Electronic and ionic conduction in some simple lithium salts

The electrical conductivity () and thermoelectric power (S) of solidified melt samples of Li₂MoO₄, Li₂WO₄ and Li₂SO₄ are presented in the temperature range 415 K to melting point of each compound. The ratio of ionic to electronic contribution to has been obtained with the help of a time-dependence study of d.c. electrical conductivity. It has been shown that in Li₂MoO₄ electronic contribution to remains high up to its melting point (about 8% just below the melting point) and it shows no superionic phase. However, in Li₂WO₄ and Li₂SO₄ a superionic phase is obtained in which the ionic contribution to is more than 99.99%. However, in normal ionic (or) phase it is small and decreases with decreasing temperature. Separate temperature variations of ionic ( _i) and electronic ( _e) conductivities are presented and the conduction mechanisms are discussed. It is shown that ionic conduction in the-phase is dominated by Schottky-type defects.     

Ionic conductivity of lithium phosphate-doped lithium orthosilicate

The ionic conductivities of samples of lithium orthosilicate containing up to 50 mole % of lithium phosphate have been measured by both a c and d c techniques. Results indicate a large enhancement in lithium ion conduction due to the presence of the phosphate, making these materials attractive candidates for use as solid electrolytes in applications such as battery systems.     

Ionic conductivity and hopping rate data for some NASICON analogues

The a.c. conductivity of ionic materials shows two regions of frequency-dependent conductivity over a wide range of frequencies. Jonscher’s law of dielectric response for ionic conductors enables us to characterize the conductivities. The region of low frequency dispersion approximates to a frequency-independent plateau enabling us to obtain the d.c. conductivity. In some other conductors, the presence of low-frequency dispersion cannot be neglected while determining the effective d.c. conductivity. We have used this method to extract the d.c. conductivity and hopping rate as well as to estimate concentrations of the mobile ions (carriers) in some NASICON analogues.     

Ionic conductivity in dehydrated zeolites

The ionic conductivity of pressed pellets of dehydrated synthetic offretite, cancrinite and zeolite A, with various alkali metal ions, was determined by low-frequency impedance spectroscopy. Experiments were carried out in the frequency range 10 Hz–10 MHz at temperatures from 100–600°C. The conduction activation energies range between 55 kJ mol^?1 (Na-zeolite A) and 108 kJ mol^?1 (Li-cancrinite). The best conductivity value obtained was that of Na-zeolite A with 2.9×10^?3Ω^?1cm^?1 at 600°C.     

Ionic conductivity in samarium-doped NaCl

A study of ionic conductivity as a function of temperature has been carried out in NaCl and NaCl doped with 0.5 and 1.0 mol% samarium. The conductivity-temperature plot of NaCl exhibits a well-known three-stage conductivity in the temperature range 100 to 650° C. The knee separating intrinsic and extrinsic regions is at a temperature of about 525° C. The conductivity-temperature plots of samarium-doped NaCl exhibit three-stage extrinsic (II, III and IV) conductivity in the temperature range 100 to 525° C. The intrinsic region I, was not observed in these plots, as the conductivity measurements were taken up to 525° C. From the analysis of these plots activation energies for the migration of cation vacancy, the formation of Schottky pairs, the association of the samarium ion with a cation vacancy and the dilution of samarium ions in the lattice of NaCl are calculated. These values are compared with previously reported ones.     

Ionic conductivity in wide-range halide-pyrophosphate glasses

Recently we have reported the existence of fast ionic conduction in silver halide-rich all-halide glasses. In the present paper we report glass formation from x = 0.08−1.0 in a pseudobinary halide-pyrophosphate system x(AgCl)_0.64(CsI)_0.36 + (1−x)(Ag₂PO_3.5) and study the composition dependence of the conductivity. Glass transition temperatures and activation energies for d.c. conductivity increases smoothly as the pyrophosphate concentration increases, while the conductivity correspondingly decreases. The frequency dependence of the conduction process has been analysed. The conductivity relaxation process becomes increasingly non-exponential as the conductivity at some fixed temperature (eg. 298 K) increases.     

Ionic conductivity of fluoroaluminoindate glasses

(54 - 2.4x)InF₃ + xA1F₃ + (36 -1.6x)BaF₂ + 3xPbF₂ + 1OLiF glasses (nine compositions,x varying from 0 to 18 mol % at 2.25 mol % intervals) were prepared. The glass compositions were taken between the 60InF₃ + 40BaF₂ and 25A1F₃ + 75 PbF₃ eutectics, of which the former is glass-forming (10 mol % LiF was added for glass stabilization). The electrical properties of the glasses were studied by impedance spectroscopy at frequencies from 5 Hz to 500 kHz and temperatures from 20 to 200‡C. The 400-K ionic conductivity of the glasses was found to rise from 4.3 x 10^-6 S/cm in the PbF₂-free glass to 1.4 x 10^-5 S/cm in the glass containing 54 mol % PbF₂; concurrently, the 300-K static dielectric permittivity increases from 17 to 29.     

Fast ionic conductivity in lithium nitride

Analysis of the frequency dependence of ac measurements with ionically-blocking electrodes, as well as transmission electron microscopic observations have enabled the transcrystalline and intercrystalline resistances of polycrystalline Li₃N to be separately evaluated. At 25°C the transcrystalline ionic conductivity is 6.6×10^?4 (ohm cm)^?1 and the activation enthalpy is 24.1 kJ/mole. The intercrystalline conductivity has an activation enthalpy of 68.5 kJ/mole, and its magnitude varies with thermal history. By optimized thermal treatment, the microstructure can be controlled so the bulk conductivity becomes approximately equal to that for transport in the fast direction in this very anisotropic structure.     

Micro-nano structured VNb9O25 anode with superior electronic conductivity for high-rate and long-life lithium storage

The oxygen vacancies and micro-nano structure can optimize the electron/Li+migration kinetics in anode materials for lithium batteries(LIBs).Here,porous micro-nano structured VNb9O25 composites with rich oxygen vacancies were reasonably prepared via a facile solvothermal method combined with annealing treatment at 800℃for 30 h(VNb9 O25-30 h).This micro-nano structure can enhance the contact of active material/electrolyte,and shorten the Li+diffusion distance.The introduction of oxygen vacancies can further boosts the intrinsic conductivity of VNb9O25-30 h for achieving excellent LIB performance.The as-prepared VNb9O25-30 h anode showed advanced rate capability with reversible capacity of 122.2 mA h g-1 at 4 A g-1,and delivered excellent capacity retention of～100％after 2000 cycles.Meanwhile,VNb9O25-30 h provides unexpected long-cycle life(i.e.,reversible capacity of 165.7 mA h g-1 at 1 A g-1 with a high capacity retention of 85.6％even after 8000 cycles).Additionally,coupled with the LiFePO4 cathode,the LiFePO4//VNb9O25-30 h full cell delivers superior LIB properties with high reversible capacities of 91.6 mA h g-1 at 5C for 1000 cycles.Thus,such reasonable construction method can assist in other high-performance niobium-based oxides in LIBs.     

Composition dependence of lithium ionic conductivity in lithium nitride-lithium iodide system

Two minima in the lithium ionic conductivity vs. composition curve in the lithium nitride-lithium iodide system are observed at Li₅NI₂ and Li₇N₂I. It is shown that ionic conductivity minimum at the stoichiometric Li₅NI₂ is caused by the increase in the lithium ion concentration.     

Ionic conductivity in Li5AlO4 and LiOH

The ionic conductivity and thermal properties of Li₅AlO₄ and LiOH have been measured in wet and dry environments. Results show that an endothermic reaction at ～ 415°C and an associated large increase in conductivity is observed both in Li₅AlO₄ in a wet environment and in LiOH. These features are not observed in Li₅AlO₄ prepared and examined in a dry environment. This suggests that the large conductivity increase in Li₅AlO₄ results from LiOH retained within the material. The reaction(s) for formation of LiOH within Li₅AlO₄ and the associated electrical changes appear to be reversible as the environment switches from wet to dry at high temperatures (? 450°C). There is a significant (> 1%) electronic contribution to the conductivity in these materials.     

Improving the intrinsic electronic conductivity of NiMoO4 anodes by phosphorous doping for high lithium storage

Heteroatom doping is one of the most promising strategies toward regulating intrinsically sluggish electronic conductivity and kinetic reaction of transition me...     

锂离子电池电解质用含硼锂盐研究进展

电解质材料是锂离子电池的关键材料之一。LiBF4、双草酸硼酸锂(LiBOB)及草酸二氟硼酸锂(LiODFB)是极具应用前景的3种含硼锂盐。介绍了3种锂盐各自的优缺点及研究近况,重点综述了它们的离子传导特性及与电极材料的相容性能。     

Thermal conductivity and viscosity of lithium vapors

We give the calculated values of the thermal conductivity and viscosity of lithium vapors (T=800–2000°K, p=3·10^–3-3 bar). No experiment was conducted for lithium. A comparison with experiments conducted on sodium and potassium is given.Translated from Inzhernerno-Fizicheskii Zhurnal, Vol. 38, No. 3, pp. 429–433, March, 1980.     

Ionic conductivity and crystal structure of fired crystalline zirconium phosphate completely and half exchanged with some monovalent cations

For LiLi-form, the decomposition of dilithium zirconium phosphate with a layered structure and formation of lithium dizirconium triphosphate and zirconium pyrophosphate was achieved by firing at 600°C or above. For NaNa- and KK-forms, any distinct variations of the external apperance were not confirmed by heat-treatments, while the crystal growth was detected for RbRb- and CsCs-forms fired at 900°C. For half ion-exchanged forms, monovalent cation dizirconium triphosphate was mainly formed on heating up to 600°C or above. The activation energy in ionic conduction decreases with increasing monovalent cation radius. This dependency can be realized by Anderson and Stuart's model based on the classical ideas of ionic crystal theory and elasticity theory. The activation energy for the fully exchanged form is slightly higher than that for the half-exchanged form and the pre-exponential factor in σT=σ₀ exp (-E/kT) for the former is less than that for the latter.     

六氟磷酸盐吡啶离子液体的合成及电导率研究

采用二溴丁烷和3-甲基吡啶(物质的量之比为1.0∶2.2)为原料,以异丙醇为溶剂,温度控制在70～80℃,反应4～6h,得到吡啶溴盐离子液体。用吡啶溴盐与六氟磷酸盐发生置换反应,搅拌反应4h,得到六氟磷酸盐吡啶离子液体。测定了[C4(MPy)2][PF6]2离子液体在有机溶剂中的电导率;及离子液体在不同溶剂、不同浓度、不同温度下的电导率。结果表明:溶液的电导率随着温度升高而增大;随着浓度的增大而增大。相同温度、浓度下,乙腈的电导率最大;环丁砜的电导率最小。