Reversible cell

Japanese: 可逆電池 - かぎゃくでんち（英語表記）reversible cell

A battery in which both the positive and negative electrodes are in equilibrium in the open circuit state, such as a Daniell cell or a lead-acid battery. For example, in a Daniell cell that combines a copper/copper sulfate solution electrode system with a zinc/zinc sulfate solution electrode system, the two solutions are separated by a biscuit-like diaphragm, and unless the two electrodes are connected by a wire, both electrode systems are in a nearly equilibrium state, and the battery can be considered a reversible battery. In contrast, in a Voltaic cell, which is simply copper and zinc immersed in a sulfuric acid solution, there is no reaction that determines the equilibrium of the copper electrode in the open circuit state. In addition, zinc also dissolves as zinc (II) ions while generating hydrogen in the open circuit state, making it a non-equilibrium electrode system, and the Voltaic cell cannot be considered a reversible battery.

Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information

Japanese:

ダニエル電池，鉛蓄電池などのように，開回路の状態で正極，負極がともに平衡状態にある電池。たとえば銅/硫酸銅溶液の電極系と亜鉛/硫酸亜鉛溶液の電極系とを組合せたダニエル電池では，素焼のような隔膜で両溶液をへだててあり，両極を導線で結ばないかぎり，いずれの電極系もほぼ平衡状態にあり，可逆電池とみなせる。これに対して硫酸溶液に銅と亜鉛を浸しただけのボルタ電池の場合には，開回路の状態で銅電極の平衡を決定する反応がない。また亜鉛も開回路の状態で水素を発生しながら亜鉛 (II) イオンとして溶解する非平衡な電極系であり，ボルタ電池は可逆電池とみなせない。

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