Electronic structure lithium battery

An example of a layer structure mixed conductor is provided by the cathode material L CoC used in lithium batteries. In this solid the ionic conductivity component is due to the migration of Li+ ions between sheets of electronically conducting C0O2. The production of a successful mixed conductor by doping can be illustrated by the oxide Cei-jPxx02- Reduction of this solid produces oxygen vacancies and Pr3+ ions. The electronic conductivity mechanism in these oxides is believed to be by way of electron hopping between Pr4+ and Pr3+, and the ionic conductivity is essentially vacancy diffusion of O2- ions. 

These materials are known as insertion or intercalation hosts. The overall electrochemical process of a lithium battery is illustrated schematically in Fig. 7.2. During discharge it involves the dissolution of lithium ions at the anode, their migration across the electrolyte and their insertion within the crystal structure of the host compound, while the compensating electrons travel in the external circuit to be injected into the electronic band structure of the same host. The charging process is the reverse and the cell reaction may be written as ... 

Although the motion of protons does not lead to electrical conduction in the case of benzoic acid, electronic and even ionic conductivity can be found in other molecular crystals. A well-studied example of ionic conduction is a film of polyethylene oxide (PEO) which forms complex structures if one adds alkaline halides (AX). Its ionic conductivity compares with that of normal inorganic ionic conductors (log [cr (Q cm)] -2.5). Other polymers with EO-units show a similar behavior when they are doped with salts. Lithium batteries have been built with this type of... 

Figures 13 and 14 display the discharge processes for the two kinds of lithium battery. During discharge at the anode the lithium ions are formed from the lithium metal or are released from an Li,A, B < host material at the cathode the lithium ions are inserted into the void spaces of the structure of the A B insertion material. The lithium-ion battery behaves almost like a concentration cell lithium ions move from a lithium-rich source toward the cathode, which acts as sink, while electrons flow through the external circuit from anode to the cathode.

One of the most important practical applications of lithium compounds is as fast ion conductors with potential electronic applications such as solid electrolytes for lithium batteries. Li20 is a fast ion conductor in which the Li ions occupy a simple cubic sublattice with the antifluorite structure. Both MAS and static Li NMR spectra of Li20 have been reported, the former recorded as a function of temperature up to 1000 K (Xie et al. 1995). The effect of introducing vacancies on the Li sites by doping with LiF has been studied by high-temperature static Li NMR, which reveals the interaction of the Li defects > 600 K and the appearance of 2 distinct quadrupolar interactions at about 900 K. Measurements of the relative intensities of the satellite peaks as a function of temperature have provided evidence of thermal dissociation of an impurity-vacancy complex (Xie et al. 1995). 

Transition metal compounds are important materials for electrochemistry due to their ability to exist in various valence states. Several transition metal oxides (M0O3, V2O5, Mn02, etc.) have gained additional attention in the field of secondary lithium batteries due to their layered structure. These layers can be propped open by intercalated species such as solvated lithium and sodium ions, as well as larger molecules [5]. The layered structure intercalates lithium while the mixed valence transition metal centers allow for electron transfer. 

Liu, G.,Xun, S., Vukmirovic, N., Song,X., Olalde-Velasco, R, Zheng, H., Battaglia, V.S., Wang, L.,Yang,W., 2011a. Polymers with tailored electronic structure for high capacity lithium battery electrodes. Adv. Mater. 23, 4679-4683. 

Fister T. T, Schmidt M., Fenter R, Johnson C. S., Slater M. D., Chan M. K. Y, Shirley E. L. Electronic structure of lithium battery interphase compounds Comparison between inelastic x-ray scattering measurements and theory, J. Chem. Phys. 2011, 135,224513-224515. 

Leung, K., Electronic Structure Modeling of Electrocheinical Reactions at Electrode/ Electrolyte Interfaces in Lithium Ion Batteries. J. Phys. Chem. C 2013,117, 1539-1547. 

Johansson, P., Electronic Structure Calcirlations on Lithium Battery Electrolyte Salts. Phys. Chem. Chem. Phys. 2007, 9,1493-1498. 

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