Characterization of structured ultra-thick LiNi0.6Co0.2Mn0.2O2 lithium-ion battery electrodes by mercury intrusion porosimetry

Abstract

In this work, a method to characterize reliably the porosity and pore size distribution of ultra-thick LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622) electrodes with mercury intrusion porosimetry is presented. In terms of sample preparation, a large sample area and low sample mass are essential to prevent inter-sample voids during analysis. The sample mass must be high enough to achieve a low relative error in terms of intrusion volume. Moreover, it was demonstrated that during analysis the protective oxide layer of the aluminum foil appears to be breached due to the high applied pressure and Al⋅Hg alloy is formed. The influence of this effect on the mercury intrusion porosimetry results was analyzed by investigations with blank aluminum foil. Thick electrodes with pore size distributions varied by the overall density, mechanical perforation and preparation with a pore forming agent were analyzed with the developed method and the results obtained for the very different structures are discussed. • Appropriate sample preparation is important for Mercury Porosimetry analysis. • Accuracy can be enhanced by adjusting the sample mass and shape. • Hg⋅Al alloy formation takes place during analysis possibly due to high pressure. • Different methods for structuring ultra-thick NCM622 electrodes were applied. • Mercury Porosimetry provided insight into their varying pore size distributions.