Intercalation electrode interface

The electrochemical process at the intercalation electrode interface is basically reversible in polymer electrolyte media, as revealed by the cycling voltammetry of a typical example, namely that of the Li(i+x)V308 electrode in (PEO)8LiC104 cells (Figure 6.23) after a few initial activation cycles, the peaks become reproducible and well defined, both in the anodic and in the cathodic region. 

From a fundamental point of view, insertion electrochemistry deals with the thermodynamics and kinetics of intercalation processes starting at the electrodesolution and current collector-electrode interfaces, and occurring (propagating) into the electrodes interior. Very often (but not mandatory) intercalation processes into host electrodes occur in the form of first-order phase transition, and thus the classical galvanostatic charging of the electrode can be beneficially combined with simultaneous in situ XRD characterization. The latter allows the distinction between solid-solution and the two-phase coexistence paths of the intercalation process. 

The most frequent method for the analysis of CTs from intercalation electrodes is based on the grounds that lithium diffusion in the electrode is the rate-determining process in lithium intercalation/deintercalation. " This involves the following the system is so kinetically fast that the equilibrium concentration of lithium is quickly reached at the interface... 

The contribution of electric field to lithium transport has been considered by a few authors. Pyun et argued on the basis of the Armand s model for the intercalation electrode that lithium deintercalation from the LiCo02 composite electrode was retarded by the electric field due to the formation of an electron-depleted space charge layer beneath the electrode/electrolyte interface. Nichina et al. estimated the chemical diffusivity of lithium in the LiCo02 film electrode from the current-time relation derived from the Nernst-Planck equation for combined lithium migration and diffusion within the electrode. 

The fraction a has values between 0 and 1. When a =0.5, the CPE is called the Warburg element, W. The Warburg element is used to describe ionic diffusion (Macdonald, 1992) and the impedance is termed as Warburg impedance. In the case of intercalation electrodes, ionic species can diffuse at the interfaces, in the electrolyte or electrode and charge transfer can occur across the interfaces with resistance R... 

M. Atanasov, C. Daul, J.-L. Barras, L. Benco, and E. Deiss [1999] Polarizahle Continnum Model for Lithium Interface Transitions Between a Liqnid Electrolyte and an Intercalation Electrode. Solid State Ionics 121, 165-174. 

A general transport phenomenon in the intercalation electrode with a fractal surface under the constraint of diffusion mixed with interfadal charge transfer has been modelled by using the kinetic Monte Carlo method based upon random walk approach (Lee Pyim, 2005). Go and Pyun (Go Pyun, 2007) reviewed anomalous diffusion towards and from fractal interface. They have explained both the diffusion-controlled and non-diffusion-controlled transfer processes. For the diffusion coupled with facile charge-transfer reaction the... 

Interaction parameters for polymer blends, 20 322 in surfactant adsorption, 24 138 Interaortic balloon pump, 3 746 Intercalated disks, myocardium, 5 79 Intercalate hybrid materials, 13 546-548 Intercalation adducts, 13 536-537 Intercalation compounds, 12 777 Intercritical annealing, 23 298 Interdiffusion, 26 772 Interdigitated electrode capacitance transducer, 14 155 Interesterification, 10 811—813, 831 Interest expense, 9 539 Interface chemistry, in foams, 12 3—19 Interface metallurgy materials, 17 834 Interfaces defined, 24 71... 

The desire to realise technological goals has spurred the discovery of many new solid electrolytes and intercalation compounds based on crystalline and amorphous inorganic solids. In addition an entirely new class of ionic conductors has been discovered by P. V. Wright (1973) and M. B. Armand, J. M. Chabagno and M. Duclot (1978). These polymer electrolytes can be fabricated as soft films of only a few microns, and their flexibility permits interfaces with solid electrodes to be formed which remain intact when the cells are charged and discharged. This makes possible the development of all-solid-state electrochemical devices. 

Figure 5.12 Possibilities to deposit metal onto a SAM-modified electrode, (a) intercalation of metal at the SAM/substrate interface, (b) deposition originating at the substrate with subsequent mushroom-like growth, (c) deposition on top of a SAM resulting in a metal-SAM-metal sandwich structure.

Some of the very interesting applications of these layered intercalates are in material design [3], ion exchange [4], catalysis [5], in the study of quantum-sized semiconductor particles [6], assembly of molecular multilayers at solid-liquid interfaces [7], designer electrode surfaces [8], preparation of low-dimensional conducting polymers [9], and so forth. 

This section summarizes some of the most significant electrochemical results obtained to date for selected electrodes cleaned and characterized under UHV in PEO-lithium-based solutions, and include nonalloy (Ni)- and alloy-forming metals (Ag and Al), a noninteracting substrate (boron-doped diamond, BDD) and a material capable of intercalating Li+ (graphite). It is expected that the information herein contained will serve to illustrate the power of this methodology for the study of highly reactive interfaces. 

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