The Theoretical Limit of Energy Per Unit Weight

The reversible cell potential in 30% KOH is 1.29 V. The electrical energy produced per mole is given by 

The sum of the molecular weights of the reactants is 331.8, leading to a theoretical energy density of 

This should be compared to a practical value of about 40 Wh kg, namely, just under 

What is the purpose of this kind of calculation In the development of a battery it is important to know how far we are from its theoretical limit, since the practical limit, which is typically half the theoretical limit, can be reached asymptotically and the effort in approaching it grows exponentially. Thus, if current technology represents only 20% of the theoretical limit, there is a very good probability that it could be developed to 50%, namely by a factor of 2.5. On the other hand, if current technology has reached 45% of the theoretical limit, it is probably dose to its practical limit, and the wisdom of attempting to develop it further may be questioned. 

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