Lithium conductor

Tlie aim of this chapter is to provide an overview of materials where fast transport of alkali metal cations and protons is observed. A general discussion of factors affecting conductivity and techniques used to study ion migration paths is followed by a review of the large number of cation conductors. Materials with large alkali ions (Na-Cs) are often isostructural and therefore examined as a group. Tire lithium conductors with unique crystal structure types and proton conductors with unique conduction mechanisms are also discussed. 

Imanaka N, Kawasato T, Adachi G (1991) Selective CO detection with a lithium conductor based sensor. Chem Lett 1991 13-16... 

This structural model suggests that the limited lithium mobility that does occur in these compounds proceeds via a percolation pathway for lithium migration. This path is composed of portions of the material that contain either lithium cations or vacancies in the large interstitial void. The presence of a lanthanide cation in 55% of the subcells prevents the occupation of the immediately adjacent tetrahedrally coordinated lithium positions and so blocks the passage of Li. Thus the lithium conductivity in these structures will be limited first by the ability of lithium cations to exit the tetrahedrally coordinated site and secondly, by the availability of an empty interstitial site in an adjacent subcell. Given these limitations on ion movement through the structure, it would be surprising if these materials were fast lithium conductors. 

Figure 3.24 The total conductivity of Li5La3Ta20i2 as a function of temperature. Data from other important lithium conductors are shown for comparison...

The dc asymmetric polarization technique has been used quite extensively to evaluate the partial conductivity of the electronic minority charge carriers in marty solid electrolytes, e.g., doped zirconia, silver halides, copper halides,and solid lithium conductors. ... 

Doyle, R.P., Chen, X.R., Macrae, M., Srimgavarapu, A., Smith, L.J., Gopinadhan, M., Osuji, C.O., Granados-Focil, S. 2014. Poly(efhylenimine)-based polymer blends as single ion lithium conductors. Macromolecules 47 3401-3408. 

Vl L, J R Walker and C R A Catlow 1984. A Molecular Dynamics Simulation Study of the iperionic Conductor Lithium Nitride I. Journal of Physical Chemistry 17 6623-34. 

A second type of soHd ionic conductors based around polyether compounds such as poly(ethylene oxide) [25322-68-3] (PEO) has been discovered (24) and characterized. These materials foUow equations 23—31 as opposed to the electronically conducting polyacetylene [26571-64-2] and polyaniline type materials. The polyethers can complex and stabilize lithium ions in organic media. They also dissolve salts such as LiClO to produce conducting soHd solutions. The use of these materials in rechargeable lithium batteries has been proposed (25). 

Lithium is isolated in a protective film [8]. During the deposition of lithium, the protective film may be heated locally by ion transport in the film itself. As a result of this local heating, part of the protective film (SEI) becomes an electronic conductor, and therefore lithium metal is deposited in the film. If local heating does not occur during stripping, the isolated lithium becomes electrochemically inactive. 

Figure 3. Schematic representation of the lithium-ion conductor LiAICl4. The A1C14 may be considered as tetrahedral anions, as indicated by green. The lithium ions are located between them.

The structure of the perovskite-type lithium ion conductor Li0 29La0 57Ti03 is represented in Fig. 6. The small gray circles depict the lithium ions, the big gray circles the lanthanum ions. These are randomly distributed over the A sites 14 per-... 

Figure 6. Structure of the perovskite-type lithium-ion conductor Li 2yLa057TiO3. The lithium ions (small, gray) and the lanthanum ions (large, gray) are randomly distributed over the A sites, of which 14 percent are vacancies, enabling the lithium ions to be mobile. Titanium forms TiOh octahedra, as shown in yellow. The unit cell is indicated.

From Eq. (18) the concentration of electrons, and according to Eq. (11) the concentration of holes also, depend on the lithium activity of the electrode phases with which the electrolyte is in contact. Since anode and cathode have quite different lithium activities, the electronic concentration may vary to a large extent and an ionically conducting material may readily turn into an electronic conductor. 

Table 1. Conductivities, activation enthalpies, and other aspects of fast lithium-ion solid conductors...

Quite a large variety of interesting fast lithium-ion solid conductors is now known, as compiled in Fig. 9 and Table 1. In the case of sodium- and potassium-ion conductors only the / / / " -alumina fam-... 

The third aspect, the stability range of solid electrolytes, is of special concern for alkaline-ion conductors since only a few compounds show thermodynamic stability with, e.g., elemental lithium. Designing solid electrolytes by considering thermodynamic stability did lead to very interesting compounds and the discovery of promising new solid electrolytes such as the lithium nitride halides [27]. However, since solid-state reactions may proceed very slowly at low temperature, metasta-... 

In practice, for a ternary system, the decomposition voltage of the solid electrolyte may be readily measured with the help of a galvanic cell which makes use of the solid electrolyte under investigation and the adjacent equilibrium phase in the phase diagram as an electrode. A convenient technique is the formation of these phases electrochemically by decomposition of the electrolyte. The sample is polarized between a reversible electrode and an inert electrode such as Pt or Mo in the case of a lithium ion conductor, in the same direction as in polarization experiments. The... 

Since the realization in the early 1980s that poly (ethylene oxide) could serve as a lithium-ion conductor in lithium batteries, there has been continued interest in polymer electrolyte batteries. Conceptually, the electrolyte layer could be made very thin (5im ) and so provide higher energy density. Fauteux et al. [31] have recently reviewed the present state of polymer elec-... 

The uncertainty principle is negligible for macroscopic objects. Electronic devices, however, are being manufactured on a smaller and smaller scale, and the properties of nanoparticles, particles with sizes that range from a few to several hundred nanometers, may be different from those of larger particles as a result of quantum mechanical phenomena, (a) Calculate the minimum uncertainty in the speed of an electron confined in a nanoparticle of diameter 200. nm and compare that uncertainty with the uncertainty in speed of an electron confined to a wire of length 1.00 mm. (b) Calculate the minimum uncertainty in the speed of a I.i+ ion confined in a nanoparticle that has a diameter of 200. nm and is composed of a lithium compound through which the lithium ions can move at elevated temperatures (ionic conductor), (c) Which could be measured more accurately in a nanoparticle, the speed of an electron or the speed of a Li+ ion ... 

The electrolyte used in lithium cells, i.e., for aU hthium couples, must be completely anhydrous (< 20 ppm H2O) alkali metals in general are compatible with neutral salt solutions in aprotic solvents or neutral molten salts or solid ion-conductors. 

Instrumentation. Traditional methods of alpha and beta spectrometry instrumentation have changed little over the past decade. Alpha spectrometric methods typically rely on semi-conductor or lithium-drifted silicon detectors (Si(Li)), or more historically gridded ion chambers, and these detection systems are still widely used in various types of uranium-series nuclide measurement for health, environmental, and... 

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