The electrochemical properties of an electrode material based on a high-capacity silicon/reduced graphene oxide composite are studied. It was determined that the optimal potentials for reversible insertion/extraction of lithium are in the range of 50–2000 mV. The discharge capacity is 980 mAh g–1 at the charge rate 0.3 C and discharge rate 1.0 C. The addition of vinylene carbonate to the electrolyte solution leads to the stabilization of the solid electrolyte layer on the electrode surface. The discharge capacity is 866 mAh g–1 at the 170th charge/discharge cycle.

The processes of adsorption of a silicon oxide cluster onto the surface of reduced graphene oxide (GO) have been considered. The calculations have been performed at the PBE/PAW, ωB97XD/6-31G( d , p ), and ωB97XD/6-31G( d , p )/6-311G( d , p )BSSE levels with inclusion of periodic conditions and in the cluster approximation. Upon the formation of GO, graphene sheets are distorted in the vicinity of bonding with oxygen. It is energetically favorable for the Si n O x cluster to be located on the concave side of the surface (opposite of adsorbed oxygen). This stabilizes the position of the clusters and prevents the “drift” of silicon oxide during lithiation. The lithiation involves oxygen and silicon atoms. The lithium conductivity will depend on the Li/O and Li/O c ratios, where O and O c are the numbers of oxygen atoms on the silicon oxide and graphene oxide surfaces, respectively. Lithium migration occurs through oxygen atoms bound to silicon in the case of a small ratio Li/O ≤ 1/2 and captures O c oxygen atoms covering graphene in the case of Li/O ≥ 1.

A composite consisting of silicon nanoparticles and reduced graphene oxide nanosheets (Si/RGO) was studied as a promising material for the negative electrode of lithium-ion batteries. Commonly used polyvinylidene fluoride (PVdF) and carboxymethyl cellulose (CMC) served as a binder. To reveal the influence of the binder on the electrochemical behaviour of the Si/RGO composite, binder-free electrodes were also prepared and examined. Anode half-cells with composites comprising CMC as a binder demonstrated the best properties: capacity over 1200 mAh∙g-1, excellent cycling performance and good rate capability up to 1.0C.

Two types of treatment of the initial mechanical mixture [silicon nanopowder and graphene oxide (GO)] for obtaining Si/RGO nanocomposites were used: reduction in hydrazine vapor and heat treatment at 550°C in an argon atmosphere. It was shown that the type of reduction has an influence on the morphological and electrochemical characteristics of the composites due to the formation of defects and the presence of nitrogen in the graphene network. Less defective and nitrogen doped Si/RGO composites have a better electrochemical behavior as an active material of negative electrode for lithium-ion batteries. The discharge capacity of electrodes based on Si/RGO nanocomposites amounted to 437 mA h g–1 without polymer binder and 1192 mA h g–1 with CMC as a binder.

The effect of a protective coating of fused lithium borate, Li3BO3, on the physicochemical and electrochemical characteristics of LiCoO2 has been studied. A cathode material produced by the SCS method using binary organic fuel, glycine and citric acid. The influence of the experiment conditions on the morphology, crystal structure and specific surface of lithium cobaltite was studied. Electrochemical testing of LiCoO2∙nLi3BO3 samples, n = 5 and 7 mass %, has been performed in the cathode Li|Li+-electrolyte|LiCoO2∙nLi3BO3 half-cell using 1M LiPF6 in EC/DMC mixture (1:1) as electrolyte in the 2.7-4.3 V range at normalized discharge current С/10, С/5, С/2. The maximal initial discharge capacity of 185 mAh/g was detected for the samples with 5 mass % Li3BO3. The coulomb efficiency of optimal materials in the 40th cycle was 99.1%.

The method of producing low-density carbon materials by thermal destruction of grinded graphite foil saturated with aqueous solutions of: 1) ammonium nitrate, 2) carbamide, or 3) surfactant was developed. The electrophysical properties of low-density carbon materials and expanded vermiculite/low-density carbon material composites were investigated. Percolation thresholds for electrical conductivity for studied systems were determined. Critical exponents in classic theory electrical conductivity were calculated

We present the results of investigation of the kinetics of oxidation of a composite material based on discrete carbon fibers and modified phenol formaldehyde resin. According to the results of thermal analysis performed under the conditions of oxidizing medium, we proposed a model of oxidation of separate components and the composite as a whole. The processes of oxidation of fibers and resin are realized in one and two stages, respectively. At the same time, the composite material is characterized by the three-stage realization of the process of oxidation. According to the computed parameters of the reaction, we plotted the isotherms for the interval 220 – 300°C with steps of 10°C and holding for up to 5 h. It was established that, for 300°C, the process of oxidation leads to the loss of the initial mass of the composite that does not exceed 5% for 5 h.

The investigating results are given for the oxidation kinetics of the composite material on base of both the discontinuous carbon fibers and the phenolformaldehyde resin. According to the results of the thermal analyses amid the oxidation condition the oxidation model was elaborated both for single components and for the composite material in total. The fiber's oxidizing is one-stage, the resin's oxidizing is two-stage, the composite oxidizes in three stages. Based on the calculated parameters of the reaction the isothermal curves were plotted for the temperature within 220‒300 °C at intervals of 10 °C and holding at the heating time up to 5 hours. It was established that at 300 °C during 5 hours the composite material by oxidation lost no more than 5 % of its initial mass. Ill. 3. Ref. 14. Tab. 2.