Drying of NCM Cathode Electrodes with Porous, Nanostructured Particles Versus Compact Solid Particles: Comparative Study of Binder Migration as a Function of Drying Conditions

Abstract

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]

Drying of Compact and Porous NCM Cathode Electrodes in Different Multilayer Architectures: Influence of Layer Configuration and Drying Rate on Electrode Properties

“…This is because the binder is not highly concentrated between the particles clogging the pores, but a certain amount of binder is fixed in the particles and does not migrate during drying. [ 1 ]…”

(Near‐) Infrared Drying of Lithium‐Ion Battery Electrodes: Influence of Energy Input on Process Speed and Electrode Adhesion

“…[ 5 ] The application of high drying rates can lead to a migration of additives like binder and carbon black to the surface of the electrode layer, resulting in low adhesion between active material and current collector foil. [ 6–10 ] Furthermore, the electrochemical performance deteriorates compared with gently dried electrodes due to the accumulation of insulating binder and carbon black at the surface, resulting in an increased electrical resistance. [ 6,11 ]…”

“…[5] The application of high drying rates can lead to a migration of additives like binder and carbon black to the surface of the electrode layer, resulting in low adhesion between active material and current collector foil. [6][7][8][9][10] Furthermore, the electrochemical performance deteriorates compared with gently dried electrodes due to the accumulation of insulating binder and carbon black at the surface, resulting in an increased electrical resistance. [6,11] Binder migration is attributed to the capillary pressure-driven induction of concentration differences during the emptying of the porous electrode structure, leading to an inhomogeneous distribution of components over the electrode height.…”

Optimization of Edge Quality in the Slot‐Die Coating Process of High‐Capacity Lithium‐Ion Battery Electrodes

“…The main challenges in coating and drying are edge elevations, process handling, binder migration, and the processing of water‐based formulations, especially for cathodes. [ 1,4–12 ]…”

“…The main challenges in coating and drying are edge elevations, process handling, binder migration, and the processing of water-based formulations, especially for cathodes. [1,[4][5][6][7][8][9][10][11][12] Edge elevations occur during slot-die coating at the beginning of the process chain of electrode production. Slot-die coating is a premetered process and state of the art in large-scale battery-cell production.…”