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. 2021 Nov 4;12:6369. doi: 10.1038/s41467-021-26632-x

Fig. 2. Lithium metal–LLZO interface at 2 MPa.

Fig. 2

Polarization test of Li (s)–LLZO interface at 2 MPa stack pressure conducted in a Li/LLZO/Li cell. After a few hours of initial mechanical equilibration, 0.2 mA/cm2 is applied galvanostatically until the voltage cutoff of 5 V, followed by a 25 h OCV rest step, a second polarization step in the same direction, and a second OCV rest step. a Normalized acoustic amplitude (intensities relative to first waveform intensity). b Voltage showing increase in overpotential to voltage cutoff during the first galvanostatic current step of 0.2 mA/cm2, and rapid overpotential increase during the second step. Vertical guidelines (dotted blue lines) are shown as a visual aid to delineate start and stop of galvanostatic current. c Voltage and amplitude curves zoomed in on the second polarization region. d 1D slices of the ex situ 7Li chemical shift imaging (CSI) experiment in the z-direction highlighting the lithium metal region between 200 and 280 ppm, as indicated by the dashed region in e. e Contour plot of ex situ 7Li CSI depicting a strong lithium metal resonance (~250 ppm) extending into the electrolyte region (0 ppm) in the z-direction. Stripped side is on top (positive z-direction) and the stripped foil at low stack pressures is missing because it immediately delaminates from the LLZO surface following disassembly. f Nyquist plot from potentiostatic EIS conducted during initial OCV, after the first galvanostatic step, after the subsequent 25 h OCV hold, and after the second galvanostatic step, indicating an increase in cell impedance following the polarization steps and incomplete impedance recovery following the 25 h OCV step. The open circle indicates the high-frequency start point (7 MHz), and the cross indicates the low-frequency end point (0.5 Hz). g Simplified cartoon illustration of interface behavior (showing extent of contact loss and presence/absence of voids) implied by the experimental data; not drawn to scale.