The cell was placed in a custom-made pressure application jig with hard plastic plates. The battery was mounted at the edge of the plates in order to allow easy access to the metal current collecting tabs. The pressure jig with battery was then immersed in a water bath with the water level just below the edge of the current leads, and the whole setup placed on the home-built SAM to enable ultrasonic measurement. The battery was connected to a potentiostat (Admiral Instruments Squidstat Plus) and open circuit voltage (OCV) and EIS were measured every 30 minutes for three days. EIS was measured at open circuit with a 10 mV amplitude at a frequency range of 1 MHz to 1 Hz with 10 measurements per decade. SAM images were measured using 2.25 MHz transducers rastered over a 27.0 mm by 27.0 mm square with 0.5 mm step size, repeated every 30 minutes. Each ultrasonic wave was sampled 1000 times over a 16.000 μs period (16 ns time resolution) with an 18.000 μs delay from pulse start to measurement start. The measurement at each pixel in the scan was repeated 1000 times and the average of these measurements saved.