Vyacheslav S. Dyadyun

Advanced electrochemical performance of hybrid nanocomposites based on LiFePO4 and lithium salt doped polyaniline

LiFePO4 (LFP) is one of the commercially usable cathode materials for lithium batteries. To overcome its main drawback—low conductivity—LFP particles are usually covered by carbon shell. But this approach lowers the capacity of the whole cathode due to electrochemical inactivity of the carbon shell at the required potentials. In the present work, we propose a novel approach which is based on mechanochemical insertion of LFP particles inside polyaniline doped with lithium salt. It is established that during charge–discharge of these nanocomposites, both LFP and polyaniline are redox active. It is shown that the prepared nanocomposites exhibit improved electrochemical performance as a cathode in lithium batteries compared with the individual LFP. It is shown that the presence of the polyaniline in the nanocomposite could facilitate the transport of lithium ions inside (outside) the inorganic component during discharge (charge).

Mechanochemical Preparation of a MoS2/Polyaniline Nanocomposite with High Electrochemical Capacity

A hybrid polyaniline nanocomposite derived from polyaniline in the emeraldine base state and nanostructurized MoS2was prepared by a mechanochemical method. The electrochemical properties of the MoS2/PAni nanocomposite as the active component of a lithium battery cathode were studied. This material has a high specific capacity of ~270 A·h/kg, which is due to the significantly greater specific capacities of the organic and inorganic components relative to their characteristics in the individual states. This enhancement may be attributed to the effects of the nanocomposite components on the electrochemical behavior of each other.

Effect of the Composition and Post-Synthesis Heat Treatment on the Electrochemical Characteristics of Polypyrrole/V2O5 Nanocomposites Prepared by a Mechanochemical Method

Effects were shown for the composition and post-synthesis heat treatment in an oxygen atmosphere on the electrochemical properties of nanocomposites derived from polypyrrole (PPy) and a V2O5 xerogel with host–guest structure. PPy0.05V2O5 was found to have the highest specific discharge capacity of about 290 mA·h/g and high stability upon prolonged charge-discharge cycling among the PPyxV2O5 nanocomposites prepared (where x = 0.1, 0.05, 0.025). Post-synthesis heat treatment in an oxygen atmosphere leads to oxidation of the reduced portion of the inorganic nanocomposite component and nanostructurization of the composite with formation of nanofibers that facilitate a considerable increase in the specific capacity and stability upon cycling.

Mechanochemically Prepared Nanocomposites Based on Polyaniline and Molybdenum and Tungsten Disulfides as Electrode Materials for Supercapacitors

Hybrid nanocomposites with different composition prepared from polyaniline (PAni) and exfoliated MoS2 and WS2 were prepared by a mechanochemical method and studied as electrodes of symmetrical supercapacitors (SSC). Nanoparticles of MoS2 and WS2 have been found to promote electrochemical reversibility of redox conversion in PAni at high potentials and contribute to the stability of these nanocomposites during prolonged charge-discharge cycling. The specific capacity of such materials can reach 600 F/g and the specific power of SSC can reach ~4.1 kW/kg for specific energy ~23.5 W·h/kg.

Effect of the Nature of Exfoliating Agents on the Structure of Graphenes with Various Degrees of Oxidation Obtained by Mechanochemical Treatment

Graphenes with various degree of oxidation and capable of forming stable aqueous dispersions were prepared by a mechanochemical method using Na2SO4, KMnO4, and KMnO4 with the addition of a stoichiometric amount of H2SO4 as exfoliating agents in the mechanochemical treatment of graphite. It was established that the lateral dimension of the predominantly monolayer particles of such graphenes amounts to 100-500 nm and decreases with increase of the degree of oxidation. It was shown that various oxygen-containing groups formed as a result of interaction of the nanostructured graphite with atmospheric oxygen and water are present on the surface of the obtained graphenes. It was found that the initial high specific discharge capacity of graphene oxide is reduced during charge–discharge cycling as a result of the irreversibility of the reduction of the oxygen-containing groups and is stabilized at 90 A·h/kg.

Effect of Carbon Nanotube Functionalization on the Structure and Electrochemical Characteristics of Their Hybrid Nanocomposites with Polyaniline and Polypyrrole

Hybrid nanocomposites were prepared on the basis of polyaniline (PAn) and polypyrrole (PPy) with functionalized multiwall carbon nanotubes (CNTs). It was shown that the method of functionalization of the CNT and the nature of the polymer have a substantial effect on the structure and electrochemical characteristics of the synthesized nanocomposites. It was established that the conductivity and the capacity characteristics of the PPy/CNT nanocomposites are determined largely by the content of carbon nanotubes, whereas for the PAn/CNT materials they are also determined by the method of functionalization of the CNT. It was shown that the highest capacity (366 and 294 F/g) is characteristic of the nanocomposites based on PAn and CNT (N-CNT) functionalized with the surface catalyst Aliquat 336.

Effect of synthesis conditions and doping of mesoporous tin dioxide on the properties of electrodes for rechargeable lithium-ion batteries based on it

We have conducted a study of the effect of synthesis conditions and doping of tin dioxide-based mesoporous materials on the electrochemical characteristics of electrodes for rechargeable lithium-ion batteries based on them. The mesoporous materials were synthesized in the presence of templates (the cationic surfactant CTABr and the nonionic Pluronic F127) in aqueous and ethanol media; In2O3 and SiO2 were used as the dopants. We have studied the characteristic features of the effect of the synthesis conditions on the thermal stability, surface area, and pore volume for the materials obtained. The initial capacity of the lithium-ion battery based on the microporous material containing SiO2 was 507 mA∙h∙g–1, where the capacity decreased by 11% after 30 charge/discharge cycles.