(Invited) Evolution of the Electrode−Electrolyte Interface of Ni-Rich Layered Oxides

Abstract

Commercial high capacity lithium ion batteries employ Ni-rich layered oxides (derived from LiCoO2) as cathodes with practical capacities of ~190 mA h g-1. However, the practical capacity is still far below the theoretical capacity of layered structures which can exceed 250 mA h g-1. Reactions at the cathode-electrolyte interfaces (CEI) are known to contribute to capacity fade and impedance growth particularly when cycling to high voltages (≥4.5 V) and at high temperatures. The capacity fade and impedance growth arise from a combination of electrolyte decomposition, surface oxygen loss, and transition metal dissolution resulting from reactions at the CEI. I will summarize a range of spectroscopy, microscopy, transport studies of model systems under thermal and electrochemical stress that provide insight into what drives the evolution of the CEI layer and how it impacts the battery performance.[1-5] These studies reveal how the negative aspects of the CEI can be suppressed in order to reduce the gap between practical and theoretical capacities. This work was supported as part of NECCES, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DESC0012583 [1] Journal of The Electrochemical Society (Editor’s Choice), 164, A3727-A3741 (2017) [2] Chemistry of Materials 29, 7345–7352 (2017) [3] Langmuir 33, 9333–9353 (2017) [4] Applied Physics Letters 108, 263902 (2016) [5] Chemistry of Materials, 30 958–969 (2018)