A Perspective on Innovative Drying Methods for Energy‐Efficient Solvent‐Based Production of Lithium‐Ion Battery Electrodes

Abstract

The process step of drying represents one of the most energyintensive steps in the production of lithium-ion batteries (LIBs). [1,2] According to Liu et al., the energy consumption from coating and drying, including solvent recovery, amounts to 46.84% of the total lithium-ion battery production. [3] The starting point for drying battery electrodes on an industrial scale is a wet film of particulate solvent dispersions, which are applied to a current collector foil by slot-die coating. Conventional convective drying removes the solvent from the wet film and solidifies the layer as the drying time progresses (Figure 1). According to the state-of-the-art, electrodes are produced at a web speed of 25-80 m min À1 . [2,[4][5][6][7][8] The deviations in the coating/drying speeds are related to the constant improvement of the system technologies and the different coating thicknesses and types. For example, coatings can be applied intermittently or continuously. [9][10][11] Furthermore, double-sided coatings can be applied simultaneously or sequentially, meaning that the first side is dried first and then the second side. [4,6,7,12] In addition to the actual application methods, parameters such as mass loading and solids content determine the achievable drying rate. Pfleging et al. report typical coating speeds for thick electrodes of 30 m min À1 , whereas Mauler et al. assume that processing speeds of up to 100 m min À1 are realistic in the future. [6,7] However, the influence of the drying intensity on the structure of the electrode must be taken into account. Increasing the drying rate leads to a segregation of binder and carbon black particles contained in the formulation. [13,14] This results in a decrease in binder and carbon black at the interface between the current collector foil and the coating. Jaiser et al. divide the drying process into two different phases. During the first phase, the evaporation of the solvent leads to a shrinkage of the coated layer, the second starts once this shrinkage stops and the solvent is evaporated by capillary transport. The latter phase is mainly responsible for the binder migration. [15] For this reason, drying must be very gentle during this phase. Reducing the drying rate of anode slurries during this stage from 1.19 to 0.52 g m 2 s À1 leads to a 50% increase in adhesive strength. [15] Clearly, an elevation of the drying intensity and the associated production speed is not possible compromising electrode quality. [13,14] Regardless of the electrode parameters, however, throughput can be increased by lengthening the dryer. The difficulty here lies in handling very thin foils, which tend to wrinkle with an increase in dryer length and place new demands on the web tension controls. [4] To be able to increase production speeds and, thus, maximize throughputs, a carefully chosen

Roll-to-roll double side electrode processing for the development of pre-lithiated 80 F lithium-ion capacitor prototypes

“…There have been several studies on LIB manufacturing investigating different approaches to find the most appropriate drying technique. Von Horstig et al evaluated different drying technologies for simultaneous double-side coating [33]. Classified by the higher to the lower technological readiness level, convection, infrared, laser, microwave, and joule heating technologies were proposed.…”

Novel high-power laser modules for drying applications based on VCSEL arrays

“…Their early work laid the foundation for subsequent in-depth investigations, exploring the feasibility and advantages of incorporating lasers into the drying process. From a broader perspective, the insights from [ 4 ] highlight the transformative potential of VCSELs, particularly in driving innovation towards energy-efficient solvent-based production of LIB electrodes. Together, these studies not only showcase the promise of VCSELs but also suggest a shift in simplifying and enhancing lithium-ion battery electrode production, emphasizing both innovation and heightened energy efficiency.…”

Optimized LiFePO4-Based Cathode Production for Lithium-Ion Batteries through Laser- and Convection-Based Hybrid Drying Process

“…Furthermore, high operational expenditures (OpEx) result from the substantial energy demand and the high CapEx are attributed to dryer lengths of up to 100 m [4]. The already high space requirements further increase with higher production speeds and, thus, limit the scalability of electrode production [5,6].…”

“…Laser-based drying is a promising process alternative to convection-based drying that has been developed and investigated in recent years [6]. The direct and high energy input into the material through the absorption of laser radiation holds the potential for reduced energy consumption and space requirements by accelerated drying rates [7][8][9].…”