T. L. Kulova

Electrode nanomaterials for lithium-ion batteries

The state-of-the-art in the field of cathode and anode nanomaterials for lithium-ion batteries is considered. The use of these nanomaterials provides higher charge and discharge rates, reduces the adverse effect of degradation processes caused by volume variations in electrode materials upon lithium intercalation and deintercalation and enhances the power and working capacity of lithium-ion batteries. In discussing the cathode materials, attention is focused on double phosphates and silicates of lithium and transition metals and also on vanadium oxides. The anode materials based on nanodispersions of carbon, silicon, certain metals, oxides and on nanocomposites are also described. The bibliography includes 714 references.

Sol–gel fabrication and lithium insertion kinetics of the Mo-doped lithium vanadium oxide thin films Li1+xMoyV3−yO8

Abstract Thin films of molybdenum-doped vanadium oxide bronzes Li 1+ x Mo y V 3− y O 8 (0≤ y ≤0.20) were synthesized by sol–gel process in metal alkoxides solution. The influence of the applied hydrolysis ratio on the particles shape and size, their location and orientation on the substrate has been investigated. The variation of both material morphology and unit cell geometry changes the lithium galvanostatic discharge capacity significantly. There are two factors resulted in increasing of material capacity: decreasing of (100) crystallite faces contribution to the whole particle surface and increasing of Mo-doping level y . Lithium chemical diffusion coefficient and exchange current density on the interface “film/aprotic Li + -conducting electrolyte” were determined on materials having optimized Mo-doping level and particle morphology at various Li concentrations in the host structure by electrochemical impedance spectroscopy.

Growth of thin vanadia nanobelts with improved lithium storage capacity in hydrothermally aged vanadia gels

A process of hydrothermal ageing of vanadia gels yields 10–20 nm thick and 90–100 nm wide nanobelts exceeding 10 microns in length. The diminished thickness and networking of anisotropic nanobelts lead to lithium intercalation capacities exceeding 450–500 mA h g−1 at a C/25 rate. The observed morphology features depend essentially on preparation conditions and allow to assume that this particular route results in a suitable morphology of nanobelts via chemical bond rearrangement in the course of olation and oxolation in the aged bulk gel. “Unzipping” of the layered structure of the precursor gel into single-crystalline nanobelts, and optimization of post-hydrothermal processing resulted in nanomaterials with enhanced electrochemical characteristics, making vanadia gels a precursor of choice for simple preparation of new battery nanomaterials.

Lithium Diffusion in Materials Based on LiFePO 4 Doped with Cobalt and Magnesium

We have studied lithium intercalation/deintercalation kinetics in magnesium- and cobalt-doped lithium iron double phosphates in a cathode material for lithium ion batteries. The results demonstrate that the incorporation of divalent cations reduces the charge and discharge capacities of the samples, the effect being stronger in the magnesium-doped materials. In addition, magnesium doping markedly increases the resistivity of the material in both the lithiated and delithiated states, whereas the resistivity of the cobalt-doped materials is considerably lower in comparison with the undoped material, which leads to an increase in the charging/discharging rate of batteries despite the marked increase in particle size. These findings can be understood in terms of different doping mechanisms: it seems likely that cobalt substitutes for iron, whereas magnesium is accommodated predominantly in the lithium site.

Influence of a carbon coating on the electrochemical properties of lithium-titanate-based nanosized materials

The influence of treatment temperature and a carbon precursor on the formation of a Li4Ti5O12-based anodic material and its electrochemical characteristics as part of a lithium-ion battery have been investigated. It is demonstrated that the variation of annealing temperature and the addition of saccharose prior to final annealing allow for the variation of Li4Ti5O12 particle sizes. At annealing temperatures of 400–600°C, lithium titanate forms as part of an anatase titanium oxide composite. Thermogravimetry, Raman spectroscopy, and electrochemical testing results show that a preannealing of the sample at temperatures of no less than 400°C and the addition of saccharose with subsequent annealing in an inert atmosphere are required for the formation of a conducting carbon coating. The formation of the carbon coating facilitates the inclusion of the anatase phase into the charging and discharging processes, which significantly increases the electrochemical capacity of samples obtained at low annealing temperature. The highest electrochemical capacity values (140 mA h/g) of anodic Li4Ti5O12 samples were obtained only after annealing at 800°C. We note the unexpected formation of carbon nanotubes in samples with a final annealing temperatures of 600°C.

Effect of particle size on the conductive and electrochemical properties of Li2ZnTi3O8

We have studied the effect of final annealing temperature on the formation of lithium zinc titanate, its electrical conductivity, and its electrochemical performance. Li2ZnTi3O8 has been shown to form in a wide range of annealing temperatures, from 673 to 1073 K. Its particle size increases systematically with increasing annealing temperature, whereas its conductivity decreases. The highest electrochemical capacity at low currents is offered by the materials annealed at 773 and 873 K, and the highest cycling stability is offered by the material prepared at 873 K.

Electrochemical properties of Li 4 Ti 5 O 12 /C and Li 4 Ti 5 O 12 /C/Ag nanomaterials

We have prepared and characterized lithium titanate-based anode materials, Li4Ti5O12/C and Li4Ti5O12/C/Ag, using polyvinylidene fluoride as a carbon source. The formation of such materials has been shown to be accompanied by fluorination of the lithium titanate surface and the formation of a highly conductive carbon coating. The highest electrochemical capacity (175 mAh/g at a current density of 20 mA/g) is offered by the Li4Ti5O12-based anode materials prepared using 5% polyvinylidene fluoride. The addition of silver nanoparticles ensures a further increase in electrical conductivity and better cycling stability of the materials at high current densities.

Sodium-Ion Batteries (a Review)

State-of-the-art in the studies of sodium-ion batteries is discussed in comparison with their deeper developed lithium-ion analogs. The principal problem hindering the development of competitive sodium-ion batteries is the low effectiveness of the electrode materials at hand. The principal efforts in the formation of anodes for the sodium-ion batteries are reduced to the development of materials based on carbon, metals, alloys, and transition metal oxides. Cathode materials are searched among oxides (first of all, layered) and salt systems. Synthesis of electrolytes for the sodium-ion batteries is not sufficiently attended to. Nowadays it is sodium salt solutions in organic solvents that are dominated; however, polymer and solid electrolytes with sodium conductivity may be thought of as very perspective. Reference list contains 584 items.

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.

Synthesis of LiFePO4 nanoplatelets as cathode materials for Li-ion batteries

Lithium iron phosphate with plateletlike morphology (length of 200 nm and thickness of 15–25 nm) was obtained using the solvothermal method. The resulting particles have the smallest dimension along the 1D channels, which are paths of Li+ ion migration. The discharge capacity of composite based on synthesized LiFePO4 and carbon was equal to 160 mAh/g at a current density of 20 mA/g and 80 mAh/g at a current density of 800 mA/g.