Galvanostatic Intermittent Titration Technique Reinvented: Part II. Experiments

Following a critical review of the galvanostatic intermittent titration technique in Part I, here we experimentally demonstrate how to extract chemical diffusivity with a modified method. We prepare dense bulk samples that ensure diffusion-limitation. We utilize the scaling with t relax + τ − t relax (t relax: relaxation time; τ: pulse duration), avoiding problems with composition-dependent overpotentials. The equilibrium Nernst voltage is measured separately using small porous particles. This separation between the diffusion measurement and the titration procedure is critical for performing each measurement in a reliable setting. We report the chemical diffusion coefficients of LixNi1/3Mn1/3Co1/3O2 and their activation energy. We extract ionic conductivity and compare it with total conductivity to confirm ion-limitation in chemical diffusion. The measurements suggest that the time scale for diffusion in typical Li-ion battery particles could be much shorter than that of the intercalation/deintercalation processes at the particle surface (Biot number less than 0.1).

Ionic Conductivity of Ce0.91Ca0.09O2 as an Electrolyte for Intermediate Temperature Solid Oxide Fuel Cells

The search for new cost-effective electrolyte materials for IT-SOFC towards its mass scale commercialization has gained momentum in recent years. The Ca- doped ceria having composition Ce0.91Ca0.09O2 was prepared using the facile conventional solid-state method. The structural and electrical properties of low sintered ceramic samples have been characterized by X-ray diffraction (XRD), UV–VIS diffuse reflectance spectroscopy (DRS) and A.C. impedance technique respectively. The oxide ion conductivity was measured between the temperatures 573 K−973 K in air. The obtained results showed that total conductivity is mainly dependent on the grain boundary effect. The nanocrystalline Ce0.91Ca0.09O2 exhibited the high total ionic conductivity of 7.36  103 S cm1 at 973 K with a lower activation energy of 0.96 eV. The obtained results highlight the use of cost-effective dopant in ceria lattice to develop commercially viable electrolyte materials for IT-SOFC.

Thermal Conductivity Structure and Anisotropy of the Colossal Carbon Mesotubes

A model of a tube with a square cross-section was compiled for the mathematical analysis of the mesotube in Cartesian coordinates, with the selection of an element of a representative volume. To estimate the effective thermal conductivity of the structure, the generalized theory of conductivity with linearization of heat flux streamlines was used. The presence of anisotropy leads to the division of the problem into a separate estimate of the longitudinal and transverse thermal conductivity. The cross-section of the model was divided into elementary sections by a system of auxiliary adiabatic and isothermal planes, then the sections of the model were presented in the form of thermal resistances connected in chains - electrical circuits. Using the analogy of the identity of thermal and electrical resistances, the total conductivity of the sections and the effective thermal conductivity of the structure were determined. This methodology satisfies the test for limit transitions.

Surface and Bulk Oxygen Kinetics of BaCo0.4Fe0.4Zr0.2−XYXO3−δ Triple Conducting Electrode Materials

Triple ionic-electronic conductors have received much attention as electrode materials. In this work, the bulk characteristics of oxygen diffusion and surface exchange were determined for the triple-conducting BaCo0.4Fe0.4Zr0.2−XYXO3−δ suite of samples. Y substitution increased the overall size of the lattice due to dopant ionic radius and the concomitant formation of oxygen vacancies. Oxygen permeation measurements exhibited a three-fold decrease in oxygen permeation flux with increasing Y substitution. The DC total conductivity exhibited a similar decrease with increasing Y substitution. These relatively small changes are coupled with an order of magnitude increase in surface exchange rates from Zr-doped to Y-doped samples as observed by conductivity relaxation experiments. The results indicate that Y-doping inhibits bulk O2− conduction while improving the oxygen reduction surface reaction, suggesting better electrode performance for proton-conducting systems with greater Y substitution.

Energy-efficient variable frequency asynchronous electric drive

Currently, there are quite a large number of various scientific papers on the creation of a controlled asynchronous engine and the optimization of its modes, and the availability of acceptable results for practical implementation, but there is still no single generally accepted approach to solving the problem. In this regard, the issue of synthesis of scalar control systems that provide the minimum value of one or another criterion of energy efficiency is relevant. In this paper, we consider the obtained mathematical model of an asynchronous engine (AE), which differs from the known ones in that the parameters of the substitution scheme are expressed in terms of the stator and rotor conductivities. The energy characteristics of the AE in the sliding function are obtained, which make it possible to determine the dependences of the active and reactive components of the AE current and the possibility of their redistribution within the nominal value of the AE phase current. The principle of optimal frequency-current control of AE is formulated, which differs from the known ones in that, as an energy efficiency indicator, the value of the maximum energy efficiency of AE is used, expressed as the ratio of the active resistance of the rotor circuit to the total conductivity of the AE phase.

Properties of Barium Cerate-Zirconate Thin Films

In this work, we review several experimental results showing the electrical properties of barium cerate-zirconate thin films and discuss them in view of the possible influence of various factors on their properties. Most of the presented Ba(Ce, Zr, Y)O3 thin films were formed by the pulsed laser deposition (PLD) technique, however thin films prepared using other methods, like RF magnetron sputtering, electron-beam deposition, powder aerosol deposition (PAD), atomic layer deposition (ALD) and spray deposition are also reported. The electrical properties of the thin films strongly depend on the film microstructure. The influence of the interface layers, space-charge layers, and strain-modified layers on the total conductivity is also essential but in many cases is weaker.

Densification of a NASICON-Type LATP Electrolyte Sheet by a Cold-Sintering Process

A NASICON-type Li1.3Al0.3Ti1.7(PO4)3 (LATP) electrolyte sheet for all-solid-state batteries was fabricated by a cold sintering process (CSP). The microstructure of the LATP sheet was controlled to improve the wettability which is an essential factor in CSP. The porous sheets of LATP were prepared by calcination the green sheets to remove the organic components and form the porous structure. By the CSP using the porous sheets, the densification of grain boundary was observed and further densified with increasing reaction time. The total conductivity of the prepared LATP sheet was improved from 3.0 × 10−6 S/cm to 3.0 × 10−4 S/cm due to the formation of necks between the particles at the grain boundary.

Accelerated design and discovery of perovskites with high conductivity for energy applications through machine learning

We use machine learning tools for the design and discovery of ABO3-type perovskite oxides for various energy applications, using over 7000 data points from the literature. We demonstrate a robust learning framework for efficient and accurate prediction of total conductivity of perovskites and their classification based on the type of charge carrier at different conditions of temperature and environment. After evaluating a set of >100 features, we identify average ionic radius, minimum electronegativity, minimum atomic mass, minimum formation energy of oxides for all B-site, and B-site dopant ions of the perovskite as the crucial and relevant predictors for determining conductivity and the type of charge carriers. The models are validated by predicting the conductivity of compounds absent in the training set. We screen 1793 undoped and 95,832 A-site and B-site doped perovskites to report the perovskites with high conductivities, which can be used for different energy applications, depending on the type of the charge carriers.

Investigation of an asynchronous electric drive with frequency control

Currently, there are quite a large number of various scientific papers on the creation of a controlled asynchronous motor and optimization of its modes, and the availability of acceptable results for practical implementation, but there is still no single generally accepted approach to solving the problem. In this regard, the issue of synthesis of scalar control systems that provide the minimum value of a particular energy efficiency criterion is relevant. In this paper, we consider the obtained mathematical model of an asynchronous motor (AD), which differs from the known ones in that the parameters of the substitution circuit are expressed in terms of the stator and rotor conductivities. The energy characteristics of the AD in the sliding function are obtained, which make it possible to determine the dependences of the active and reactive components of the AD current and the possibility of their redistribution within the nominal value of the AD phase current. The principle of optimal frequency-current control of AD is formulated, which differs from the known ones in that, as an energy efficiency indicator, the value of the maximum energy efficiency of AD is used, expressed as the ratio of the active resistance of the rotor circuit to the total conductivity of the AD phase. Keywords: ASYNCHRONOUS MOTOR, ASYNCHRONOUS ELECTRIC DRIVE, EFFICIENCY, POWER FACTOR, ENERGY EFFICIENCY, CIRCUIT CONDUCTIVITY, REPLACEMENT CIRCUIT, SLIP

Co-Precipitation Synthesis and Electrochemical Properties of NASICON-Type Li1.3Al0.3Ti1.7(PO4)3 Solid Electrolytes

NASICON-type solid-state electrolytes have gathered wide attention to meet the requirements of high-energy-density batteries. In this study, Li1.3Al0.3Ti1.7(PO4)3 (LATP) were synthesized through co-precipitation method. The composition, phase transformation, microstructure and particle size of LATP powder were characterized in detail. Pure LATP without any detectable secondary phases can be obtained at 800 ℃ with size about 590 nm. The relatively dense surface microstructure for LATP ceramics was clearly observed. In addition, the ionic conductivities of LATP pellets increased at first and then decreased with the increased sintering temperature and time. Owing to the highest relative density (95.6%), LATP (sintered at 900 ℃ for 6h, LATP-9006) exhibited a highest total conductivity of 2.19×10− 4 S/cm with a low activation energy of 0.32 eV. The results suggest that co-precipitation synthesized LATP-9006 ceramic electrolyte could be a promising alternative towards achieve a safe solid-state battery. Moreover, the co-precipitation method is suitable for the preparation of other oxide ceramic electrolytes.