Why doesn't anyone manufacture 4.5 V cells?

Every 4.5 V lantern batteries are a series of three 1.5 V cells. It would have more capacity if it consisted of single 4.5 V cell. But I don't see any 4.5 V cell.

According to Wikipedia's Standard Electrode Potential data page, there are vast possibilities of a 4.5 V cell. The one I think most plausible is:

\begin{align} \text{Anode:} &\quad &\ce{Ca + 2 H2O &→ Ca(OH)2 + 2 H+ + 2 e-} \quad|\cdot 5\\ \text{Cathode:} &\quad &\ce{2 BrO3- + 12 H+ + 10 e- &→ Br2 + 6 H2O}\\ \hline \text{Overall:} &\quad &\ce{5 Ca + 2 HBrO3 + 4 H2O &→ 5 Ca(OH)2 + Br2} \end{align}

Have anyone tried this or anything else 4.5 V?

• To put it mildly, I'd say that your perspective on what is and what isn't plausible in chemistry is rather skewed. Aug 20 '19 at 10:18
• @IvanNeretin Well, to be honest, I thought it's plausible because it's a calcium battery. Aug 20 '19 at 10:19
• Calcium is not that good in a battery, for it will react with water by itself. (Sure, some workaround might be possible.) Bromine is not good anywhere near you. HBrO3 is even worse, and moreover, it doesn't even exist in a pure form. Aug 20 '19 at 10:22
• @IvanNeretin HBrO3 is in aqueous solution. (The cathode reaction was edited accordingly.) Aug 20 '19 at 10:34
• Would it really 'have more capacity' if it were a single 4.5V cell? That depends on many factors that have nothing to do with the electrode potentials. Engineering a useful product is way harder than you think. Aug 20 '19 at 12:34