Capacity charge-density profile

This contribution involves the positive-ion and electron density profiles of the metal, and the former is often assumed not to change with charging of the interface. In 1983 and 1984, several workers30-32,79 showed how certain features of the interfacial capacity curves should depend on the metal. 

In addition to the ion-clustered gel morphology and microcrystallinity, other structural features includes pore-size distribution, void type, compaction and hydrolysis resistance, capacity and charge density. The functional parameters of interest in this instance include permeability, diffusion coefficients, temperature-time, pressure, phase boundary solute concentrations, cell resistance, ionic fluxes, concentration profiles, membrane potentials, transference numbers, electroosmotic volume transfer and finally current efficiency. 

The electronic properties of a monolayer of Pb [8] and T1 [9] on Ag(lll) electrode surfaces have been calculated by using a density functional formalism. Calculations show that, as for metal surfaces in general, the excess charge in the electronic-density profile lies in front of the metal surface. The work function of the T1 monolayer on Ag(l 11) was found to be close to the bulk T1 value [9]. For a Pb monolayer, calculations predict almost the same interfacial capacity as for a surface of Ph(l 11). The latter result is in accord with the experimental data for polycrystalline Ag [6]. 

Examination of the structure of the packing of 3-centre carbon dioxide at different pore sizes revealed a clear pattern of change with respect to pore size, associated with layer formation. Both the density profiles and the profiles of molecular orientation showed a monolayer of carbon dioxide oriented parallel to the pore walls at small pore size below about H = 0.71 nm. However, with increase in pore width above 0.68 nm there is a tendency for the flat molecules to rotate, in order to permit additional molecules to adsorb. Above about 0.71 nm an additional layer is formed, with molecules near the wall tending to tie flat and those at the centre tending to rotate relative to the axis. This pattern of behaviour is repeated as the pore size is increased. Fig. 3. depicts snapshots of the structure at different pore sizes. They reveal the formation of a central relatively flat layer, followed by rotation and subsequent separation of two distinct rotated layers. This pattern is consistently followed as the pore size increases, and in this way additional layers are created. This was confirmed fix)m the simulation results, by examination of profiles of density and the molecular orientation. Simulations with the 3-centre fluid without charges at the sites were also conducted, and yielded similar trends as given by the fluid with charges, with only a small reduction in capacity. Thus, the difference in liehavior compared to the U fluid is clearly related to the different molecular shape represented by the 3-center fluid, and not to electrostatic effects. 

However, two penalties, both associated with the energy density, arise from the disordered anode structure (1) a smaller Coulombic capacity than the theoretical value for LiCe and (2) a sloping potential profile during both charging and discharging. 

High-crystallinity natural graphite materials are attractive active materials in the negative electrode of lithium-ion batteries due to their high theoretical reversible charge capacity of 372 mAh g 1 as well as the low and flat potential profile below 0.2 V vs. Li/Li+, which are important features which are needed to improve the energy density of portable lithium-ion batteries. The drawbacks for the... 

Discharge-charge profile of LIB (coin cell) measured before (left, dotted line) and after annealing (right, solid line) the cathode active material, LiFeVPOx, at 450 °C for 120 min. The coin cell consists of an electrolyte of 1 M LiPFs mixed with EC/DMC and an anode of metallic Li. Capacity was measured under a current density of 0.2mAcm between 2.0 and 4.0V [14]. 

Figure 8.H Charge/dischai e voltage profiles (third cycle) of the as-prepared GNS and Vulcan XC-72 carbon. Capacities are per gram of carbon in the electrode. Cycling was carried out at a current density of 50 mA/g in 1 atm O2 atmosphere at room temperature (20°C). The cut voltage ranges were 2.0-4.4 V for the GNS electrode and 2.0-4.6 V for the Vulcan carbon electrode. Reprinted from Ref. 57, Copyright 2012, with permission from Elsevier.

Figure 3.12 Potential vs. capacity profiles of the electrodeposited SngjNigg on Cu substrate. The Sn52Ni3a electrode was cycled in the potential range of 0.01-2.0 V vs. Li/Li at the constant current density of 50 mA/g with three-electrodes cell using Li foils as counter and reference electrode In IM LiC104/EC-PC [1 1 vol%]. The letters Cand D In the figure stand for charge and for discharge. Reprinted with permission fromJ. Electrochem. Soc., 152[3], A560 [2005]. Copyright 2005, The Electrochemical Society.

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