Comparative Evaluation of LMR-NCM and NCA Cathode Active Materials in Multilayer Lithium-Ion Pouch Cells: Part II. Rate Capability, Long-Term Stability, and Thermal Behavior
Ludwig Kraft, Tanja Zünd, David Schreiner, Rebecca Wilhelm, Florian J. Günter, Gunther Reinhart, Hubert A. Gasteiger, Andreas Jossen
Abstract
A lithium- and manganese-rich layered transition metal oxide-based cathode active material (LMR-NCM) with a reversible capacity of 250 mAh g −1 vs graphite is compared to an established NCA/graphite combination in multilayer lithium-ion pouch cells with a capacity of 5.5 Ah at a 1C discharge rate. The production of the cells, the electrode characterization as well as the formation is described in Part I of this study. In Part II, the two cell types are evaluated for their rate capability and their long-term stability. The specific capacity of the LMR-NCM pouch cells is ≈30% higher in comparison to the NCA pouch cells. However, due to the lower mean discharge voltage of LMR-NCM, the energy density on the cell level is only 11% higher. At higher discharge currents, a pronounced heat generation of the LMR-NCM pouch cells was observed, which is ascribed to the LMR-NCM voltage hysteresis and is only detectable in large-format cells. The cycling stability of the LMR-NCM cells is somewhat inferior due to their faster capacity and voltage fading, likely also related to electrolyte oxidation. This results in a lower energy density on the cell level after 210 cycles compared to the NCA pouch cells.