Practical gravimetric capacity

The practical gravimetric capacity is the ratio between the amount of electricity generatable with a given current to the total mass of the secondary battery. It is necessary to specify the discharge current in which the secondary battery is discharged. 

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Materials Theoretical gravimetric capacity (mAh/g) Theoretical gravimetric capacity (mAh/g) with account taken of the degree of insertion Average practical gravimetric capacity (mAh/g) Cost... 

Practical gravimetric capacity to be compared with theoretical capacity 145Ah/kg (for 50% material used) 5.2 Ah/kg 98.6 Ah/kg ... 

In this section we will focus on four alanates with high practical potential such as NaAlH, LiAlH and Mg(AlH )2/Ca(AlH )2. Alanates with theoretical gravimetric capacities lower than that of NaAlH, being impractical for mobile applications, will not be discussed. 

The highest gravimetric capacity element is LiH (12.7 wt%) shown in Fig. 12.3. Many of these hydrides are not practical as their thermodynamic properties are out of range as discussed earlier the only metal hydride that has practical volumetric hydrogen storage capacity is VH2 (at 2.8 atm.) which can be hydrided at room temperature. A covalent compound hydride... 

The theoretical gravimetric capacity of this system is thus 11.5 wt% for 4 moles of H atoms to 1 mole of starting Li3N. In practice, the amount of stored hydrogen from nitride through to amide was found to be somewhat less, with uptake of 9.3 wt% and c. 10 wt% from gravimetric and volumetric measurements respectively. Taking the standard enthalpies of formation [41], the overall heat of the reaction in Eq. (16.5) was calculated to be... 

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