Lithium cell capacity and specific energy density

W_cell = w_Li f_A + w_Li f_C + w_aux

where

w_Li is the weight (wt.) of lithium in the cell;
f_A is the multiplier for the anode wt.;
f_C is the multiplier for the cathode wt.;
w_aux is the auxiliary wt. of the cell (which includes the wt. of the electrolyte, separator, connectors etc. and typically comprises of 20% of the wt. of the active part of the cell).

Thus, as a first approximation:

W_cell ≈ 1.2 w_Li (f_A + f_C)

And the specific capacity of the cell (as mAh/g of the cell wt.) is given by:

w_Li 3860/1.2 w_Li (f_A + f_C) = 3860/1.2 (f_A + f_C)

The specific energy density (which is energy density, E divided by the weight of the cell) is the product of the specific capacity and the operating voltage in one full discharge cycle. The values are often quoted for an average voltage and less frequently for the maximum voltage in the discharge sequence. For a constant current drain I, the specific energy density can be written as:

[ I w_Li \(\int {V{\rm{d}}t} \) ] / w_cell

The integration is carried out over the full specified discharge time. The specified discharge time is related to a maximum and a minimum voltage threshold value to allow for recharging the battery. Outside the threshold values, the battery may attain an irreversible state. The specific energy density (Wh/kg of the cell) is related to the specific capacity as follows:

Specific energy density = specific capacity × average operating voltage

= w_Li 3860 / 1.2 w_Li (f_A + f_C) V_ave

= 3860 / 1.2  (f_A + f_C) V_ave