Flexible Zn-ion Electrochromic Batteries with Multiple-color Variations

Electrochromic batteries as emerging smart energy devices are highly sought after owing to their real-time energy monitoring through visual color conversion. However, their large-scale applicability is hindered by insufficient capacity, inadequate cycling stability, and limited color variation. Herein, a flexible Zn-ion electrochromic battery (ZIEB) was assembled with sodium vanadate (VONa+) cathode, ion-redistributing hydrogel electrolyte, and Zn anode to address these challenges. The electrolyte contains anchored -SO3 - and -NH3 +, which facilitates ionic transportation and prevents Zn dendrite formation by promoting orientated Zn2+ deposition on the Zn (002) surface. The ZIEB exhibits a continuous reversible color transition, ranging from fully charged orange to mid-charged brown and drained green. It also demonstrates a high specific capacity of 302.4 mAh ⋅ g-1 at 0.05 A ⋅ g-1 with a capacity retention of 96.3 % after 500 cycles at 3 A ⋅ g-1. Additionally, the ZIEB maintains stable energy output even under bending, rolling, knotting, and twisting. This work paves a new strategy for the design of smart energy devices in wearable electronics.

Lone-pair-induced formation of intrinsic one-dimensional SbSX (X = Cl, Br, I) helix chain materials

Intrinsic one-dimensional (1D) helix chain materials are extremely rare in inorganic chemistry due to their novel structural features and complex syntheses. Herein, we report a class of inborn 1D helix chains, namely 1D SbSX (X = Cl, Br, I), that can exist stably. Through ab initio calculations, we demonstrate that the formation of this helical feature is facilitated by the lone pairs in antimony atoms. Owing to the different chemical bonds induced by the lone pairs, a phase transition between different helix chain phases can occur by applying extra elongation strain. More importantly, 1D SbSX helix chains possess superior flexibility. Under large elongation strains, the elastic energy is stored via bond angle redistributions, while the average bond lengths can remain invariant. Our work not only enriches the family of intrinsic 1D helical materials, but also provides a novel avenue for the diversification of low-dimensional phase change and flexible materials.

Single-Crystal Inorganic Helical Architectures Induced by Asymmetrical Defects in Sub-Nanometric Wires

Constructing single-crystal inorganic helical structures is a fascinating subject for a large variety of research fields. However, the driving force of self-coiling, particularly in helical architectures, still remains a major challenge. Here, using MoO_3-x sub-nanometric wires (SNWs) as an example, we identified that spontaneous helical architecture with different dimensional features is closely related with their surface asymmetrical defects. Specifically, the surface defects of SNWs are critical to produce the self-coiling process, thereby achieving the ordered helical conformations. Theoretical calculations further suggest that the formation of in-plane and out-of-plane coiling structures is determined by the asymmetrical distribution of the surface defects, and the inhomogeneous charge separation with strong Coulomb attraction dominates the different structural configurations. The resulting MoO_3-x SNW exhibits excellent photothermal behaviors in both aqueous solutions and hydrogel matrixes. Our study provides a novel protocol to achieve helical structure design for their future applications.

Na2V6O16·3H2O Barnesite Nanorod: An Open Door to Display a Stable and High Energy for Aqueous Rechargeable Zn-Ion Batteries as Cathodes

Owing to their safety and low cost, aqueous rechargeable Zn-ion batteries (ARZIBs) are currently more feasible for grid-scale applications, as compared to their alkali counterparts such as lithium- and sodium-ion batteries (LIBs and SIBs), for both aqueous and nonaqueous systems. However, the materials used in ARZIBs have a poor rate capability and inadequate cycle lifespan, serving as a major handicap for long-term storage applications. Here, we report vanadium-based Na₂V₆O₁₆·3H₂O nanorods employed as a positive electrode for ARZIBs, which display superior electrochemical Zn storage properties. A reversible Zn²⁺-ion (de)intercalation reaction describing the storage mechanism is revealed using the in situ synchrotron X-ray diffraction technique. This cathode material delivers a very high rate capability and high capacity retention of more than 80% over 1000 cycles, at a current rate of 40C (1C = 361 mA g^-1). The battery offers a specific energy of 90 W h kg^-1 at a specific power of 15.8 KW kg^-1, enlightening the material advantages for an eco-friendly atmosphere.

NaV3O8 nanosheet@polypyrrole core-shell composites with good electrochemical performance as cathodes for Na-ion batteries

Novel NaV3O8 nanosheet@polypyrrole core-shell composites have been successfully prepared for the first time via a chemical oxidative polymerization method. Based on the morphological and microstructural characterization, it was found that polypyrrole (PPy) was uniformly wrapped on the surfaces of the NaV3O8 nanosheets. When used as a cathode for Na-ion batteries, the as-synthesized NaV3O8@10% PPy composite showed significantly improved cycling performance (with a discharge capacity of 99 mA h g(-1) after 60 cycles at 80 mA g(-1)) and better rate capacity (with a discharge capacity of 63 mA h g(-1) at a high current density of 640 mA g(-1)) than pristine NaV3O8 nanosheets. The greatly enhanced performance benefits from the unique core-shell structure, where the PPy coating not only prevents the pulverization and aggregation of the lamellar NaV3O8 nanosheets during cycling, which can improve the cycling stability, but also enhances the electrical conductivity of the composite, which can facilitate Na(+) ion diffusion.

Rational design of one-dimensional vanadium(v) oxide nanocrystals: an insight into the physico-chemical parameters controlling the crystal structure, morphology and size of particles

This highlight deals with the recent advances on the synthesis in aqueous solution of one-dimensional vanadium(v) oxide nanocrystals.

Controllable synthesis and morphology evolution from two-dimensions to one-dimension of layered K2V6O16·nH2O

In a hydrothermal process, layered K₂V₆O₁₆·2.7H₂O platelike crystals are split into layered K₂V₆O₁₆·1.5H₂O fiberlike crystals.

Na₂V₆O₁₆·xH₂O nanoribbons: large-scale synthesis and visible-light photocatalytic activity of CO₂ into solar fuels

An ultra-thin and super-long Na₂V₆O₁₆·xH₂O nanoribbon of ∼5 nm thickness and ∼500 μm length was synthesized by a hydrothermal method, using a freshly prepared V(3+) species precursor solution by directly dissolving a vanadium metal thread in a NaNO₃ solution using a solid-liquid phase arc discharge (SLPAD) technique. Field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques were used to characterize the structure, morphology, and chemical composition. The super-long and ultra-thin geometry of the Na₂V₆O₁₆·xH₂O nanoribbons is proven to greatly promote the photocatalytic activity toward reduction of CO₂ into renewable hydrocarbon fuel (CH₄) in the presence of water vapor under visible-light irradiation.