1/3 Mn 1/3 )O 2 (NCM111), morphologies such as preferentially oriented crystals in the particles, [2] nanobrick morphology, [3] one-dimensional hierarchical microrods, [4] and hierarchically structured particles [5][6][7][8][9] were investigated. The latter is achieved by forming secondary particles with open intraparticle pore structure from assembled primary particles. The advantages of such structures are higher rate capability and improved cycling stability, due to a larger interface between active material and electrolyte, smaller diffusion paths and lower mechanical stress during cycling. By modifying the particle morphology of commercial compact materials in a few additional process steps, a comparison can be made between the commercial starting material and the produced structured material. This approach was applied in the work of Wagner et al. [9] by grinding, spray drying and calcination commercial NCM111. The influences of the process parameters in the production of such structures on the electrochemical properties as a function of the particle morphology were investigated. The optimum sintering temperature was found to be between 850 and 900 C, resulting in primary particle diameters of 350 and 550 nm. It is the optimum between the demands of the ionic conductivity of the primary particles and the electrical conductivity of the secondary particles. During the sintering process, the primary particles grow, which aggravates ion diffusion but increases the electrical conductivity due to sinter necks. The specific capacity was improved from 20 to 100 mAh g À1 at 10C for the original and the structured particles, respectively. [9]

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Previous investigations on porous NCM particles with shortened diffusion paths and an enlarged interface between active material and electrolyte showed improved rate capability and cycle stability compared to compact particles. Due to the additional intragranular porosity of the active material, the pore structure of the overall electrode, and, as consequence, the ionic transport in the pore phase, is altered. In addition, the particle morphology influences the ohmic contact resistance between the current collector and electrode film. These effects are investigated using impedance spectroscopy in symmetrical cells under blocking conditions. The ionic resistance and the tortuosity of the electrodes are determined and analyzed by a transmission line model. Tortuosity is higher for porous particles and increases more during calendering. This limits the options for densifying these electrodes to the same level as with compact particles. In a further approach, the method is used to explain the drying related performance differences of these electrodes. At higher drying rates, the contact and the ionic resistance of electrodes with compact particles increases more strongly as for electrodes with porous particles. These investigations provide new insights into the ion transport behavior and enable a better understanding of the impact of the electrode processing condition.

Understanding and reducing edge elevations at the lateral edges are crucial aspects to reduce reject rates during electrode production for lithium‐ion batteries (LIB). Herein, different process conditions to reduce edge elevations at the lateral edges of water‐based, shear‐thinning coatings in the production of LIB electrodes are presented. The reduction of edge elevations is transferred from state‐of‐the‐art electrodes to high‐capacity electrodes. The developed process configuration greatly reduces reject caused by cutting off the edge areas in the industrial roll‐to‐roll process for electrode production. Compared with state‐of‐the art electrodes, the reject rate for high‐capacity electrode production is significantly higher because the edge geometry in crossweb direction of the electrodes is wider. An optimization can be achieved by a combined adjustment of the coating gap and the slot‐die angle to the substrate (angle of attack) to affect the pressure field in the coating bead. Therefore, a systematic investigation and optimization of these process parameters are presented. In addition, the investigation of the process stability of the coating is required. Based on this optimization, a reduction of edge elevations for high‐capacity electrode coatings (5 mAh cm−2) of 69% and ultrathick high‐capacity electrode coatings (7 mAh cm−2) of 48% is possible.

Lithium-ion batteries (LIB) and sodium-ion batteries (SIB) are both based on similar intercalation/insertion electrodes of the respective alkali ions into the active materials during charging and discharging. [1] Due to the larger and heavier sodium (Na) ion, a lower gravimetric and as well volumetric capacity than with lithium can be achieved. [2,3] However, given the resource availability of active materials from sustainable raw materials, at potentially low cost, SIB is one of the most promising post-Li batteries for widespread commercialization in the coming years. [4][5][6] Electrode processing of materials for SIB is expected to be very similar to the processing of LIB materials. However, the producibility and material processing challenges of potential electrode materials for anodes and cathodes are poorly investigated.Unlike for the LIB, graphite cannot be recommended as anode material for the SIB, because the formation of a Na-graphite-intercalation compound is energetically unfavorable and has a very low capacity. [7][8][9][10] Instead, hard carbon (HC) is considered to be a promising anode active material with good electrochemical performance for alkali-metal-ion batteries, such as SIBs. [8] The low material costs, the fact that HC can be produced from sustainable raw materials, and the low electrode potential are advantageous for the use of HC as an anode material for SIB. [11,12] However, high capacity losses in the first cycles and at high current rates are still challenging. The performance characteristics of HC active materials, which result from different synthesis methods, are different. [8] The selected precursor and the carbonization conditions, namely, the carbonization temperature, influence the nongraphitic structure of the HC produced and thus, its properties. [2,8,10] The non graphitic structure of the HC offers various areas where Na ions can be deposited. These include especially the regions between the graphite-like domains consisting of micropores and defect sites. Various models describing the storage mechanism, which are controversially discussed, can be found in the literature. [2,10,13,14]

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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.

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