Charging-Discharging Curve

1 Capacitance, Maximum Energy and Power Densities, and Equivalent Series Resistance Measurements 

As discussed in Chapter 2, immediately after charging starts (charging time t 0), the supercapacitor charging voltage (V j) can be expressed as Equation (7.21) if the two-electrode test cell and the constant current (I u) charging modes are employed  

Cj is 0.127 F.cm or 0.509 F for the entire cell with an electrode area of 4 cm. The specific capacitance is 34 F.g i for the carbon loading of 0.015 g, the maximum cell voltage (V )max IS 0.991 V, and the equivalent series resistance = 0.806 n.cm or 0.202 fi for the entire cell. Using these values, the maximum energy and power densities ((EJ ax ( Jmax/ respectively) can be calculated according to the equations presented in Chapter 2  

For pseudosupercapacitors, charging-discharging curves can also be used to measure capacitance, maximum energy and power densities, and equivalent series resistance by simulating experimental charging and discharging curves. For more information, see Chapter 3. 

2 Cycle Life Measurement Using Charging-Discharging Curves 

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Figure 8. Charge-discharge Curves for Li Sn (x=0.8 to 2.5) at ambient temperature. Solid points are at a current density of 0.24 mAcm 2, and open points at a current density of 0.5 rnAcrn-2. The equilibrium potential is also shown [41 ].

Figure 14. Charge-discharge curves for the upper plateau in the LirSi system inside a matrix of the Li2 f)Sn phase at 415 °C. The upper panel shows the effect of current density, whereas the lower panel shows that the potential overshoot related to the nucleation of the second phase is mostly eliminated if the electrode is not cycled to the ends of the plateau (441.

Figure 17. Sixth charge-discharge curve of a composite Li Sn/Li-Cd electrode at a current density of 0.1 m Acm 2 at ambient temperature [48],...

Figure 7. First- and second- cycle constant-current charge/discharge curves of graphite Timrex KS44 in LiN(S02CF3)2/ethylene carbonate/dimethyl carbonate as the electrolyte (CilT irreversible specific charge Crev =reversible specific charge) [2J.

Figure 12. Top Schematic model showing the mechanism of lithium storage in hydrogen containing carbons as proposed in Ref. [2471. Below Schematic charge/discharge curve of a hydrogen containing carbon.

Figure 15. First- cycle constant-current charge/discharge curve of hard carbon ("Carbotron P"). The figure has been reproduced with kind permission of Kureha Chemical Industry Co., Ltd. [2381.

Wang et al. [96] constructed a Na/S battery with a sodium metal anode, liquid electrolyte, and a sulfur (dispersed in polyacrylonitrile) composite cathode and tested its electrochemical characteristics at room temperature. The charge/discharge curves indicated that sodium could reversibly react with the composite cathode at room temperature. Average charge and discharge voltage was 1.8 and 1.4 V, respectively. Similar to lithium batteries, dendrite formation was noted as a critical problem for these cells. 

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

Figure 11. First cycle constant current charge/discharge curves of synthetic graphite TIMREX SFG 44 using 1 MLiCl04 in PC PS (propylene sulfite) (95 5 by volume) as electrolyte, i = +20 mA g1, cut-off = 1.8/0.025 Vvs. Li/Li+.

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. Initial charge/discharge curve of graphite sample SL-20, in 1.2MLiPF6, EC/PC/MEC (3 3 4) electrolyte. Test cell was cycled at C/5 rate.

Figure 4. Charge/discharge curves of the surface treated natural graphite SLC1015 vs. Li/Lt in MLiPF6, EC.DMC (50 50 wt%).

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],... 

Thus, in the process of Li+ reaction with tin, theoretical capacity of Li-Sn alloys can reach up to 790 mA-h/g. Theoretical capacity of pure Sn is 994 mA-h/g (7234 mA-h/cm3). Formation of such alloys occurs in the range of potentials from 0 to 0.8V versus lithium (Table 2) or in the temperature window 0-800°C. Charge-discharge curves have an inclined form. 

We made attempts to deposit 1 mp layer of P-tin film on 20 mp tungsten foil. This foil was previously etched in nitric acid. We showed by XRD the absence of Sn-0 and Sn-Mo bonds (Figure 2). Charge-discharge curves in all cases have sloping shape typical of tin (Figure 3). 

Figure 3. Charge-discharge curves of tin on tungsten current collector.

Figure 5. Charge-discharge curves of Hohsen Carbon-Type Material in the course of long-term cycling.

The theoretical charge (discharge) curves calculated with the help of equation (24) at the following values of P10 = P20 = 1 and... 

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]. 

FIG. 23. Charge discharge curves for nanotubular (a) and thin film (b) LiMn204/ polypyrrole electrodes. Current density = 0.1 mA cm. Electrolyte was 1 M LiC104 in 1 1 (vol.) propylene carbonate dimethoxyethane. 

Ag VjOj is a vanadium bronze with a composition range of 0.3 < x < 1.0, the bronze with x = 0.29-0.41 has the / -phase structure and that with X = 0.67-0.89 the 5-phase one. The 5-phase shows good reversibility for silver intercalation and deintercalation. The typical charge-discharge curves at a constant current of 0.3 mA cm for cell [11.3] are shown in Fig. 11.3. No significant deterioration was observed for several hundred... 

Traces of potassium compounds are also found due to reactions with the molten electrolyte. The sequence of phase changes during the charging process are even more complex. Typical charge/discharge curves are shown in Fig. 8.11. 

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