![]() Whether the cathode is negatively polarized (such as recharging a battery) or positively polarized (such as a battery in use), the cathode will draw electrons into it from outside, as well as attract positively charged cations from inside.Ī battery or galvanic cell in use has a cathode that is the positive terminal since that is where conventional current flows out of the device. Inside a device or a cell, positively charged cations always move towards the cathode and negatively charged anions move towards the anode, although cathode polarity depends on the device type, and can even vary according to the operating mode. The electrode through which conventional current flows the other way, into the device, is termed an anode.Ĭonventional current flows from cathode to anode outside the cell or device (with electrons moving in the opposite direction), regardless of the cell or device type and operating mode.Ĭathode polarity with respect to the anode can be positive or negative depending on how the device is being operated. For example, the end of a household battery marked with a + (plus) is the cathode. Consequently, the mnemonic cathode current departs also means that electrons flow into the device's cathode from the external circuit. Electrons have a negative electrical charge, so the movement of electrons is opposite to that of the conventional current flow. A conventional current describes the direction in which positive charges move. This definition can be recalled by using the mnemonic CCD for Cathode Current Departs. Positively charged cations move towards the cathode allowing a positive current i to flow out of the cathode.Ī cathode is the electrode from which a conventional current leaves a polarized electrical device. To find out more about BioLogic potentiostats which are used in battery research and battery testing among other research fields of interest please click our potentiostat overview page and Battery Testing/Battery Cycling overview page.Electrode where reduction takes place Diagram of a copper cathode in a galvanic cell (e.g., a battery). Let us not hesitate to write, paraphrasing Rutherford, implicit is nothing but poor explicit.įind out more about potentiostats and battery cyclers Texts describing battery anodes or cathodes certainly implicitly consider the case of the discharge. During charge the positive is an anode, the negative is a cathode.During discharge the positive is a cathode, the negative is an anode. ![]() On the other hand, the role of each electrode is switched during the discharge/charge cycle. 1).įigure 3: Discharge/charge of a secondary battery represented as an electrochemical cell, with electrons and current direction.ĭuring normal use of a rechargeable battery, the potential of the positive electrode, in both discharge and recharge, remains greater than the potential of the negative electrode. The electrochemical reaction that takes place at the negative of the zinc electrode of a Nickel-Zinc battery during discharge :
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