Effect of Ultrasonic Treatment on the Properties of Pyrophyllite and Thermodynamic and Kinetic Regularities of its Intercalation with Lithium

Abstract

We study the influence of the ultrasonic treatment of pyrophyllite in different media on its structure and charge transfer and analyze the dependences of changes in the Gibbs free energy, resistance to charge transfer, and capacitance of the Helmholtz layer caused by the acoustic action on the amount of "guest" lithium x . It is shown that abnormally high diffusion coefficients of lithium cations for all investigated values of x represent a specific feature of the kinetics of intercalation in Li x Al 2 (OH) 2 [Si 2 O 5 ] 2 . At present, the major part of known systems for the electrochemical generation and accumulation of energy contain cathodic substances whose reserves are exhausted [1]. In view of severe requirements of the market to the cost of one watt-hour of energy and ecological safety, we encounter a problem of creation of a new resource base for the devices of autonomous power supply from the collection of low-cost, ecologically safe, and widespread natural substances. Since at present, there are no acceptable materials satisfying these requirements among the available synthetic structures, the most promising way is clearly connected with the formation of a base of natural minerals with sufficiently large resources. However, numerous natural minerals prove to be inefficient for the direct generation and accumulation of electric energy. Thus, the development of the procedures of their modification is a primary task.Among promising natural minerals, we can mention pyrophyllite ( Al 2 (OH) 2 [Si 2 O 5 ] 2 ) whose crystalline structure is shown in Fig. 1. It has "guest" positions required for intercalation and located between weakly connected aluminosilicate layers [2]. Polymorphism, isovalent isomorphism [3,4], and impurities (together with weak bonds between the layers) typical of pyrophyllite make it suitable for the efficient modification by ultrasonic irradiation [5][6][7][8], which belongs to possible and safe production-and-technological operations. In the literature, there is no information about the influence of ultrasound on the thermodynamic and kinetic properties of pyrophyllite important for the intercalation current formation. This fact motivated the appearance of the present work. Materials and Experimental ProcedureIn our experiments, we used ground pyrophyllite. We performed the ultrasonic irradiation of pyrophyllite with a mass of 0.2 g placed in heptane and in 1 mliter of 1М LiBF4 in γ -butyrolactone for 60 min at a frequency of 22 kHz.

Layered Crystals as Porous Materials: the Effect of Ultrasonic Treatment

“…The transcendental equation (6) has been solved by us using Maple, Mathematica, and Fortran software packages to search for graphical intersections of the left and right sides of such an equation [10]. The set of allowed zones, separated by gaps at the points kx  0 and kx   /d, has been finally obtained [10]:…”

“…Ultrasonic treatment is another active factor in the 01019-2 change of the van der Waals gap [1,6,7]. Variation in the physical characteristics of layered crystals or porous structures by means of intercalation or by ultrasonic treatment makes it possible to solve such an urgent scientific and technological problem as the creation of high-capacity electric energy storages, in particular, on the basis of sodium and potassium, unlike it is in lithium-ion energy storage [8].…”

Electronic Spectrum of a Quasi-2D Semiconductor in Strong Electromagnetic Field

“…The structure of the well-known representative of the layered crystals of A3B6-type GaSe completely coincides with the structure of MoS2 crystals after replacing the layer of metal atoms M by a Ga-Ga double layer. Different types of bonds are the cause of pronounced anisotropy concerning physical characteristics of quasi-two-dimensional crystals, which anisotropy can be widely varied by intercalation [1,2], by external compression [3], etc. Therefore, such structures were (and remain) objects of intensive scientific researches and their practical use in nanoelectronics, spintronics, and optoelectronics [4][5][6]; and especially, they are promising in solving the current scientific and technological problem -the creation of high-capacity electrical energy storage [7].…”