Polymer‐based dielectric materials play a key role in advanced electronic devices and electric power systems. Although extensive research has been devoted to improve their energy‐storage performances, it is a great challenge to increase the breakdown strength of polymer nanocomposites in terms of achieving high energy density and good reliability under high voltages. Here, a general strategy is proposed to significantly improve their breakdown strength and energy storage by adding negatively charged Ca2Nb3O10 nanosheets. A dramatically enhanced breakdown strength (792 MV m−1) and the highest energy density (36.2 J cm−3) among all flexible polymer‐based dielectrics are observed in poly(vinylidene fluoride)‐based nanocomposite capacitors. The strategy generalizability is verified by the similar substantial enhancements of breakdown strength and energy density in polystyrene‐based nanocomposites. Phase‐field simulations demonstrate that the further enhanced breakdown strength is ascribed to the local electric field, produced by the negatively charged Ca2Nb3O10 nanosheets sandwiched with the positively charged polyethyleneimine, which suppresses the secondary impact‐ionized electrons and blocks the breakdown path in nanocomposites. The results demonstrate a new horizon of high‐energy‐density flexible capacitors.

The developments of next‐generation electric power systems and electronics demand for high temperature (≈150 °C), high energy density, high efficiency, scalable, and low‐cost polymer‐based dielectric capacitors are still scarce. Here, the nanocomposites based on polyimide‐poly(amic acid) copolymers with a very low amount of boron nitride nanosheets are designed and synthesized. Under the actual working condition in hybrid electric vehicles of 200 MV m−1 and 150 °C, a high energy density of 1.38 J cm−3 with an efficiency higher than 96% is achieved. This is about 2.5 times higher than the room temperature energy density (≈0.39 J cm−3 under 200 MV m−1) of the commercially used biaxially oriented polypropylene, the benchmark of dielectric polymer. Especially, the energy density and efficiency at 150 °C show no sign of degradation after 20 000 cycles of charge‐discharge test and 35 days’ high‐temperature endurance test. This research provides an effective and low‐cost strategy to develop high‐temperature polymer‐based capacitors.

Flexible ferroelectric devices have been a hot-spot topic because of their potential wearable applications as nonvolatile memories and sensors. Here, high-quality (111)-oriented BiFeO 3 ferroelectric films are grown on flexible mica substrates through an appropriate design of SrRuO 3 /BaTiO 3 double buffer layers. BiFeO 3 exhibits the largest polarization (saturated polarization P s ≈ 100 μC/cm 2 , remnant polarization P r ≈ 97 μC/cm 2 ) among all the reported flexible ferroelectric films, and ferroelectric polarization is very stable in 10 4 bending cycles under 5 mm radius. Accordingly, the ferroelectric memristor behaviors are demonstrated with continuously tunable resistances, and thus, the functionality of spike-timing-dependent plasticity is achieved, indicating the capability of flexible BiFeO 3 -based memristors as solid synaptic devices. Moreover, in artificial neural network simulations based on the experimental characteristics of the memristor, a high recognition accuracy of ∼90% on handwritten digits is obtained through online supervised learning. These results highlight the potential wearable applications of flexible ferroelectric memristors for data storage and computing.

Addressing microstructure-property relations of polymer nanocomposites is vital for designing advanced dielectrics for electrostatic energy storage. Here, we develop an integrated phase-field model to simulate the dielectric response, charge transport, and breakdown process of polymer nanocomposites. Subsequently, based on 6615 high-throughput calculation results, a machine learning strategy is schemed to evaluate the capability of energy storage. We find that parallel perovskite nanosheets prefer to block and then drive charges to migrate along with the interfaces in x-y plane, which could significantly improve the breakdown strength of polymer nanocomposites. To verify our predictions, we fabricate a polymer nanocomposite P(VDF-HFP)/Ca2Nb3O10, whose highest discharged energy density almost doubles to 35.9 J cm−3 compared with the pristine polymer, mainly benefit from the improved breakdown strength of 853 MV m−1. This work opens a horizon to exploit the great potential of 2D perovskite nanosheets for a wide range of applications of flexible dielectrics with the requirement of high voltage endurance.

α-Fe2O3/reduced graphene oxide (α-Fe2O3/rGO) composites are rationally designed and prepared to integrate organic pollutants detection and their photocatalytic degradation. Specifically, the composites are used as the substrate for surface-enhanced Raman scattering (SERS) to detect rhodamine 6G (R6G). Repeatable strong SERS signals could be obtained with R6G concentration as low as 10(-5) M. In addition, the substrate exhibits self-cleaning properties under solar irradiation. Compared with pure α-Fe2O3 and α-Fe2O3/rGO mechanical mixtures, the α-Fe2O3/rGO composites show much higher photocatalytic activity and much greater Raman enhancement factor. After 10 cycling measurements, the photodegradation rate of R6G could be maintained at 90.5%, indicating high stability of the photocatalyst. This study suggests that the α-Fe2O3/rGO composites would serve both as recyclable SERS substrate and as excellent visible light photocatalyst.