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The COVID-19 pandemic has had a very serious impact on societies and caused large-scale economic changes and death toll worldwide. The first cases were detected in China, but soon the virus spread quickly worldwide and the intensity of newly reported infections grew high during this initial period almost everywhere. Later, despite all imposed measures, the intensity shifted abruptly multiple times during the two-year period between 2020 and 2022 causing waves of too high infection rates in almost every part of the world. To target this problem, we assume the data heterogeneity as multiple consecutive regime changes. The research study includes the development of a model based on automatic regime change detection and their combination with the linear birth-death process for long-run data fits. The results are empirically verified on data for 38 countries and US states for the period from February 2020 to April 2022. Finally, the initial phase (conditions) properties of infection development are studied.

Lithium-manganese-cobalt oxides, LiMn 2-x Co x O 2 with 0 < x < 0.2 were synthesized by a solid-state multi-steep reaction, in air, from a mixed manganese-cobalt oxide with lithium hydroxide. The samples were characterized by X-ray diffraction and electrochemical tests. The crystal structure of the obtained compounds is spinel-related. The discharge capacity of an Li/LiMn 2-x Co x O 2 cell with x = 0.1 was 114 mAh/ g for the fifth discharge and stayed almost the same at the cycle no. 100 - 107 mAh/g - related to the cathode capacity. The demonstrated cycling stability for 100 cycles reaches 99.93%. The improvement in cycleability can be attributed to the stabilizing role of Co 3+ ions, substituting Mn 3+ in the initial structure.

The synthesis of LiNiO2 in air is studied by means of X-ray diffraction (XRD) characterization using a new fast method based on the splitting of the (108) and (110) peaks and the depth of the minimum between these peaks. From the evolution of these XRD parameters during the heat treatment of the starting mixture of LiOH and NiO the optimum synthesis time is determined, where the separation angle has a maximum, implying a good stoichiometry and low cation disorder; the minimum between the peak is deepest, indicating a better crystallinity. Selected samples of LiNiO2 were cycled as cathodes in laboratory-coin cells between constant charge and discharge end voltages at a constant current. It is found that the capacity decay rate is related to the phase transitions occurring during cycling. This rate is dependent on the minimum lithium content x in LixNi2 − xO2 at the end of charge. As the cycling proceeds xmin increases despite that the end charge voltage is kept constant, whereby the capacity decay rate diminishes.

LiMn 2 O 4 spinel samples, synthesized by the reaction of Li 2 CO 3 and MnCO 3 in air in several steps, have been evaluated as the electrode materials in 4 V lithium-ion cells. It was shown that the synthesis in the temperature range 500–750 °C leads to compounds with very poor electrochemical behavior. This is explained by a model of the chemistry of LiMn 2 O 4 preparation proposed by Howard. On the basis of this model a new scheme of LiMn 2 O 4 preparation is proposed. It was established experimentally that compounds with very high electrochemical characteristics can be obtained by a stepwise synthesis process, proceeding at three narrow temperature intervals.

Natural Brazilian graphite has been investigated as a reversible Li+-intercalating electrode for lithium-ion cells. Its performance is greatly influenced by the electrode preparation technique. A short compacting time (1 s or less), when pressing the powders, increases the specific capacity because the porosity remains sufficiently high. Low pressures (

A method is described for the estimation of the volumetric specific capacity of balanced Li-ion cells. The effect of the material balance or the cathode/anode mass ratio, r, in Li-ion cells on the volumetric specific capacity, qv, of the electrode pair is studied in the example of a petroleum coke/LiNiO2 couple. The values of qv of several electrode pairs used in Li-ion cells, calculated on the basis of present experimental and previously published data are juxtaposed. A good agreement between calculated and experimentally determined qv values is found. The qv value of the natural graphite/LiNiO2 pair exceeds by nearly 28% that of the commercialized PFA-C/LiCoO2 pair, considered so far as the best available. This advantage will however be reduced by 30 to 50% in a real cell, when the volumes of all cell components are taken into account. The influence of r on the cycling stability is also demonstrated experimentally. The possibility of using unbalanced cells with moderately overcharged anodes appears feasible, while cells with precharged anodes from an auxiliary Li source seem impractical.

The properties of natural Brazilian graphite have been investigated in a three-electrode laboratory button cell containing 1 M LiPF 6 dissolved in ethylene carbonate-dimethyl carbonate (EC-DMC) as the electrolyte. The charge/discharge behaviour of the graphite is greatly affected by the preliminary treatments and techniques used for the preparation of the electrode. By optimizing these procedures, a specific capacity very close to the theoretical value can obtained. When using LiPF 6 /EC-DMC electrolyte, a high charge/discharge coulombic efficiency is observed.

The scaling-up problems connected with the LiMn2O4 synthesis were studied. A strong effect of the mass of the starting materials and of the air flow rate through the furnace during the synthesis on the specific capacity was observed. The increase of the batch amount brings about a reduction in the specific surface area of the product, which cannot be compensated by grinding because it leads to considerable reduction of its electrochemical utilization. The very fast or slow cooling of the synthesized material have a negative effect on the specific capacity. The process of preparation of LiMn2O4 spinel with high electrochemical performance is a rather complex procedure, but it is possible to obtain a product, which is capable to exchange reversibly up to 0.9 equiv. Li per mole.

Samples of LixNi2−xO2 (0.91

A preparation method of LiAl anodes by compression of foils of the two metals at room and elevated temperatures is described. The chemical diffusion coefficient of lithium in the LiAl anodes is measured as a function of the lithium concentration of the β-phase range. The cycleability of the anodes prepared by this method with and without manganese is studied in laboratory coin cells, with L x MnO 2 cathodes, as a function of the depth-of-discharge (DOD). The cycling efficiency of the Mn-free anodes at DOD = 22% is very low, 88.9%, while that of the anodes with 1.0 and 2.6% Mn is considerably higher: 95.5% at DOD 17% and 94.4% at DOD 38%, respectively.

The electrochemical properties of the lithium spinel Li1−xMn2O4 (0 < x < 1) synthesized by three different methods are discussed. The synthesis of spinel LiMn2O4 for secondary lithium cells should be performed at temperatures lower than 750 °C, since a thermal treatment above this limit can cause a significant chemical reduction and thus decrease its specific capacity. Moreover, the increase of the synthesis temperature above 750 °C leads to a considerable reduction of the specific surface area of the samples and correspondingly to deterioration of their utilization at high discharge rates. The use of λ-MnO2 produced by chemical oxidation of LiMn2O4 cannot be justified in real systems, since, despite the higher specific surface area of the chemically oxidized samples, they display lower mean discharge voltage and reversibility.

The effect of the starting products and the synthesis temperature on electrochemical parameters of Li 1− x Mn 2 O 4 (0 x 2 O 4 spinel for lithium cells operating at low and medium discharge rates is not essentially affected by the nature of the starting products. Use of chemically-obtained manganese dioxide, instead of electrochemically obtained one, or LiNO 3 and LiOH, instead of Li 2 CO 3 , displays significant advantages at high discharge rates. Thermal pretreatment of the reaction mixture in the temperature range of 350 to 550 °C improves the electrochemical behavior of the samples. Optimum results were obtained by a following reaction time of the main synthesis from 75 to 200 h at temperatures in the 650–750 °C range.

The composition and structure of layered compounds described by the general formula LixCr1 − yVyS2 (0 < y < 0.5), synthesized in potassium polysulphide melts, have been investigated. The electrochemical performance of these compounds with regard to their application in high-energy-density, secondary lithium batteries is discussed. It is found that when Cr3+ is replaced with V3+ in the range 0.1 < y < 0.5, the specific capacity of the samples varies from 185 to 205 A h g−1. All electrodes tested exhibit remarkably high reversibility, which is not affected by their vanadium content, and display about 20% loss of their initial capacity after 300 cycles. Significant differences are observed in the initial capacity distribution versus electrode potential, depending on the V3+ content. After long term cycling, however, the capacity distribution of all samples tends to display similar form, independent of the chromium/vanadium ratio. These redistributions determine a mean discharge voltage of about 2.4 V for the LixCr1 − yVyS2 (0.1 < y < 0.5) electrodes subjected to long term cycling tests.

The rate of lithium ion insertion in different types of manganese dioxide, depending on their pretreatment temperature, was investigated. To obtain maximum utilization at heavy discharge drains, the optimum thermal pretreatment temperature for different chemical and electrochemical manganese dioxides (CMD and EMD) was determined. For most types of MnO2 samples this temperature is 300 °C. The manganese dioxides studied display a correlation between their specific surface area and specific capacity by weight. The specific capacity by volume of different CMD and EMD samples was compared in lithium button cells. Their specific electrochemical characteristics were studied at high discharge rates in a wide temperature range. Owing to its high utilization CMD Faradiser M appears to be an excellent cathode material, especially at heavy discharge drains and low temperatures.

To overcome the incompatibility between microporous polypropylene separator and electrolyte solutions based on cyclic esters, three methods of preliminary impregnation of the separator with electrolyte solution, without using surface active agents, are investigated. Values of the specific resistance of the separator, measured in 1M solutions of lithium salts in propylene carbonate, depending on the method of preliminary treatment, are obtained. Experimental data from the tests of secondary lithium button cells supplied with pretreated separators are presented. It is concluded that the pretreatment methods discussed can be used successfully. The best results are obtained by thermal pretreatment with the basic solvent.

The behaviour of the Li/Li1+xV3O8 system in a secondary button cell has been investigated. It is shown that when using electrolytes based on LiAsF6 (without stabilizing additives) the best results are achieved with cyclic esters. It is established that the charging conditions influence significantly the cell cyclability, while the discharge conditions have a limited effect. It is also demonstrated that mixtures of ethylene and propylene carbonate lead to a considerably better reversibility of the system. A satisfactory electrode performance has been obtained: 180 Ah kg−1 at the 100th cycle for the positive electrode material and over 95% utilization of the Li electrode.

Phagocytic number (PN) and phagocytic index (PI) of neutrophils isolated from blood of patients with autoimmune diseases, allergy to Staphylococcus aureus and from blood of healthy individuals were examined. Our results concerning the influence of lactoferrin (Lf); (6.7 mg/l) on the PI of PMN showed that: 1) Lf enhances reliable PI of PMN at the 30-th minute starting the phagocytic reaction in patients with autoimmune disease in an active stage, in blood donors treated as healthy with the presence of autoantibodies, in patients with autoimmune diseases and proved autoantibodies against tissue, cell antigens and collagen, 2) Lf influences non-significantly PI of PMN in patients with autoimmune collagen diseases in remission, 3) Lf increases PI of PMN with 19% only in 58% from the assessed patients with Staphylococcus aureus, and 4) Lf decreases non-significantly PI of PMN in the healthy controls. Our studies on the effect of Lf on the phagocytic activity of PMN suggest that Lf has stronger effect on the PN compared to the PI: 1) Lf enhances with 86% the PN in patients with Staphylococcus aureus, 2) Lf increases PN of PMN in all of the assessed patients with autoimmune collagen diseases in active stage (mean with 72%), and 3) Lf increases PN of PMN in 4 from the 5 investigated healthy controls (mean with 22%). Our results show a "corrective" effect of Lf on the phagocytic functions in the investigated groups of patients. The possible mechanisms, by which Lf increases PN and PI of neutrophils, is discussed: 1) they may concern the antioxidative properties of Lf to block the iron ions in their catalytic inactive form or to take part as ferric-Lf in an oxidative-reduction processes on the plasma membrane and controlling transmembrane transport systems, 2) Lf decreases the negative surface charge and thus enhances the adherent ability of the PMN. Probably to this stimulated adherent ability dues the increased ingestion of bacteria in the presence of Lf, and 3) The "changed" membrane of PMN may have higher number receptors for Lf to bind more molecules of exogenous Lf. The increase of Lf binding which enhances the adherence and aggregation of neutrophils, facilitates the phagocytosis.

A method for the improvement of the electrochemical properties of Li1+xV3O8 is presented based on the partial modification of its crystal structure by the introduction of small amounts of inorganic compounds, such as H2O, CO2 and NH3. The modification is performed by preliminary insertion of these molecules at high (H2O) or ambient pressure (CO2) or by use of appropriate method of synthesis (NH3). A remarkable specific capacity of about 280 mAh/g has been achieved corresponding to the reversible intercalation of 3 equivalents of Li per mol Li1+xV3O8. The high capacity performance and the good reversibility observed is assigned to the preliminary expansion of the interlayer spacing by the inorganic compounds inserted into it, this leading to an increased mobility and enhanced distribution of the Li+ ions in the Li1+xV3O8 layers.

The electrochemical performance of the phases K3V5O14, KV3O8, K2V8O21 and KV5O13, in view of their use as positive electrodes for secondary lithium cells, has been investigated. While the two potassium richer compounds showed very low recharge efficiency, a good revesibility and high capacity performance have been observed for the K2V8O21 and KV5O13 compounds. The remarkable specific capacity of KV5O13, which is about 210 mA h g−1 at 2 h discharge rate, and its excellent cycleability proves it as a promising alternative for a positive electrode of secondary lithium batteries.

Li/Li/sub 1-x/V/sub 3/O/sub 8/ cells have been compared with analogous cells based on TiS/sub 2/, V/sub 6/O/sub 13/, and ..beta..-Na/sub 0.17/V/sub 2/O/sub 5/ cathodes. The results have demonstrated that this bronze can be ranked among the most promising cathode materials for high rate rechargeable Li cells. This has encouraged attempts aimed at improving the electrochemical performance of the bronze through substitution of V with such transition metals as Cr and Mo, and substitution of Li with Na. None of these substituted materials performed better than the parent compound. On the other hand, controlled H/sub 2/O intercalation within the layers resulted in an increased interlayer distance and in higher capacities. A remarkable improvement in cell performance at high rate (10 mA/cm/sup 2/) was obtained with a new technique at cathode preparation.

The rate of lithium ion insertion in different types of manganese dioxide, depending on their pretreatment temperature, has been studied. At high discharge rates different manganese dioxides have specific optimum temperatures of thermal treatment at which they show maximum utilization. For most types of manganese dioxide that temperature is 300°C. The manganese dioxides which we have studied display a correlation between the specific surface area and specific capacity by weight. Under the experimental conditions in the test electrodes high discharge rates are obtained even at low temperatures.

By electrochemical oxidation of in Li cells, phases of the type have been prepared, which provide host structures for Li+ intercalation. More than 1 eq. Li+/mole may be reversibly intercalated at sufficiently high rates. The three‐dimensional layered structure of these phases proves to be particularly rugged, thus allowing repeated cycling with minor performance losses. The high potentials of couples allow high energy densities to be obtained. Starting from a theoretical value of 518 W‐hr/kg, a calculation based on the performance at 1.0 mA/cm2 and on the real battery weight still gives a value of 142 W‐hr/kg for an 8 hr discharge rate. Values of the Li+ chemical potential in and of the free energy of intercalation have large negative values typical of efficient chalcogenide cathodes. Nonlinearly and continuously decreasing plots seem to indicate the formation of a single phase through Li+ occupation of energetically different lattice sites.

The effect of the macrostructure (grain size) and the microstructure (crystal lattice parameters) factors on the coulombic efficiency of Na0.1CrS2 cathodes in secondary Li cells is studied. An attempt is made to employ Atlung's model in assessing the chemical diffusion coefficient of Li+ in the host structure leading to more realistic values with respect to effective interface area. The possibility of enhancing the mobility rate of Li+ by intercalation of water in the host structure is revealed. Using Atlung's model as a guideline it was possible to improve considerably the performance of the Na0.1CrS2 cathodes, while retaining their good cycling stability.

With the aim of optimizing the performance of Li/Li1+xV3O8 cells, several aspects of cathode preparation have been examined. The influence of synthesis technique, nature and amount of conductive additives, compacting pressure, cathode loading, and particle size, has been investigated. Furthermore, the role played by the solutions on cathode efficiency has been outlined. The formulations which perform best are based on small-sized particles blended with about 20% acetylene black and compacted at very high pressures to improve the contact between particles. Such cathodes can provide high capacities at high rates and good cycling efficiencies. The kinetic loss of capacity, observed during the first few cycles, may be alleviated by choosing solutions with high fluidity and conductivity.

The introduction of 0.10–0.15 eq mol of V3+ into the layered structure of NaCrS2 substantially raises its conductivity and lowers its magnetic susceptibility without changing its crystal lattice parameters or nucleating a new phase, this implying considerable changes in the electron band structure of the dichalcogenide. When used as a cathode in a Li cell the partially desodiated vanadium substituted thiochromite exhibits a considerable increase in the equilibrium potential as compared to that of the nonsubstituted compound. Chemical and X-ray analysis reveal that in single phase samples (V3+⩽0.15 eq/mol) practically all the V3+ ions are incorporated into the disulfide slabs, replacing equivalent amounts of Cr3+. It is demonstrated that the partially desodiated host structure Na0.2Cr0.9V0.1S2 can reversibly intercalate up to 1 eq Li/mole. The energy density, power capability and cycle life of this layered compound make it an attractive cathode material for secondary Li cells.

A dozen CuO samples prepared under various conditions and from different starting materials were evaluated as cathode materials for a primary Li/CuO cell. The “thin electrode” method was used for rapid evaluation of the samples. Both coulombic efficiency and discharge voltage depend considerably on the method of synthesis. No correlation was found between the specific surface area and the resistivity of the samples on the one hand and the cathode performance on the other. Best results were obtained from CuO prepared by the oxidation of Cu 2 O under controlled temperature and time of oxidation.

The catalytic activity for the oxidation of CO of 48 alloys of silver, palladium and ytrium has been studied in the temperature range 320–670 K. A partial or total oxidation of the catalysts during the reaction, leading to their transformation into mixed catalysts of the ytrium oxide - metal type, has been established. These catalysts are marked for their high catalytic activity in respect to the oxidation of CO. No direct correlation can be found between the catalytic activity and the phase diagram, which shows the existence of 13 intermetallic compounds.

The dependence of the specific capacity of carbon cathodes used in Li/SO 2 cells on the cathode thickness and the binder content has been studied. At low c.d. the specific capacity increases with decrease in thickness, while at high c.d. the relation shows a maximum. For cathodes with a thickness above 1 mm the relation between the specific capacity and the c.d. is exponential. The pre-exponent in this relationship is determined by the pore volume and the volume electrochemical equivalent of lithium dithionate. The spatial distribution of the current in the cathode has also been investigated.

A Li-MnO 2 counterpart of the standard 6F22 Leclanche battery was designed in 3 different versions — paper lined, spiral wound, and layer stacked. The performance of all 3 types was tested according to the IEC discharge conditions, and the results were juxtaposed with Leclanche and zinc-air batteries of identical size and voltage. The merits and shortcomings in terms of capacity, polarization, ability to withstand continuous discharge, and technological back up are discussed. Although all 3 designs displayed superior characteristics as compared with the Leclanche batteries, optimum performance can be achieved by observing several critical requirements concerning the design, materials, and technology.

A Li rechargeable battery with a cathode based on small particle-size Li1+x V3O8 has a high cathode utilization and a long cycle life at high discharge rates. It is shown that decreasing the particle diameter from 10 to 1 μm decreases 10 times the current density really applied to the cathode. This is particularly beneficial by limiting the cathodic capacity losses and thereby increasing the life to several hundreds of cycles. The high rate capability afforded by the use of small particles results in good power-energy characteristics.

The chemical desodiation of non-doped and vanadium-doped sodium thiochromites has been studied. The changes in the chemical composition and X-ray diffraction patterns during desodiation of the stoichiometric compound reveal that the vanadium-doped thiochromite can be more effectively desodiated. The presence of vanadium in the disulfide layers enhances the covalency of the MS bond; this probably facilitates a first order phase transition of the vanadium-doped material during deintercalation of both Na + and Li + . The electrochemical performance of cathodes prepared from the chemically desodiated, vanadium-doped thiochromite is assessed by cycling in a 1 M LiClO 4 /PC + DME solution at a 3 h rate between 1.8 and 3.4 V. The volumetric energy density of the pressed cathodes is 0.51 W h cm −3 at the 100th cycle and drops to 0.35 W h cm −3 after 500 cycles.

By changing the conditions of synthesis and oxidation of NaCrS2, the coulombic efficiency and cycling life of NixNa0.1CrS2 cathodes is significantly improved. The importance of studying the main physical and structural properties of the intercalation compound during the optimization of its electrochemical performance is demonstrated. Imitating the nonexistant CrS2 in composition and possessing the rugged crystal structure of NaCrS2, the optimized LixNa0.1CrS2 cathodic material exhibits high coulombic efficiency, excellent cycling resistance, and moderate power capability in nonaqueous secondary Li cells. Having in mind also the simple and reproducible preparation technique and the availability of its raw materials, LixNa0.1CrS2 appears to be a serious candidate for the future secondary Li nonaqueous cell.

A method of selective measurement of released oxygen and water during thermal treatment of MnO2 has been developed. It is shown that in inert medium up to 300°C the basic weight losses are due to water release, while above 300°C they are determined by oxygen evolution. Above 350°C MnO2 is thermodynamically unstable in inert atmosphere. The existence of characteristic temperatures, not exceeding 300°C, and corresponding to the different natures of the bonded water, is confirmed. The re-absorbed water after thermal treatment of MnO2 is of a nature similar to that contained in the untreated commercial material.

On the basis of the condition for optimum cell design, expressions are derived for the determination of the optimum thickness and length of the electrodes as well as of the maximum capacity. There is good agreement between the experimental values and those calculated by the derived expressions. The dependence of the cell capacity on the discharge rate is explained in terms of the relationship between the partial capacities of the separate components and the current. The possibility of an extension of the safe operation range by means of cell optimisation is suggested.

Following a preliminary investigation, Li/Li1+xV3O8 cells have been examined. Using samples of low x content, up to 3 eq Li+ could be accepted both chemically and electrochemically by one mole of active material. Li+ is accomodated in the tetrahedral sites existing between the (V3O8)(1+x)- layers. Li+ jumping from site to site is fast and permits high rate capabilities: at 10 mA/cm2, 1.1 eq Li+ per mole could still be inserted. The structure does not show irreversible alterations upon extended lithiation, allowing long cycle lives to be achieved. Kinetic constraints limit the recovery of the full capacity of the first discharge at medium-high rates, but the second-discharge capacity declines slowly with cycle number.