Facile Synthesis of Ordered Mesoporous Orthorhombic Niobium Oxide (T-Nb2_2O5_5) for High-Rate Li-Ion Storage with Long Cycling Stability

Herein, we describe the synthesis and evaluation of hierarchical mesoporous orthorhombic niobium oxide (T-Nb$_2$O$_5$) as an anode material for rechargeable lithium-ion batteries (LIB). The as-synthesized material addresses key challenges such as beneficial porous structure, poor rate capability, and cycling performance of the anode for Li-ion devices. The physicochemical characterization results reveal hierarchical porous nanostructure morphology with agglomerated particles and a 20 to 25 nm dimension range. Moreover, the sample has a high specific surface area (~65 m$^2$ g$^{−1}$) and pore volume (0.135 cm3 g$^{−1}$). As for the application in Li-ion devices, the T-Nb$_2$O$_5$ delivered an initial discharging capacity as high as 225 mAh g$^{−1}$ at 0.1 A g$^{−1}$ and higher rate capability as well as remarkable cycling features (~70% capacity retention after 300 cycles at 250 mA g$^{−1}$) with 98% average Coulombic efficiency (CE). Furthermore, the scan rate-dependent charge storage mechanism of the T-Nb$_2$O$_5$ electrode material was described, and the findings demonstrate that the electrode shows an evident and highly effective pseudocapacitive Li intercalation behaviour, which is crucial for understanding the electrode process kinetics. The origin of the improved performance of T-Nb$_2$O$_5$ results from the high surface area and mesoporous structure of the nanoparticles

Unraveling (electro)-chemical stability and interfacial reactions of Li 10 SnP 2 S 12 in all-solid-state Li batteries

Abstract(#br)Li 10 SnP 2 S 12 (LSPS) with high ionic conductivity and moderate price is a promising solid electrolyte for all-solid-state batteries. However, the instability of LSPS and LSPS/electrodes interfaces would cause poor cycle performance issues in the LSPS-based all-solid-state batteries, which have not been well understood. Herein, we address and unravel the decomposition products of LSPS and their Li + transfer characteristics, especially on the surface of LSPS/electrodes by using solid-state nuclear magnetic resonance (ss NMR) spectroscopy coupled with X-ray photoelectron spectroscopy (XPS). The results reveal that the high mechanical energy during ball-milling process leads to the decomposition of LSPS into Li 4 SnS 4 and Li 3 PS 4 . During charge/discharge cycling, specific capacity fading of batteries originates from the formation of new interfacial layer at LSPS/Acetylene black cathode and LSPS/Li metal anode interfaces. Furthermore, our results demonstrate that the rough and porous morphology of the interface formed after cycling, rather than the decomposition products, is the critical factor which results in the increases of the interfacial resistance at LSPS/Li interface and serious formation of Li dendrite. Our results highlight the significant roles of (electro)chemical and interfacial stability of sulfide solid electrolyte in the development of all-solid-state batteries

Tuning the Surface Morphology and Pseudocapacitance of MnO₂ by a Facile Green Method Employing Organic Reducing Sugars

In the present work, three different MnO₂ nanostructures, nanoneedles, hollow tubes, and nanorods of MnO₂, have been synthesized by a simple redox reaction between permanganate and organic sugars at room temperature. The MnO₂ samples were characterized by a variety of analytical techniques. The results illustrate that the organic reducing sugars of mannose, galactose, and glucose effectively tune the morphology, crystallinity, and pore structure of the MnO₂ material. The nanoneedles and hollow tubes were found to be β-MnO₂, while the nanorods were α-MnO₂. The formation of different MnO₂ nanostructures appears to be a kinetically driven process that proceeds in a quite distinctive way in the presence of different organic reducing sugars. Cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS) tests were conducted to evaluate the charge storage behavior of the α- and β-MnO₂ nanostructures. Among all three MnO₂ samples, β-MnO₂ composed of nanoneedles delivered a large specific capacitance, <i>C</i>_S (∼365 F g^–1 at 0.5 A g^–1) with improved rate capability (56% retention at 12 A g^–1) and excellent cyclability (82% retention at 2000 cycles). The elegant combination of the high specific surface area (∼146 m² g^–1) and 1D-nanoneedle structure of β-MnO₂, enhances the electrode–electrolyte contact area and hence provides a number of active sites for fast charge–discharge propagations

Stabilizing Li₁₀SnP₂S₁₂/Li Interface via an in Situ Formed Solid Electrolyte Interphase Layer

Despite the extremely high ionic conductivity, the commercialization of Li₁₀GeP₂S₁₂-type materials is hindered by the poor stability against Li metal. Herein, to address that issue, a simple strategy is proposed and demonstrated for the first time, i.e., in situ modification of the interface between Li metal and Li₁₀SnP₂S₁₂ (LSPS) by pretreatment with specific ionic liquid and salts. X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy results reveal that a stable solid electrolyte interphase (SEI) layer instead of a mixed conducting layer is formed on Li metal by adding 1.5 M lithium bis­(trifluoromethanesulfonyl)­imide (LiTFSI)/<i>N</i>-propyl-<i>N</i>-methyl pyrrolidinium bis­(trifluoromethanesulfonyl)­imide (Pyr₁₃TFSI) ionic liquid, where ionic liquid not only acts as a wetting agent but also improves the stability at the Li/LSPS interface. This stable SEI layer can prevent LSPS from directly contacting the Li metal and further decomposition, and the Li/LSPS/Li symmetric cell with 1.5 M LiTFSI/Pyr₁₃TFSI attains a stable cycle life of over 1000 h with both the charge and discharge voltages reaching about 50 mV at 0.038 mA cm^–2. Furthermore, the effects of different Li salts on the interfacial modification is also compared and investigated. It is shown that lithium bis­(fluorosulfonyl) imide (LiFSI) salt causes the enrichment of LiF in the SEI layer and results in a higher resistance of the cell upon a long cycling life