Elementary processes of electro mass transfer in the nanocomposite polymer electrolyte system by pulse field gradient, spin echo NMR spectroscopy and the high-resolution NMR method together with electrochemical impedance spectroscopy are examined. The new nanocomposite polymer gel electrolytes consisted of polyethylene glycol diacrylate (PEGDA), salt LiBF₄ and 1—ethyl—3—methylimidazolium tetrafluoroborate (EMIBF₄) and SiO₂ nanoparticles. Kinetics of the PEGDA matrix formation was studied by isothermal calorimetry. The flexible polymer–ionic liquid films were studied by IRFT spectroscopy, differential scanning calorimetry and temperature gravimetric analysis. The total conductivity in these systems was about 10⁻⁴ S cm⁻¹ (−40 °C), 10⁻³ S cm⁻¹ (25 °C) and 10⁻² S cm⁻¹ (100 °C). The method of quantum-chemical modeling of the interaction of SiO₂ nanoparticles with ions showed the advantage of the mixed adsorption process, in which a negatively charged surface layer is formed from Li⁺ BF₄^— ions on silicon dioxide particles and then from ions of the ionic liquid EMI⁺ BF₄⁻. These electrolytes are promising for use both in lithium power sources and in supercapacitors. The paper shows preliminary tests of a lithium cell with an organic electrode based on a pentaazapentacene derivative for 110 charge–discharge cycles.

The effect of the composition of liquid electrolytes in the bulk and at the interface with the LiFePO₄ cathode on the operation of a solid-state lithium battery with a nanocomposite polymer gel electrolyte based on polyethylene glycol diacrylate and SiO₂ was studied. The self-diffusion coefficients on the 7Li, 1H, and 19F nuclei in electrolytes based on LiBF₄ and LiTFSI salts in solvents (gamma-butyrolactone, dioxolane, dimethoxyethane) were measured by nuclear magnetic resonance (NMR) with a magnetic field gradient. Four compositions of the complex electrolyte system were studied by high-resolution NMR. The experimentally obtained ¹H chemical shifts are compared with those theoretically calculated by quantum chemical modeling. This made it possible to suggest the solvate shell compositions that facilitate the rapid transfer of the Li⁺ cation at the nanocomposite electrolyte/LiFePO₄ interface and ensure the stable operation of a solid-state lithium battery.

The reversibility of electrode reactions in Li//LiFePO₄ cells with two liquid electrolyte compositions modified by 15-crown-5 and benzo-15-crown-5 is tested. By cycling Li//LiFePO₄ batteries, it is shown that crown ethers enhance the stability of discharge capacity and Coulomb efficiency in both electrolytes: 1 М LiPF₆ in ethylene carbonate/dimethyl carbonate (1 : 1) and 1 M LiN(CF₃SO₂)₂ in dioxolane/dimethoxyethane (2 : 1), which differ by their ability to form solid-electrolyte layers on the electrode surface. The energy of Li⁺-ion transport through the layer of crown ethers under study is modeled by quantum-chemical methods. The conclusions of quantum chemical calculations well agree with the results of electrochemical measurements.

The methods of 7Li spin relaxation and pulsed field gradient NMR were used to reveal the features of local transport of Li+ cations in two polymer gel electrolytes containing an ionic liquid, the salt LiBF4 and a solvent, diglyme (G2) or tetraglyme (G4). It was found that the macroscopic mass transfer of Li+ cations is affected by their solvate environment from both glyme solvents and the polymer matrix. In the presence of G4, a denser three-dimensional network is formed, hindering the transport of all ions.

New lithium solid–state batteries with an asymmetric polymer nanocomposite electrolyte based on polyethylene glycol diacrylate and SiO₂ have been developed, the use of which made it possible to obtain the theoretical capacity of the LiFePO₄ cathode. To achieve non-dendritic and non-corrosive highly reversible deposition/dissolution of lithium, the nanocomposite polymer solid state electrolyte can be positioned on the lithium anode side. In turn, the so-called “liquid-phase therapy” can facilitate the simple intercalation of lithium into the olivine crystal structure to ensure high charge/discharge cycleability of the battery by applying microscopic amounts of liquid electrolyte to the surface of the porous LiFePO₄ cathode. Electrolytes based on LiBF₄ and LiN(CF₃SO₂)₂ salts in gamma-butyrolactone, dioxolane, and dimethoxyethane were investigated by pulsed field gradient NMR on ⁷Li nuclei and by electrochemical impedance. It has been shown that the “liquid-phase therapy” of the polymer electrolyte/porous cathode interface effectively increases the electrode reaction only in the case of a liquid electrolyte composition of 1 M LiN(CF₃SO₂)₂ in a mixture of dioxolane and dimethoxyethane (1 : 2 vol). The nanocomposite polymer gel electrolyte, which is a 1 M solution of LiBF₄ in gamma-butyrolactone, on the other hand, turns the border non-conductive. The calculated binding energies of the solvate complexes of the lithium cation with the surface of the SiO₂ nanoparticles and the measured lithium self-diffusion coefficients suggest that solvation at the nanocomposite interface in 1 M LiN(CF₃SO₂)₂ in dioxolane/dimethoxyethane is facilitated, whereas solvation at the interface in 1 M LiBF₄ in gamma-butyrolactone is challenging.