As moisture presents a critical contamination in lithium-ion batteries (LIBs), electrodes and separators need to be post-dried before cell assembly. The moisture adsorption, desorption and re-adsorption of electrodes during processing is strongly dependent on their material system, manufacturing route and microstructure. The microstructure, in turn, is significantly defined by the coating density, which is adjusted by calendering. As a consequence, the calendering step is expected to directly influence the moisture sorption behavior of electrodes. This is why the influence of different coating densities and structural properties on the moisture content of NCM622 cathodes was investigated in this study. For increasing density, an increasing moisture content was detected by Karl Fischer Titration and sorption measurements. SEM and BET analyses showed an increasing amount of NCM622 particle breakage, accompanied by a rising surface area. Hence, the increased moisture uptake of cathodes with higher density is mainly caused by a higher surface area, which results from particle cracking and breakage during calendering. Electrochemical analysis showed that the increased active surface area of cathodes with higher densities leads to a good performance during formation and at low C-rates. However, the reduced porosity impairs the ionic conductivity and causes capacity loss at higher C-rates.

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Increased Moisture Uptake of NCM622 Cathodes after Calendering due to Particle Breakage

For batteries with high energy density and good fast-charge capability, NCM cathode active materials with ≥80 mol% nickel are promising due to their high specific capacities. Unfortunately, the increase in nickel content is accompanied by a high susceptibility to moisture. Therefore, nickel-rich NCM is coated or doped by the manufacturers to increase its stability. However, it is unclear if special requirements regarding ambient humidity must still be met during the whole production chain, or only after post-drying and during cell assembly. Therefore, the structure and properties of three different nickel-rich NCM active materials (one doped monocrystalline, two coated polycrystalline materials) processed at ambient atmosphere were investigated. At every process step, moisture content and microstructure were examined. Prior to cell assembly, two different post-drying procedures were applied and investigated. As validation, electrochemical tests were performed. Both polycrystalline cathodes demonstrated good physical and electrochemical properties, despite the ambient process atmosphere. Higher moisture reduction led to improved electrochemical performances at higher C-rates. Finally, a comparison between dry and normal atmosphere of the best performing material indicates that a production of high-quality nickel-rich electrodes at ambient atmosphere is possible if their exposure to moisture is short and well-designed post-drying techniques are applied.
 
 
 
 


https://iopscience.iop.org/article/10.1149/1945-7111/ac7358/pdf

Investigation of Moisture Content, Structural and Electrochemical Properties of Nickel-Rich NCM Based Cathodes Processed at Ambient Atmosphere

Lithium-ion batteries are used in a wide range of applications, with the electromobility sector being the main contributor to the increasing demand predicted for the next decade. Although batteries play an important role in decarbonizing the transportation sector, their production includes energy-intensive processes that hinder a more sustainable production. Moreover, the production processes are characterized by a manifold of parameters leading to complex cause–effect relations along the process chain which influences the battery cell quality. Therefore, a sustainable future for battery production and the electromobility sector depends on the environmentally and economically efficient production of high-performance batteries. Against this background, this work presents a digitalization platform based on the coupling of mechanistic models to digitally reproduce the battery cell production and provide a deeper understanding of the interdependencies on the process, production, and product levels. In addition to a description of the individual models contained in the platform, this work demonstrates their coupling on a use case to study the effects of different solids contents of the coating suspension. Besides providing a multilevel assessment of the parameter interdependencies, considering quality, environmental and economic aspects, the presented framework contributes to knowledge-based decision support and improvement of production and battery cell performance. 

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/ente.202200801

Digitalization Platform for Sustainable Battery Cell Production: Coupling of Process, Production and Product Models

Solid-state batteries possess the potential to combine increased energy densities, high voltages, as well as safe operation and therefore are considered the future technology for electrical energy storage. In particular, sulfides as solid electrolyte are promising candidates due to their high ionic conductivities and the possibility of a scalable production. This review aims to demonstrate ways to manufacture suspension-based sulfidic solid-state batteries both on a laboratory scale and on an industrial level, focusing on the assessment of current knowledge and its discussion from a process engineering point of view. In addition to the influence of process parameters during mechanochemical synthesis of the solid electrolyte, formulation strategies for electrodes and separators are presented. The process chain from dispersion to cell assembly is evaluated. Scale-up technologies are considered in comparison to established techniques in the field of conventional lithium-ion batteries with liquid electrolyte summarizing the current status of sulfidic solid-state battery production. 

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/batt.202200328

Current Status of Formulations and Scalable Processes for Producing Sulfidic Solid‐State Batteries

Moisture management and postdrying are crucial for Li-ion battery lifetime and performance as well as overall energy efficiency of electrode production. An optimization of these processes by a fundamental comprehension of sorption and mass transport mechanisms in the electrode holds potential to increase sustainability of this technology. The composition of electrodes determines which of these mechanisms govern the interaction of electrodes with water from atmosphere. In this study, the influence of the binder system, temperature, and pressure of Li-ion battery anodes on postdrying is focused on. Anodes with the binder system carboxymethylcellulose (CMC)/styrene–butadiene–rubber (SBR) and polyvinylidene fluoride represent a mostly absorbing and mostly adsorbing material system, respectively. Variation of the process parameters temperature and pressure reveals that both material systems show a similar impact of pressure on water mass transport in the electrode during water removal, although a reduced pressure impact for the CMC/SBR system is expected, since in this case most water is absorbed into the polymers and should diffuse independently of the system pressure. Temperature affects water mass transport in the absorbing material system stronger than in the adsorbing material system, due to the strong temperature dependency of the water diffusion inside the absorbing polymers. 

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/ente.202200859

Experimental investigation of the temperature, pressure, and binder system influence on vacuum post‐drying processes and moisture management of Li‐ion battery electrodes

In order to reduce the residual moisture in lithium-ion batteries, electrodes and separators need to be post-dried prior to cell assembly. On an industrial scale, this is often conducted batch-wise in vacuum ovens for larger electrode and separator coils. Especially for electrodes, the corresponding post-drying parameters have to be carefully chosen to sufficiently reduce the moisture without damaging the sensitive microstructure. This requires a fundamental understanding of structural limitations as well as heat transfer and water mass transport in coils. The aim of this study is to establish a general understanding of the vacuum post-drying process of coils. Moreover, the targeted design of efficient, well-adjusted and application-oriented vacuum post-drying procedures for electrode coils on the basis of modelling is employed, while keeping the post-drying intensity as low as possible, in order to maintain the sensitive microstructure and to save time and costs. In this way, a comparatively short and moderate 2-phase vacuum post-drying procedure is successfully designed and practically applied. The results show that the designed procedure is able to significantly reduce the residual moisture of anode and cathode coils, even with greater electrode lengths and coating widths, without deteriorating the sensitive microstructure of the electrodes.

Design of Vacuum Post-Drying Procedures for Electrodes of Lithium-Ion Batteries

To improve the performance of lead-free piezoelectric composites, the functionalization of the filler particles has been suggested as a successful strategy in several recent reports. The details of the functionalization process, however, are not clear, nor is its influence on the dielectric properties of the composites. This study reports a systematic investigation of the functionalization process parameters of barium titanate nanoparticles (BTONP) with 3-(trimethoxysilyl)propyl methacrylate (TMSPM) used as a linker to an acrylate-based matrix polymer. Functionalization process temperature, time, functionalization agent ratio, solvent, and catalyst influence on the functionalization degree were measured by thermogravimetric analysis (TGA), elemental analysis, and Fourier-transform infrared (FTIR) spectroscopy. Elevated temperature and average functionalization time led to the highest functionalization degree in the form of a TMSPM monolayer on the particle surface. Three solvents, with and without catalysts, were investigated and two types of functionalized BTONP were selected for composite manufacturing. To this end, the functionalized particles were used to manufacture 10 vol.% BTONP/photopolymer UV light-curable composite suspensions. After solidification of the suspensions by exposure to UV light, the microstructure and dielectric properties of the resulting composites were investigated. It was seen that functionalization improves the dispersion of particles, increases suspension viscosity, and decreases the curing depth and dielectric properties.

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Processing of 3-(Trimethoxysilyl)propyl Methacrylate (TMSPM) Functionalized Barium Titanate/Photopolymer Composites: Functionalization and Process Parameter Investigation

Axel Marth

Papers

Design of Vacuum Post-Drying Procedures for Electrodes of Lithium-Ion Batteries

Processing of 3-(Trimethoxysilyl)propyl Methacrylate (TMSPM) Functionalized Barium Titanate/Photopolymer Composites: Functionalization and Process Parameter Investigation