Conductor, lithium cation

It is also noteworthy that the ionic conductivity of a simple mixture of PEO and alkali metal salt was improved 10 to 100 times by employing larger cations such as sodium or potassium ions [17], whereas numerous lithium cation conductors are known to date. The improved ionic conductivity is attributed to the weaker... 

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. 

Ti,Nb)-0, and La-deficient La2-02 layers (Fig. 6.7(a)). Two-dimensional lithium cation conduction has also been reported in the orthorhombic layered perovskite-type compound Lao.62Lio.i6Ti03 [55], in which the Li cation exists and migrates only near the La-deficient La2-02 layer. This work has thus revealed that oxide ion diffusion in an ionic conductor with a double perovskite structure is two dimensional. 

Two types of solid ionic conductors are of special interest—those in which metallic cations such as lithium ions can be transported across the polymer membrane, and others in which protons can move from one side of the membrane to the other. The first... 

In the case of NiO which is p-type metal-deficient material we have a structure with Ni2+, O2- and Ni3+ in nickel vacancy sites. Addition of lithium ion impurity to NiO makes it a p-type conductor and oxide growth rate is reduced compared with the Ni-02 system alone. On the other hand addition of Cr to Ni results in greater ease of oxidation than nickel alone due to higher cation diffusivity. 

Appreciable ionic conductivity is found in open framework or layered materials containing mobile cations (see Ionic Conductors). Several phosphates have been found to be good ionic conductors and are described above NASICON (Section 5.2.1), a-zirconium phosphates (Section 5.3.1), HUP (Section 5.3.3), and phosphate glasses (Section 5.4). Current interest in lithium ion-conducting electrolytes for battery apphcations has led to many lithium-containing phosphate glasses and crystalline solids such as NASICON type titanium phosphate being studied. ... 

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. 

A similar approach is used in CO2 gas sensors based on electrolyte chains of YSZ and cation conductors. Specifically, YSZ has been used with magnesium- [223], aluminum- [96, 105, 224, 225], or scandium- [225-227] conducting electrolytes and Li2CO3-containing electrodes. The sensitivity to CO2 is attributed to the dissolution of lithium in the electrolyte rather than to the formation of a new carbonate phase. 

By far the largest class of ternary lithium nitrides are those with the antifluorite structure, prepared largely by Juza, and reviewed by him [42], The ternaries are more thermally stable than the binaries which would seem to indicate a relaxation of the internal strain (both cation- cation and anion-anion repulsions) of binary nitrides. Many of these compounds are in fact ordered superstructures of antifluorite and it is remarkable that most of the transition metals are observed in high oxidation states--much higher than those in the binaries (e.g. Li7Mn + N4 vs Mn5 + N2). They are Li+ conductors at elevated... 

The second type of polymer electrolyte does not itself possess charged moieties along its chain. Rather, the polymer acts as the solvent for electrolyte ions which are able to move through the polymer matrix much as in a liquid electrolyte. Thus, the polymer serves as a solid ionic conductor. An example of this type of polymer is polyethylene oxide in which lithium and other small cations have high mobility [2]. 

The last few years have witnessed a high level of activity pertaining to the research and development of all-solid, thin-film polymer electrolyte batteries most of these use lithium as the active anode material, polymer-based matrices as solid electrolytes, and insertion compounds as active cathode materials. High-performance prototypes of such batteries stand currently under research, whose trends are expected to include the development of amorphous polymers with very low glass-transition temperatures, mixed polymer electrolytes, and fast-ion conductors in which the cationic transport number approaches unity. 

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