Dry coating of battery electrodes is a promising technology for reducing the environmental footprint and the cost of lithium-ion battery cell manufacturing. However, obtaining a homogeneous electrode microstructure without a solvent is a key challenge. Here, we demonstrate the potential of twin-screw extrusion as a solvent-free, continuous dry-mixing method enabling precise polytetrafluoroethylene (PTFE) fibrillation and carbon black dispersion during NMC electrode production. Through in-depth microstructural characterization, we reveal a strong correlation between the microstructure of the extrudates and the calendered electrodes, underscoring the crucial role of mixing in controlling microstructure. Electrochemical cycling of high-areal-capacity (5.9 mAh cm-2) dry-coated NMC622 electrodes paired with graphite in coin cells yields 150 mAh g-1 upon discharge at C/2 with 79% capacity retention after 500 cycles. Our results highlight the industrial potential of twin-screw extrusion for continuous dry coating of battery electrodes.

This study investigates correlations between the process steps of dry mixing and dry electrode coating for lithium-iron-phosphate (LFP) cathodes. Active material, conductive additive and PTFE binder were mixed in a continuous twin-screw extrusion process at different intensities via variation of the screw configuration. Suitable characterization methods for the dry mixed powders were applied to conclude on process-property relationships between kneading intensity and granule properties. Intensive kneading with a high specific mechanical energy input resulted in a more homogeneous and fine PTFE fibril network and in more compact and size-reduced granules. These differences in micro-and macrostructure lead to a higher electrical resistivity, higher bulk density and better flowability. The processing window concerning the applicable roll shearing ratio for one-step calendering in the DRYtraec (R) process broadened for high kneading intensity compared to softer kneading. Thinner electrodes could be obtained due to the higher sensitivity of a fine PTFE fibril network to shearing forces within the calender gap. Resulting electrodes demonstrated a higher adhesion strength and higher electrical resistivity as well as slight breakage of LFP particles and a lower C-rate performance. These results provide detailed insights into the dry processing chain of LFP mixtures including intermediate products and their processability, highlighting the importance of understanding the correlation between different dry coating process steps. With extrusion mixing it is possible to tailor granule properties concerning their processability, electrode structure and electrochemical performance via applying an optimal amount of mechanical energy during mixing for each specific material system.

Solid-state batteries (SSBs) represent a promising alternative to conventional lithium-ion batteries (LIBs) by substituting liquid electrolytes with solid-state materials, significantly improving safety and energy density. However, traditional manufacturing methods for LIBs face substantial challenges in scalability and performance once they are applied for SSBs. Wet-chemical methods are used for electrode preparation involving toxic solvents and energy-intensive drying processes. Moreover, especially for sulfidic solid electrolytes, the ionic conductivity is negatively affected by the solvent in the wet coating process. In contrast, the solvent-free fabrication of electrodes for SSBs faces substantial challenges in scalability. To address these issues, specifically dry electrode processes can be used, such as DRYtraec (R). The latter enables direct calendering in a single step, from powder feeding to electrode lamination. In this study, the feasibility of coating using various process parameters is evaluated, demonstrating continuous production and comparing the electrochemical performance of these components with manual dry films and bulk powders.

The increasing demand for clean and efficient energy storage makes the environmentally friendly and cost‐effective production of lithium‐ion batteries a focal point in current battery research and development. Dry battery electrode (DBE) coatings play a crucial role in future production schemes as this technique does not require the use of toxic solvents and energy‐intensive drying steps. This review article focuses on the most advanced DBE method today, based on fibrillated polytetrafluoroethylene (PTFE) binder. PTFE‐based DBE coatings are suitable for both laboratory scale and mass production, which places them in a prominent position among DBE methods. The article covers the historical development of the process as well as current research in the field of lithium‐ion batteries (LIB) and next‐generation batteries such as lithium–sulfur batteries (LSB) and solid‐state batteries (SSB). Both the suitability and existing drawbacks of PTFE‐based dry coatings for these cell types are discussed. The article also provides insights into production research and describes approaches for scaling the method. Characteristic features and differences of the most important methods, the DRYtraec and Maxwell‐process, are outlined. Finally, existing challenges in commercializing the technology are discussed, and an outlook on environmentally friendly PTFE‐alternative binders is given.

All-solid-state batteries (SSB) show great promise for the advancement of high-energy batteries. To maximize the energy density, a key research interest lies in the development of ultrathin and highly conductive solid electrolyte (SE) layers. In this work, thin and flexible sulfide solid electrolyte membranes are fabricated and laminated onto a non-woven fabric using a scalable and solvent-free, continuous roll-to-roll process (DRYtraec). These membranes show significantly improved tensile strength compared to unsupported sheets, which facilitates cell assembly and allows a continuous component production using a single-step calendering process. By tuning the thickness, densified membranes with thicknesses ranging from 40 to 160 mu m are obtained after a compression step. The resulting SE membranes retain a high ionic conductivity (1.6 mS cm(-1)) at room temperature. An excellent rate capability is demonstrated in a SSB pouch cell with a Li2O-ZrO2-coated LiNi0.9C0.05Mn0.05O2 cathode, a 55 mu m thin SE membrane, and a columnar silicon anode fabricated by a scalable physical vapor deposition process. At stack level, a promising energy density of 673 Wh L-1 (and specific energy of 247 Wh kg(-1)) is achieved, showcasing the potential for high energy densities by reducing the SE membrane thickness while retaining good mechanical properties.

Solid-state batteries with argyrodite-based electrolytes have great potential to reach 500 Wh kg-1 and higher, but still suffer from reversible electrochemical cyclability. The main reason for this is the required metallic lithium anode that creeps along the grain boundaries of the solid electrolyte during the high pressures of prototype cell manufacturing. To solve this issue, trials with different pressure procedures are required to fabricate cells. Since the argyrodite-based sulfidic electrolyte is still quite cost-intensive, recycling of the cathode material including the catholyte is much favored. Consequently, this study evaluates the DRYtraec (R) dry coating technology for the resource-efficient, scalable fabrication of solid-state lithium-sulfur battery (LS-SSB) cathodes, particularly with a focus on the reusability of cost-intensive argyrodite-based electrode scrap waste. Using the solvent-free approach, cathodes can be produced with consistent thickness and sulfur loading, enabling simplified recycling of the electrode material up to four times without significant loss in quality or electrochemical performance. Electrochemical testing confirms high initial capacities of up to 1480 mAh gS-1 and stable cycling behavior in both lab-scale and pouch cell formats. Notably, the study demonstrates, for the first time, the successful cycling of an LS-SSB pouch cell incorporating a metallic lithium anode, achieving 1500 mAh gS-1 and over 20 cycles. These findings underscore the potential of DRYtraec (R) for sustainable, high-performance LS-SSB production and mark a significant step toward practical solid-state battery commercialization.

Achieving commercial viability for more sustainable sodium-ion batteries (SIB) necessitates reducing the environmental impact of production, particularly originating from electrode drying and the use of toxic solvents like N-methyl-2-pyrrolidone (NMP). This study presents the dry-processing of commercial P2-type Na0.75Ni0.25Fe0.25Mn0.50O2 (NFM) via the DRYtraec (R) process, aiming to lower the binder content of 1 wt.% polytetrafluoroethylene (PTFE) and eliminating the need for electrode drying and NMP recovery. Assessments of electrode morphology and active material crystallinity were conducted to gauge the effects of mechanical stress during processing. The resulting cathodes, loaded at a commercially relevant 2.3-2.7 mAh cm-2 loading, were successfully paired with aqueous-processed hard carbon (HC) anodes, demonstrating stable performance in full-cells. Comparative analysis with entirely wet-processed electrodes revealed comparable capacity accessibility and comparable long-term stability. This showed the competitiveness of dry-processed cathodes. Finally, the integration of NMP-free, dry-processed cathodes and aqueous-processed anodes was scaled to the commercially relevant prototype pouch-cell. The cell demonstrates stable cycling for 400 cycles with an energy density of 102 Wh kg-1 as well as reduced processing costs and environmental footprint.

The development of environmentally friendly processing techniques is a key requisite for future sustainable battery development. The so-called DRYtraec® process is a solvent-free process developed as a viable approach to replace slurry-based binders by fibrous polymers and produce laminated electrodes with a low carbon footprint. It has been demonstrated to work for both, liquid and solid electrolyte batteries. NMC cathodes can be produced in a wide range of loading. For lithium sulfur batteries carbon/sulfur composites can be processed without sulfur loss. In particular in the field of solid state batteries it shows significant advantages. All-solid-state lithium-ion batteries are promising candidates to overcome safety and energy limitations of established lithium-ion batteries (LIBs). Excellent results have been reported for sulfide based electrolytes on a small scale. More and more companies announce their first pilot production lines. Therefore, scalable concepts for material and component development are of crucial need. We evaluate this process for the fabrication of thin argyrodite separator films and compare it with slurry-based separators in ASSBs. To test new cell concepts and components under relevant conditions, it is important to manufacture prototype cells with thin separator layers and flexible housing. Therefore, we prepared slurry-free pouch cells based on Ni-rich NMC cathodes and PVD-synthesized Si anodes. The presentation highlights recent developments of the DRYtraec® process and its application to ASSBs, LiS and LIBs.

Lithium-sulfur batteries with liquid electrolytes are discussed as the most promising post-lithium-ion-battery technology in literature due to their high theoretical specific energy and first prototype cells delivering >470 Wh kg(-1). Although several electrolyte and material concepts are developed that partially solve the issue of the so-called shuttle mechanism, the most promising concept to genuinely confine sulfur species in the cathode is all-solid-state argyrodite-sulfur cathodes leading to almost theoretical active material utilization by maintaining reasonable sulfur loadings and electrolyte to sulfur ratios. However, this battery concept has so far not achieved reversible cycling against metallic lithium anodes as it requires high pressures for manufacturing, and ductile lithium metal creeps along the grain boundaries of the solid electrolyte particles leading to short cuts of the cells. Recent findings show that metallic lithium, however, can be stably cycled with dimethoxyethane/lithium-bis(fluorosulfonyl)imide (DME/LiFSI)-based electrolytes. Herein, for the first time, a semisolid concept is presented combining the benefits of an argyrodite-based solid-state cathode and a DME/LiFSI/hydrofluoroether-based anolyte concept - in coin cells and first pouch cells. This disruptive approach enables projected specific energies higher than 600 Wh kg(-1) at cell stack level.

The lithium–sulfur battery is a promising electrochemical storage solution, especially for aviation and aeronautical applications, due to its high‐gravimetric energy density (specific energy) and the abundance of sulfur. In recent years, the number of reported prototype cells and their realized energy have increased. This underlines the progress of technology readiness of the lithium–sulfur system. However, the influence of the cathode porosity as well as the porosity of the carbon material on the performance of prototype cells is still not fully understood. Consequently, in this study, the porosity of solvent‐free processed cathodes is investigated, with varying carbon matrix composition, via mercury intrusion porosimetry and synchrotron tomography. Moreover, the swelling behavior of the S/C dry‐film cathodes is investigated and mitigated. These cathodes are then electrochemically evaluated at pouch cell level with ether‐based electrolytes with varying E/S ratios. The combination of the gained findings in pouch cells enables specific energies of 425 Wh kg −1 and 558 Wh L −1 at cell level.

To increase the energy density of today's lithium batteries, it is necessary to develop an anode with higher energy density than graphite or carbon/silicon composites. Hence, research on metallic lithium has gained a steadily increasing momentum. However, the severe safety issues and poor Coulombic efficiency of this highly reactive metal hinder its practical application in lithium-metal batteries (LMBs). Herein, the development of an artificial interphase is reported to enhance the reversibility of the lithium stripping/plating process and suppress the parasitic reactions with the liquid organic carbonate-based electrolyte. This artificial interphase is spontaneously formed by an alloying reaction-based coating, forming a stable inorganic/organic hybrid interphase. The accordingly modified lithium-metal electrodes provide substantially improved cycle life to symmetric Li||Li cells and high-energy Li||LiNi0.8Co0.1Mn0.1O2 cells. For these LMBs, 7 μm thick lithium-metal electrodes have been employed while applying a current density of 1.0 mA cm-2, thus highlighting the great potential of this tailored interphase.

The user demands for Lithium ion batteries in mobile applications and electric vehicles request steady improvement in terms of capacity and cycle life. State-of-the-art lithium ion batteries irreversibly loose about 10 % of the capacity during the first cycles due to SEI formation. Therefore, 10 % of the cathode material is not used during the rest of the cells life which results in a waste of cathode material and leads to a lowered range of battery electric vehicles. Therefore, these losses must be compensated to ensure efficient resource utilization and to further increase the capacity of the lithium ion battery. We have developed a method to compensate these capacity losses by pre-lithiation: A fast and simple approach of electrolyte-free direct contact pre-lithiation leads to targeted degrees of pre-lithiation in a range of 7-50 % for state-of-the-art graphite electrodes. The parameters pressure (0-40 MPa), temperature (20-150°C) and time (0-60 min) are used to transfer lithium from a temporary substrate to the graphite anode. This process uses 1-5 µm thin lithium films made by the Fraunhofer IWS lithium melt deposition process as a lithium source.[1] The degree of pre-lithiation can be controlled by the lithium loading of the temporary substrate. NCM full cells built with pre-lithiated graphite electrodes where electrochemically evaluated in comparison to unlithiated electrodes. They show 6.5 % capacity increase after the first cycles using the additional lithium to form the SEI during the first cycles. The parameter influence of the pre-lithiation process on the initial coulomb efficiency of cells with pre-lithiated graphite electrodes is examined in half cells showing an ICE of 99.91 % for the best parameters. This method of electrolyte-free direct contact pre-lithiation shows an efficient way to further increase the capacity of state-of-the-art LIBs with graphite electrodes by increasing the cathode material utilization. It can potentially be scaled up to a roll-to-roll process using a heated calender nip. The temporary substrates with tailored lithium loading can be processed by lithium melt deposition in an efficient way with high lithium yield and high precision. [1] K. Schönherr, B. Schumm, F. Hippauf, R. Lissy, H. Althues, C. Leyens, S. Kaskel, Chemical Engineering Journal Advances 2022, 9, 100218. Figure 1

The user demands lithium-ion batteries in mobile applications, and electric vehicles request steady improvement in terms of capacity and cycle life. This study shows one way to compensate for capacity losses due to SEI formation during the first cycles. A fast and simple approach of electrolyte-free direct-contact pre-lithiation leads to targeted degrees of pre-lithiation for graphite electrodes. It uses tailor-made lithium thin films with 1–5 µm lithium films produced by lithium melt deposition as a lithium source. These pre-lithiated graphite electrodes show 6.5% capacity increase after the first cycles in NCM full cells. In this study, the influence of the pre-lithiation parameters—applied pressure, temperature and pressing time—on the pre-lithiation process is examined.

Lithium metal anodes are among the most promising candidates for further increasing the energy density of lithium ion batteries and all-solid-state batteries. A reduction of the anode thickness by using ultrathin lithium metal films is a crucial requirement to achieve a significant overall reduction of thickness on cell level. However, besides anode stabilization, realizing scalable technologies for an efficient production of thin lithium metal anodes is one of the most challenging obstacles for the success of various next-generation battery chemistries. In this publication we introduce a disruptive lithium melt deposition process for thin lithium metal coating on thin copper current collector foils. The wetting of molten lithium on the substrate can only be achieved through a lithiophilic interlayer. As a result fast and homogeneous lithium spreading on the substrate is enabled allowing roll-to-roll coating with liquid-deposition technologies as demonstrated in this contribution with a speed of several meters per minute and reaching 100 mm width. With this new process the anode thickness can be tuned in a wide range (1–30 µm). Evaluation in a prototype solid battery system shows high electrochemical lithium utilization and no detrimental effects compared to commercially available lithium reference foils.

In the market for next-generation energy storage, lithium-sulfur (Li-S) technology is one of the most promising candidates due to its high theoretical specific energy and cost-efficient ubiquitous active materials. In this study, this cell system was combined with a cost-efficient sustainable solvent-free electrode dry-coating process (DRYtraec®). So far, this process has been only feasible with polytetrafluoroethylene (PTFE)-based binders. To increase the sustainability of electrode processing and to decrease the undesired fluorine content of Li-S batteries, a renewable, biodegradable, and fluorine-free polypeptide was employed as a binder for solvent-free electrode manufacturing. The yielded sulfur/carbon dry-film cathodes were electrochemically evaluated under lean electrolyte conditions at coin and pouch cell level, using the state-of-the-art 1,2-dimethoxyethane/1,3-dioxolane electrolyte (DME/DOL) as well as the sparingly polysulfide-solvating electrolytes hexylmethylether (HME)/DOL and tetramethylene sulfone/1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TMS/TTE). These results demonstrated that the PTFE binder can be replaced by the biodegradable sericin as the cycle stability and performance of the cathodes was retained.

Lithium-sulfur (Li-S) batteries are among the targeted candidates for future generation secondary batteries with high specific energy. Herein, a scalable synthesis is presented to produce highly porous, nitrogen-doped carbons from a commercial carbon black material by melamine impregnation and subsequent thermolysis. The process up-scaling up was demonstrated at > 100 g batch level. The nitrogen doping was controlled through pyrolysis temperatures and carbon to melamine ratio. The sulfurcarbon cathodes exhibit an enhanced cycle life at a moderate electrolyte to sulfur ratio of 7 mu L mgs(-1). In particular, under lean conditions at low electrolyte amount of 5 mu L mgs(-1) , the nitrogen functionalities improved active material utilization and capacity retention significantly. The nitrogen-doped scaffold was integrated into five-layered prototype cell (71 x 46 mm(2)) with a capacity of up to 0.87 Ah reaching a specific energy density of 238 Wh kg(-1) on stack level. These results provide new insights into realistic application of nitrogen-doped carbons on pouch cell level. (C) 2020 Published by Elsevier Ltd.

Lithium-sulfur (Li-S) technology was identified as a promising candidate to overcome energy density limitations of common lithium-ion batteries given the world-wide abundance of sulfur as a low-cost alternative to state-of-the-art active materials, such as Ni and Co. Li-S cells have received tremendous recognition in recent years, both from a scientific and industrial perspective. However, only few data on adequate multilayer-pouch cell characterization are available so far, and transparent calculations on components require more consideration. Because of the gap of lab cell characterization and prototype cell development, misinterpretations and false expectations are frequently reported, mostly resulting from lithium and electrolyte excess. For the commercialization of the Li-S technology, rapid transfer of new concepts on the prototype cell level is essential. Furthermore, fundamental studies should concentrate on fundamental scientific questions related to the main bottlenecks of Li-S cells: understanding anode and electrolyte degradation phenomena and realistic evaluation of stabilizing interfaces.