Nature Materials最新文献

High-power autonomous soft actuators are in high demand yet face challenges related to tethered power and dedicated control. Light-driven oscillation by stimuli-responsive polymers allows for remote energy input and control autonomy, but generating high output power density is a daunting challenge requiring an advanced material design principle. Here, inspired by the flight muscle structure of insects, we develop a self-oscillator based on two antagonistically contracting photo-active layers sandwiching an inactive layer. The actuator produces an output power density of 33 W kg⁻¹, 275-fold higher than other configurations and comparable to that of insects. Such oscillators allow for broad-wavelength operation and multifunction integration, including proprioceptive actuation and energy harvesting. We demonstrate high-performance flapping motion enabling various locomotion modes, including a wing with a thrust-to-weight ratio of 0.32. This work advances autonomous, sustained and untethered actuators for powerful robotics.

We report on single-phase Na_xV₂(PO₄)₃ compositions (1.5 ≤ x ≤ 2.5) of the Na super ionic conductor type, obtained from a straightforward synthesis route. Typically, chemically prepared c-Na₂V₂(PO₄)₃, obtained by annealing an equimolar mixture of Na₃V₂(PO₄)₃ and NaV₂(PO₄)₃, exhibits a specific sodium-ion distribution (occupancy of the Na(1) site of only 0.66(4)), whereas that of the electrochemically obtained e-Na₂V₂(PO₄)₃ (from Na₃V₂(PO₄)₃) is close to 1. Unlike conventional Na₃V₂(PO₄)₃, when used as positive electrode materials in Na-ion batteries, the Na_xV₂(PO₄)₃ compositions lead to unusual single-phase Na⁺ extraction/insertion mechanisms with continuous voltage changes upon Na⁺ extraction/insertion. We demonstrate that the average equilibrium operating voltage observed upon Na⁺ deintercalation from single-phase Na₂V₂(PO₄)₃ is increased up to an average value of ~3.70 V versus Na⁺/Na (thanks to the activation of the V⁴⁺/V⁵⁺ redox couple) compared to 3.37 V versus Na⁺/Na in conventional Na₃V₂(PO₄)₃, thus leading to an increase in the theoretical energy density from 396.3 Wh kg^–1 to 458.1 Wh kg^–1. Electrochemical and chemical Na⁺ deintercalation from c-Na₂V₂(PO₄)₃ enables complete Na-ion extraction, increasing energy density.

Spin or valley degrees of freedom hold promise for next-generation spintronics. Nonetheless, the macroscopic coherent spin current formations are still hindered by rapid dephasing due to electron scattering, specifically at room temperature. Exciton polaritons offer excellent platforms for spin-optronic devices via the optical spin Hall effect. However, this effect could neither be unequivocally observed at room temperature nor be exploited for practical spintronic devices due to the presence of strong thermal fluctuations or large linear spin splitting. Here we report the observation of room-temperature optical spin Hall effect of exciton polaritons, with the spin current flow over 60 μm in a formamidinium lead bromide perovskite microcavity. We provide direct evidence of long-range coherence in the flow of polaritons and the spin current carried by them. Leveraging the spin Hall transport of polaritons, we further demonstrate two polaritonic devices, namely, a NOT gate and a spin-polarized beamsplitter, advancing the frontier of room-temperature polaritonics in perovskite microcavities.

Non-reciprocal charge transport has gained significant attention due to its potential in exploring quantum symmetry and its promising applications. Traditionally, non-reciprocal transport has been observed in the longitudinal direction, with non-reciprocal resistance being a small fraction of the ohmic resistance. Here we report a transverse non-reciprocal transport phenomenon featuring a quadratic current–voltage characteristic and divergent non-reciprocity, termed the non-reciprocal Hall effect. This effect is observed in microscale Hall devices fabricated from platinum (Pt) deposited by a focused ion beam on silicon substrates. The transverse non-reciprocal Hall effect arises from the geometrically asymmetric scattering of textured Pt nanoparticles within the focused-ion-beam-deposited Pt structures. Notably, the non-reciprocal Hall effect generated in focused-ion-beam-deposited Pt electrodes can propagate to adjacent conductors such as Au and NbP through Hall current injection. Additionally, this pronounced non-reciprocal Hall effect facilitates broadband frequency mixing. These findings not only validate the non-reciprocal Hall effect concept but also open avenues for its application in terahertz communication, imaging and energy harvesting.

Delithiation of layered oxide electrodes triggers irreversible oxygen loss, one of the primary degradation modes in lithium-ion batteries. However, the delithiation-dependent mechanisms of oxygen loss remain poorly understood. Here we investigate the oxygen non-stoichiometry in Li_1.18–xNi_0.21Mn_0.53Co_0.08O_2–δ electrodes as a function of Li content by using cycling protocols with long open-circuit voltage steps at varying states of charge. Surprisingly, we observe substantial oxygen loss even at moderate delithiation, corresponding to 2.5, 4.0 and 7.6 ml O₂ per gram of Li_1.18–xNi_0.21Mn_0.53Co_0.08O_2–δ after resting at upper capacity cut-offs of 135, 200 and 265 mAh g⁻¹ for 100 h. Our observations suggest an intrinsic oxygen instability consistent with predictions of high oxygen activity at intermediate potentials versus Li/Li⁺. In addition, we observe a large chemical expansion coefficient with respect to oxygen non-stoichiometry, which is about three times greater than those of classical oxygen-deficient materials such as fluorite and perovskite oxides. Our work challenges the conventional wisdom that deep delithiation is a necessary condition for oxygen loss in layered oxide electrodes and highlights the importance of calendar ageing for investigating oxygen stability.

Correction to: Nature Materials https://doi.org/10.1038/s41563-024-01981-2, published online 24 September 2024