Li-ion battery technology is approaching its limits in terms of capacity density and energy density based on current anode and cathode materials, which poses a technical challenge for increasing the range of electric vehicles and minimizing overall battery pack size. An alternative lithium battery technology utilizing a high capacity cathode such as a Ni-rich layered oxide can theoretically deliver an energy density upwards of 500 Wh/kg [1].

Combined with a lithium anode and a suitable liquid electrolyte, one such Nickel–rich layered oxide, LiNi_0.6Mn_0.2Co_0.2O₂ (NMC 622), has the theoretical potential to deliver batteries with an energy density of at least 500 Wh/kg [2, 3]. Here we have studied the performance of such high energy density full cells comprised of a Li metal anode, NMC622 cathode, and 1.2 M in LiPF₆ (3:7) EC:EMC electrolyte.

In order to better understand and compare the performance of different systems, a deep understanding of cell variability and its impact on fade mechanisms is necessary [4]. Hence, challenges in identifying true fade mechanisms due to cell variability will be discussed The presentation will cover the different fade mechanisms and their gradual progression as observed during cycling of these cells. Differential capacity analysis was applied to identify different fade mechanisms and to quantify degradation modes. The different fade mechanisms are related to variations in cells. Statistical analyses will be presented to characterize and quantify cell variability based on the different fade mechanisms observed.

References:

[1] M. Stanley Whittingham, “Ultimate Limits to Intercalation Reactions for Lithium Batteries,” Chem. Rev, 114, 11414 (2014)

[2] Hyung-Joo Noh, Sungjune Youn, Chong Seung Yoon, and Yang-Kook Sun, “Comparison of the Structural and Electrochemical Properties of Layered Li[Ni_xCo_yMn_z])2 (x = 1/3, 0.5, 0.6, 0.7, 0.8 and 0.85) Cathode Material for Lithium-ion Batteries,” J Power Sources, 233, 121 (2013)

[3] Arumugam Manthiram, Bohang Song, and Wangda Li, “A Perspective on Nickel-rich Layered Oxide Cathodes for Lithium-ion Batteries,” Energy Storage Materials, 6, 125 (2017)

[4]Matthieu Dubarry, Nicolas Vuillaume, and Bor Yann Liaw, “Origins and Accommodation of Cell Variations in Li-ion Battery Pack Modeling,” Intl J of Energy Res, 34, 216 (2009)