Understanding the energy produced from oxidizing 1 kg of lithium

I am reading the following paper in preperation for a research project on the theoretical energy density of batteries: [*Lithium - Air Battery: Promise and Challenges*](http://www.researchgate.net/publication/231667201_LithiumAir_Battery_Promise_and_Challenges) and on the second page they describe the following calculation:



> 
> The oxidation of 1 kg of lithium metal releases 11,680 Wh/kg
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> 
> 


I was wondering specifically how this number was obtained. I think that this would be the right chemical equation to use for this type of approximation but I am not sure:


$$\ce{4Li (s) + O2 (g) -> 2Li2O}$$


I am wondering if anyone can explain to me how this number was produced.


