Traditional ferroelectric materials, such as lead zirconate titanate (PZT) ceramics, exhibit positive strain when subjected to an electric field along the polarization direction. In contrast, the piezoelectric polymer polyvinylidene fluoride (PVDF) and its copolymer P(VDF-TrFE) display unique negative strain properties. While extensive research has focused on understanding the origin and mechanisms of this negative strain, limited efforts have been directed toward regulating these properties. This study optimizes the electro-strain and ferroelectric properties of P(VDF-TrFE) piezoelectric films through the synergistic effect of PbTiO₃ nanosheets and an in-situ electrostatic field. Our results demonstrate that while the incorporation of PbTiO₃ nanosheets does not notably enhance ferroelectricity, it significantly improves electro-strain properties, particularly negative strain, which increases from −0.097% to −0.185%, an enhancement of 91%. Moreover, the ferroelectric polarization and positive strain of P(VDF-TrFE) are further enhanced under the combined influence of PbTiO₃ nanosheets and in-situ electrostatic field, increasing maximum polarization from 10.79 μC/cm² to 13.16 μC/cm², a 22% improvement, and positive strain from 0.213% to 0.267%, a 25% enhancement. We propose a possible mechanism for these improvements, attributed to the enhanced flexibility of the amorphous phase and increased content of polar β-phase in P(VDF-TrFE) films under this synergistic effect. This work highlights novel strategies for controlling the electro-strain and ferroelectric properties of P(VDF-TrFE) piezoelectric films.

Piezoelectric materials that can effectively convert natural mechanical energy into electrical energy without time and space constraints have been widely applied for energy harvesting and conversion. The piezocomposites with high piezoelectricity and flexibility have shown great promise for renewable electric energy generation that can power implantable and wearable electronics. This minireview aims to summarize the recent progress of the piezocomposites with different composite structures, as well as the role of the theoretical understandings and designs in the development of new piezoelectric nanogenerator materials. Thereinto, the most common composite structural types (0-3, 1-3, and 3-3) have been discussed systematically. Several strategies for high output performance of piezocomposites are also proposed on the basis of current experimental and simulation results. Finally, the review concludes with perspectives on the future design of flexible piezoelectric nanocomposites for energy harvesters.

Surface energy is one of the most important physical and chemical properties for crystals, which has a significant impact on surface catalysis, surface adsorption, epitaxial growth, nucleation, and dendrite growth. Rapid calculation and prediction of crystal surface energies can favor accelerating the design and optimization of catalysis materials, battery materials, and alloys. In this paper, a data-driven machine learning algorithm was proposed with a crystal graph convolutional neural network framework for the prediction of metal surface energy from the crystal structure. Using a physics-based surface representation that couples the surface dimensions to the atomic and bonding features of the crystal, we obtained an MAE value of less than 0.002 eV/Ų, which surpasses other math-based surface models. Compared with the first-principles calculation, the computation time is reduced by approxiamtely 5 orders of magnitude. In addition, we discussed the main challenges and solutions towards the surface energy prediction of more complicated systems such as Silicates. It is expected that this work could be a paradigm for the surface energy prediction with machine learning.

The development of high-performance binders is a simple but effective approach to address the rapid capacity decay of high-capacity anodes caused by large volume change upon lithiation/delithiation. Herein, we demonstrate a unique organic/inorganic hybrid binder system that enables an efficient in situ crosslinking of aqueous binders (e.g., sodium alginate (SA) and carboxymethyl cellulose (CMC)) by reacting with an inorganic crosslinker (sodium metaborate hydrate (SMH)) upon vacuum drying. The resultant 3D interconnected networks endow the binders with strong adhesion and outstanding self-healing capability, which effectively improve the electrode integrity by preventing fracturing and exfoliation during cycling and facilitate Li⁺ ion transfer. SiO anodes fabricated from the commercial microsized powders with the SA/0.2SMH binder maintain 1470 mAh g⁻¹ of specific capacity at 100 mA g⁻¹ after 200 cycles, which is 5 times higher than that fabricated with SA binder alone (293 mAh g⁻¹). Nearly, no capacity loss was observed over 500 cycles when limiting discharge capacity at 1500 mAh g⁻¹. The new binders also dramatically improved the performance of Fe₂O₃, Fe₃O₄, NiO, and Si electrodes, indicating the excellent applicability. This finding represents a novel strategy in developing high-performance aqueous binders and improves the prospect of using high-capacity anode materials in Li-ion batteries.

(Bi, Sb)₂(Te,Se)₃ alloys are widely used commercial thermoelectric (TE) materials for solid-state refrigeration around room temperature. The composition-induced structural phase transition could be realized by varying the compositions in these alloys, which may largely alter the electronic structure and phonon dispersion. Among them, the Se-alloyed Sb₂Te₃ accompanied with structural transition is seldom reported. Herein, the interrelations of Se-alloying induced changes in structural phase transition, band structure and TE properties of p-type zone-melted Sb₂Te_3-xSe_x (x = 1.5–2.4) alloys near phase transition boundary are systematically investigated. The results demonstrate that Sb₂Te_3-xSe_x shows a structural transition from a rhombohedral phase to mixed structure at x = 2.0. The carrier concentration and bandgap at room temperature of Sb₂Te_3-xSe_x (x = 1.5–2.4) constantly decrease with increasing Se contents x. The zT peak of the Sb₂TeSe₂ matrix is improved and shifted to higher temperature by optimizing carrier concentration via Ag doping. A maximum zT of ~0.4 is obtained at 680 K in Sb_1.97Ag_0.03TeSe₂ alloy, about 100% enhancement compared with the undoped sample.