(1) In order to clarify this problem, we must first clarify the definitions of positive and negative poles, cathodes and anodes.
Positive and negative electrodes: The high potential electrode is the positive electrode and the low potential electrode is the negative electrode.
Anode and cathode: The electrode where the oxidation reaction occurs is the anode, and the electrode where the reduction reaction occurs is the cathode.
(2)For an electrochemical device, the positive and negative electrodes always exist, while the cathode and anode only exist when a reaction occursC' that is to say if the battery. is in an open circuit state, there is no current. If current passes through it, there will only be positive and negative poles but no cathode or anode.
(3) Example: For a system using Cu and Zn as electrodes and CuSO4 as electrolyte, the electrode potential of Cu is alwaysbear greater than Zn,So whether it is a primary battery or an electrolytic battery the Cu cell is always the positive electrode and Zn is always the negative electrode. But this is not the case for the distinction between cathode and anode. It will change depending on the reaction of the electrode.
For the primary battery: the negative electrode of Zn undergoes an oxidation reaction, it is therefore an anode, and the positive electrode of Cu undergoes a reduction reaction, it is therefore an cathode (cathode).
For electrolytic cells (copper on Zn): the negative electrode of Zn undergoes a reduction reaction, it is therefore the cathode (cathode), and the positive electrode of Cu undergoes a reaction of Oxidation is therefore the anode (anode).
In summary: In the primary battery, the negative electrode is the anode and the positive electrode is the cathode. The button cell that we usually do electrochemistry research on is a batteryie primary, so the material of the positive electrode is called cathode material. and the negative electrode material is called anode material.
In the electrolytic cell, the negative electrode is the cathode and the positive electrode is the anode.
In short, there is no certain correspondence between the positive and negative electrodes and the cathode and the anode The most important thing is to distinguish which type of device electrochemical it is about and to judge. Remember that positive and negative electrodes only. The anode and cathode are distinguished based on the potential level of the electrode, and the anode and cathode are distinguished based on the redox reaction.