Jiuxiang Dai

Publication date: September 2022

Source: Materials Today, Volume 58

Author(s): Ya Deng, Chao Zhu, Yu Wang, Xiaowei Wang, Xiaoxu Zhao, Yao Wu, Bijun Tang, Ruihuan Duan, Kun Zhou, Zheng Liu

Nature Nanotechnology, Published online: 04 July 2022; doi:10.1038/s41565-022-01153-w

A non-volatile silicon photonics switch based on phase-change materials actuated by graphene heaters shows a switching energy density that is within an order of magnitude of the fundamental thermodynamic limit.

An ultrathin (<1 µm) multilayered protective (composed of lithiophilic seeds, 2D blocking layer, and vertically porous membrane) is strategically designed for tackling the chronic issue of dendritic growth of lithium (Li). The synergetic interactions between the layers enhance mechanical robustness and facilitate fast and homogenized Li-ion flux, which result in smooth and stabilized Li growth and outstanding cycling stability.

Abstract

A novel strategy for robust and ultrathin (<1 µm) multilayered protective structures to address uncontrolled Lithium (Li) dendrite growth at Li-metal battery anodes is reported. Synergetic interaction among Ag nanoparticles (Ag NPs), reduced graphene oxide (rGO) films, and self-assembled block-copolymer (BCP) layers enables effective suppression of dendritic Li growth. While Ag NP layer confines the growth of Li metal underneath the rGO layer, BCP layer facilitates the fast and uniformly distributed flux of Li-ion transport and mechanically supports the rGO layer. Notably, highly aligned nanochannels with ≈15 nm diameter and ≈600 nm length scale interpenetrating within the BCP layer offer reversible well-defined pathways for Li-ion transport. Dramatic stress relaxation with the multilayered structure is confirmed via structural simulation considering the mechanical stress induced by filamentary-growth of Li metal. Li-metal anodes modified with the protective layer well-maintain stable reaction interfaces with limited solid-electrolyte interphase formation, yielding outstanding cycling stability and enhanced rate capability, as demonstrated by the full-cells paired with high-loading of LiFePO₄ cathodes. The idealized design of multilayer protective layer provides significant insight for advanced Li-metal anodes.

Nature Communications, Published online: 05 July 2022; doi:10.1038/s41467-022-31606-8

Bi2O2Se holds potential for the realization of 2D optical modulators due to its broadband nonlinear response, air stability and carrier mobility. Here, the authors report the realization of defect-engineered Bi2O2Se nanoplates as saturable absorbers for femtosecond solid-state lasers, showing improved output power and pulse duration.

Transition Metal Carbo-Chalcogenides

In article number 2200574, Michael Naguib and co-workers report on the synthesis of 2D transition metal carbo-chalcogenides (TMCCs) by exfoliating their bulk layered counterparts (e.g., Nb₂S₂C and Ta₂S₂C) through electrochemical Li-ion intercalation followed by agitation in water. 2D TMCCs combine the surface of 2D TM dichalcogenides (TMDCs) and the core of 2D TM carbides (MXenes) offering unique characteristics of both TMDCs and MXenes.

Grain boundary engineering in 2D electronic materials for emergent properties is reviewed. Reported structural engineering methods and emergent properties are introduced for various stacking and stitching boundaries such as twist boundary, tilt boundary, stacking fault, and dislocation arrays. Also, remaining challenges and outlook for the future research directions are discussed.

Abstract

Engineering the boundary structures in 2D materials provides an unprecedented opportunity to program the physical properties of the materials with extensive tunability and realize innovative devices with advanced functionalities. However, structural engineering technology is still in its infancy, and creating artificial boundary structures with high reproducibility remains difficult. In this review, various emergent properties of 2D materials with different grain boundaries, and the current techniques to control the structures, are introduced. The remaining challenges for scalable and reproducible structure control and the outlook on the future directions of the related techniques are also discussed.

Nature Photonics, Published online: 30 June 2022; doi:10.1038/s41566-022-01021-y

Strained NbOI2 flakes with a thickness of 20 nm exhibit a record SHG absolute conversion efficiency of >0.2% and an effective bulk-like nonlinear susceptibility of 1.1 × 10−9 m V−1 at the fundamental wavelength of 1,050 nm. The spatial profile of the polarized second-harmonic generation response can be tuned by the fundamental wavelength.