Galvanostatic Charging

If the flux is taken to be independent of time, as assumed for a constant charging current, and the initial concentration is zero, the anodic current is obtained from the derivative of the concentration as 

As with potentiostatic charging, multiple values of D can be determined from successive transients obtained for different charging conditions. In a generalized series of transients, the. th transient is initiated after the (.s—l)th transient has reached a steady state.At t = ts, the sth initial hydrogen concentration attained under galvanostatic charging is 

At this instant, the cathodic charging current is instantaneously increased so that a new flux J (t) exists at the cathode side. The new concentration for the sth transient can be obtained by using the new initial and boundary conditions. If J t) is independent of time, the general anodic current relationship for multiple transient galvanostatic experiments is found to be 

This time again provides a convenient parameter for computing the diffusivity. The relationship between and thickness for galvanostatic charging is similar to that for potentiostatic charging except that the constant is different.  

The diffusivity can be determined from Eq. (41) by taking the first few terms of the series and evaluating the current at t = assuming that the steady-state anodic current equals the charging current. Similarly, Eq. (44) can be used to evaluate the current at t—ts = and so a value of D can be obtained after each transient in the sequence reaches a steady state. For t — = Eq. (44) can be written as 

---

FIGURE 10.9 Galvanostatic charging curve for a platinized platinum electrode in 0.1 M H2SO4 solution (1) anodic scan, (2) cathodic scan. 

Recent studies of the processes of activation and deactivation111 have shown, as seen in Fig. 20, that the time dependences of the potential, upon the application of current steps, resemble those characteristic of porous film formation and that the differences are of a quantitative nature. The initial part, representing a typical galvanostatic charging curve (with the initial jump due to the... 

Figure 3. Galvanostatic charge/discharge characteristics of a capacitor built from KOH activated carbon A-PM (mass of electrodes 12.2 mg/12.8 mg) 1=2 mA. Electrolytic solution ...

Figure 4. Impedance spectra of a supercapacitor based on the PPy/CNTs composite before (a) and after performing 500 galvanostatic charge/discharge cycles (b).

Figure 5. Galvanostatic charge/discharge curves of the coin cell mockups of Zn-Air battery...

Figure 1. Initial Galvanostatic Charge/Discharge Curves of Three Types of Active Carbonaceous Materials at C/20 rate.

Figure 6. Galvanostatic charge/discharge curves of natural SLA 1015 at C/20, C/l 0, C/3, C/2 and C rates. Electrolyte EC-DMC (1 1) LiPF6 (1M).

The electrochemical galvanostatic charge-discharge curves at different rates are presented by Figure 6. The data is also summarized in Table 6. In our testing, the irreversible capacity loss of SLC1015 was seen to... 

Figure 2. Galvanostatic charge/discharge of the as-received carbon cloth outgassed at 150°C under vacuum.

Figure 3. Galvanostatic charge/discharge of the carbon cloth outgassed 24 hours under vacuum at 900°C.

Figure 1. Typical galvanostatic charge (1) - discharge (2) curves of the lithium-ion battery grade graphite, SL-20 (Superior Graphite Co., USA), as tested at C/20 rate in 2016 coin cells having Li metalfoil as counter electrode and electrolyte EC.DMC + lMLiPFf,.

The conducting polymers show a significant non-faradaic component of the electrochemical mechanism. The essential differences of faradaic and non-faradaic systems in equilibrium behavior, trends of galvanostatic charge - discharge curves and cyclic voltammograms have been shown, and criteria for the identification of these mechanisms are proposed [8],... 

The electrochemical intercalation of Li was studied for carbon electrodes modified by the 2Co-Ni complex, which showed the best effect in the reaction of oxygen electroreduction. Galvanostatic charge-discharge technique (PC governed automatic bench) in 2016 coin type cells was used for this purpose. 

The observed small and interconnected pores are expected to perform as electrodes of supercapacitors. Cyclic voltammetry (CV) and galvanostatic charge/discharge curves were used to characterize the capacitive properties the resulting data in simple acid (1 mol L 1 II2S0/() are shown in Fig. 7.11. 

Fig. 7.11 Electrochemical performance of different carbons using a three-electrode cell in 1 mol L 1 H2S04 (a) cyclic voltammograms at a scan rate of 1 mV s 1, (b) galvanostatic charge/discharge curves at a current density of 0.2 Ag 1, (c) relationship of the specific capacitance with respect to the charge/discharge specific currents, and (d) Ragone plots.

Fig. 11.8 (a) Galvanostatic charge-discharge curve of the supercapacitor using G/CNTs (10 1) as the active material at constant current densities of 100, 250, 500, and 1000 mAg-1 using 30wt% KOH electrolyte, (b) Specific capacitance of 3D hybrid G/CNTs (10 1) measured at different current densities. Reprinted with permission from [88]. 

Hence, under the stated conditions, a plot of the varying overpotential T (, during decay against In t gives the Tafel coefficient a. The intercept will yield i0 if CDL is known from an independent source, e.g., a galvanostatic charging curve. 

---