Size-Tunable Natural Mineral-Molybdenite for Lithium-Ion Batteries Toward: Enhanced Storage Capacity and Quicken Ions Transferring

Interfacial Mo-S-C Bond with High Reversibility for Advanced Alkali-Ion Capacitors: Strategies for High-Throughput Production

The high-throughput scalable production of low-cost and high-performance electrode materials that work well under high power densities required in industrial application is full of challenges for the large-scale implementation of electrochemical technologies. Here, motivated by theoretical calculation that Mo-S-C heterojunction and sulfur vacancies can reduce the energy band gap, decrease the migration energy barrier, and improve the mechanical stability of MoS2 , the scalable preparation of inexpensive MoS2-x @CN is contrived by employing natural molybdenite as precursor, which is characteristic of high efficiency in synthesis process and energy conservation and the calculated costs are four orders of magnitude lower than MoS2 /C in previous work. More importantly, MoS2- x @CN electrode is endowed with impressive rate capability even at 5 A g-1 , and ultrastable cycling stability during almost 5000 cycles, which far outperform chemosynthesis MoS2 materials. Obtaining the full SIC cell assembled by MoS2- x @CN anode and carbon cathode, the energy/power output is high up to 265.3 W h kg-1 at 250 W kg-1 . These advantages indicate the huge potentials of the designed MoS2- x @CN and of mineral-based cost-effective and abundant resources as anode materials in high-performance AICs.

Digital laser-induced printing of MoS2

Due to their atomic-scale thickness, handling and processing of two-dimensional (2D) materials often require multistep techniques whose complexity hampers their large-scale integration in modern device applications. Here we demonstrate that the laser-induced forward transfer (LIFT) method can achieve the one-step, nondestructive printing of the prototypical 2D material MoS2. By selecting the optimal LIFT experimental conditions, we were able to transfer arrays of MoS2 pixels from a metal donor substrate to a dielectric receiver substrate. A combination of various characterization techniques has confirmed that the transfer of intact MoS2 monolayers is not only feasible, but it can also happen without incurring significant defect damage during the process. The successful transfer of MoS2 shows the broad potential the LIFT technique has in the emerging field of printed electronics, including printed devices based on 2D materials.

Improving the electrochemical performance of a natural molybdenite/N-doped graphene composite anode for lithium-ion batteries via short-time microwave irradiation

In the present work, low-cost natural molybdenite was used to make a MoS2/N-doped graphene composite through coulombic attraction with the aid of (3-aminopropyl)-triethoxysilane and the electrochemical performance was greatly improved by solvent-free microwave irradiation for tens of seconds. The characterization results indicated that most (3-aminopropyl)-triethoxysilane can decompose and release N atoms to further improve the N-doping degree in NG during the microwave irradiation. In addition, the surface groups of N-doped graphene were removed and the particle size of MoS2 was greatly decreased after the microwave irradiation. As a result, the composite electrode prepared with microwave irradiation exhibited a better rate performance (1077.3 mA h g-1 at 0.1C and 638 mA h g-1 at 2C) than the sample prepared without microwave irradiation (1013.6 mA h g-1 at 0.1C and 459.1 mA h g-1 at 2C). Therefore, the present results suggest that solvent-free microwave irradiation is an effective way to improve the electrochemical properties of MoS2/N-doped graphene composite electrodes. This work also demonstrates that natural molybdenite is a promising low-cost anode material for lithium-ion batteries.

Chalcopyrite-Derived NaxMO2 (M = Cu, Fe, Mn) Cathode: Tuning Impurities for Self-Doping

Discovering cathode materials composed of earth-abundant elements has become the current priority for developing sodium-ion batteries (SIBs) to meet the ever-increasing demand of large-scale energy storage. Herein, for the first time, layered Na_xMO₂ (M = Cu, Fe, Mn) cathodes are successfully prepared by directly using concentrated chalcopyrite ores as precursors. Greatly, impurity elements like Si and Ca are found to be crucial to tailoring the phase structure of as-obtained layered oxides as a P2 or O3 type, which removes the traditional concern that the impurities may restrict the utilization of natural ores. More interestingly, a certain amount of the Ca elements remaining in the Na sites through a self-doping process endows the P2-type products with enhanced structural stability. In half-cells, P2-type Na_xMO₂ with self-doped Ca elements shows superior rate capability and cycling stability (56 mAh g^-1 at 5 C and 90% capacity retention after 100 cycles at 1 C). In contrast, less impurity elements are favorable for O3-type oxides to achieve a high capacity of 107 mAh g^-1 at 0.1 C and 84% capacity retention after 200 cycles at 2 C. This new strategy would efficiently shorten the process for preparing electrode materials and open a feasible route to construct cheap and durable SIBs.

Facile one-pot synthesis of Ge/TiO2 nanocomposite structures with improved electrochemical performance

Germanium (Ge) as an alternative to graphite exhibits a fairly high theoretical energy density and improved Li⁺ ion diffusivity. However, the seriously deteriorated electrochemical performance of Ge during cycling and the difficulty in the preparation of Ge-based nanostructures can hinder the utilization of Ge as an anode. Thus, in this study, a nanocomposite structure with Ge and TiO₂ (Ge/TiO₂) was synthesized using a facile one-pot method with different ratios of a Ge source with a dominant GeO₂ phase and titanium isopropoxide. From X-ray diffraction, electron microscopy, and X-ray photoelectron spectroscopy, the Ge/TiO₂ nanocomposites were found to be spherical structures homogeneously consisting of the reduced Ge as an active material and amorphous TiO₂ as a matrix. In particular, the Ge/TiO₂ nanocomposite with an appropriate amount of TiO₂ exhibited improved electrochemical properties, i.e., a coulombic efficiency of 97% and a retention of 61% for 100 cycles, compared to commercial Ge (a coulombic efficiency of 82% and a retention of 16%). This demonstrates that the amorphous TiO₂ matrix could relieve a volumetric expansion of the Ge active material in the nanocomposite electrode generated during the cycling process.

Sintering Temperature Induced Evolution of Microstructures and Enhanced Electrochemical Performances: Sol-Gel Derived LiFe(MoO4)2 Microcrystals as a Promising Anode Material for Lithium-Ion Batteries

A facile sol-gel process was used for synthesis of LiFe(MoO₄)₂ microcrystals. The effects of sintering temperature on the microstructures and electrochemical performances of the as-synthesized samples were systematically investigated through XRD, SEM and electrochemical performance characterization. When sintered at 650°C, the obtained LiFe(MoO₄)₂ microcrystals show regular shape and uniform size distribution with mean size of 1–2 μm. At the lower temperature (600°C), the obtained LiFe(MoO₄)₂ microcrystals possess relative inferior crystallinity, irregular morphology and vague grain boundary. At the higher temperatures (680 and 700°C), the obtained LiFe(MoO₄)₂ microcrystals are larger and thicker particles. The electrochemical results demonstrate that the optimized LiFe(MoO₄)₂ microcrystals (650°C) can deliver a high discharge specific capacity of 925 mAh g⁻¹ even at a current rate of 1 C (1,050 mA g⁻¹) after 500 cycles. Our work can provide a good guidance for the controllable synthesis of other transition metal NASICON-type electrode materials.