Fig. 5. Schematic and characterization of structural changes for uncoated SC-NMC particles after high-voltage cycling.
A Schematic showing structural changes occurring in uncoated SC-NMC532 particles when cycled to different voltage limits. Upon repeated cycling to high-voltage limits (>4.3 V vs Li/Li+), uncoated particles undergo irreversible structural changes (spinel and rock-salt phase formations), and (sub)surface and intra-particle cracking. HAADF-STEM images after 500 cycles at 1C rate (3 mA·cm−2) for (B) uncoated cycled at 4.3 V vs Li/Li+ and (C) uncoated cycled at 4.7 V vs Li/Li+ are presented. FFT patterns and zoomed-in views of marked regions are also presented as insets. (D–F) Ex-situ XRD scans of uncoated samples before cycling and from samples after rate capability tests at 4.3 V and 4.7 V limits.