Volume changes of the active material lead to a cyclic mechanical loading of composite electrodes during operation. Active material particles and the binder mechanically interact, resulting in an evolution of the structure of the electrode. Here, we mechanically test electrodes in a cyclic compression experiment and measure their strain and resistance under conditions close to application. We investigate the effect of temperature, rate, and the presence of an electrolyte solvent on the electrode dimensions/mechanics and resistivity. We further compare the pure polymeric binder material with composite electrodes to study how the binder affects the electrode mechanics. The results demonstrate that under application conditions electrodes are even less stable and more dynamic than dry model systems. Their viscous, time-dependent mechanical behavior originates from the binder itself and is strongly affected by the presence of the electrolyte solvent, which strongly reduces the stiffness and enhances the flow of the binder. During mechanical loading and unloading, the structure of the composite evolves over the course of several cycles and adapts to the prevailing operating conditions. The properties of battery electrodes, e.g., their dimensions and their resistance, strongly depend on the state of charge, but also on their history of cycling and mechanical load.

Sodium-ion batteries are treated as a drop-in technology to complement lithium-ion batteries in applications such as entry-level cars and stationary storage. This study compares water-based processing of the sodium-ion battery active material sodium vanadium phosphate (NVP/C) with processing using slurries based on the organic solvent NMP. By utilizing CMC/SBR as a binder, the adhesion strength, flexibility, electrical resistance, and rate capability were improved. These superior properties could be maintained at increasing the drying rate by a factor of 8. However, electrodes processed with the water-based binder system also suffered from binder migration at higher drying rates. To enable high-throughput processing, a strategy involving simultaneous multilayer coating of a primer and electrode slurry was explored. This approach helped mitigate the negative effects of binder migration.

This study examines the effects of sodium carboxymethyl cellulose (NaCMC) on the performance of graphite anodes in lithium‐ion batteries, focusing on variations in degrees of substitution (DS), molecular weights (MW), and gel particles. The results indicate that the best electrochemical performance is achieved by balancing the residual water content introduced by NaCMC while maintaining the anode's volume resistivity. A NaCMC with a low molecular weight and DS of 0.7 shows the best results for this particular formulation. An impurity (in batteries yet unreported)in NaCMC is also reported that significantly impacts electrochemical performance, called gel particles. By reducing the gel particles, cell performance is enhanced by 5%, without further optimization of the formulation. It is highlighted that both DS and MW influence electrode properties. A decrease in DS enhances adhesion but negatively affects volume resistivity. Increasing the MW improves adhesive strength and reduces interfacial resistivity due to greater chain entanglements. Higher gel particle levels negatively impact electrode properties, making low‐gel NaCMC more effective for better adhesion and resistance. Water retention in electrodes again is influenced by both DS and MW. Higher DS leads to increased water retention due to greater hydrophilicity, while high MW contributes to this effect through enhanced entanglements.

Mechanical and electrochemical experiments are used to infer changes in composite electrodes during cell operation. Macroscopic stress levels are determined by operando substrate curvature measurements of LiFePO4 (LFP) electrodes containing different types of binders. A reduction in the stress oscillation within a few cycles indicates that the benefits of calendering can be quickly diminished due to structural changes in the electrode. The use of a relatively stiff PAA binder allows for detailed observations of the phase transition during (de)lithiation of LFP, while softer, more viscous binders lead to significantly reduced and blurred macroscopic stresses. To separate mechanical from electrochemical contributions to the electrode mechanics, electrodes are tested with a stress-controlled compression setup, which mimics the macroscopic stress states during electrochemical cycling. This experiment reveals differences in the evolution of strain and electrode resistance, which are consequences of different particle rearrangement processes. Their motion is linked to the mechanical properties of the binder, which highlights its decisive role in the resulting mechanical and time-dependent properties of composite electrodes. The results of this work demonstrate that composite electrodes cannot be considered stationary during operation. Electrodes structurally change and develop towards "steady-state" configurations depending on the operating conditions and the externally imposed load.

The selective staining of cellulose materials is crucial for the accurate investigation of the binder distribution in electrodes of lithium-ion batteries. This paper investigates how (heptadecafluorodecyl)trimethoxysilane selectively reveals the binder distribution via EDS. Selectivity was granted by investigating individual electrode components: graphite, carbon black (CB), styrene-butadiene rubber (SBR), and sodium carboxymethyl cellulose (NaCMC). Each component was treated with the staining agent, stored at 60 degrees C for 16 h, washed with ethanol, and analyzed via energy dispersive spectroscopy (EDS). Only NaCMC shows a significant increase in fluorine concentration, proving selective staining. The study further explores the reaction mechanism by varying the degree of substitution (DS) of NaCMC, showing a correlation between carboxyl moieties and fluorine concentration and identifies 16 h of heated storage as a viable staining condition. Finally, the method's applicability was demonstrated by comparing binder distribution in electrodes dried at different rates, revealing the NaCMC binder distribution via EDS.

Sodium manganese hexacyanoferrate Na2Mn[Fe(CN)6] (NaMnHCF) is a promising cathode material for sodium-ion batteries, owing to its voltage profile similar to that of lithium iron phosphate (LFP) and its use of abundant, inexpensive resources. This study presents full cell cycling data for NaMnHCF against hard carbon (HC) anodes with various common carbonate-based electrolytes across different voltage windows. Post-mortem analyses indicate that, in addition to NaMnHCF degradation, Na+-ion inventory loss significantly contributes to capacity decline during cycling. Surprisingly, an ICP-OES analysis of the post-mortem anodes show that the correct electrolyte choice can entirely prevent the commonly cited manganese dissolution of NaMnHCF during cycling. This work also highlights methods for characterizing and processing NaMnHCF and the broader Prussian White family of materials, helping to introduce these materials to a wider audience. Finally, a comparison between NaMnHCF/HC and LFP/graphite is provided, examining both cost and electrochemical performance.

The surface free energy of materials plays a crucial role in defining the interactions between interfaces. In this study, we introduce the theory behind surface free energy and extend its application to solvent-based manufacturing processes of positive (cathode) and negative (anode) electrodes for lithium-ion batteries. By employing binders, namely polyvinylidene difluoride latices and sodium carboxymethyl cellulose, with differing surface free energy compositions, we systematically investigate how surface free energy influences key electrode properties. The binder properties are shown to affect adhesion strength, electrical resistance, and water retention in electrodes, with analogous effects observed in both cathodes and anodes. For cathodes, these differences translate to measurable impacts on cell performance, particularly in terms of rate capability and long-term cycling stability. We also explore how binder induced variations in water retention influence the formation and stability of the solid electrolyte interphase. The findings highlight the critical role of the binder’s surface free energy composition in optimizing electrode manufacturing and provide new insights into the interplay between electrode surface chemistry, microstructure, and electrochemical performance.

Primers are used to promote adhesion and reduce electrical interface resistance. Normally, the process of applying primer and electrode coating happens in two separate, sequential steps. Herein, primer and electrode are applied simultaneously, wet-in-wet. For fast drying of electrode coatings, a binder-redistribution by binder migration happens. A normally unwanted binder migration is tried to be utilized. The goal is to use less binder in the electrode coating and dry it faster without losses in adhesion and performance. By using simultaneous primer coatings incorporating LAPONITE, the adhesion can be promoted by over 200%. This allows to eliminate the styrene-butadiene-rubber-binder in the electrode slurry, saving in total of 70% of the binder. For eight times faster drying up to 30% improved specific capacity at 2C can be shown. This promising approach shows potential for any materials that lack adhesion, extending it, e.g., to porous, nanostructured particles and materials used in sodium-ion batteries.

This study identifies the critical aspects of binder distribution and mechanical integrity in aqueously processed LNMO cathodes, employing a comprehensive approach involving surface characterization techniques, adhesion strength testing, and electrochemical characterization. The investigation includes the use of the Washburn and Sessile Drop methods for surface free energy analysis, revealing key insights into the interfacial free energy of adhesion between cathode constituents. The results explain the formation of carbon-binder-domains and their impact on adhesion strength, with a particular focus on the conductive additives’ (CA) surface area. The study demonstrates the effectiveness of reducing CA surface area and employing alternative conductive additives, such as vapor-grown carbon fibers (VGCF), in improving adhesion strength and mitigating capacity fade attributed to delamination during cycling. Furthermore, the research emphasizes the role of heat treatment beyond the melting point of the polyvinylidene fluoride (PVDF) latex binder, showcasing its influence on wetting and enhancing mechanical integrity. The presented methodology provides a valuable tool for predicting and optimizing binder distribution, offering insights into improving the overall performance and reliability of aqueously processed cathodes for advanced lithium-ion batteries.

Nanoparticles have many advantages as active materials, such as a short diffusion length, low charge transfer resistance, or a reduced probability of cracking. However, their low packing density makes them unsuitable for commercial battery applications. Hierarchically structured microparticles are synthesized from nanoscale primary particles by targeted aggregation. Due to their open accessible porosity, they retain the advantages of nanomaterials but can be packed much more densely. However, the intrinsic porosity of the secondary particles leads to limitations in processing properties and increases the overall porosity of the electrode, which must be balanced against the improved rate stability and increased lifetime. This is demonstrated for an established cathode material for lithium-ion batteries (LiNi0.33Co0.33Mn0.33O2, NCM111). For active materials with low electrical or ionic conductivity, especially post-lithium systems, hierarchically structured particles are often the only way to produce competitive electrodes.

Sodium-ion batteries (SIBs) are a promising alternative to LIBs, but selecting low hazard cathode materials is challenging. Our screening covers three hazard perspectives in early TRLs of SIBs and supports the sustainable by design discourse.

Herein we investigate the influence of surface free energy (SFE) on the processing and the resulting properties of water-based LNMO cathodes using a blend of PVDF latex and CMC. Starting with the examination of surface free energy through Sessile Drop and Washburn method the interaction or lack thereof between the different components inside the aqueous slurries can be explained. Four different PVDF latices were applied with particular focus on their SFE. The influence of surface free energy was investigated with regard to adhesion strength, interface resistance, bulk resistivity and water retention of the cathodes. The electrochemical performance (rate capability and long-term capacity retention over 1000 cycles) of the different cathode compositions was compared in full-cell configuration. The electrodes were subsequently analyzed post-mortem by EDS analysis.

Two main goals for the industrial, slurry‐based electrode processing are a high process speed and the maximum possible material efficiency. This makes an increased drying rate and active material share favorable, but both are limited by adverse effects on the electrode quality. The adverse effects of fast drying are associated with the migration of binder. In this article, the slurry properties of water‐based graphite slurries are manipulated using a synthetic, layered silicate as additive. The influence of the polymer‐particle composite network on the viscosity, adhesion strength, and cell performance is investigated. By addition of a small amount of additive (0.5 wt% of the dry electrode), the binder migration is mitigated up to a drying rate of 6 g m−2 s−1 for graphite anodes with ≈4.2 mAh cm−2 (corresponding with 30 s drying time) leading to a possible increase of eight times the process speed compared to drying with 0.75 g m−2 s−1 if adverse effects on the tortuosity of the electrodes can be solved. In this work, a combination of additive usage is pointed out with a multilayer approach and first insights are provided in how the binder migration may be mitigated to gain structurally optimized fast‐dried electrodes without losses in electrode quality.

To change the solvent in LIB electrodes to water, a water-based polymer binder has to replace the current PVdF binder. This led to Sodium Carboxymethylcellulose (NaCMC) being introduced as a water-soluble binder for LIBs. Due to NaCMC creating a weak connection with the current collector, usually, another additive like SBR rubber is usually added to increase adhesion. Nevertheless, NaCMC dominates the properties of the slurry and influences the structure of the final electrode decisively. Combining the multitude of functionalities of the NaCMC with it being produced from the most abundant polymer in the world, it creates a highly attractive binder, also from an industrial point of view. However, despite widespread use, there is only limited knowledge on how the NaCMC influences key battery properties and battery performance. The objective of this research is to provide valuable insights into optimizing the composition of lithium-ion battery electrodes for enhanced energy storage and cycling stability, based on a better understanding of the influence of NaCMC. Especially, the influence of varying properties of the NaCMC, like degree of substitution and molecular weight are explained in more detail, which were analysed via adhesion strength testing, Karl-Fischer titration, electrical resistance and potentiostatic cycling. Finally, the influence of the varying NaCMC properties on the battery performance and SEI formation was investigated with post-mortem liquid NMR.

Sodium‐ion batteries are considered to be one of the most promising postlithium batteries on the verge of commercialization. The electrode processing is expected to be similar to lithium‐ion batteries. However, the producibility and material processing challenges of potential electrode materials for anodes and cathodes are poorly understood. For industrial electrode production, a deep understanding of the processing of electrode materials with different particle morphologies is of great importance. In particular, the correlation between the process conditions and the electrode properties needs to be investigated further to understand the complex interactions between the battery slurry materials, the binder system, the drying process, and the microstructure formation. One promising anode material is hard carbon. The water‐based processing of hard carbon slurries presented in this article shows that the drying behavior is strongly interconnected with the particle size and particle interactions in the drying electrode. This study shows that all the hard carbons investigated do not exhibit binder migration at moderate drying rates. Even at very high drying rates (9 g m −2 s −1 , 12 s drying time), an increase in adhesion force of up to 39% is observed for comparatively smaller particles compared to the adhesion force at lower drying rate.

Battery storage systems have become an important pillar in the transformation of the energy and transportation sector over the last decades. Lithium-ion batteries (LIBs) are the dominating technology in this process making them a constant subject of analysis regarding their sustainability. To assess their environmental performance, several Life Cycle Assessments (LCA) of LIBs have been performed over the last years. Yet, the amount of available primary data on their production remains low, leading to recurrent reliance on a few disclosed datasets, mostly at industrial scale. Thus, there is a need for new LCA studies at different scales (lab, pilot, industrial) using transparent datasets to facilitate more reliable and robust assessments. This work presents a screening of recent environmental assessments for LIBs at different production scales aiming at identifying remaining gaps and challenges, and deriving a detailed LCA of a lab-scale battery cell production. For the first time the environmental impact of a lab-scale battery production based on process-oriented primary data is investigated. The results are flanked by sensitivity analyses and scenarios and compared with literature values. The hotspots identified in this study, cathode slurry, anode current collector, as well as the energy demand of the dry room and coating process, are consistent with the literature, although the absolute values are an order of magnitude larger. The main reason for this are the inefficiencies inherent in lab-scale production. In order to analyze the effects of production scale, an upscaling to the pilot scale is performed.

Porous, nanostructured particles ensure the wetting of electrolyte up to the particle core and shortened diffusion paths, which is relevant not only for lithium‐ion batteries but also for postlithium systems like sodium‐ion batteries. The porous structure leads to a high C‐rate capability. However, compared to conventional compact NCM, porous NCM shows a reduced adhesion force but no or only slight negative influence on C‐rate capability by binder migration at higher drying rates. Herein, a multilayer concept is used to increase the adhesion force with equal or better electrochemical performance compared to single‐layer electrodes. Compact particles of high volumetric energy density and porous particles with high C‐rate capability are combined in a simultaneously coated multilayer electrode. Multilayers with compact NCM toward the current collector and porous NCM with reduced binder content toward the separator side show an about 16‐times higher adhesion force at lower drying rate and an about ten‐times higher adhesion force at increased drying rate compared to electrodes produced of porous NCM only. The specific discharge capacity of the multilayers is increased by 88% at the lower and 67% at the higher drying rate for a discharge rate of 3C compared to a single layer with compact NCM.

The dry manufacturing of battery electrodes has the potential to significantly reduce costs and the environmental impact of battery production but deteriorates the electrode quality due to drawbacks in the processability of the materials. By varying the mixing intensity of the powder mixtures, this work investigates the impact of blend homogeneity on the flow properties and the processability of the dry mixtures. Furthermore, the electrochemical performance of dry laminated electrodes made of LiNi0.6Mn0.2Co0.2O2 is investigated with respect to their initial mixture homogeneities and compared to slurry-based electrodes. An improvement of the powder flowability is observed for mixtures with a homogeneously distributed PVDF binder, which acts as a temporary lubricant in dry electrode manufacturing due to its ability to shear, resulting also in filament formation. Capacity and rate performance of electrodes made of homogeneous mixtures are the highest with 169 mAh/g at C/20 and 70 mAh/g at 3C compared to 169 and 49 mAh/g for the slurry-based electrodes, respectively. Cyclic voltammetry indicates lower overpotentials for incompletely homogenized electrodes due to the existence of carbon black aggregates that establish better long-range conductivity. Overall, electrodes from highly homogenized powders show the best electrochemical performance in terms of C-rate capability due to their favorable electrode thickness and porosity resulting from better processability in combination with a sufficiently distributed carbon binder domain.

Sodium-ion batteries are an emerging technology that is still at an early stage of development. The electrode processing for anode and cathode is expected to be similar to lithium-ion batteries (drop-in technology), yet a detailed comparison is not published. There are ongoing questions about the influence of the active materials on processing parameters such as slurry viscosity, coating thicknesses, drying times, and behavior during fast drying. Herein, the expected drying time for the same areal capacity of anodes (graphite vs. hard carbon) and cathodes (lithium iron phosphate vs. Prussian blue analogs) are compared based on respective specific capacities reported in the literature. Estimates are made for the materials' impact on production speed or dryer length. Within the experimental part, water-based slurries of the same composition are mixed using different active materials according to identical procedure and the viscosity is compared. When drying at a constant drying rate (0.75 g m-2 s-1), lithium iron phosphate electrodes with different areal capacities (1-3 mAh cm-2) are shown to have the highest adhesion. For high drying rates (3 g m-2 s-1) at constant areal capacity, especially the investigated electrodes based on hard carbon show that no binder migration occurs. LIB vs. SIB: This paper compares the expected drying time, production speed, dryer length based on specific capacities from the literature. For the same production speed, the drying time for SIB materials needs to be reduced. For a very high drying rate, especially the investigated hard carbon shows that no binder migration occurs.image

Fluorine-containing Li-salts are used as slurry cathode additives for tunable rheology in super high solid content slurries for the first time.