Investigation of Drying Curves of Lithium‐Ion Battery Electrodes with a New Gravimetrical Double‐Side Batch Dryer Concept Including Setup Characterization and Model Simulations

Abstract

Herein, an experimental setup comprised of a stationary convection dryer (Comb Nozzle Dryer) supplemented by a measurement for gravimetric drying curves is introduced. The drying process of anodes for lithium‐ion batteries is experimentally investigated and compared to modeling results, showing very good agreement for the investigated films. Heat transfer coefficients of the issued impinging nozzles are characterized and measured quantitatively and are used for the drying simulation of the gravimetric drying experiments. In situ temperature changes in the films are measured and presented using an infrared camera setup.

Influence of Layer Thickness on the Drying of Lithium‐Ion Battery Electrodes—Simulation and Experimental Validation

“…To obtain gravimetric drying curves, the experimental setup using the stationary comb nozzle dryer which was introduced in detail in a previous work was used and is explained here in short. [ 16 ] In a second experiment, which was also conducted using the comb nozzle dryer, the pore breakthrough to the film bottom was observed. All slurries used in the experiments were mixed using the same procedure and composition.…”

“…The heat and mass transfer coefficients can be adjusted by regulating the flow rate as explained in more detail in a previous work. [ 16 ] Thus, the drying conditions from the top can be controlled. The heat input from the bottom was adjusted by the heating plate, which ensures heat transfer by free convection, because an air gap between the film and plate is set accordingly.…”

“…For simulative validation, a model proposed in a previous work was used. [16] To account for transport resistances within the film during drying of thicker electrodes, the approach proposed by Krischer and further developed by Schlünder was introduced into the simulation. [5,6] At one point during drying, the meniscus of the uppermost capillary recedes into the film and mass and heat transfer are not solely governed by the drying conditions outside the film, as shown schematically in Figure 3.…”

“…Using the simulation introduced in a previous work and the moving drying front model based on Krischer as explained in Section 3, drying curves of electrodes of four different area weights m 1 to m 4 were simulated and compared to the experiments as shown in Figure 9. [5,16] It was assumed for all area weights that a resistance due to the meniscus of the uppermost capillary moving into the film would build up at the theoretical end of film shrinkage. This point was chosen as a first assumption due to the theoretical accessibility and the resulting easy implementation into the simulation, without the necessity of further experiments.…”

“…As a feasible way to predict the drying behavior of battery electrodes while circumventing huge computing efforts, a simple simulative model was used and experimentally validated based on solvent‐loading drying curves. [ 16 ] In the model it is assumed that solvent evaporation would solely take place at the electrode surface where it is transported by capillary pressure. For the low electrode thicknesses examined there, it was shown that no resistance within the film for mass and heat transport has to be considered, as was justified by evaluating the heat and mass transport Biot numbers.…”