A Review of Lithium‐Ion Battery Electrode Drying: Mechanisms and Metrology

Abstract

Lithium‐ion battery manufacturing chain is extremely complex with many controllable parameters especially for the drying process. These processes affect the porous structure and properties of these electrode films and influence the final cell performance properties. However, there is limited available drying information and the dynamics are poorly understood due to the limitation of the existing metrology. There is an emerging need to develop new methodologies to understand the drying dynamics to achieve improved quality control of the electrode coatings. A comprehensive summary of the parameters and variables relevant to the wet electrode film drying process is presented, and its consequences/effects on the finished electrode/final cell properties are mapped. The development of the drying mechanism is critically discussed according to existing modeling studies. Then, the existing and potential metrology techniques, either in situ or ex situ in the drying process are reviewed. This work is intended to develop new perspectives on the application of advanced techniques to enable a more predictive approach to identify optimum lithium‐ion battery manufacturing conditions, with a focus upon the critical drying process.

Data Specifications for Battery Manufacturing Digitalization: Current Status, Challenges, and Opportunities

“…This is completed by evaporating the solvent from the slurry with a typical drying rate of 25-50 m min À 1 . [114] Hot-air convection and infrared radiation drying are among the most common drying techniques, [115] although we focus on the hot-air drying type in this work. Under hot air, in the first stage of the drying process (film shrinkage), the solvent evaporates from the film's top surface, causing it to shrink until the rigid AM particles make contact with each other, stopping any further decrease in film thickness.…”

“…Neither of these existing models can be relied upon to predict the whole optimal LIB electrode drying step. [114] CGMD models consider the solvent only implicitly, and thus, its evaporation deals by using a change of FF parameters. The machine parameters are weighted using a few parameters related to the conversion rate from the "wet" state to the "dry" form and the difference in conversion rate between horizontal layers of the domain.…”

“…In this step, the coating is fixed on the current collector surface, consolidating the uniform electrode structure and morphology formation to achieve the desired cell performance. This is completed by evaporating the solvent from the slurry with a typical drying rate of 25–50 m min −1 [114] …”

“…However, in most cases, this is valid only for a specific part of the whole drying process, either the initial film shrinkage stage or the subsequent pore emptying stage). Neither of these existing models can be relied upon to predict the whole optimal LIB electrode drying step [114] …”

Applications of advanced metrology for understanding the effects of drying temperature in the lithium-ion battery electrode manufacturing process

“…1 To maintain consistency within cell electrodes, a homogeneous and defect-free electrode coating is required to enable uniform current densities and to facilitate lithium-ion transport between electrodes, reducing degradation and failures rates. 2 The porous electrode structure, and physical, mechanical and electrochemical properties of the electrode coatings are extremely important in maintaining good consistency in LIBs. The electrode physico-chemical properties are controlled by the mixing, coating and, most importantly, the drying and subsequent calendering processes, which in turn relate to the various parameters/variables during the drying process (DP).…”