Phase Evolution of Multi-Metal Dichalcogenides With Conversion-Alloying Hybrid Mechanism for Superior Lithium Storage.

Traditional lithium-ion battery (LIB) anodes, whether intercalation-type like graphite or alloying-type like silicon, employing a single lithium storage mechanism, are often limited by modest capacity or substantial volume changes. Here, the kesterite multi-metal dichalcogenide (CZTSSe) is introduced as an anode material that harnesses a conversion-alloying hybrid lithium storage mechanism. Results unveil that during the charge-discharge processes, the CZTSSe undergoes a comprehensive phase evolution, transitioning from kesterite structure to multiple dominant phases of sulfides, selenides, metals, and alloys. The involvement of multi-components facilitates electron transport and mitigates swelling stress; meanwhile, it results in formation of abundant defects and heterojunctions, allowing for increased lithium storage active sites and reduced lithium diffusion barrier. The CZTSSe delivers a high specific capacity of up to 2266 mA h g-1 at 0.1 A g-1; while, maintaining a stable output of 116 mA h g-1 after 10 000 cycles at 20 A g-1. It also demonstrates remarkable low-temperature performance, retaining 987 mA h g-1 even after 600 cycles at -40 °C. When employed in full cells, a high specific energy of 562 Wh kg-1 is achieved, rivalling many state-of-the-art LIBs. This research offers valuable insights into the design of LIB electrodes leveraging multiple lithium storage mechanisms.

A Temperature Self-Adaptive Electrolyte for Wide-Temperature Aqueous Zinc-Ion Batteries.

The advancement of aqueous zinc-ion batteries (AZIBs) is often hampered by the dendritic zinc growth and the parasitic side reactions between the zinc anode and the aqueous electrolyte, especially under extreme temperature conditions. This study unveils the performance decay mechanism of zinc anodes in harsh environments, characterized by "dead zinc" at low temperatures and aggravated hydrogen evolution and adverse by-products at elevated temperatures. To address these issues, a temperature self-adaptive electrolyte (TSAE), founded on the competitive coordination principle of co-solvent and anions, is introduced. This electrolyte exhibits a dynamic solvation capability, engendering an inorganic-rich solid electrolyte interface (SEI) at low temperatures while an organic alkyl ether- and alkyl carbonate-containing SEI at elevated temperatures. The self-adaptability of the electrolyte significantly enhances the performance of the zinc anode across a broad temperature range. A Zn//Zn symmetrical cell, based on the TSAE, showcases reversible plating/stripping exceeding 16 800 h (>700 d) at room temperature under 1 mA cm-2 and 1 mAh cm-2, setting a record of lifespan. Furthermore, the TSAE enables stable operation of the zinc full batteries across an ultrawide temperature range of -35 to 75 °C. This work illuminates a pathway for optimizing AZIBs under extreme temperatures by fine-tuning the interfacial chemistry.

Manipulating coordination environment for a high-voltage aqueous copper-chlorine battery.

Aqueous copper-based batteries have many favourable properties and have thus attracted considerable attention, but their application is limited by their low operating voltage originating from the high potential of copper negative electrode (0.34 V vs. standard hydrogen electrode). Herein, we propose a coordination strategy for reducing the intrinsic negative electrode redox potential in aqueous copper-based batteries and thus improving their operating voltage. This is achieved by establishing an appropriate coordination environment through the electrolyte tailoring via Cl- ions. When coordinated with chlorine, the intermediate Cu+ ions in aqueous electrolytes are successfully stabilized and the electrochemical process is decoupled into two separate redox reactions involving Cu2+/Cu+ and Cu+/Cu0; Cu+/Cu0 results in a redox potential approximately 0.3 V lower than that for Cu2+/Cu0. Compared to the coordination with water, the coordination with chlorine also results in higher copper utilization, more rapid redox kinetics, and superior cycle stability. An aqueous copper-chlorine battery, harnessing Cl-/Cl0 redox reaction at the positive electrode, is discovered to have a high discharge voltage of 1.3 V, and retains 77.4% of initial capacity after 10,000 cycles. This work may open up an avenue to boosting the voltage and energy of aqueous copper batteries.

Unlocking High-Performance Ammonium-Ion Batteries: Activation of In-Layer Channels for Enhanced Ion Storage and Migration.

Ammonium-ion batteries, leveraging non-metallic ammonium ions, have arisen as a promising electrochemical energy storage system; however, their advancement has been hindered by the scarcity of high-performance ammonium-ion storage materials. In this study, an electrochemical phase transformation approach is proposed for the in situ synthesis of layered VOPO4 ·2H2 O (E-VOPO) with predominant growth on the (200) plane, corresponding to the tetragonal channels on the (001) layers. The findings reveal that these tetragonal in-layer channels not only furnish NH4 + storage sites but also enhance transfer kinetics by providing rapid cross-layer migration pathways. This crucial aspect has been largely overlooked in previous studies. The E-VOPO electrode exhibits exceptional ammonium-ion storage performance, including significantly increased specific capacity, enhanced rate capability, and robust cycling stability. The resulting full cell can be stably operated for 12 500 charge-discharge cycles at 2 A g-1 for over 70 days. The proposed approach offers a new strategy for meticulously engineering electrode materials with facilitated ion storage and migration, thereby paving the way for developing more efficient and sustainable energy storage systems.

Optimization Strategies of Electrolytes for Low-Temperature Aqueous Batteries.

Aqueous rechargeable batteries (ARBs) are considered promising electrochemical energy storage systems for grid-scale applications due to their low cost, high safety, and environmental benignity. With the demand for a wide range of application scenarios, batteries are required to work in various harsh conditions, especially the cold weather. Nevertheless, electrolytes would freeze at extremely low temperatures, resulting in dramatically sluggish kinetics and severe performance degradation. Here, we discuss the behaviors of hydrogen bonds and basic principles of anti-freezing mechanisms in aqueous electrolytes. Then, we present a systematical review of the optimization strategies of electrolytes for low-temperature aqueous batteries. Finally, the challenges and promising routes for further development of aqueous low-temperature electrolytes are provided. This review can serve as a comprehensive reference to boost the further development and practical applications of advanced ARBs operated at low temperatures.

High-Energy Aqueous Ammonium-Ion Hybrid Supercapacitors.

The development of novel electrochemical energy storage devices is a grand challenge. Here, an aqueous ammonium-ion hybrid supercapacitor (A-HSC), consisting of a layered δ-MnO2 based cathode, an activated carbon cloth anode, and an aqueous (NH4 )2 SO4 electrolyte is developed. The aqueous A-HSC demonstrates an ultrahigh areal capacitance of 1550 mF cm-2 with a wide voltage window of 2.0 V. An amenable peak areal energy density (861.2 µWh cm-2 ) and a decent capacitance retention (72.2% after 5000 cycles) are also achieved, surpassing traditional metal-ion hybrid supercapacitors. Ex situ characterizations reveal that NH4 + intercalation/deintercalation in the layered δ-MnO2 is accompanied by hydrogen bond formation/breaking. This work proposes a new paradigm for electrochemical energy storage.

Analysis of the Influence of Ferromagnetic Material on the Output Characteristics of Halbach Array Energy-Harvesting Structure.

Due to the particular arrangement of permanent magnets, a Halbach array has an significant effect of magnetism and magnetic self-shielding. It can stretch the magnetic lines on one side of the magnetic field to obtain an ideal sinusoidal unilateral magnetic field. It has a wide application range in the field of energy harvesting. In practical applications, magnetic induction intensity of each point in magnetic field is not only related to the induced current and conductor but also related to the permeability of the medium (also known as a magnetic medium) in the magnetic field. Permeability is the physical quantity that represents the magnetism of the magnetic medium, which indicates the resistance of magnetic flux or the ability of magnetic lines to be connected in the magnetic field after coil flows through current in space or in the core space. When the permeability is much greater than one, it is a ferromagnetic material. Adding a ferromagnetic material in a magnetic field can increase the magnetic induction intensity B. Iron sheet is a good magnetic material, and it is easy to magnetize to generate an additional magnetic field to strengthen the original magnetic field, and it is easy to obtain at low cost. In this paper, in order to explore the influence of ferromagnetic material on the magnetic field and energy harvesting efficiency of the Halbach array energy harvesting structure, iron sheets are installed on the periphery of the Halbach array rotor. Iron sheet has excellent magnetic permeability. Through simulation, angle between iron sheet and Halbach array, radian size of iron sheet itself and distance between iron sheet and Halbach array can all have different effects on the magnetic field of the Halbach array. It shows that adding iron sheets as a magnetic medium could indeed change the magnetic field distribution of the Halbach array and increase energy harvesting efficiency. In this paper, a Halbach array can be used to provide electrical power for passive wireless low-power devices.

High-Performance MoC Electrocatalyst for Hydrogen Evolution Reaction Enabled by Surface Sulfur Substitution.

Molybdenum carbides have been expected to be one of the promising catalysts for the hydrogen evolution reaction (HER) due to their similar d-band electronic structures to the Pt-group metals. However, the weaker hydrogen-adsorption ability of MoC severely hinders its applications. Guided by density functional theory calculations, we put forward a strategy to design the novel MoC-based electrocatalyst with surface reconstruction through sulfur doping. The incorporation of minor sulfur not only greatly increases the number of active sites and intrinsic activity but also optimizes the electronic structure to improve the electron transfer efficiency. As a result, the as-prepared sulfur-substituted MoC tackles the limitation of the Volmer step and exhibits superior HER performance with a small Tafel slope of 48 mV dec-1. Theoretical investigations demonstrate that the terminal sulfur plays a critical role in facilitating a close to zero hydrogen adsorption energy (ΔGH*) and a lower hydrogen release barrier.

MoS2-Decorated/Integrated Carbon Fiber: Phase Engineering Well-Regulated Microwave Absorber.

Phase engineering is an important strategy to modulate the electronic structure of molybdenum disulfide (MoS2). MoS2-based composites are usually used for the electromagnetic wave (EMW) absorber, but the effect of different phases on the EMW absorbing performance, such as 1T and 2H phase, is still not studied. In this work, micro-1T/2H MoS2 is achieved via a facile one-step hydrothermal route, in which the 1T phase is induced by the intercalation of guest molecules and ions. The EMW absorption mechanism of single MoS2 is revealed by presenting a comparative study between 1T/2H MoS2 and 2H MoS2. As a result, 1T/2H MoS2 with the matrix loading of 15% exhibits excellent microwave absorption property than 2H MoS2. Furthermore, taking the advantage of 1T/2H MoS2, a flexible EMW absorbers that ultrathin 1T/2H MoS2 grown on the carbon fiber also performs outstanding performance only with the matrix loading of 5%. This work offers necessary reference to improve microwave absorption performance by phase engineering and design a new type of flexible electromagnetic wave absorption material to apply for the portable microwave absorption electronic devices.