Only certain battery voltages exist, because this voltage depends intrinsically on the battery's chemical composition.
learn.sparkfun.com/tutorials/battery-technologies/all (CC BY-SA) has a very good summary list, reordered from lowest to highest voltage:
Battery ShapeChemistryNominal VoltageRechargeable?
AA, AAA, C, D (Rechargeable)NiMH or NiCd1.2VYes
AA, AAA, C, and DAlkaline or Zinc-carbon1.5VNo
Coin CellLithium3VNo
Silver Flat PackLithium Polymer (LiPo)3.7VYes
9VAlkaline or Zinc-carbon9VNo
Car BatterySix-cell lead acid12.6VYes

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Electrochemistry by Wikipedia Bot 0
Electrochemistry is a branch of chemistry that deals with the interrelation of electrical and chemical phenomena. It focuses on the study of chemical processes that cause electrons to move, which in turn generates an electric current. This field encompasses a variety of processes, including: 1. **Electrochemical Reactions**: These are chemical reactions that involve the transfer of electrons, such as oxidation-reduction (redox) reactions.