The post‐drying of electrodes and separators for lithium‐ion batteries just before cell assembly aims at reducing the water content in the cells below a critical value. This is important as the remaining water can lead to cell degradation and thus cause a safety risk. In addition, it can impede the formation of an effective solid electrolyte interface. Nevertheless, the post‐drying of lithium‐ion battery electrodes and separators is still poorly investigated. Considering this, three different post‐drying procedures are investigated on pouch cells and compared with the non‐post‐dried state. The remaining water contents are measured via coulometric Karl Fischer Titration and correlated to the resulting electrochemical performance. Surprisingly, the most intensely post‐dried cells show the worst electrochemical performance despite reaching the lowest water content. In contrast, the mildest post‐dried cells, which show the highest water content, achieve the best electrochemical performance. Further analyses show that extreme post‐drying can cause irreparable damages within the electrode structures. Therefore, a good electrochemical performance is not only guaranteed by low remaining water content but also, in particular, by gentle post‐drying.

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.

Low-cost and high-performance lithium ion batteries (LIBs) are a key technology in these days. One promising candidate for cathodes is the layered nickel (Ni)-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) active material due to its high energy density, high specific capacity and lower material costs as well as social aspects concerning mining due to the diminished cobalt content. However, the lower thermal stability and higher sensitivity to H2O and CO2 result in a potential stronger performance degradation and lower safety. Therefore, process adaptions are inevitable. In this paper the current status and challenges of the entire cathode production process with NCM811 as active material are reviewed taking quality, cost and environmental aspects into account. General important aspects within the process are presented which are specially extended to NCM811 cathode production. Process recommendations are highlighted and innovative approaches like a water-based or solvent-free processing are discussed in comparison to conventional production technologies.

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.

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.

The selection of an appropriate cathode active material is important for operation performance and production of high‐performance lithium‐ion batteries. Promising candidates are nickel‐rich layered oxides like LiNixCoyMnzO2 (NCM, x+y+z=1) with nickel contents of ‘x’ ≥ 0.8, characterized by high electrode potential and specific capacity. However, these materials are associated with capacity fading due to their high sensitivity to moisture. Herein, two different polycrystalline NCM materials with nickel contents of 0.81 ≤ ‘x’ ≤ 0.83 and protective surface coatings are processed in dry‐room atmosphere (dew point of supply air TD ≈ −65 °C) at lab scale including the slurry preparation and coating procedure. In comparison, cathodes are produced in ambient atmosphere and both variants are tested in coin cells. Moreover, processing at pilot scale in ambient atmosphere is realized successfully by continuous coating and drying of the cathodes. Relevant electrode properties such as adhesion strength, specific electrical resistance, and pore‐size distribution for the individual process steps are determined, as well as the moisture uptake during calendering. Furthermore, rate capability and cycling stability are investigated in pouch cells, wherein initial specific discharge capacities of up to 190 mAh g−1 (with regard to the cathode material mass) are achieved at 0.2C.

Binders are one of the essential components in lithium‐ion battery electrodes. Developments are focusing on high‐capacity anodes in particular, which place special requirements on the water‐based binder system, depending on material composition. Typically, the binders used are carboxymethyl cellulose (CMC) in combination with styrene butadiene rubber, but more environmentally friendly binders such as alginates (ALG) are also gaining importance. While many studies have addressed the synthesis and chemical interactions of these binders, most of them refer only to the material level and do not consider scalable manufacturing processes of the anodes. Moreover, the influence of binders on electrode structure and residual moisture is usually not, or insufficiently, considered. Accordingly, this study addresses the influence of CMC and ALG with different polymer structures (degree of substitution; M‐/G‐ratio) and molecular masses on processability, electrode structure, and performance. The findings suggest that different rheological properties (slurry) and electrode structures are produced, depending on the polymer type (CMC/ALG), and that both polymer type and electrode structure significantly influence residual moisture and adhesion strength. The electrochemical analysis is performed in coin full‐cells. From this, recommended actions for binder material development as well as knowledge‐based production processes for these anode material systems can be developed.

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