Ionic conductivity and chemical diffusion in LixCu2−xSe superionic alloys

Abstract

Results of studies on the ionic conductivity and chemical diffusion coefficients of stoichiometric LixCu2_xSe (0<x<0.20) ternary alloys in the temperature range 350-405 ~ are presented. It is observed that in the stoichiometric copper selenide the substitution of part of copper by lithium leads to a strong change for the deterioration of ionic transport conditions.

Some Thermoelectric Phenomena in Copper Chalcogenides Replaced by Lithium and Sodium Alkaline Metals

“…The control of the chemical composition of NC was carried out by regulating the reduction potential in the sonoelectrochemical method, by regulating the PH value in the hydrothermal method, and by selecting the pre-treatment of precursors in the dry thermolysis method. The use of the electrochemical method of doping with lithium allowed the authors to obtain and study solid solutions Li x Cu 2−x S (0 < x < 0.25) [24,26,28], Li x Cu (2−x)−δ Se (x ≤ 0.25) [22,23], promising for thermoelectric applications. To obtain Li x Cu (2−x)−δ Se nanopowders, Ishembetov R. Kh.…”

“…The high cationic conductivity of copper chalcogenides is possible due to the action of several factors, and the main ones are the strong disorder of the cation sublattice in the superionic phase and the presence of a connected network of free interstitial sites, which are shallow potential wells in the path of mobile ions. The value of the ionic conductivity in the superionic phase of Cu 2 Se reaches 2.2 S/cm at 400 °C, and the self-diffusion coefficient equals 2.5 × 10 −5 cm 2 /s at 350 °C [ 22 ]. Due to the high concentration of free interstitial sites in the cation sublattice, the activation energy for copper diffusion does not include the energy of defect formation and consists only of the activation energy for migration of cations.…”

“…In works [151,152], it was found that copper and silver ions make comparable contributions to the total ionic conductivity of Cu 2 X-Ag 2 X solid solutions (where X = S, Se, Te). It was found that substitution by silver results in increasing ionic conductivity [151][152][153] of copper chalcogenides, while substitution by lithium leads to a strong decreasing in the ionic conductivity [22,24,26]. Balapanov M.Kh.…”

“…Studying copper sulfides and copper selenides substituted with lithium, it was found that the ionic conductivity and diffusion rate of copper in materials decrease by almost an order of magnitude compared to the initial binary compositions, and the thermoelectric coefficient remains high and even increases [22][23][24][25][26][27][28][29]. This significantly improves the prospects of copper chalcogenides for practical use.…”

Effect of lithium doping on electrophysical and diffusion proper-ties of nonstoichiometric superionic copper selenide Cu1.75Se

“…Substitution by lithium revealed a significant decrease in both the ionic and the electronic conductivity, a decrease of the self-diffusion coefficients of cations and the chemical diffusion coefficients [32][33][34][35][36], while maintaining and even increasing the electronic Seebeck coefficient were observed.…”