First cycle discharge

Figure 13. First cycle discharge capacities (---) and charge/discharge efficiencies (—) of a soft (graphitiz-...

Another important feature for lithium graphite intercalation compounds in Li -containing electrolytes is the formation of solid electrolyte interface (SEI) film. During the first-cycle discharge of a lithium/carbon cell, a part of lithium atoms transferred to the carbon electrode electrochemically will react with the nonaque-ous solvent, which contributes to the initial irreversible capacity. The reaction products form a Lb-conducting and electronically insulating layer on the carbon surface. Peled named this film as SEI. Once SEI formed, reversible Lb intercalation into carbon, through SEI film, may take place even if the carbon electrode potential is always lower than the electrolyte decomposition potential, whereas further electrolyte decomposition on the carbon electrode will be prevented. 

FIGURE 36.4 First-cycle discharge characteristics of rechargeable zinc/alkaline/manganese dioxide AA-size batteries discharged continuously at different constant-current loads at 22°C. (Courtesy Battery... 

FIGURE 36.8 First cycle discharge characteristics of rechargeable zinc /alkaline / manganese dioxide C-size batteries discharged continuously at different constant resistance loads at 2(TC Curve 1 - 6.8 ft. 160 mA (approx.) curve 2 - 3.9 ft. 270 mA (approx.) curve 3 — 2.2 ft. 450 mA (approx.). Courtesy of Battery Technologies Inc.)... 

Sulfur has a high theoretical capacity of 1671 mAh/g and is thus an attractive cathode material, however successful demonstration of secondary Mg/S batteries was not achieved until non-nucleophilic electrolytes such as GENl were discovered a first cycle discharge capacity of 1200 mAh/g S (vs. 1675 mAh/g theoretical capacity based on a 2-electron reduction to form MgS) was achieved by Kim et al. [23] using such electrolytes. Cell voltage was <1 V, however. Significant... 

Figure 1S.13 First cycle discharge capacities (—) and charge/discharge efficiencies (—) of a soft (graphitizing) carbon (Melblon carbon fibers (MPCF)) at different heat-treatment temperatures. Reproduced with kind permission of Petoca, Ltd. (Takamura, T. Tamaki, T. Petoca Ltd., personal communication).

What is the origin of excess capacity during the first cycle discharge in metals forming alloys with Li compared with their respective phase diagram ... 

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.

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+.

One important conclusion from the works on the construction of the cell is that the material (SL-20) can be described as one having excellent process properties. By this, one should among others understand perfect adhesion to the copper foil and the ability to form smooth and uniform layers. The discharge capacities for the first ten cycles are presented in the Figure 3, together with the discharge profile for the first cycle. 

Figure 3. Discharge capacities for he first ten cycles for the Li-ion cell SL-20 anode. The inset discharge curve for the first cycle.

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