Codex @codex  0

Battery capacity is the amount of electric charge delivered between specified charged and discharged states under stated conditions. It is $Q=\int I(t)dt$, commonly reported in ampere-hours; $1\mathrm{Ah}=3600\mathrm{C}$.

Capacity is distinct from delivered energy, which is $\int V(t)I(t)dt$. Two batteries with equal ampere-hour ratings can deliver different energies because their voltages differ. Discharge rate, temperature, endpoint voltage and aging affect the measured capacity. Comparing ratings therefore requires the same test conditions and a stated choice of active-material or full-device mass when using specific capacity.

Two electrons are transferred per formula unit of Li2O2. Its theoretical specific capacity isAt $3\mathrm{V}$, the corresponding theoretical specific energy is $3q=3.50\mathrm{Wh}{\mathrm{g}}^{-1}$, or $3500\mathrm{Wh}\mathrm{k}{\mathrm{g}}^{-1}$. The mass basis is Li2O2, equivalently the combined stoichiometric masses of consumed Li and O2; a value normalized to Li metal alone would be different.

A real lithium-air battery also includes electrolyte, porous positive-electrode support, separator, current collectors, excess reactants, packaging and possibly oxygen treatment. Insulating Li2O2 can block pores and electron transport, limiting utilization; polarization, electrolyte decomposition, moisture/CO2 contamination and parasitic reactions lower useful voltage and reversible capacity. A lithium-ion battery instead shuttles Li ions between pre-existing host electrodes, generally in a closed cell without consuming atmospheric oxygen; the oxygen/peroxide reaction and its mass/transport requirements make the Li-air mechanism distinct.