Discharge Cycles

Fig. 12. Diaphragm pump (a) suction cycle, and (b) discharge cycle.

IndiAdual cells are usually precycled before assembling into batteries. Tliese early charge—discharge cycles, often called fomiation cycles, improv e the capacity of the cell by increasing the surface area of the active material and effecting cry stal structure changes. 

In most cases, the impregnation process is followed by an electrochemical formation where the plaques are assembled into large temporary cells filled with 20—30% sodium hydroxide solution, subjected to 1—3 charge—discharge cycles, and subsequentiy washed and dried. This eliminates nitrates and poorly adherent particles. It also increases the effective surface area of the active materials. 

Electrochemistry and Kinetics. The electrochemistry of the nickel—iron battery and the crystal stmctures of the active materials depends on the method of preparation of the material, degree of discharge, the age (Life cycle), concentration of electrolyte, and type and degree of additives, particularly the presence of lithium and cobalt. A simplified equation representing the charge—discharge cycle can be given as ... 

Li—Al/FeS cells have demonstrated good performance under EV driving profiles and have deUvered a specific energy of 115 Wh/kg for advanced cell designs. Cycle life expectancy for these cells is projected to be about 400 deep discharge cycles (63). This system shows considerable promise for use as a practical EV battery. 

Cyclic tests can be perfonned in just a few months to simulate years of fill and discharge cycles. The adsorbent filled ANG tank is repeatedly charged with natural gas to a preset pressure, then discharged through a flow meter to determine the quantity of gas delivered from each cycle. 

Two electrochemical lithium/carbon cells were made for each of the pyrolyzed materials. We used currents of 18.5 mA/g (20-hour rate) for the fust three charge-discharge cycles and 37 mA/g (10-hour rate) for the extended cycling test. 

The lithium-ion-polymer battery, which uses a cathode that contains lithium instead of cobalt, is likely to eventually replace lithium-ion. Lithium-ion-polymer batteries boast a longer life expectancy (over 500 charge-and-discharge cycles as opposed to around 400), much more versatility (they are flat and flexible and can be cut to fit almost any shape), and better safety (far less likely to vent flames while recharging). 

For smart cards, micro-robots and small precision instruments, thin laminated micro-cells are being developed. Some of these developmental thin-film devices—using an electrolyte of lithium, a copper cathode, and lithium again for the electrode—can charge and discharge up to 3 volts, and can be expected to tolerate up to 1,000 charge-and-discharge cycles. 

Reduce the amount of change in the electrolyte and electrodes per charge-and-discharge cycle to extend life expectancy. 

Figure 10. Charge-discharge cycle characteristics of an Ni-Cd battery (cell type 1200SC).

Figure 10 shows the charge-discharge cycle characteristics. As shown in this fig-... 

Figure 16 shows the charge-discharge cycle characteristics of alloys in which part of the nickel component was replaced with cobalt. Misch metal (Mm), which is a mixture of rare earth elements such as lanthanum, cerium, praseodymium, and neodymium, was used in place of lanthanum. It was found that the partial replacement of nickel with cobalt and the substi-... 

These techniques are useful for improving cell characteristics such as cell capacity and charge-discharge cycle life. 

Figure 46. Cycling performance of the Li-Al-CDMO cell (ML2430). The number of 100% charge-discharge cycles is calculated until the capacity drops to 100% of the nominal value (end voltage 2.0 V). The number of 5%, 20% and 60% charge-discharge cycles is calculated until an end voltage of 2.0 V.

The lithium-titanium oxides are prepared by heating a mixture of anatase (Ti02) and LiOH at a high temperature. The product heated at 800-900 °C has a spinel structure of Li4/3Ti5y304. When the charge and discharge cycles are performed... 

One of the most important factors determining whether or not secondary lithium metal batteries become commercially viable is battery safety, which is affected many factors insufficient information is available about safety of practical secondary lithium metal batteries [91]. Vanadium compounds dissolve electrochemi-cally and are deposited on the lithium anode during charge-discharge cycle. The... 

Figure 6. Concentration of the complexing cations MEP1 (A) and MEM1 (0) in the complex electrolyte phase during one total charge-discharge cycle of a model zinc-flow battery. Taken from Ref. [90],...

Deterioration of electrode performance due to corrosion of electrode components is a critical problem. The susceptibility of MHt electrodes to corrosion is essentially determined by two factors surface passivation due to the presence of surface oxides or hydroxides, and the molar volume of hydrogen, VH, in the hydride phase. As pointed out by Willems and Buschow [40], VH is important since it governs alloy expansion and contraction during the charge-discharge cycle. Large volume changes... 

Figure 9. Charge capacity, Q, vs. number of charge-discharge cycles for three mischmetal AB5 electrodes. Note the high decay rate in charge capacity for Co-free electrode [42].

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