| Neglecting the additional mass for a heater and for thermal insulation, the specific capacity in ampere-hour per kg should be less than for non-rechargeable lithium batteries (which have a slightly lighter lithium metal electrode and also lighter organic electrolyte), but much higher than for lithium-ion rechargeable batteries. The mass of the heater and of the thermal insulation will diminish the specific capacity only a little for large batteries, but much more for small batteries. To get the specific energy we also need the output voltage, which is mentioned neither in the paper abstract nor in the press release. In any case, the voltage will be much lower than for lithium-ion batteries, so it is likely that despite the higher specific capacity such Al-S batteries will have lower specific energy. Even so, the difference in cost could be so large that this would not matter. It is hard to say which will be the output voltage, because the enthalpy of the reaction can vary a lot in function of the structure of the sulfur deposited on the electrode during charging and on the type of sulfide that forms during discharging. Googling for the enthalpy of formation of aluminum sulfides provides contradictory information, with various values corresponding to output voltages between 0.7 V and 1.4 V. Anyway, it is probable that the output voltage of an Al-S battery would be at most half, but more likely no more than a third of that of a Li-ion battery. Probably the specific energy will be less than for Li-ion, but it is hard to predict if the difference will be significant or negligible. On the other hand, for the energy per volume it is much more likely that it could exceed the energy per volume of the Li-ion batteries. |