Complete Three-Electron Vanadium Redox in NASICON-Type Na3VSc(PO4)3 Electrode Material for Na-Ion Batteries

Here we introduce a new NASICON-type Na3VSc(PO4)3 positive electrode material for Na-ion batteries demonstrating reversible (de)intercalation of 3 Na cations per formula unit within a wide voltage range with complex voltage-composition dependence. The total electrochemical capacity of the material is 170 mAh/g, which corresponds to the complete three-electron V2+/V3+/V4+/V5+ process. All the (de)sodiation stages follow a predominantly solid-solution mechanism, as shown by operando X-ray powder diffraction. The oxidation of vanadium up to +5 upon the charge of Na3VSc(PO4)3 to 4.5 V vs. Na/Na+ causes the significant transformation of the unit cell. According to ex situ Fourier-transformed infrared spectroscopy it is accompanied by the increasing distortion of the vanadium coordination environment and shortening of the vanadium-oxygen bonds. This leads to the irreversible character of the charge-discharge curve, and the initial structure can be restored after the strong overdischarge to ≈1.5 V vs. Na/Na+.

Influence of 1.5 wt.% Bi on the Microstructure, Hardness, and Shear Strength of Sn-0.7Cu Solder Joints after Isothermal Annealing

This manuscript reports the isothermal annealing effect on the mechanical and microstructure characteristics of Sn-0.7Cu-1.5Bi solder joints. A detailed microstructure observation was carried out, including measuring the activation energy of the intermetallic compound (IMC) layer of the solder joints. Additionally, the synchrotron µX-ray fluorescence (XRF) method was adopted to precisely explore the elemental distribution in the joints. Results indicated that the Cu6Sn5 and Cu3Sn intermetallic layers thickness at the solder/Cu interface rises with annealing time at a rate of 0.042 µm/h for Sn-0.7Cu and 0.037 µm/h for Sn-0.7Cu-1.5Bi. The IMC growth’s activation energy during annealing is 48.96 kJ mol-1 for Sn-0.7Cu, while adding Bi into Sn-0.7Cu solder increased the activation energy to 55.76 kJ mol−1. The µ-XRF shows a lower Cu concentration level in Sn-0.7Cu-1.5Bi, where the Bi element was well dispersed in the β-Sn area as a result of the solid solution mechanism. The shape of the IMC layer also reconstructs from a scallop shape to a planar shape after the annealing process. The Sn-0.7Cu hardness and shear strength increased significantly with 1.5 wt.% Bi addition in reflowed and after isothermal annealing conditions.

Product formation during discharge: a combined modelling and experimental study for Li–O$$_2$$ cathodes in LiTFSI/DMSO and LiTFSI/TEGDME electrolytes

Li–air or Li–$$\text{O}_2$$ O 2 batteries are a promising energy storage technology due to the potentially high energy density. However, significant challenges related to reversible charge/discharge of these cells need to be solved. The discharge reaction is generally agreed to proceed via two main routes, which may occur simultaneously. These are the surface mechanism, leading to $$\text{Li}_2\text{O}_2$$ Li 2 O 2 product formation as surface films, or the solution mechanism, with solid particles formed in the pore structure of the cathode. A detailed understanding of the reaction mechanisms and the dynamic performance of the electrodes is key to further improvements. Here, we present a mathematical model for the discharge process, based on porous electrode theory, including effects of reactant transport and kinetic limitations, as well as the continuous change of properties due to the formation of reaction products via the solution mechanism and the surface mechanism. The model describes the dynamic change in the ratio of the surface and solution mechanism as a function of growth of film thickness, in line with recent findings. The model is able to predict the differences in experimentally obtained discharge curves between dimethyl sulfoxide and tetra ethylene glycol dimethyl ether solvents with 1M LiTFSI, with a minimum of free parameters. The model parameters are based on physical characterization of the materials and the electrodes, or determined by fitting to impedance spectra recorded during the discharge. The developed model and the methodology will provide a powerful tool for optimization of such electrodes. Graphic abstract

Efficient corrosion inhibition by sugarcane purple rind extract for carbon steel in HCl solution: mechanism analyses by experimental and in silico insights

The anticorrosive mechanism of extracted components from sugarcane purple rind for carbon steel in HCl solution is clarified by weight loss, electrochemical and theoretical (novel DFT calculation and molecular dynamics simulation) analyses.

Tetramethylpyrazine: an electrolyte additive for high capacity and energy efficiency lithium–oxygen batteries

TMP has a strong interaction with Li+, which promotes the solution mechanism of Li2O2, thereby increasing the discharge capacity.