Lithium (Li) metal electrodes are not deployable in rechargeable batteries because electrochemical plating and stripping invariably leads to growth of dendrites that reduce coulombic efficiency and eventually short the battery. It is generally accepted that the dendrite problem is exacerbated at high current densities. Here, we report a regime for dendrite evolution in which the reverse is true. In our experiments, we found that when the plating and stripping current density is raised above ~9 milliamperes per square centimeter, there is substantial self-heating of the dendrites, which triggers extensive surface migration of Li. This surface diffusion heals the dendrites and smoothens the Li metal surface. We show that repeated doses of high-current-density healing treatment enables the safe cycling of Li-sulfur batteries with high coulombic efficiency.

Spin and valley degrees of freedom in materials without inversion symmetry promise previously unknown device functionalities, such as spin-valleytronics. Control of material symmetry with electric fields (ferroelectricity), while breaking additional symmetries, including mirror symmetry, could yield phenomena where chirality, spin, valley, and crystal potential are strongly coupled. Here we report the synthesis of a halide perovskite semiconductor that is simultaneously photoferroelectricity switchable and chiral. Spectroscopic and structural analysis, and first-principles calculations, determine the material to be a previously unknown low-dimensional hybrid perovskite (R)-(−)-1-cyclohexylethylammonium/(S)-(+)-1 cyclohexylethylammonium) PbI3. Optical and electrical measurements characterize its semiconducting, ferroelectric, switchable pyroelectricity and switchable photoferroelectric properties. Temperature dependent structural, dielectric and transport measurements reveal a ferroelectric-paraelectric phase transition. Circular dichroism spectroscopy confirms its chirality. The development of a material with such a combination of these properties will facilitate the exploration of phenomena such as electric field and chiral enantiomer–dependent Rashba-Dresselhaus splitting and circular photogalvanic effects.

Crystallographic dislocation has been well-known to be one of the major causes responsible for the unfavorable carrier dynamics in conventional semiconductor devices. Halide perovskite has exhibited promising applications in optoelectronic devices. However, how dislocation impacts its carrier dynamics in the ‘defects-tolerant’ halide perovskite is largely unknown. Here, via a remote epitaxy approach using polar substrates coated with graphene, we synthesize epitaxial halide perovskite with controlled dislocation density. First-principle calculations and molecular-dynamics simulations reveal weak film-substrate interaction and low density dislocation mechanism in remote epitaxy, respectively. High-resolution transmission electron microscopy, high-resolution atomic force microscopy and Cs-corrected scanning transmission electron microscopy unveil the lattice/atomic and dislocation structure of the remote epitaxial film. The controlling of dislocation density enables the unveiling of the dislocation-carrier dynamic relation in halide perovskite. The study provides an avenue to develop free-standing halide perovskite film with low dislocation density and improved carried dynamics.

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The reconfigurability of the electrical heterostructure featured with external variables, such as temperature, voltage, and strain, enabled electronic/optical phase transition in functional layers has great potential for future photonics, computing, and adaptive circuits. VO2 has been regarded as an archetypal phase transition building block with superior metal–insulator transition characteristics. However, the reconfigurable VO2-based heterostructure and the associated devices are rare due to the fundamental challenge in integrating high-quality VO2 in technologically important substrates. In this report, for the first time, we show the remote epitaxy of VO2 and the demonstration of a vertical diode device in a graphene/epitaxial VO2/single-crystalline BN/graphite structure with VO2 as a reconfigurable phase-change material and hexagonal boron nitride (h-BN) as an insulating layer. By diffraction and electrical transport studies, we show that the remote epitaxial VO2 films exhibit higher structural and electrical quality than direct epitaxial ones. By high-resolution transmission electron microscopy and Cs-corrected scanning transmission electron microscopy, we show that a graphene buffered substrate leads to a less strained VO2 film than the bare substrate. In the reconfigurable diode, we find that the Fermi level change and spectral weight shift along with the metal–insulator transition of VO2 could modify the transport characteristics. The work suggests the feasibility of developing a single-crystalline VO2-based reconfigurable heterostructure with arbitrary substrates and sheds light on designing novel adaptive photonics and electrical devices and circuits.