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

Abstract

During the production process of lithium‐ion battery cells, the filling, which consists of dosing and wetting steps, of the cell and its components with an electrolyte liquid is important for the quality and costs of the final product. The cell format as a combination of housing and cell arrangement not only determines the type of filling process but also influences the distribution of the electrolyte within the cell. The cell format also has an influence on the wetting state as a function of time. Herein, in situ neutron radiography is used to analyze the filling process of two different cell types – pouch cells with a z‐folded stack and hardcase cells with a flat wound roll. The results are then analyzed and transferred to other common cell formats to identify a fillable cell design and format‐dependent process improvement possibilities to enable faster processing.

Classification of Calendering‐Induced Electrode Defects and Their Influence on Subsequent Processes of Lithium‐Ion Battery Production

“…Geometrical defects generally have an influence on stacking and electrolyte filling. The internal cell structure of the lithium‐ion cell has a major influence on the electrolyte filling process . Any obstacles or deviations in shape interfere with the free electrolyte flow and hinder the complete wetting of the electrodes.…”

“…Nevertheless, local effects are to be expected here. For example, in a pouch cell, the flow of the electrolyte liquid was observed from three sides . If corrugations at the coating edge form, one or two sides are provided with shape deviations that can disturb the free flow of the electrolyte liquid.…”

Current and future lithium-ion battery manufacturing

“…With the help of neutron radiography, Günter et al. visualized the electrolyte distribution in pouch cells and proposed a pressure cycle wetting procedure to accelerate the electrolyte wetting ( Günter et al., 2019 ). To achieve a lower cost and better visualization, Deng et al.…”

Transforming Materials into Practical Automotive Lithium‐Ion Batteries

“…Neutron radiography recording during the filling process in a pouch cell with a z‐folded stack and a hardcase cell with a flat wound roll was performed. [ 143 ] It was found that during dosing, the electrolyte enters through the filling opening, and due to gravity, it accumulates in the empty space of the cell. The electrolyte then wets the cell assembly depending on the accessible axes of penetration, providing two and four wetting directions.…”

“…The electrolyte then wets the cell assembly depending on the accessible axes of penetration, providing two and four wetting directions. [ 143 ] It was also observed that the most important factor during wetting seems to be the pressure cycles among flushing (with inert gas) and evacuation, multiple dosing, pumping (pressure cycles), and afterwetting. [ 143 ] The X‐ray based visualization of the filling process of LIBs was implemented and visually analyzing the recording, the parameters of the amount of entrapped gasses, the filling level, and the characteristics of the fluids flow front were derived.…”