Ultrathin Nanoribbons of in Situ Carbon-Coated V3O7·H2O for High-Energy and Long-Life Li-Ion Batteries: Synthesis, Electrochemical Performance, and Charge-Discharge Behavior

In-situ texturing hollow carbon host anchored with Fe single atoms accelerating solid-phase redox for Li-Se batteries

Se-based cathodes have caught tremendous attention owing to their comparable volumetric capacity and better electronic conductivity to S cathodes. However, its low utilization ratio and sluggish redox kinetics due to the high reaction barrier of solid-phase transformation from Se to Li2Se limit its practical application. Herein, an in-situ texturing hollow carbon host by gas-solid interface reaction anchored with Fe single-atomic catalyst is designed and prepared for advanced Li-Se batteries. This Se host presents high pore volume of 1.49 cm3 g-1, Fe single atom content of 1.53 wt%, and its specific structure protects single-atomic catalyst from the destructive reaction environment, thus balancing catalytic activity and durability. After Se loading by reduction of H2SeO3, this homogenous Se-based cathode delivers a superior rate capacity of 431.3 mA h g-1 at 4C, and great discharge capacity of 301.8 mA h g-1 after 1000 cycles at 10C, with high Li-ion diffusion coefficient and capacitance-contributed ratio. The distribution of relaxation times analysis verifies solid-phase transformation mechanism of this cathode and density functional theory calculations confirm the adsorption and bidirectionally catalysis effect of Fe single-atomic catalyst. This work provides a new strategy to prepare high-efficient Se cathode associated with non-noble metal single atoms for high-performance Li-Se batteries.

Mesoporous copper-doped δ-MnO2 superstructures to enable high-performance aqueous zinc-ion batteries

Aqueous zinc-ion batteries (AZIBs) are competitive alternatives for large-scale energy-storage devices owing to the abundance of zinc and low cost, high theoretical specific capacity, and high safety of these batteries. High-performance and stable cathode materials in AZIBs are the key to storing Zn2+. Manganese-based cathode materials have attracted considerable attention because of their abundance, low toxicity, low cost, and abundant valence states (Mn2+, Mn3+, Mn4+, and Mn7+). However, as a typical cathode material, birnessite-MnO2 (δ-MnO2) has low conductivity and structural instability. The crystal structure may undergo severe distortion, disorder, and structural damage, leading to severe cyclic instability. In addition, its energy-storage mechanism is still unclear, and most of the reported manganese oxide-based materials do not have excellent electrochemical performance. Herein, we propose a copper-doped Cu0.05K0.11Mn0.84O2·0.54H2O (Cu2-KMO) cathode, which exhibits a large interlayer spacing, a stable structure, and accelerated reaction kinetics. This cathode was prepared using a simple hydrothermal method. The AZIB assembled using Cu2-KMO showed high specific capacity (600 mA h g-1 at 0.1 A g-1 after 75 cycles). The dissolution-deposition energy storage mechanism of Cu-KMO in AZIBs with double electron transfer was revealed using ex situ tests. The good electrochemical performance of the Cu2-KMO cathode fabricated by the doping strategy in this study provides ideas for the subsequent preparation of manganese dioxide using other strategies.

Modified H2 V3 O8 to Enhance the Electrochemical Performance for Li-ion Insertion: The Influence of Prelithiation and Mo-Substitution

Nanostructured H₂ V₃ O₈ is a promising high-capacity cathode material, suitable not only for Li⁺ but also for Na+, Mg²⁺ , and Zn²⁺ insertion. However, the full theoretical capacity for Li⁺ insertion has not been demonstrated experimentally so far. In addition, improvement of cycling stability is desirable. Modifications like substitution or prelithiation are possibilities to enhance the electrochemical performance of electrode materials. Here, for the first time, the substitution of vanadium sites in H₂ V₃ O₈ with molybdenum was achieved while preserving the nanostructure by combining a soft chemical synthesis approach with a hydrothermal process. The obtained Mo-substituted vanadate nanofibers were further modified by prelithiation. While pristine H₂ V₃ O₈ showed an initial capacity of 223 mAh g^-1 and a retention of 79 % over 30 cycles, combining Mo substitution and prelithiation led to a superior initial capacity of 312 mAh g^-1 and a capacity retention of 94 % after 30 cycles.

Engineering Na-Mo-O/Graphene Oxide Composites with Enhanced Electrochemical Performance for Lithium Ion Batteries

Sodium molybdate (Na−Mo−O) wrapped by graphene oxide (GO) composites have been prepared via a simple in‐situ precipitation method at room temperature. The composites are mainly constructed with one dimension (1D) ultra‐long sodium molybdate nanorods, which are wrapped by the flexible GO. The introduction of GO is expected to not merely provide more active sites for lithium‐ions storage, but also improve the charge transfer rate of the electrode. The testing electrochemical performances corroborated the standpoint: The Na−Mo−O/GO composites delivers specific capacities of 718 mAh g⁻¹ after 100 cycles at 100 mA g⁻¹, and 570 mAh g⁻¹ after 500 cycles at a high rate of 500 mA g⁻¹; for comparison, the bare Na−Mo−O nanorod shows a severe capacity decay, which deliver only 332 mAh g⁻¹ after 100 cycles at 100 mA g⁻¹. In view of the cost‐efficient and less time‐consuming in synthesis, and one‐step preparation without further treatment, these Na−Mo−O nanorods/GO composites present potential and prospective anodes for LIBs.

Graphene oxide wrapped Cu3V2O7(OH)2 · 2H2O nanocomposite with enhanced electrochemical performance for lithium-ion storage

Transition metal oxides (TMOs) are widely accepted as one of the alternatives for the graphite anode in lithium-ion batteries (LIBs) owing to the high specific capacity and facile synthesis of nanoscale materials facilitating fast ionic transfer. However, the lower electronic conductivity always impedes the application of TMOs. Herein, we report a graphene oxide wrapped layer-structured Cu₃V₂O₇(OH)₂ · 2H₂O nanocomposite (CVO/GO) synthesized via an in situ co-precipitation method. It is corroborated that the introduction of GO not only provides more active sites for lithium-ion storage, but also improves the charge transfer rate of the electrode, issuing an enhanced electrochemical performance. As expected, the CVO/GO nanocomposite exhibits an ultrahigh specific capacity of 870 mA h g^-1 at 0.1 A g^-1 compared with CVO nanoparticles. Even at a high current density of 5 A g^-1, a specific capacity of 158 mA h g^-1 could be achieved for the CVO/GO nanocomposite.

Controlled Hydrothermal Growth and Li+ Storage Performance of 1D VOx Nanobelts with Variable Vanadium Valence

One-dimensional (1D) vanadium oxide nanobelts (VO_x NBs) with variable V valence, which include V₃O₇·H₂O NBs, VO₂ (B) NBs and V₂O₅ NBs, were prepared by a simple hydrothermal treatment under a controllable reductive environment and a following calcination process. Electrochemical measurements showed that all these VO_x NBs can be adopted as promising cathode active materials for lithium ion batteries (LIBs). The Li⁺ storage mechanism, charge transfer property at the solid/electrolyte interface and Li⁺ diffusion characteristics for these as-synthesized 1D VO_x NBs were systematically analyzed and compared with each other. The results indicated that V₂O₅ NBs could deliver a relatively higher specific discharge capacity (213.3 mAh/g after 50 cycles at 100 mA/g) and median discharge voltage (~2.68-2.71 V vs. Li/Li⁺) during their working potential range when compared to other VO_x NBs. This is mainly due to the high V valence state and good crystallinity of V₂O₅ NBs, which are beneficial to the large Li⁺ insertion capacity and long-term cyclic stability. In addition, the as-prepared VO₂ (B) NBs had only one predominant discharge plateau at the working potential window so that it can easily output a stable voltage and power in practical LIB applications. This work can provide useful references for the selection and easy synthesis of nanoscaled 1D vanadium-based cathode materials.

Controllable synthesis of 3D Fe3O4 micro-cubes as anode materials for lithium ion batteries

In this study, we adopt a facile two-step annealing strategy to synthesize different structural 3D Fe₂O₃ micro-cubes and 3D Fe₃O₄ micro-cubes using Prussian blue (PB) as a precursor.

Hierarchical bilayered hybrid nanostructural arrays of NiCo2O4 micro-urchins and nanowires as a free-standing electrode with high loading for high-performance lithium-ion batteries

Fabrication of free -standing binary transition metal oxides, especially NiCo₂O₄, has attracted significant research interests since these metal oxides are promising candidates for free-standing anodes of lithium-ion batteries (LIBs). However, there remain some problems, especially low loading, for the existing NiCo₂O₄ anodes. To address the abovementioned issue, it will be a quite feasible solution to combine the advantages of both hierarchical micro/nano-structures and free-standing electrodes to fabricate a free-standing hierarchical micro/nano-structural NiCo₂O₄ electrode. Herein, we proposed an effective method to controllably synthesize hierarchical bilayered hybrid nanostructural arrays of NiCo₂O₄(HNAs) micro-urchins and nanowires, denoted as NiCo₂O₄ HNAs/NF, based on Ni foam (NF) with a high loading via a simple surfactant-assisted hydrothermal and subsequent annealing treatment. In this synthesis, NF was applied as a Ni source for NiCo₂O₄ without the addition of other Ni-containing reagents, and the pH value played an important role in the synthesis of NiCo₂O₄ HNAs/NF. Furthermore, the reasonable reaction mechanism of NiCo₂O₄ HNAs/NF has been discussed in detail and proposed. The as-synthesized NiCo₂O₄ HNAs/NF possess unique structural advantages such as a large surface area, hierarchical porous structures, and robust connection of NFs and NiCo₂O₄ active materials. Thus, these unique NiCo₂O₄ HNAs/NF display excellent electrochemical performance such as a large reversible capacity of 1094 mA h g^-1 at a current density of 500 mA g^-1 and a good rate capability of 875 mA h g^-1 at a large 1000 mA g^-1. Especially, a high loading (7 mg cm^-2) of NiCo₂O₄ HNAs/NF, which is much higher than those of other NiCo₂O₄ electrodes, is beneficial towards the achievement of lightweight and miniaturized LIBs.