Abstract
The range of electrode porosity, electrode internal void volume, cell capacity, and capacity ratio that result from electrode coating and calendering tolerance can play a considerable role in cell-to-cell and lot-to-lot performance variation. Based on a coating loading tolerance of ±0.4 mg/cm2 and calender tolerance of ±3.0 μm, the resulting theoretical range of physical properties was investigated. For a target positive electrode porosity of 30%, the resulting porosity can range from 19.6% to 38.6%. To account for this variation during the manufacturing process, as much as 41% excess or as little as 59% of the target electrolyte quantity should be added to cells to match the positive electrode void volume. Similar results are reported for a negative electrode of 40% target porosity, where a range from 30.8% to 48.0% porosity is possible. For the negative electrode as little as 72% up to 28% excess electrolyte should be added to fill the internal void space. Although the results are specific to each electrode composition, density, chemistry, and loading the presented process highlight the possible variability of the produced parts. These results are further magnified as cell design moves toward higher power applications with thinner electrode coatings.
Highlights
Lithium ion cells have been the pinnacle method of providing energy for portable electronics, with numerous manufacturers around the world providing batteries of different chemistries [1], dimensions, capacity [2], and power [3]
Focusing solely on the impact calender tolerance will have on electrode porosity for the three previously highlighted positive and negative electrode loadings, as expected, it can be seen in Figure 1 that the largest impact occurs for the lightest electrode loading
Physical experimental data are not presented for the theoretical design and resulting variation, it is understood that all manufactured parts, whether in industry or academia, will have an associated deviation from the target value. This variation in the produced parts may be the result of the non-uniformity of laboratory scale calender rolls, or the industrial manufacturing process where parts are presented as having a target value and accepted tolerance range
Summary
Lithium ion cells have been the pinnacle method of providing energy for portable electronics, with numerous manufacturers around the world providing batteries of different chemistries [1], dimensions, capacity [2], and power [3]. In manufacturing LiCoO2 cells at both the commercial and laboratory scale, variability is introduced. These tolerances on produced parts, present during any manufacturing process, can have a large impact on the final product’s reliability, repeatability, and functionality. Lithium ion cells are no exception to this and manufacturing variation must be considered during cell performance evaluations [6]. Whether it be the formed aluminum laminate package dimensions for prismatic cells, electrode dimensions, electrode coating mass loading, or electrode calender thickness, as well as other production steps, these variations inevitably affect the final product [7]. The influence of positive [10], and negative [11] electrode density was demonstrated to show that as electrode density is increased, internal electrode electrolyte volume is decreased, leading to increased polarization and Batteries 2020, 6, 23; doi:10.3390/batteries6020023 www.mdpi.com/journal/batteries
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
