Strontium has a very low standard electrode potential and fluorine has a very high one.
$$ E_{\ce{F2 + 2e^- -> 2F^-}} = 2.87\mathrm{V} $$ $$ E_{\ce{Sr -> Sr^+ + e^-}} = -4.10\mathrm{V} $$
In theory a strontium-fluorine battery would have a voltage of $6.97\mathrm{V}$ although there are many practical reasons such as danger and rarity of materials for such batteries not to be made.
Is a strontium-fluorine battery the theoretically highest voltage chemical battery using pure elements or is it possible to obtain a higher one?