Electrodes capacity

Figure 5. Electrode capacity balance of a sealed Ni-Cd battery.

Umax = (Qd/Qch) -100% - is the maximum value of current efficiency Qch- charge electrode capacity) ... 

Comparison of Electrode Capacity Loss with the Loss of Graphite Electrodes Mass... 

Electrode capacity loss Weight loss of electrode... 

The comparison of electrode capacity loss with loss of their mass during the cycling unambiguously shows, that degradation of electrical characteristics cannot be explained only by CO2 derivation with appropriate decrease of an active material. The main mechanism depends strongly on the type of graphite. 

Figure 6. Temperature dependence of the electrode capacity of copper and silver (taken from ref. 16, with permission of the Electrochemical Society, Pennington, NJ).

Fig. 5-46. Differential capacity estimated for an electrode of intrinsic semiconductor of germanium by calculation as a function of electrode potential C = electrode capacity solid curve = capacity of a space charge broken curve = capacity of a series connection of a space charge layer and a compact layer. [From Goischer, 1961.)...

Fig. 6-47. Mott-Schottky plot of electrode capacity observed for n-type and p-type semiconductor electrodes of gallium phosphide in a 0.05 M sulfuric add solution. [From Meouning, 1969.]...

The flat band potential cem be estimated from the Mott-Schottl r plot of electrode capacity in the range of electrode potential where a depletion layer is formed as shown in Fig. 5-47 and in Fig. 5-49. The flat band potential can also be estimated by measuring the photopotential of semiconductor electrodes as shown in Fig. 5-62 the photopotential is zero at the flat band potential. 

Pig. 10-18. (a) PolarizatioD curves of anodic dissolution and (b) Mott-Schottky plots of an n-type semiconductor electrode of molybdenum selenide in the dark and in a photo-excited state in an acidic solution C = electrode capacity (iph) = anodic dissolution current immediately after photoexdtation (dashed curve) ipb = anodic dissolution current in a photostationary state (solid curve) luph) = flat band potential in a photostationary state. [From McEv( -Etman-Memming, 1985.]... 

Pocket plate design is not suitable for the positive electrode because of the infiltration of soluble zincate and the consequent decrease in positive electrode capacity. Porous matrix positives do not suffer so badly from... 

Table IV. Summary of Electrode Capacity Determinations from Selected...

The electrode capacities are adjusted so that the CFx cathode has about 10% less capacity than the SVO. During an operation of the defibrillator, the SVO supplies the pulse requirement and the CFx recharges the SVO during low demand periods. As a result, a drop in cell voltage indicates an end to the life of the battery. Physicians can use the change in cell voltage to determine when to replace the device. The principal use of Li-CFx is in miniature cells for use in memory protection, watches and cameras. 

The changes of initial electrode capacity as a function of grinding time are presented in Fig. 4. It clearly shows that the specific capacity markedly increased with increasing grinding time up to 72 h and then dropped to nearly nil with 240 h of milling. In particular, the discharge capacity for the electrode fabricated from the composite ground for 72 h was ca 378 mAh/g at the first cycle. Flowever, the electrode capacity of the material milled for... 

Fig. 5. Variation of the electrode capacity decay with different milling times 1, 1 h 2, 12 h 3, 72 h 4, 240 h.

As shown in Figure 3.5.7, the capacities for most cathode materials do not differ drastically. From the 1980s when LiCoOi (125 mA h g ) was produced to recently, with the development of LiNCM (180 mA h g-1), capacities were increased by less than 50%. From chemical and structural considerations, there is a clear reason not to expect drastic increases in electrode capacities within these classes of materials (and storage mechanisms). For example, the lithium insertion and extraction reaction in LiFeP04 reads... 

Typical commercial lithium battery cells nowadays have capacities > 1 A h. At electrode capacities of 100 mA h g"1, and typical electrode loading on the order of 10-3 g cm 2, electrode areas as high as 104 cm2 are required. Figure 3.5.9 shows a cylindrical cell, where the electrodes are wound around a core. Similarly, in case of prismatic cells, electrodes are folded on top of each other. For both principles, the current collector foils are coated on both sides with electrode material, and winding or folding leads to an extended stack of single cells. Positive and negative... 

An often very helpful strategy therefore is to modify existing materials. Compared to new compounds, such attempts would primarily not address thermodynamic quantities, such as open cell voltage. Instead, kinetic parameters can be optimized, and quantities such as practical cell voltage, electrode capacity, and power density can be drastically improved. 

The most convenient method to obtain information about the distribution of charges at a charged interface is the measurement of the electrode capacity and its dependence upon the potential drop at the interface and the frequency of the a-c used. 

While a number of investigations have dealt with different properties of semiconductor electrodes (8), the first measurements of the differential electrode capacity have been carried out by the present authors (9). An a-c bridge with a Wagner... 

The equivalent circuit for the calculation of the differential electrode capacity is shown in Fig. 2. It consists of a series resistance Rg, which represents the internal ohmic resistance of the germanium disk and of the metal contact. Since... 

If no surface charge is present at the semiconductor or if it does not change, we can neglect the potential drop outside the space charge or its change. The differential electrode capacity for an intrinsic semiconductor then is given by... 

The concentration of the carriers near the surface is increased by illumination. The steady state concentration increase corresponds to np = (n + An ). Thus the applied light increases the electrode capacities also. This increase is proportional to n/1 + A nj/hj[ for intrinsic samples. For doped Ge it is most pronounced if the minority carriers are enriched in the space charge, in agreement with theoretical considerations. As already shown by Brattain and Garrett (8), illumination increases the dissolution current of Ge. If Ai is the change... 

---