It is studied how the treatment of a metal lithium surface with a 1 M LiN(CF3SO2)2 solution in the 1,3-dioxolane/1,2-dimethoxyethane (2 : 1) mixture affects the resistance of the interphases formed by lithium with the polymer and nanocomposite electrolytes based on the 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid. The liquid-phase therapy is shown to reduce the resistance at the Li/electrolyte interphase by a factor of 2.5 at room temperature and extend the working temperature range to –30°C. The introduction of TiO2 nanoparticles into the polymer electrolyte, along with the liquid-phase therapy of both the cathode and the Li-anode, provides a high and stable discharge capacity of the Li//LiFePO4 battery for 100 charge–discharge cycles.

A comparative study of the influence of TiO 2 and SiO 2 nanoparticles on the physicochemical properties of nanocomposite polymer electrolytes (NPEs) based on polyethylene glycol diacrylate, the LiBF 4 salt, the ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF 4 ), and ethylene carbonate has been carried out. The stability of NPE films was studied by thermogravimetric analysis, the distribution of nanoparticles and ions was determined by Raman spectroscopy and microscopy, and conductivity was measured using the electrochemical impedance method. It has been shown that SiO 2 -based NPEs have the best thermal stability and conductivity characteristics.

Electrolytes providing a high capacity (up to 400 mA h g−1) of an organic anode material, which is based on a polymeric product of a condensation of triquinoyl with an aromatic amine, in a lithium half-cell have been developed and studied. A complex study of a 1 M solution of LiPF6 in tetraglyme, which belongs to the gelled electrolytes, has been carried out. It is shown that practically no solid electrolyte interphase is formed at the interfaces with lithium and organic electrodes, which makes it possible to monitor the reaction occurring on the electrodes.

Design of prototype for a solid-state lithium battery with LiFePO4 cathode and nanocomposite polymer gel electrolyte is developed. The concept of an asymmetric solid-state electrolyte was used for better compatibility of the solid electrolyte/electrode interface. According to the concept, a silica-nanoparticle-based transition layer is used facing the lithium anode; a liquid electrolyte layer; facing the cathode. The composition of the liquid electrolyte is optimized. 1 M lithium bis-trifluoromethanesulfonyl imide solution in a dioxolane/dimethoxyethane mixture (2 : 1) is shown to be the best electrolyte for the forming of a transition ion-conducting layer between the nanocomposite polymer gel electrolyte and the LiFePO4 cathode; 1 M LiBF4 in gamma-butyrolactonee, for the synthesis of a cross-linked polymer gel electrolyte, as an inert liquid medium for the radical-polymerization reaction. Comparative tests of Li/LiFePO4 battery prototypes showed the maximal capacity of the LiFePO4 cathode to be as large as 170 mA h g–1 when using a nanocomposite polymer gel electrolyte based on polyethylene glycol diacrylate with 6 wt % SiO2 with asymmetric interface.

Nanocomposite polymer electrolytes based on the system poly(vinylidene fluoride-co-hexafluoropropylene)–liquid electrolyte 1 mol/L LiBF4 in gamma-butyrolactone which is modified by introducing up to 10 wt % of SiO2 nanopowder (an average particle size of 7 nm) are synthesized and characterized. The introduction of SiO2 nanoparticles worsens the elasticity of films but increases their fracture stress to 24 MPa. The conductivity of the nanocomposite electrolytes containing SiO2 nanoparticles is higher than that without SiO2 and attains 3.7 mS/cm at 20°C for the electrolyte containing 1.25 wt % SiO2. Upon the introduction of SiO2 nanoparticles, the electrochemical stability of electrolytes grows by 0.50–0.85 V and attains 6.7 V relative to Li/Li+.

Nanocomposite polymer electrolytes represent a perspective class of polymer electrolytes for electrochemical devices in which nanodisperse filler is introduced to the “solvating matrix + lithium salt” base composition. This three-section paper reviews studies devoted to the preparing and investigating of different types of novel nanocomposite polymer electrolytes for lithium power sources carried out for the last 15 years. Its first section is devoted to the solid nanocomposite polymer electrolyte consisting of polyethylene oxide, lithium salt, and nanodisperse filler (Al 2 O 3 , TiO 2 , SiO 2 , etc.); the second section, to nanocomposite polymer membranes based on the polyvinylidene fluoride- co -hexafluoropropylene that can be used as a substitute for inert polyolefine separator of polypropylene, polyethylene, or their alternating layers. It is this type of the nanocomposite polymer electrolytes that is the most perspective one; the great majority of publications are dedicated to this electrolyte. The third section of the review covers the studies of the nanocomposite polymer electrolytes based on different polymers, oligomers, and co-polymers prepared by different methods. Nanoparticles of Al 2 O 3 , TiO 2 , SiO 2 , ZnO, MgO, Fe 3 O 4 , Ca 3 (PO 4 )2, ZrO 2 , clay, ferroelectric ceramics SrBi 4 Ti 4 O 15 , a compound SO 4 2- –ZrO 2 , molecular sieves, nanochitin, etc., are discussed as possible additives to the nanocomposite polymer electrolytes. The reference list contains 101 items.

Quantum chemical calculations of molecular structures and magnetic shielding constants for H and C nuclei were performed by the density functional method. The structures of the polyester diacrylate degradation products formed under sonication in the presence of TiO2 or Li2TiO3 nanoparticles in the electrolyte polyester diacrylate—LiClO4—ethylene carbonate—nanopowder were proposed based on agreement of the goodness-of-fit with the experimental NMR spectra of the polymer electrolytes. The surface centers on TiO2 and Li2TiO3 under the ultrasonic energy absorption conditions were concluded to catalyze the unexpected metathesis of σ-C—H bonds in the α-positions to the carbonyl group.

To optimize the compositions of liquid organic electrolytes for lithium power sources, it is useful to have the dependence of the conductivity on the lithium salt concentration in a convenient analytical form. An empirical formula was suggested on the basis of the modified Kohlrausch equation for the concentration dependence of the conductivity of organic electrolytes in the vicinity of a maximum. The accuracy of this equation was checked on solutions of LiBF4 in propylene carbonate; LiClO4 in ethylene carbonate; and LiPF6 in ethylene carbonate/diethyl carbonate (1: 1), ethylene carbonate/ethylmethyl carbonate (1: 1), and ethylene carbonate/methyl acetate (1: 1) at different temperatures. The calculated data are in good agreement with experiment for all the systems. The new empirical formula allows the determination of the maximum conductivity of organic electrolytes based on a few points with good accuracy, which is very important in choosing the electrolyte salt concentration in practice.

Синтезированы и исследованы сополимерные сетчатые электролиты на основе полиэфирдиакрилатов с различными строением и длиной цепи – полиэфирдиакрилата и диакрилата полиэтиленгликоля. Найдено, что оптимальная матрица для ионного транспорта в электролите формируется на основе только одного вида олигомера. Исследовано влияние добавок нанопорошка TiO2 ( 60 нм) на проводимость сополимерного электролита. Показано, что при добавлении 10 мас. % TiO2 проводимость при 30°С повышается на порядок, эффективная энергия активации проводимости при этом уменьшается на 20%. При повышении температуры подвижность полимерных цепей увеличивается и вклад наночастиц TiO2 в ионный транспорт дает только 0.5 порядка величины проводимости при 100°С. Увеличение проводимости полимерного электролита при введении TiO2, по-видимому, обусловлено образованием более подвижного состояния иона лития вблизи поверхности наночастицы, что было показано методом ЯМР с импульсным градиентом магнитного поля на ядрах 7Li.

Network copolymer electrolytes were synthesized from polyether (polyester) diacrylates with different structures and chain lengths of polyester diacrylate and polyethylene glycol diacrylate. The optimum matrix for ion transport in the electrolyte was formed from only one type of oligomer. The influence of TiO2 nanopowder additions (∼60 nm) on the conductivity of the copolymer electrolyte was studied. The addition of 10 wt % TiO2 led to an increase in the conductivity by an order of magnitude at 30°C; the effective activation energy decreased by 20%. At elevated temperatures, the mobility of polymer chains increased and the contribution of TiO2 nanoparticles in ion transport was only half of the order of magnitude of the conductivity at 100°C. The increase in the conductivity of the polymer electrolyte after the addition of TiO2 was presumably caused by the formation of a more mobile state of the lithium ion near the nanoparticle surface, as shown by pulsed field gradient (PFG) 7Li NMR.

New polymer gel electrolytes containing superbranched polymers were developed. The gel electrolyte containing 20 wt % superbranched polymer, 6 wt % methylmethacrylate, 4 wt % triethyleneglycol dimethacrylate, and 70 wt % 1 M propylene carbonate solution of LiClO4 was found to have a maximum conductivity of ∼9 × 10−4 S/cm at room temperature and an effective activation energy of conductivity of 18 kJ/mol. The physicochemical properties of the gel electrolyte were correlated with its composition using electrochemical impedance spectroscopy, thermomechanics, and differential scanning calorimetry. The glass-transition temperature of these electrolytes depended only on the liquid electrolyte content and decreased from −80 to −93°C when the concentration of 1 M LiClO4/PC increased from 60 to 80 wt %. As the content of the superbranched polymer increased from 0 to 20 wt % at positive temperatures, the modulus of elasticity decreased, while the conductivity increased. When the content of the superbranched polymer increased at the expense of the liquid electrolyte, the conductivity of the system decreased.

Ion transport in the new three-dimensional network polymer electrolytes that are completely amorphous in the solid state has been studied on the example of the matrix model with a monomer—polyethylene glycol diacrylate, cross-linked by radical polymerization. The nature of ionic conductivity in solid polymer electrolytes based on polyethylene glycol diacrylate at different concentrations of salt LiClO4 was studied by methods of electrochemical impedance, differential scanning calorimetry analysis, Fourier transform infrared spectroscopy and quantum chemical modeling. The maximum value of conductivity in the range of 20–100 °C is realized at 20 wt% content of LiClO4. The reason for the low conductivity of the SPE studied is the small degree of dissociation of contact ion pairs. At the increase in the salt content associates of contact pairs Li+ClO 4 − , dimers and trimers (at LiClO4 >20 wt%) are formed. The appearances of trimers are accompanied by a decrease in conductivity due to lowering of contact pair content.

New polymer electrolytes based on poly(ester diacrylate) (PEDA), LiClO 4 , and additives of ethylene carbonate (EC) have a Li + ion conductivity comparable with that of liquid electrolytes. The conductivity first decreases by an order of magnitude at an EC content of ∼5 wt.% and then increases by three orders of magnitude at 55 wt.% EC. To understand the nature of this extreme dependence, a comprehensive study using IR spectroscopy and quantum chemical modeling was performed. It was found that the changes in the IR spectra with an increase in the EC content were stepwise to form at final stage the same absorption peaks that were observed for the IR spectra of LiClO 4 solutions in EC. The density functional theory studies of the energy and structures of mixed Li + complexes and LiClO 4 with EC and PEDA, which was modeled by oligomers H-((CH 2 ) 2 COO(CH 2 ) 2 O) n -CH 3 ( n ≤ 10) showed a stronger binding of the lithium ion with the polymer matrix in the mixed complexes with one EC molecule at a low content of EC resulting, most likely, in a decrease in the conductivity. Less stable mixed complexes with three EC molecules can be formed with an increase in the EC fraction and they become unstable in EC excess because of the transition of the Li + ions to solvate complexes containing only EC molecules.

The structure and dynamics of polymer network electrolytes for lithium batteries based on polyester diacrylate, lithium perchlorate, and ethylene carbonate were studied. The polyester diacrylate contained diacrylate units, 2-hydroxyethyl acrylate units, and product of dimerization of the initial monomer (to 10% by mass). An (1) H NMR study revealed three phases corresponding to ethylene carbonate in the polymer, ethylene carbonate bound to Li+ ions, and cyclic dimer of 2-hydroxyethyl acrylate.

The processes of ionic conductivity are studied in a polymer gel electrolyte synthesized based on polyesterdiacrylate and a low-molecular solvent ethylene carbonate. The self-diffusion coefficients of solvent molecules and Li+ cations are measured by the NMR with the pulsed magnetic field gradient. The Li+ self-diffusion coefficients increase with the increase in the solvent content and are independent of the diffusion time in the interval from 10 to 1600 ms. The latter values imply the absence of limitations for the translational mobility of lithium ions in the spatial range from 10−7 to 10−5 m. Based on the Nernst-Einstein equation, the ionic conductivities are calculated and compared with the experimental conductivities measured by the impedance method. These values coincide for high contents of solvent; for low ethylene carbonate concentrations, the calculated conductivities much exceed the experimental values.