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With the growing popularity of Li‐ion batteries in large‐scale applications, building a safer battery has become a common goal of the battery community. Although the small errors inside the cells trigger catastrophic failures, tracing them and distinguishing cell failure modes without knowledge of cell anatomy can be challenging using conventional methods. In this study, a real‐time, non‐invasive magnetic field imaging (MFI) analysis that can signal the battery current‐induced magnetic field and visualize the current flow within Li‐ion cells is developed. A high‐speed, spatially resolved MFI scan is used to derive the current distribution pattern from cells with different tab positions at a current load. Current maps are collected to determine possible cell failures using fault‐simulated batteries that intentionally possess manufacturing faults such as lead‐tab connection failures, electrode misalignment, and stacking faults (electrode folding). A modified MFI analysis exploiting the magnetic field interference with the countercurrent‐carrying plate enables the direct identification of defect spots where abnormal current flow occurs within the pouch cells. [ABSTRACT FROM AUTHOR]

Electric switching of ultrathin ferroelectric films is vital for electronic elements such as multiferroic tunnel junctions, but the large required field may induce ionic motions as addressed here. Unipolar current–voltage (I–V) characteristics of ultrathin (3 nm) PbZr0.2Ti0.8O3 (PZT) grown on La0.7Sr0.3MnO3 (LSMO) by pulsed laser deposition have been investigated in an ambient‐condition force microscope. Topographic changes have been recorded after the I–V measurements. No ferroelectric switching is found, but resistive switching with features in agreement with earlier work on similar perovskite titanates. The onset of hysteretical I–V loops is correlated with a clear height increase in the contacted area under the Pt‐covered tip. The onset voltage of 4.5 V (−2.5 V) for positive (negative) tip bias is clearly different for the two voltage polarities. The observed height changes after applying electrical voltage reveal a volume expansion that must be attributed to chemical changes in both the PZT and the LSMO layers. A fast and a slow process of ionic motion or electrochemical reaction contributing to the observed features is identified. The slow one occurs at negative voltage, causes very large height increase, and is hypothetically attributed to processes following the electro‐splitting of the adsorbed surface water. [ABSTRACT FROM AUTHOR]

P(VdF-HFP) films are fabricated via a solution casting doctor blade method using high (HVS) and low (LVS) volatile solvents, respectively. The structural properties and the ferroelectric behavior are investigated. The surface structure and crystal phase composition are found to be strongly dependent on the type of solvent. LVS leads to a rougher copolymer surface structure with large spherulites and a lower crystallinity in contrast with HVS. The crystalline phase of copolymer films fabricated with HVS consists almost exclusively of α-phase domains, whereas films from LVS solution show a large proportion of γ-phase domains, as concluded from Raman and X-ray diffraction spectra. Virgin films show no ferroelectric (FE) switching polarization at electric field amplitudes below 180 MV/m, independent of the solvent type, observed in bipolar dielectric displacement—electric field measurements. After applying electric fields of above 180 MV/m, a FE behavior emerges, which is significantly stronger for LVS films. In a repeated measurement, FE polarization switching already occurs at lower fields. A shielding effect may be related to this observation. Additionally, Raman bands of polar γ-phase increase by high-electric-field cycling for the LVS sample. The solvent used and the resulting crystal phase composition of the virgin sample is crucial for the copolymer behavior during bipolar electrical cycling. [ABSTRACT FROM AUTHOR]