Charge/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 ... 

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. 

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.

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].

The cycle lives of several AB2 electrodes are illustrated in Fig. 20 [56], In some cases alloys require many charge-discharge cycles to become fully activated preactivation via direct reaction with H2 gas is helpful in this regard. Some pertinent properties and results are given in table 9. 

Electrode corrosion is the critical problem associated with the use of metal hydride anodes in batteries. The extent of corrosion is essentially determined by two factors alloy expansion and contraction in the charge-discharge cycle, and chemical surface passivation by the formation of corrosion—resistant oxides or hydroxides. 

Figure 3. Charge-discharge cycling characteristics of an Li/LiMn, yCo0, 04 coin-type cell (thickness 2 mm, diameter 23 mm). Charge 4.3 V, 1 niAcm-2 discharge 3.3 V, 3 mAcm 2 I molL-1 LiPF6 - EC/DMC (jr I00-x).

Matsuda and co-workers [39-41] proposed the addition of some inorganic ions, such as Mg2+, Zn2+, In3+, Ga3+, Al3+,and Sn2+, to PC-based electrolytes in order to improve cycle life. They observed the formation of thin layers of Li/M alloys on the electrode surface during the cathodic deposition of lithium on charge-discharge cycling. The resulting films suppress the dendritic deposition of lithium [40, 41]. The Li/Al layer exhibited low and stable resistance in the electrolyte, but the... 

The first 1.5 charge-discharge cycles of lithium/carbon cells are presented in Fig. 4 for both graphite (b) and petroleum coke (a) [71], In both cases, the first intercalation capacity is larger than the first deintercalation capacity. 

---