Electron-rich hybrid matrix to enhance molybdenum oxide-based anode performance for Lithium-Ion batteries.

Although MoO2-based electrodes have been intensively studied as potential candidate anodes for lithium-ion batteries (LIBs) based on their high theoretical capacity (840 mAh g-1 and 5447 mAh cm-3), common issues such as severe volume variation, electrical conductivity loss, and low ionic conductivity, are prevalent. In this study, we demonstrate enhanced Li-ion kinetics and electrical conductivity of MoO2-based anodes with ternary MoO2-Cu-C composite materials. The MoO2-Cu-C was synthesized via two-step high energy ball milling where Mo and CuO are milled, followed by the secondary milling with C. With the introduction of the Cu-C hybrid matrix in MoO2 nanoparticles via the element transfer method using mechanochemical reactions, the sluggish Li-ion diffusion and unstable cycling behavior were significantly improved. The inactive Cu-C matrix contributes to the increase in electrical and ionic conductivity and mechanical stability of active MoO2 during cycling, as characterized by various electrochemical analyses and ex situ analysis techniques. Hence, the MoO2-Cu-C anode delivered promising cycling performance (674 mAh g-1 (at 0.1 A g-1) and 520 mAh g-1 (at 0.5 A g-1), respectively, after 100 cycles) and high-rate property (73% retention at 5 A g-1 as comparison with the specific capacity at 0.1 A g-1). The MoO2-Cu-C electrode is a propitious next-generation anode for LIBs.

Inorganic Fillers in Composite Gel Polymer Electrolytes for High-Performance Lithium and Non-Lithium Polymer Batteries.

Among the various types of polymer electrolytes, gel polymer electrolytes have been considered as promising electrolytes for high-performance lithium and non-lithium batteries. The introduction of inorganic fillers into the polymer-salt system of gel polymer electrolytes has emerged as an effective strategy to achieve high ionic conductivity and excellent interfacial contact with the electrode. In this review, the detailed roles of inorganic fillers in composite gel polymer electrolytes are presented based on their physical and electrochemical properties in lithium and non-lithium polymer batteries. First, we summarize the historical developments of gel polymer electrolytes. Then, a list of detailed fillers applied in gel polymer electrolytes is presented. Possible mechanisms of conductivity enhancement by the addition of inorganic fillers are discussed for each inorganic filler. Subsequently, inorganic filler/polymer composite electrolytes studied for use in various battery systems, including Li-, Na-, Mg-, and Zn-ion batteries, are discussed. Finally, the future perspectives and requirements of the current composite gel polymer electrolyte technologies are highlighted.

Zinc Telluride as Electrochemical Storage Material for High-Performance Sodium-Ion Batteries.

High-energy ball milling (HEBM) is used to synthesize zinc telluride (ZnTe) and amorphous C (ZnTe-C) nanocomposites as novel anode materials for sodium-ion batteries (SIBs). A nanostruc-tured ZnTe-C composite is prepared using Zn, Te, and acetylene black as precursor materials via a facile two-step HEBM process. The initial HEBM of Zn and Te induces the formation of the ZnTe alloy nanostructure via a mechanochemical reaction. The subsequent HEBM process generates the ZnTe composite embedded in amorphous C (ZnTe-C), as confirmed using X-ray diffraction, transmission electron microscopy, and element mapping analyses. When used as SIB anode, the ZnTe-C composite exhibits good cyclic life (specific discharge capacities of 383 mAh g-1 at 0.1 A g-1 over 150 cycles and 373 mAh g-1 at 0.5 A g-1 after 500 cycles) and excellent rate capability (89% capacity retention at 10 A g-1 relative to that at 0.1 A g-1). The impedance analysis and ex situ scanning electron microscopy results reveal that the properties of ZnTe-C are superior to those of ZnTe because C serves as buffering matrix that suppresses the volume changes in ZnTe during alloying/dealloying and reduces the charge transfer resistance. The ZnTe-C nanocomposite in this study is a promising candidate for high-performance SIB anodes.

Enhanced Lithium Ion Storage by Titanium Dioxide Addition to Zinc Telluride-Based Alloy Composites.

A nanostructured ZnTe-TiO2-C composite is synthesized, via a two-step high-energy mechanical milling process, for use as a new promising anode material in Li-ion batteries (LIBs). X-ray diffraction and X-ray photoelectron spectroscopy results confirm the successful formation of ZnTe alloy and rutile TiO2 phases in the composites using ZnO, Te, Ti, and C as the starting materials. Scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray spectroscopy mapping measurements further reveal that ZnTe and TiO2 nanocrystals are uniformly dispersed in an amorphous carbon matrix. The electrochemical performances of ZnTe-TiO2-C and other control samples were investigated. Compared to ZnTe-TiO2 and ZnTe-C composites, the ZnTe- TiO2-C nanocomposite exhibits better performance, thereby delivering a high reversible capacity of 561 mAh g-1 over 100 cycles and high rate capability at a high current density of 5 A g-1 (79% capacity retention of its capacity at 0.1 A g-1). Furthermore, the long-term cyclic performance of ZnTe-TiO2-C at a current density of 0.5 A g-1 shows excellent reversible capacity of 528 mAh g-1 after 600 cycles. This improvement can be attributed to the presence of a TiO2-C hybrid matrix, which acts as a buffering matrix that effectively mitigates the large volume changes of active ZnTe during repeated cycling. Overall, the ZnTe-TiO2-C nanocomposite is a potential candidate for high-performance anode materials in LIBs.

Rapid and mass-producible synthesis of high-crystallinity MoSe2 nanosheets by ampoule-loaded chemical vapor deposition.

MoSe2 is an attractive transition-metal dichalcogenide with a two-dimensional layered structure and various attractive properties. Although MoSe2 is a promising negative electrode material for electrochemical applications, further investigation of MoSe2 has been limited, mainly by the lack of MoSe2 mass-production methods. Here, we report a rapid and ultra-high-yield synthesis method of obtaining MoSe2 nanosheets with high crystallinity and large grains by ampoule-loaded chemical vapor deposition. Application of high pressure to an ampoule-type quartz tube containing MoO3 and Se powders initiated rapid reactions that produced vertically oriented MoSe2 nanosheets with grain sizes of up to ∼100 µm and yields of ∼15 mg h-1. Spectroscopy and microscopy characterizations confirmed the high crystallinity of the obtained MoSe2 nanosheets. Transistors and lithium-ion battery cells fabricated with the synthesized MoSe2 nanosheets showed good performance, thereby further indicating their high quality. The proposed simple scalable synthesis method can pave the way for diverse electrical and electrochemical applications of MoSe2.