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A novel electrode production process, based on a minimal solvent content, is developed for highly viscous water‐based graphite anodes, using a solid mass content of 50% or more compared to conventionally processed anodes. The electrode paste is prepared by mixing the solids with solvent inside of a twin‐screw extruder. Afterward, the extrudate is cut with a strand pelletizer to granules. By inserting the granules into the gap of a two‐roller calender, the current collector foil is coated directly. It is shown that the highly viscous pastes are capable of extended storage stability over several weeks, whereby a temporal and local decoupling of paste preparation and electrode manufacturing can be realized. To enable this innovative electrode processing, a combined development incorporating a selection of new anode binder materials, machinery design, and process parameters has been essential due to strong material‐process interaction, as known in the field of battery electrode production. Because the binder is exposed to greater shear stresses and a short duration time during extrusion mixing, the selection of novel anode binder materials is particularly important. This then needs to be combined with machine design and process parameter optimization, in order to establish this innovative electrode processing method. [ABSTRACT FROM AUTHOR]

Calendering is the state‐of‐the‐art process for electrode compaction in lithium‐ion battery manufacturing through which the final electrode structure is defined. As the electrode structure determines the electrical und electrochemical transport properties, it is essential to develop a deep understanding of the interdependence between the calendering process and the deformation behavior of the electrodes. Therefore, a novel method for the investigation of the deformation behavior of electrodes, especially the springback (SB) effect, through direct‐gap detection within the calendering machine, is developed. With this installation, it is possible to directly access the maximum compression of the electrodes during calendering. With this approach, two different variations of cathodes, a variation of mass loading and a variation of binder weight content, based on lithium nickel manganese cobalt oxide (NMC622), are manufactured and investigated. Moreover, an empirical model is introduced, allowing the estimation of the SB for NMC622 cathodes considering different mass loadings and cathode compositions. Due to more space for particle rearrangement, cathodes with higher mass loading show a lower SB effect. Adding binder leads to higher plastic deformation and thus lowers also the SB effect of the electrodes. [ABSTRACT FROM AUTHOR]

Electrodes are usually calendered to enhance the energy density and improve the electrochemical cell performance. However, low porosities can compromise these two important features. To achieve the optimum porosity, a comprehensive process control is of major interest. This study further develops a Heckel‐based compaction model considering the impact of the roll temperature and discusses the effect of the composition. Increasing the temperature of the roll linearly decreases the achievable coating porosity and the line load effort due to the rise of the elastic deformability of the thermoplastic binder PVDF. Reduced contents of simultaneously less‐distributed additives increase the achievable coating porosity. Furthermore, the poor distribution is the main factor for lower line load efforts with lower additive contents. Moreover, the adhesion strength of the coating improves with increasing the temperature of the rolls due to the thermal rising of the elasticity of the binder. [ABSTRACT FROM AUTHOR]

Calendering is the common compaction process for lithium-ion battery electrodes and has a substantial impact on the pore structure and therefore the electrochemical performance of Lithium-ion battery cells. For a targeted determination of the performance-optimized pore structure, it is of decisive importance to be able to comprehensively control the compaction process. Thus, during continuous calendering of graphite anodes and lithium nickel cobalt manganese oxide (NCM) cathodes the applied line load is tracked and varied at different speeds to compact the electrode to several coating densities. The generated pore structures are measured via mercury intrusion, resulting in quite similar porosities, while the densities of graphite and NCM diverge greatly. The porosities, measured via mercury intrusion, are compared to geometrical determined data, identifying compaction resistant closed pores in the NCM. On the basis of the measured porosity reduction the compaction behavior of the line load was found to be describable by an exponential model equation. The model parameters quantify the different compaction resistances of the cathodes and anodes in converging to a maximal density, respectively minimal porosity. This substantial difference could be traced to the closer packing of the spherical and harder NCM particles. The calendering speed showed only an insignificant impact up to speeds of 5 m/min. [ABSTRACT FROM AUTHOR]