The concept of a novel all‐solid composite electrode is presented. One example of such a composite contains a finely dispersed reactant, LiynormalSi , in a solid mixed‐conducting matrix, Li2.6normalSn . Repeated charging and discharging of such electrodes without appreciable loss of capacity has been demonstrated. The polarization is found to be comparable to values typical of highly porous electrode systems in molten salt electrolytes.

A Nonlinear Least Squares Fit (NLLSF) pxogram is described, with which fzequency dispersion data of electrochemical systems can be analyzed in terms of an equivalent circuit. The NLLSF procedure uses a combination of an analytical and gradient search according to the Marquardt algorithm. Through the use of an unique Circuit Description Code (CDC) different equivalent circuits may be used with the program. The use of an analytical derivatives routine enhances the execution speed. The power of such a fit procedure is demonstrated in multi parameter fits, on synthetic and real data, performed by the program "EQIVCT".

The compositional variations of the thermodynamic and mass transport properties of the ~ phase "LiAr' in the lithium-aluminum system have been investigated over the temperature range from 415 ~ to 600~ At 415~ the emf of the single phase "LiAI" lies between 300 and 70 mV relative to pure Li and this corresponds to a 'Li activity increasing from 0.0063 to 0.31 over the phase stability range from 46.8 to 55.0 atomic percent Li. At the ideal stoichiometry, the standard Gibbs free energy of formation of "LiAI" is --29.2 kJ/mole at 415~ and the corresponding enthalpy and entropy are --43.3 kJ/mole and --20.6 J/mole ~ respectively. Two different electrochemical transient techniques have been used to measure the chemical diffusion coefficient in "LiAI" as a function of the stoichiometry; the experimental results obtained are in good agreement. On the lithium deficit side of the ideal stoichiometry, the chemical diffusion coefficient increases with decreasing Li concentration, becoming about 10 -4 cm2/sec near the phase boundary. On the other hand, it is composition independent on the Li excess side of "LiAI," varying with temperature from 2.4 • 10 -6 cm2/sec at 415~ to 1.8 • 10-~ * Electrochemical Society Active Member.

A method is described with which immittance data can be tested for Kronig-Kramers compliance. In contrast with other procedures, this method is linear in nature and is based on a predetermined set of relaxation times. The model contains as many parameters (or less) as there are data sets. Three modes of operation are described, the first two are based on a linear fit of the model function to the imaginary part or to the real part of the data set. With the fit parameters the corresponding real or imaginary dispersion can be calculated and compared with the actual measurement. In the third mode a complex model function is fitted to the complete data set. As the model function does comply with (a relaxed set of) the Kronig-Kramers (K-K) rules, it will not be able to reproduce the data set satisfactory in the case of nonK-K behavior, as can be observed from the residuals plot. Due to its linear nature, no starting values are needed for the data validation. The main limitation of this procedure is the size of the matrix and the accuracy of the matrix inversion.