Synthesis and ionic conduction of sodium titanate Na<Subscript>2</Subscript>Ti<Subscript>3</Subscript>O<Subscript>7</Subscript>

Chemical and phase transformations in the course of synthesis of sodium titanate Na₂Ti₃O₇ have been studied. Prepared sodium titanates have been characterized by X-ray powder diffraction analysis, scaning electron microscopy, and impedance spectroscopy, their electrochemical testing has been conducted. Mechanochemical interaction of titanium dioxide and sodium carbonate at the grinding stage has been revealed. The utilization of mesoporous titanium dioxide have been shown to provide a considerable decrease of final annealing temperature. Thus obtained titanates exhibit high electrochemical capacity.     

Electrodes of Germanium and Germanium Phosphide Nanowires in Lithium-Ion and Sodium-Ion Batteries (A Review)

Russian Journal of Electrochemistry - Basic studies in the application of germanium nanowires obtained by electrolysis of aqueous solutions, as well as germanium phosphide nanorods, as negative...     

From lithium-ion to sodium-ion battery

The review discusses the problems of development of sodium-ion batteries intended to replace lithium-ion batteries used in large power plants (electric transport, smart grids). The literature data, mainly for the last five years, devoted to electrode functional materials and electrolytes used in sodium-ion batteries are presented and analyzed.     

Combined Method for Reducing Irreversible Capacity of the Negative Graphite Electrode in Lithium-Ion Battery

A method for the complete removal of the irreversible capacity of the negative electrode of lithium-ion batteries is suggested. The method consists of bringing the graphite electrode in contact with metallic lithium in the electrolyte. The distinguishing feature of the modified method is that all operations (assembling and filling cells, storing electrodes) are performed in a carbon dioxide atmosphere. Performing all these operations in a carbon dioxide atmosphere improves the reproducibility of the method. The balance between the weight of lithium and graphite, which is optimum for the complete removal of the irreversible capacity, is calculated. It is shown that applying the combined method does not lead to a decrease in the reversible capacity of the negative electrode.     

Nanostructured SnO2-TiO2 films as related to lithium intercalation

The difference in degradation behavior of titania-doped tin dioxide films is explained by a pronounced effect of the doping level on the film dispersity and fine distribution of titania. A two to three times decrease in nanoparticles sizes in the doped films compared with nanoparticles in SnO₂ film (20–30 nm) is revealed by using scanning tunneling microscopy (STM). Such STM data (measured in ex situ configuration) combined with XRD and Mössbauer spectroscopy analysis confirm that the nanoparticles are composed of nanostructured heavily disordered SnO₂ and TiO₂ rutile solid solution or of amorphous phase containing both SnO₂ and TiO₂, the content of the crystalline and amorphous phases being approximately equal.

Balance between reversible and irreversible processes during lithium intercalation in graphite

The effect of the measurements’ speed on reversible and irreversible processes occurring during intercalation and deintercalation of lithium in graphite out of a 1 M LiClO₄ solution in a propylene carbonate-dimethoxyethane mixture is studied by the chronopotentiometry and cyclic voltammetry methods. Dependence of reversible and irreversible capacity on the potential scan rate during potentiodynamic measurements is shown to be quite involved. Lithium diffusion coefficients in graphite are calculated by different methods.     

Effect of Temperature on Reversible and Irreversible Processes during Lithium Intercalation in Graphite

Effect of temperature on reversible and irreversible processes during lithium intercalation in graphite from 1 M LiClO₄ solution in PC–DME is studied by galvanostatic cycling, cyclic voltammetry, and impedance spectroscopy. Reducing temperature diminishes both reversible and irreversible capacities. Conditions for the passive-film formation on graphite are discussed. If several first cycles are run at a negative temperature, the overall charge spent irreversibly decreases if the temperature is then elevated. The lower the initial-cycling temperature, the smaller the overall irreversible capacity.     

The structure and charge-storage capacitance of carbonized films based on silicon-polymer nanocomposites

New film materials for electrodes of lithium batteries were synthesized and studied. Thin-film silicon-polymer composites were prepared by vacuum cocondensation of silicon and the monomer onto a substrate cooled with liquid nitrogen; the polymerization and formation of the nanostructured composite were performed at room temperature. The films were carbonized by vacuum annealing. The film composition and microstructure were studied by AFM, SEM, Raman spectroscopy, and X-ray spectral microanalysis. It was shown that the polymer matrix became almost fully carbonized because of pyrolysis. The silicon concentration in the films varied from 2 to 5 at %. The concentration of silicon nanoparticles on carbonized film surfaces was ∼10⁶ cm⁻². Electrochemical experiments with lithium insertion into the composite films were performed in standard three-electrode cells under galvanostatic conditions. The specific capacitance of the films was measured. It was shown that the samples were capable of long-term cycling; the capacitance decreased by only 6% during the first 200 cycles; after 250 cycles, the capacitance still exceeded 80% of its initial value. The mechanism of lithium insertion into the films was discussed. It was concluded that long-term stability during cycling was caused by the presence of silicon both as nanoparticles and in the atomically dispersed form.     

Study of degradation of Na2Тi3O7-based electrode during cycling

Journal of Solid State Electrochemistry - The degradation of electrodes based on sodium titanate (Na2Ti3O7) was studied using the methods of galvanostatic cycling, cyclic voltammetry, Raman...