Electrolyte Filling of Large-Scale Lithium-Ion Batteries: Challenges for Production Technology and Possible Approaches

Abstract

Lithium-ion batteries have been the dominant energy storage technology in consumer electronics for several years and meanwhile advanced into e-mobility and stationary applications. The trend towards large-scale batteries presents manifold challenges to production technology. One decisive assembly process is filling electrolyte liquid into the battery case. This paper discusses the main influences and challenges for production technology concerning this crucial manufacturing process and how they are addressed. First preliminary results are presented.

Influence of the Cell Format on the Electrolyte Filling Process of Lithium‐Ion Cells

“…Only after a sufficient volume of electrolyte is absorbed by the cell assembly, a subsequent filling step can be performed. A pouch cell, on the other hand, has a flexible film housing that provides sufficient volume to complete dosing in a single step . The foil is usually sealed in three directions, with one side open for dosing .…”

“…Contrary to the actual function of the SEI, the resulting transfer of electrons from the electrode to the electrolyte and the blocking of ions have a negative effect on the capacity and lifetime of the cell . The increase in the number of layers, electrode thickness, and surface area per cell decelerates the time‐intensive wetting of the cell components with electrolyte even further . The small surfaces of coin cells pose no challenge for wetting, as the electrolyte can reach all cavities in a short time.…”

Concept for the Analysis of the Electrolyte Composition within the Cell Manufacturing Process: From Sealing to Sample Preparation

“…Moreover, the cell filling process is not only dependent on the cell geometry but also is strongly linked with cell wetting. The cell filling process benefits from the fast wetting behavior of the used materials, while the overall cell wetting can be enhanced by several treatments that force the electrolyte into the pores of the used materials [2a,3]. Thus, material properties such as the electrode porosity, separator material, related pore structures, and electrolyte characteristics can significantly influence the behavior of the investigated system .…”

“…Therefore, for effective filling and wetting, different optimization possibilities of this process step have been proposed, including the application of rotational forces, increased temperatures, or pressure gradients . State‐of‐the‐art manufacturing processes typically apply filling procedures using reduced‐ and over‐pressure profiles . However, the influence of these profiles on the electrolyte composition has not been given much attention by academia, and the electrolyte composition was considered to be constant until the electrochemical activation of the cell.…”

Production Research as Key Factor for Successful Establishment of Battery Production on the Example of Large‐Scale Automotive Cells Containing Nickel‐Rich LiNi0.8Mn0.1Co0.1O2 Electrodes

“…While in lab‐scale, the electrolyte can be added in one step; especially for small coin cells, in industry‐scale, the electrolyte is usually added in several portions with longer wettings times in between to guarantee a complete wetting of all layers. Hence, the electrolyte filling process for large‐format cells in mass production is one of the bottlenecks and cost drivers . This is particularly important for winded electrode–separator–composites in which only one penetration axis is assumed and the electrolyte most likely penetrates through the two shorter, welded sides (Figure i).…”