In Situ Anchoring Anion-Rich and Multi-Cavity NiS2 Nanoparticles on NCNTs for Advanced Magnesium-Ion Batteries

Defect Engineering: Can it Mitigate Strong Coulomb Effect of Mg2+ in Cathode Materials for Rechargeable Magnesium Batteries?

Rechargeable magnesium batteries (RMBs) have been considered a promising "post lithium-ion battery" system to meet the rapidly increasing demand of the emerging electric vehicle and grid energy storage market. However, the sluggish diffusion kinetics of bivalent Mg2+ in the host material, related to the strong Coulomb effect between Mg2+ and host anion lattices, hinders their further development toward practical applications. Defect engineering, regarded as an effective strategy to break through the slow migration puzzle, has been validated in various cathode materials for RMBs. In this review, we first thoroughly understand the intrinsic mechanism of Mg2+ diffusion in cathode materials, from which the key factors affecting ion diffusion are further presented. Then, the positive effects of purposely introduced defects, including vacancy and doping, and the corresponding strategies for introducing various defects are discussed. The applications of defect engineering in cathode materials for RMBs with advanced electrochemical properties are also summarized. Finally, the existing challenges and future perspectives of defect engineering in cathode materials for the overall high-performance RMBs are described.

H2O-Mg2+ Waltz-Like Shuttle Enables High-Capacity and Ultralong-Life Magnesium-Ion Batteries

Mg-ion batteries (MIBs) are promising next-generation secondary batteries, but suffer from sluggish Mg2+ migration kinetics and structural collapse of the cathode materials. Here, an H2O-Mg2+ waltz-like shuttle mechanism in the lamellar cathode, which is realized by the coordination, adaptive rotation and flipping, and co-migration of lattice H2O molecules with inserted Mg2+, leading to the fast Mg2+ migration kinetics, is reported; after Mg2+ extraction, the lattice H2O molecules rearrange to stabilize the lamellar structure, eliminating structural collapse of the cathode. Consequently, the demo cathode of Mg0.75V10O24·nH2O (MVOH) exhibits a high capacity of 350 mAh g-1 at a current density of 50 mA g-1 and maintains a capacity of 70 mAh g-1 at 4 A g-1. The full aqueous MIB based on MVOH delivers an ultralong lifespan of 5000 cycles The reported waltz-like shuttle mechanism of lattice H2O provides a novel strategy to develop high-performance cathodes for MIBs as well as other multivalent-ion batteries.

Rice powder template for hausmannite Mn3O4 nanoparticles and its application to aqueous zinc ion battery

In this study, a simple calcination route was adopted to prepare hausmannite Mn3O4 nanoparticles using rice powder as soft bio-template. Prepared Mn3O4 was characterized by Fourier Transform Infra-Red Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray microanalysis (EDX), Powder X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Brunauer-Emmett-Teller (BET) and Solid state UV-Vis spectroscopic techniques. Mn-O stretching in tetrahedral site was confirmed by FTIR and Raman spectra. % of Mn and O content supported Mn3O4 formation. The crystallinity and grain size was found to be 68.76% and 16.43 nm, respectively; tetragonal crystal system was also cleared by XRD. TEM clarified the planes of crystal formed which supported the XRD results and BET demonstrated mesoporous nature of prepared Mn3O4 having low pore volume. Low optical band gap of 3.24 eV of prepared Mn3O4 nanoparticles indicated semiconductor property and was used as cathode material to fabricate CR-2032 coin cell of Aqueous Rechargeable Zinc Ion Battery (ARZIB). A reversible cyclic voltammogram (CV) showed good zinc ion storage performance. Low cell resistance was confirmed by Electrochemical Impedance Spectroscopy (EIS). The coin cell delivered high specific discharge capacity of 240.75 mAhg-1 at 0.1 Ag-1 current density. The coulombic efficiency was found to be 99.98%. It also delivered excellent capacity retention 94.45% and 64.81% after 300 and 1000 charge-discharge cycles, respectively. This work offers a facile and cost effective approach for preparing cathode material of ARZIBs.

Electron Configuration Modulation Induced Stabilized 1T-MoS2 for Enhanced Sodium Ion Storage

1T-MoS2 has become an ideal anode for sodium-ion batteries (SIBs). However, the metastable feature of 1T-MoS2 makes it difficult to directly synthesize under normal conditions. In addition, it easily transforms into 2H phase via restacking, resulting in inferior electrochemical performance. Herein, the electron configuration of Mo 4d orbitals is modulated and the stable 1T-MoS2 is constructed by nickel (Ni) introduction (1T-Ni-MoS2). The original electron configuration of Mo 4d orbitals is changed via the electron injection by Ni, which triggers the phase transition from 2H to 1T phase, thus improving the electrical conductivity and accelerating the redox kinetics of the material. Consequently, 1T-Ni-MoS2 exhibits superior rate capability (266.8 mAh g-1 at 10 A g-1) and excellent cycle life (358.7 mAh g-1 at 1 A g-1 after 350 cycles). In addition, the assembled Na3V2(PO4)3/C||1T-Ni-MoS2 full cells deliver excellent electrochemical properties and show great prospects in energy storage devices.

Fabrication of Nitrogen-Doped Carbon-Coated NiS1.97 Quantum Dots for Advanced Magnesium-Ion Batteries

Magnesium (Mg) batteries have garnered considerable interest because of their safety characteristics and low costs. However, the practical application of Mg batteries is hindered by the slow diffusion of Mg ions in the cathode materials. In this study, we prepared NiS1.97 quantum dot composites with nitrogen doping and carbon coating (NiS1.97 QDs@NC) using a one-step sulfurization process with NiO QDs/Ni@NC as the precursor. We applied the prepared NiS1.97 QDs/Ni@NC-based cathodes to Mg batteries because of the large surface area of the quantum dot composite, which provided abundant intercalation sites. This design ensured efficient deintercalation of magnesium ions during charge-discharge processes. The fabricated NiS1.97 QDs@NC displayed a high reversible Mg storage capacity of 259.1 mAh g-1 at 100 mA g-1 and a good rate performance of 96.0 mAh g-1 at 1000 mA g-1. Quantum dot composites with large surface areas provide numerous embedded sites, which ensure effective deintercalation of Mg ions during cycling. Thus, the proposed cathode synthesis strategy is promising for Mg-ion-based energy storage systems.

Ambient ammonia synthesis via nitrite electroreduction over NiS2 nanoparticles-decorated TiO2 nanoribbon array

Nitrite (NO₂^-), as a N-containing pollutant, widely exists in aqueous solution, causing a series of environmental and health problems. Electrocatalytic NO₂^- reduction is a promising and sustainable strategy to remove NO₂^-, meanwhile, producing high value-added ammonia (NH₃). But the NO₂^- reduction reaction (NO₂^-RR) involves complex 6-electron transfer process that requires high-efficiency electrocatalysts to accomplish NO₂^--to-NH₃ conversion. Herein, we report NiS₂ nanoparticles decorated TiO₂ nanoribbon array on titanium mesh (NiS₂@TiO₂/TM) as a fantastic NO₂^-RR electrocatalyst for ambient NH₃ synthesis. When tested in NO₂^--containing solution, NiS₂@TiO₂/TM achieves a satisfactory NH₃ yield of 591.9 µmol h^-1 cm^-2 and a high Faradaic efficiency of 92.1 %. Besides, it shows remarkable stability during 12-h electrolysis test.

NiS2 nanoparticles by the NaCl-assisted less-liquid reaction system for the magnesium-ion battery cathode

Rechargeable magnesium batteries are expected to be the next generation of energy storage devices. Therefore, it is of great significance to develop low-cost and long-life magnesium (Mg) electrode materials. However, the traditional method of synthesizing electrode materials is complicated, and it is difficult to remove potentially dangerous impurities. In this study, without adding any additional solvent, the crystal water in the reactant provides a liquid environment directly for the reaction, such that the whole reaction could be carried out safely and efficiently in the less liquid reaction system. Furthermore, NiS₂ in the cotton-like form was synthesized under the spatial effect of NaCl solution in a confined space. The fabricated material was tightly connected and has abundant active sites, which promote the rapid transport of charge. This work provides a general strategy of preparation methods for metal sulfides and also points in a new direction for the improvement of electrochemical performance with less-liquid reaction systems without additional solvents.

High-Performance NiS2 Hollow Nanosphere Cathodes in Magnesium-Ion Batteries Enabled by Tunable Redox Chemistry

Two-dimensional metal dichalcogenides have demonstrated outstanding potential as cathodes for magnesium-ion batteries. However, the limited capacity, poor cycling stability, and severe electrode pulverization, resulting from lack of void space for expansion, impede their further development. In this work, we report for the first time, nickel sulfide (NiS₂) hollow nanospheres assembled with nanoparticles for use as cathode materials in magnesium-ion batteries. Notably, the nanospheres were prepared by a one-step solvothermal process in the absence of an additive. The results show that regulating the synergistic effect between the rich anions and hollow structure positively affects its electrochemical performance. Crystallographic and microstructural characterizations reveal the reversible anionic redox of S^2-/(S₂)^2-, consistent with density functional theory results. Consequently, the optimized cathode (8-NiS₂ hollow nanospheres) could deliver a large capacity of 301 mA h g^-1 after 100 cycles at 50 mA g^-1, supporting the promising practical application of NiS₂ hollow nanospheres in magnesium-ion batteries.