Self-discharge mechanism

Ikoma et al. carried out a detailed investigation to study the self-discharge mechanism and contribution of separators.They used nonwoven fabric made of conventional polyamide (FA), FF (with surfactant), and a nonwoven fabric whose main material was sulfonated-FF (hydrophilic) as separators. When nonwoven fabric made of chemically stable sulfonated-FF is used as a separator instead of a conventional polyamide separator, the self-discharge rate of the NiMH battery was strongly depressed, to the same level as that of NiCd battery. 2 >o-242.243... 

These self-discharge behaviors have been demonstrated with different capacitor samples. BCAP0007 and BCAP0008 are Maxwell commercial products. They show only a diffusion-driven self-discharge mechanism. BCAPproto which is a prototype with a high impurity content undergoes oxidation-reduction reactions. The two different plots show the respective linear drop in their respective representation. 

Figure 4. Proposed self-discharge mechanism for metal sulfide...

The electrochemical kinetic behavior described in Equations (27.19)-(27.21) are easily discernible and therefore provide a basis for diagnostics for the establishment of self-discharge mechanisms after recording the dependence of potential or voltage of an electrode or cell in an open-circuit voltage on time. The presence of... 

At present, two procedures are used to characterize the self-discharge behavior of ECSCs and batteries. One of them consists of the measurement of the time dependence of voltage drop under open circuit to distinguish between the self-discharge mechanisms, as described earlier. Another procedure is float current measurement of the dependence of current on time at a constant potential for an individual electrode or at constant voltage V on the cell. 

A number of works suggests an explanation for the self-discharge mechanism that is based on redistribution of ions within pores. This explanation agrees well with the results of measurements, but requires further studies. A mathematical model of these... 

Oickle, A. M., and H. A. Andreas. 2011. Examination of water electrolysis and oxygen rednction as self-discharge mechanisms for carbon-based, aqueous electrolyte electrochemical capacitors. Journal of Physical Chemistry C 115 4283—4288. 

The phenomenon was attributed to a reaction between the metastable Lii5Si4 phase with the electrolyte through a self-charge mechanism. The reactivity of the amorphous lithium silicides and the self-discharge mechanism may lead to capacity loss or safety concerns. However, the authors noted that the use of carboxymethylcellulose (CMC) as a binder inhibited the discharge process significantly, implicating the reduction of side reactions with the electrolyte and, hence, capacity losses. 

N. Cui and J. L. Luo [2000] An AC Impedance Study of Self-Discharge Mechanism of Nickel-Metal Hydride (Ni-MH) Battery Using Mg2Ni-Type Hydrogen Storage Alloy Anode, Electrochim. Acta 45, 3973-3981. 

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