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Polycrystalline Pt thin films of different thicknesses (0–75 nm) were introduced using magnetron sputtering in Pb(Zr0.52Ti0.48)O3 (PZT, 400 nm in thickness)/Pt/Ni multiferroic film heterostructures, aimed at optimizing the transfer efficiency of magnetostrictive strain from the bottom Ni foil to the top PZT film and thus the direct magnetoelectric (ME) coupling. The ME voltage coefficient αE31 was directly measured, while the strain transfer efficiency k was obtained by combined experimental and theoretical analysis. At the optimum Pt-thickness of 30 nm, the polycrystalline film heterostructure shows the largest αE31 of 772 mV cm−1 Oe−1 at a low dc magnetic bias field of 86 Oe, as well as the highest k of 83% that is comparable to that in epitaxial quasi-2-2 film heterostructures.

Covalent organic frameworks (COFs) have developed as a precisely tailor-made platform for integrating different functionalities into the frameworks via reticular chemistry. In this work, two COFs with a similar topology and skeleton but different charge state over the skeleton are designed and applied to clarify the contributions of cationic groups to the output performance of a triboelectric nanogenerator (TENG). The cationic functional centers are distributed alternately over both sides of the pore channels. The cationic COF possesses unconventional electrostatic functions due to the ionic interface over the skeletons. The output performance of a cationic COF decorated with an electric-dipole-based TENG is improved by a 2-fold contrast to the neutral analogue. Moreover, a cationic COF-based TENG is further employed to charge commercial capacitors (0.1 F), light up light-emitting diodes (LEDs), and power a stopwatch. This work illustrates the facile construction of a cationic COF and its application in fabricating a TENG, generating an ecofriendly and excellent-performance energy harvesting and selfpowered device.

As intercalation-type anode materials for Li-ion batteries (LIBs), the commercially used graphite and Li Ti O exhibit good cycling and rate properties, but their theoretical specific capacities are too low to meet the ever-growing demands of high-energy applications such as electric vehicles. Therefore, the development of new intercalation-type anode materials with larger capacity is very desirable. Herein, we design and synthesize novel 3 D hierarchical porous V O @C micro/nanostructures consisting of crumpled nanosheets, through self-reduction under annealing from the structurally similar VO (B)@C precursors without the addition of any other reducing reagent or gas. Excitingly, it is found for the first time through ex situ XRD technology that V O is a new, promising intercalation-type anode material for LIBs with a high capacity. V O @C micro/nanostructures can deliver a large capacity of 732 mAh g without capacity loss at 100 mA g even after 136 cycles, as well as exhibiting excellent cycling and rate performances. The application of V O for Na-ion batteries (NIBs) is elaborated for the first time, and excitingly, it is found that V O @C micro/nanostructures may be promising anode materials for NIBs.

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