Lithium ionic conductivity

Silicon, diamond, and metal deposition are all examples of elemental deposition. Compounds, particularly oxides, are also deposited by chemical vapor deposition. Some of the important oxides deposited as thin films include SiC>2, BaTiC>3, LiNbC>3, YBa2Cu30,. indium-doped SnC>2, and LiCoC>2. These materials have properties such as superconductivity or lithium ionic conductivity that make their production as thin films a much-studied area of research. If the oxide is to be deposited on the bare metal (e.g., depositing SiC>2 onto Si), chemical vapor deposition is not really needed. Controlling the oxygen partial pressure and temperature of the substrate will produce the oxide film Whether the film sticks to the substrate is another question The production of SiC>2 films on Si is an advanced technology that the integrated-circuit industry has relied on for many years. Oxide films on metals have been used to produce beautiful colored coatings as a result of interference effects (Eerden et al., 2005). 

Tsuchida, E., Ohno, H., Tsunemi, K., and Kobayashi, N., Lithium ionic conductivities in poly(methacrylic acid)-poly(ethylene oxide) complex containing lithium perchlorate. Solid State Ionics, II, 227-233 (1983). 

For the electrolyte in electrochromic devices, the requirement is high lithium ionic conductivity. At the same time, the electrolyte has to have high electronic resistivity and no defects (pinholes). The commercially introduced devices have no moving parts meaning no mobile protons to deteriorate the memory capability of the device (Cronin, 1993). The... 

Table 2 Lithium ionic conductivity of hybrid films ) Flemion LiCI04 400E 10 X Oj (S/cm)...

In addition, the dissolution of lithium salt can be promoted by introducing polar -CN groups in the polysiloxane. This can also reduce Tg and increase the lithium-ionic conductivity. Using polysiloxanes with polar groups as prepolymers and PEO terminated with trimethoxysilane as the cross-linking agent, the ionic conductivity at room temperature for the cross-linked polymer electrolyte can be up to 10 S/cm. 

Applications. Polymers with small alkyl substituents, particularly (13), are ideal candidates for elastomer formulation because of quite low temperature flexibiUty, hydrolytic and chemical stabiUty, and high temperature stabiUty. The abiUty to readily incorporate other substituents (ia addition to methyl), particularly vinyl groups, should provide for conventional cure sites. In light of the biocompatibiUty of polysdoxanes and P—O- and P—N-substituted polyphosphazenes, poly(alkyl/arylphosphazenes) are also likely to be biocompatible polymers. Therefore, biomedical appHcations can also be envisaged for (3). A third potential appHcation is ia the area of soHd-state batteries. The first steps toward ionic conductivity have been observed with polymers (13) and (15) using lithium and silver salts (78). 

Lithium Nitride. Lithium nitride [26134-62-3], Li N, is prepared from the strongly exothermic direct reaction of lithium and nitrogen. The reaction proceeds to completion even when the temperature is kept below the melting point of lithium metal. The lithium ion is extremely mobile in the hexagonal lattice resulting in one of the highest known soHd ionic conductivities. Lithium nitride in combination with other compounds is used as a catalyst for the conversion of hexagonal boron nitride to the cubic form. The properties of lithium nitride have been extensively reviewed (66). 

A second class of important electrolytes for rechargeable lithium batteries are soHd electrolytes. Of particular importance is the class known as soHd polymer electrolytes (SPEs). SPEs are polymers capable of forming complexes with lithium salts to yield ionic conductivity. The best known of the SPEs are the lithium salt complexes of poly(ethylene oxide) [25322-68-3] (PEO), —(CH2CH20) —, and poly(propylene oxide) [25322-69-4] (PPO) (11—13). Whereas a number of experimental battery systems have been constmcted using PEO and PPO electrolytes, these systems have not exhibited suitable conductivities at or near room temperature. Advances in the 1980s included a new class of SPE based on polyphosphazene complexes suggesting that room temperature SPE batteries may be achievable (14,15). 

During electrochemical reduction (charge) of the carbon host, lithium cations from the electrolyte penetrate into the carbon and form a lithiated carbon Li rCn. The corresponding negative charges are accepted by the carbon host lattice. As for any other electrochemical insertion process, the prerequisite for the formation of lithiated carbons is a host material that exhibits mixed (electronic and ionic) conductance. 

However, even if electrolytes have sufficiently large voltage windows, their components may not be stable (at least ki-netically) with lithium metal for example, acetonitrile shows very large voltage windows with various salts, but is polymerized at deposited lithium if this reaction is not suppressed by additives, such as S02 which forms a protective ionically conductive layer on the lithium surface. Nonetheless, electrochemical stability ranges from CV experiments may be used to choose useful electrolytes. 

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. 

For lithium, counterparts structurally related to the sodium- and potassium-P / /3" -aluminas and NASICON with similar high ionic conductivities were not found, possibly because of the small ionic... 

Gel electrolytes were also prepared by Allcock [605] from co-substituted polyphosphazenes with various ratios of methoxyethoxyethoxy and trifluo-roethoxy side groups, lithium triflate and propylene carbonate. These gel electrolyte systems have a better mechanical stability than MEEP. The highest ionic conductivity obtained was 7.7x10" S cm" at 25 °C for a gel containing 37.5% of polymer with 80% and 20% of methoxyethoxyethoxy and trifluoro ethoxy... 

In battery applications, new hthium ion batteries called lithium ion polymer batteries (or more simply but misleadingly, lithium polymer batteries) work with a full matrix of ionically conducting polymer, this polymer being present inside the porous electrodes and as a separator between the electrodes. They are offered in attractive flat shapes for mobile applications (mobile phones, notebooks). 

Lithium perchlorate is dissolved in PEO owing to the coordination of Li+ cation by oxygen atoms in the polymeric chain. The complex thus formed has the helical structure (Fig. 2.18), and exhibits ionic conductivities of up to 10 4 S/cm at 60°C. 

Ion-conductive properties of anion-trapping-type organoboron polymer electrolytes was evaluated after adding lithium salts (Fig. 3). In these systems, ionic conductivity of 3.05 X 10 s 5.22 X 10 6Scm 1 was observed at 50°C. This indicates... 

Figure 3 Temperature dependence of ionic conductivity for polymers 1 and 2 in the presence of various lithium salts.

In the presence of lithium salts, the temperature dependence of ionic conductivity for the polymer electrolytes obtained was evaluated. In the presence of LiCF3S03,... 

After adding lithium salts, ionic conductivity was measured by the ac impedance method (Fig. 5). Lithium salt concentration was first optimized by measurements... 

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