber diet-induced changes in the gut microbial ecology collectively contribute to a lethal colitis by the mucosal pathogen Citrobacter rodentium, which is used as a mouse model for enteropathogenic and enterohemorrhagic Escherichia coli (EPEC and EHEC, respectively). Our study indicates that modern, low-fiber Western-style diets might make individuals more prone to infection by enteric pathogens via the disruption of mucosal barrier integrity by diet-driven changes in the gut microbiota, illustrating possible implications for EPEC and EHEC infections

Komposit-Kathodenschichtaufbau für Festkörperbatterien auf Lithiumbasis und ein Verfahren zu seiner Herstellung

Die Erfindung betrifft einen Komposit-Kathodenschichtaufbau für Festkörperbatterien auf Lithiumbasis, bei dem auf einer Oberfläche einer Kathodenschicht (1), die mit einem zur temporären Speicherung von Lithiumionen geeigneten Aktivwerkstoff, einem für Lithiumionen und Elektronen leitenden Werkstoff gebildet ist, eine Sperrschicht (3), die aus einem elektronisch leitenden und für Lithiumionen nicht leitenden Werkstoff gebildet ist. Auf der gegenüberliegenden Oberfläche der Kathodenschicht (1) ist eine weitere Schicht (2), die eine Sperrschicht oder einen Festelektrolyten bildet und aus einem Werkstoff der elektronisch nichtleitend und für Lithiumionen leitend ist, gebildet ist, vorhanden und mit der jeweiligen Oberfläche der Kathodenschicht (1) stoffschlüssig infolge Sinterung verbunden

Influence of the anode graphite particle size on the SEI film formation in lithium-ion cells

Electrochemical impedance spectroscopy (EIS) is used as a tool to investigate the formation process of a lithium-ion cell. The usability of EIS was demonstrated for two anode active materials with different particle sizes. The initial charging of the cell was interrupted when a defined anode-half cell potential (vs. Li/Li+) was reached, in order to measure an impedance spectrum. This was fitted with a common equivalent circuit model and the SEI film resistance (RSEI) was extracted. Results show that for both active materials RSEI initially increases until an anode half-cell potential of approximately 0.2 V is reached. Subsequently the RSEI shows a sharp decline for both active materials. The SEI film resistance is significantly higher for smaller particles, indicating that a less conductive SEI is built on smaller particles during formation

Process development and optimization for Li-ion battery production

Li-ion Batteries with high power capability and high energy density have gained importance in the past years for automotive applications. Furthermore, the demands regarding cycle and calendar lifetime are much higher compared to portable applications where lithium technology is established since many years. Thus, manufacturing processes need optimization towards process stability, battery performance parameters and production costs. Recent results of process development for efficient battery manufacturing are presented

LLZO separator sheets manufactured by a tape casting process and their electrochemical characterization: Poster held at 2nd World Conference on Solid Electrolytes for Advanced Applications: Garnets and Competitors, Shizuoka, Japan, September 24-27, 2019

In terms of developing components for All Solid State Batteries, plenty of research focused on optimization of solid electrolyte properties. Garnet materials, especially LLZO, are considered as one very promising class of solid electrolytes due to their high reported Lithium ion conductivity in the range of 10-4 S/cm [1, 2], as well as their capability to use metallic lithium as anode. Nonetheless, scientific research mainly focusses on material properties and characterization. Until now very little research is focusing on the development of scalable technologies for the manufacturing of All Solid State Batteries. Within the project ‘Artemys’, funded by the German Federal Ministry of Education and Research – BMBF, a complete process chain for All Solid State Batteries shall be developed. One goal in this project is the development of a tape casting process for LLZO electrolyte-separator sheets. A suitable slurry recipe has been developed and process parameters for the casting as well as drying have been adapted. A sintering profile with a debinding step has been optimized to obtain dense and flat substrates. The properties of the separators were evaluated, using scanning electron microscopy and electrochemical methods. For evaluating the lithium ion conductivity, impedance spectroscopy measurements were conducted on samples with ion blocking Au electrodes as well as non-blocking lithium electrodes. The morphological and electrochemical properties of the casted and sintered LLZO sheets were compared to sintered pellets of the same powder. The correlation between sheet manufacturing parameters and the electrolyte-separator properties were investigated and will be shown in this contribution.[1] S. Ohta et al., J. Power Sources, 196 (2011), 332[2] Y. Li et al., J. Mater. Chem., 22 (2012), 1535

Synthesis and sintering of Li1.3Al0.3Ti1.7(PO4)3 (LATP) electrolyte for ceramics with improved Li+ conductivity

The key material for all-solid-state batteries is the solid electrolyte. In concepts with high energy density and capacity, this Li+ conductive component has two essential functions: Substituting the liquid electrolyte in the cathode and separating the cathode from the anode. Therefore, the research on Li+ conductive solids is one important step to realize high performing all-solid-state batteries. In this study, two different methods of preparing Li1.3Al0.3Ti1.7(PO4)3 (LATP) powder are compared with regard to particle size, phase purity and sintering properties. As top-down method the melting and as bottom-up route the sol-gel synthesis are applied. Spark Plasma Sintering (SPS) is used to densify the powders at temperatures between 800 and 1000 °C. The densities, the microstructures and the Li+ conductivities are compared in relation to the preparation method. Using sol-gel synthesis, the phase purity of the LATP powder is higher compared to the top-down route. The milling of the synthesized powder increases the homogeneity of the resulting microstructure and enhances the ionic conductivity. Room temperature Li+ conductivity of 1 × 10−3 S cm-1 with a high density of 99.4% was achieved with the milled, sol-gel synthesized powder at a sintering temperature of 1000 °C

Lattice Analysis by Synchrotron Powder Diffraction on High Voltage Spinel LNMO: Poster presented at Electrochemical Conference on Energy and the Environment: Bioelectrochemistry and Energy Storage - ECS, Glasgow, 21.-26.7.2019

The high voltage spinel LiNi0.5Mn1.5O4 (LNMO) is a promising material to increase the energy density of lithium ion batteries. A variety of research was done to investigate the material regarding its properties, synthesis and commercial viability. To investigate in detail the properties of the cathode material during the delithiation and lithiation, in situ measurements are a helpful tool to fully understand changes in the crystal structure, which can give important information how to further improve the electrochemical properties of the cathode material. Especially the ‘ordered’ crystal phase P 4332 and the ‘unordered’ F d3 ̅m, which can result from different temperature treatments during the synthesis process, need to be investigated to define the correlation between calcination temperatures, lattice parameters and electrochemical properties. The LNMO investigated was synthesized using a spray drying method. From a solution of acetate and nitrate salts precursors were produced which have been calcined under different conditions to support the crystallization into the ordered and unordered phase, respectively. First, the two powders were characterised by SEM analysis to investigate the crystal morphology. Then slurries (LiNi0.5Mn1.5O4, PVDF binder, carbon, NMP solvent) were prepared and cast on aluminium foil to prepare electrodes. The electrochemical properties of assembled test cells (capacity, cycle life, etc.) were measured. Customized coin cells were used for the in situ measurements. The in situ XRD were measured using the high energy, low-emittance synchrotron radiation source at the Petra III beamline P02.1 at the DESY in Hamburg. In our presentation we will correlate the synthesis temperatures, electrochemical properties and lattice parameters for the synthesized LNMOs. By deeply analysing the in situ measured diffraction patterns for the different state of charge we will fully demonstrate the phase transition for the different samples and correlate the lattice change to properties like the manganese(III) amount and the crystal phase. The manganese(III) amount is mostly dependent on the calcination temperature and therefore also on the received crystal phase. Furthermore, we will outline the influence on the degradation for the different samples. The degradation differences between the synthesized samples were investigated by analysing the cumulative charge and discharge capacity. The combination of those results will lead to a deeper understanding of the connection between the different influence factors for the cathode material

Lattice Analysis by Synchrotron Powder Diffraction on High Voltage Spinel LiNi0.5Mn1.5O4

The high voltage spinel LiNi0.5Mn1.5O4 (LNMO) is a promising material to increase the energy density of lithium ion batteries. A variety of research was done to investigate the material regarding its properties, synthesis and commercial viability. To investigate in detail the properties of the cathode material during the delithiation and lithiation, in situ measurements are a helpful tool to fully understand changes in the crystal structure, which can give important information how to further improve the electrochemical properties of the cathode material. Especially the ‘ordered’ crystal phase P 4332 and the ‘unordered’ F d3 ̅m, which can result from different temperature treatments during the synthesis process, need to be investigated to define the correlation between calcination temperatures, lattice parameters and electrochemical properties. The LNMO investigated was synthesized using a spray drying method. From a solution of acetate and nitrate salts precursors were produced which have been calcined under different conditions to support the crystallization into the ordered and unordered phase, respectively. First, the two powders were characterised by SEM analysis to investigate the crystal morphology. Then slurries (LiNi0.5Mn1.5O4, PVDF binder, carbon, NMP solvent) were prepared and cast on aluminium foil to prepare electrodes. The electrochemical properties of assembled test cells (capacity, cycle life, etc.) were measured. Customized coin cells were used for the in situ measurements. The in situ XRD were measured using the high energy, low-emittance synchrotron radiation source at the Petra III beamline P02.1 at the DESY in Hamburg. In our presentation we will correlate the synthesis temperatures, electrochemical properties and lattice parameters for the synthesized LNMOs. By deeply analysing the in situ measured diffraction patterns for the different state of charge we will fully demonstrate the phase transition for the different samples and correlate the lattice change to properties like the manganese(III) amount and the crystal phase. The manganese(III) amount is mostly dependent on the calcination temperature and therefore also on the received crystal phase. Furthermore, we will outline the influence on the degradation for the different samples. The degradation differences between the synthesized samples were investigated by analysing the cumulative charge and discharge capacity. The combination of those results will lead to a deeper understanding of the connection between the different influence factors for the cathode material

In situ preparation of crosslinked polymer electrolytes for lithium ion batteries

Solid polymer electrolytes for bipolar lithium ion batteries requiring electrochemical stability of 4.5 V vs. Li/Li+ are presented. Thus, imidazolium-containing poly(ionic liquid) (PIL) networks were prepared by crosslinking UV-photopolymerization in an in situ approach (i.e., to allow preparation directly on the electrodes used). The crosslinks in the network improve the mechanical stability of the samples, as indicated by the free-standing nature of the materials and temperature-dependent rheology measurements. The averaged mesh size calculated from rheologoical measurements varied between 1.66 nm with 10 mol% crosslinker and 4.35 nm without crosslinker. The chemical structure of the ionic liquid (IL) monomers in the network was varied to achieve the highest possible ionic conductivity. The systematic variation in three series with a number of new IL monomers offers a direct comparison of samples obtained under comparable conditions. The ionic conductivity of generation II and III PIL networks was improved by three orders of magnitude, to the range of 7.1 × 10−6 S·cm−1 at 20 °C and 2.3 × 10−4 S·cm−1 at 80 °C, compared to known poly(vinylimidazolium·TFSI) materials (generation I). The transition from linear homopolymers to networks reduces the ionic conductivity by about one order of magnitude, but allows free-standing films instead of sticky materials. The PIL networks have a much higher voltage stability than PEO with the same amount and type of conducting salt, lithium bis(trifluoromethane sulfonyl)imide (LiTFSI). GII-PIL networks are electrochemically stable up to a potential of 4.7 V vs. Li/Li+, which is crucial for a potential application as a solid electrolyte. Cycling (cyclovoltammetry and lithium plating-stripping) experiments revealed that it is possible to conduct lithium ions through the GII-polymer networks at low currents. We concluded that the synthesized PIL networks represent suitable candidates for solid-state electrolytes in lithium ion batteries or solid-state batteries