On electrochemistry of metal-organic framework Zn2(EDTA)(H2O).

Metal-organic compounds (MOFs) are a class of substances composed of metal ions or clusters coordinated to organic ligands to form one-, two-, or three-dimensional structures. Due to their high porosity, excellent adsorption and catalytic activity, as well as the possibility of simultaneous implementation of various charge accumulation mechanisms, they can be used as electrode materials for metal-ion batteries. However, a significant disadvantage is that most MOFs have a low electrical conductivity, and the production of conductive MOFs is a costly, time-consuming and technically difficult process. In this work, we developed a method for synthesizing the Zn2(EDTA)(H2O) MOF composite and studied the possibility of using it as an anode material for sodium-ion batteries based on aqueous electrolytes. The structure and morphology of the compound was studied using XRD, IR, TGA and SEM. Using cyclic voltammetry, the electrochemical characteristics of the organometallic framework in alkaline electrolytes 1, 10 M NaOH, as well as in saturated aqueous electrolyte NaClO4, were evaluated. It has been established that the studied compound does not give a satisfactory electrochemical response in aqueous electrolytes (both in alkaline and neutral media) due to the strong degradation of the electrode material, which is associated with the high solubility of this MOF representative. Cyclic voltammetric studies showed the presence of two redox processes due to the release of metallic zinc from an electrolyte solution, where two forms of zinc exist in equilibrium (the ZnEDTA complex and the free zinc cation). Therefore, we concluded, it is not possible to use this material as an anode for water-based sodium-ion batteries in contrary to a published research study.

Application of a conversion electrode based on decomposition derivatives of Ag4[Fe(CN)6] for aqueous electrolyte batteries.

The lack of stable electrode materials for water-based electrolytes due to the intercalation and conversion reaction mechanisms encourage scientists to design new or renovate existing materials with better cyclability, capacity, and cost-effectiveness. Ag4[Fe(CN)6] is a material belonging to the Prussian blue family that can be used, as its other family members, as an electrode material with the intercalation/deintercalation reaction or conversion-type mechanism through Ag oxidation/reduction. However, due to the instability of this material in its dry state, it decomposes to AgCN and a Prussian blue residual complex. A possible reason for Ag4[Fe(CN)6] decomposition is discussed. Nevertheless, it is shown that the decomposition products of Ag4[Fe(CN)6] have electrochemical activity due to the reversible oxidation/reduction of Ag atoms in water-based electrolytes.

Electrodeposition of Polymer Electrolyte Into Porous LiNi0.5Mn1.5O4 for High Performance All-Solid-State Microbatteries.

We report the electrodeposition of polymer electrolyte (PMMA-PEG) in porous lithium nickel manganese oxide (LiNi0.5Mn1.5O4) cathode layer by cyclic voltammetry. The cathode-electrolyte interface of the polymer-coated LNMO electrode has been characterized by scanning electron microscopy and electrochemical techniques. Electrochemical measurements consisting of galvanostatic cycling tests and electrochemical impedance spectroscopy revealed a significant improvement of the capacity values and the increase of the operating voltage. These effects are attributed to the total filling of pores by the electrodeposited polymer that contributes to improve the reversible insertion of Li+. A complete all-solid-state microbattery consisting of electropolymerized LNMO as the cathode, a thin polymer layer as the electrolyte, and TiO2 nanotubes as the anode has been successfully fabricated and tested.