Single-particle measurements of electrochemical kinetics in NMC and NCA cathodes for Li-ion batteries

By Ping‐chun Tsai, Bohua Wen, M. Wolfman, Min-Ju Choe, M. Pan, Liang Su, K. Thornton, J. Cabana, Y. Chiang. 2018

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The electrochemical kinetics of battery electrodes at the single-particle scale are measured as a function of state-of-charge, and interpreted with the aid of concurrent transmission X-ray microscopy (TXM) of the evolving particle microstructure. An electrochemical cell operating with near-picoampere current resolution is used to characterize single secondary particles of two widely-used cathode compounds, NMC333 and NCA. Interfacial charge transfer kinetics are found to vary by two orders of magnitude with state-of-charge (SOC) in both materials, but the origin of the SOC dependence differs greatly. NCA behavior is dominated by electrochemically-induced microfracture, although thin binder coatings significantly ameliorate mechanical degradation, while NMC333 demonstrates strongly increasing interfacial reaction rates with SOC for chemical reasons. Micro-PITT is used to separate interfacial and bulk transport rates, and show that for commercially relevant particle sizes, interfacial transport is rate-limiting at low SOC, while mixed-control dominates at higher SOC. These results provide mechanistic insight into the mesoscale kinetics of ion intercalation compounds, which can guide the development of high performance rechargeable batteries.

Subfields: Automotive Engineering, Electrical and Electronic Engineering

View Paper: https://www.semanticscholar.org/paper/fbcd43f8458b13e4e960551d1814790d95a67fa4