Surfacing amorphous Ni-B nanoflakes on NiCo2O4 nanospheres as multifunctional bridges for promoting lithium storage behaviors

Reaction Mechanism and Performance of Innovative 2D Germanane-Silicane Alloys: SixGe1- xH Electrodes in Lithium-Ion Batteries

The adjustable structures and remarkable physicochemical properties of 2D monoelemental materials, such as silicene and germanene, have attracted significant attention in recent years. They can be transformed into silicane (SiH) and germanane (GeH) through covalent functionalization via hydrogen atom termination. However, synthesizing these materials with a scalable and low-cost fabrication process to achieve high-quality 2D SiH and GeH poses challenges. Herein, groundbreaking 2D SiH and GeH materials with varying compositions, specifically Si0.25Ge0.75H, Si0.50Ge0.50H, and Si0.75Ge0.25H, are prepared through a simple and efficient chemical exfoliation of their Zintl phases. These 2D materials offer significant advantages, including their large surface area, high mechanical flexibility, rapid electron mobility, and defect-rich loose-layered structures. Among these compositions, the Si0.50Ge0.50H electrode demonstrates the highest discharge capacity, reaching up to 1059 mAh g-1 after 60 cycles at a current density of 75 mA g-1. A comprehensive ex-situ electrochemical analysis is conducted to investigate the reaction mechanisms of lithiation/delithiation in Si0.50Ge0.50H. Subsequently, an initial assessment of the c-Li15(SixGe1- x)4 phase after lithiation and the a-Si0.50Ge0.50 phase after delithiation is presented. Hence, this study contributes crucial insights into the (de)lithiation reaction mechanisms within germanane-silicane alloys. Such understanding is pivotal for mastering promising materials that amalgamate the finest properties of silicon and germanium.

Amorphous Anode Materials for Fast-charging Lithium-ion Batteries

Fast-charging technology is set to revolutionize the field of lithium-ion batteries (LIBs), driving the creation of next-generation devices with the ability to get charged within a short span of time. From the anode perspective, it is of paramount importance to design materials that can withstand continuous Li+ insertion/deinsertion at high charging rates and still remain unaffected by factors such as mechanical fractures, electrolyte side reactions, polarisation, lithium plating and heat generation. Herein, the recent advancements in the design of amorphous materials as anodes for fast-charging LIBs have been discussed. While the development of this particular class of materials for application in high-rate anodes has been paid limited attention in recent literature, it holds immense promise for improving the fast-charging capabilities. This concept summarizes the recent strides made in this emerging field, outlining the strategies employed in the design of amorphous anodes and emphasizing the crucial role played by the amorphous nature in achieving fast-charging performance. Further, the successive initiatives that can be undertaken to drive the progress of amorphous materials for fast charging LIBs have also been detailed, which could potentially improve their commercial viability.

0D/3D NiCo2O4/defected UiO-66 catalysts for enhanced degradation of tetracycline in peroxymonosulfate/simulated sunlight systems: Degradation mechanisms and pathways

Developing synergistic systems and taking environmental risks into account are two necessary aspects of being considered to remove persistent organic pollutants efficiently. Thus, a combined catalytic system uniting the Fenton-like process and simulated solar-light photocatalysis has been constructed. Moreover, a series of NiCo₂O₄/HP-UiO-66 catalysts (yNiCo-DUx) were also fabricated to improve tetracycline (TC) removal efficiency. The NiCo₂O₄ nanoparticles (NPs) and hierarchically porous metal-organic frameworks (HP-MOFs) were synthesised using one-step calcination. The Z-scheme structure of the catalysts was confirmed by ESR, XPS, DRS, time-resolved PL (TR-PL) spectra and the quenching experiments. The NiCo₂O₄ nanoparticles could be embedded and fixed into the defects of the MOF structure, and the leaching of toxic metals was also significantly suppressed. In the optimal reaction condition with 15NiCo-DU50, sunlight, and peroxymonosulfate (PMS), the total removal efficiency of TC could reach 98.5% within 8 min of irradiation, and the highest % RSE could reach 11.2%. Moreover, the corresponding reaction rate was 28.7, 3.6 and 1.3-10.2 times higher than photocatalysis, Fenton-like processes and other catalysts. Furthermore, the possible degradation mechanism, generation of reactive species and PMS excitation pathways were also investigated in depth. The present study sheds light on the fabrication of HP-MOFs based catalysts and the combination of various methods to eliminate organic pollutants.

Enhancing the Kinetic Process in Biphasic Crystalline NiWO4 /Amorphous Co-B Electrode Materials toward Energy Storage with Ultrahigh Rate Performance

Here, we report a two-phase crystalline NiWO₄ /amorphous Co-B nanocomposite as an electrode material for supercapacitors, which is effectively synthesized via a simple hydrothermal method and chemical precipitation method. The obtained NiWO₄ /Co-B exhibits crystal-amorphous contact, which makes it have more active sites than other crystalline-crystalline phase boundaries, thereby enhancing electron transport. The NiWO₄ /Co-B electrode with the best mass ratio of crystalline and amorphous exhibits a great specific capacitance and excellent cycle durability. Compared to individual Co-B and NiWO₄ , it also shows enhanced rate capability Besides, NiWO₄ /Co-B/activated carbon supercapacitor device can provide a good specific capacitance and a maximum energy density of 10.92 Wh kg^-1 at 200 W kg^-1 . This work provides new insights to develop novel electrode materials for energy storage and conversion.

Realizing the enhanced cyclability of a cactus-like NiCo2O4 nanocrystal anode fabricated by molecular layer deposition

Lithium-ion batteries with conversion-type anode electrodes have attracted increasing interest in providing higher energy storage density than those with commercial intercalation-type electrodes. However, conversion-type materials exhibit severe structural instability and capacity fade during cycling. In this work, a molecular layer deposition (MLD)-derived conductive Al₂O₃/carbon layer was employed to stabilize the structure of the cactus-like NiCo₂O₄ nanocrystal (NC) anode. The conductive Al₂O₃/carbon network and cactus-like NiCo₂O₄ NCs are beneficial for fast Li⁺/e^- transport. Moreover, the Al₂O₃/carbon buffer-layer can prevent the NiCo₂O₄ NCs from agglomeration and form a steady solid electrolyte interphase (SEI), thus hampering the penetration of the electrolyte. Owing to these advantages, the assembled NiCo₂O₄@Al₂O₃/carbon half battery shows a high reversible capacity (931.2 mA h g^-1 at 2 A g^-1) and long-term stability of 290 mA h g^-1 at 5 A g^-1 over 500 cycles. Quantitative analyses further reveal the fast kinetics and the capacitance-battery dual model mechanism in the 3D core-shell structures. The design and introduction of MLD-derived hybrid coating may open a new way to conversion-type and alloy-type anode materials beyond NiCo₂O₄ to achieve high cyclability.

Niobium Tungsten Oxide in a Green Water-in-Salt Electrolyte Enables Ultra-Stable Aqueous Lithium-Ion Capacitors

Aqueous hybrid supercapacitors are attracting increasing attention due to their potential low cost, high safety and eco-friendliness. However, the narrow operating potential window of aqueous electrolyte and the lack of suitable negative electrode materials seriously hinder its future applications. Here, we explore high concentrated lithium acetate with high ionic conductivity of 65.5 mS cm-1 as a green "water-in-salt" electrolyte, providing wide voltage window up to 2.8 V. It facilitates the reversible function of niobium tungsten oxide, Nb18W16O93, that otherwise only operations in organic electrolytes previously. The Nb18W16O93 with lithium-ion intercalation pseudocapacitive behavior exhibits excellent rate performance, high areal capacity, and ultra-long cycling stability. An aqueous lithium-ion hybrid capacitor is developed by using Nb18W16O93 as negative electrode combined with graphene as positive electrode in lithium acetate-based "water-in-salt" electrolyte, delivering a high energy density of 41.9 W kg-1, high power density of 20,000 W kg-1 and unexceptionable stability of 50,000 cycles.

Hollow nanoparticle-assembled hierarchical NiCo2O4 nanofibers with enhanced electrochemical performance for lithium-ion batteries

Hollow NiCo₂O₄ nanoparticle-assembled electrospun nanofibers showed tailorable electrochemical activity and tunable lithium storage properties.