The plates in wet-cell batteries can be anodes that are attached to a negative battery terminal, or alternatively cathodes attached to a positive battery terminal. When a load is attached to the terminals, a chemical reaction occurs between the lead, lead oxide, and electrolyte solution (water and acid). How does a wet electrochemical cell work?
So when the battery is hooked up to something that lets the electrons flow through it, they flow from negative to positive. You might wonder why the electrons don't just flow back through the battery, until the charge changes enough to make the voltage zero.
After continuous use over the years, a wet cell battery can no more give sufficient power to the load connected to it. This happens because with use, the plate material erodes, thereby causing reduction in their size. Is simple cell wet cell?
The lead-acid cells in automobile batteries are wet cells. Figure 3: A lead-acid battery in an automobile. In dry cell batteries, no free liquid is present. Instead the electrolyte is a paste, just moist enough to allow current flow. This allows the dry cell battery to be operated in any position without worrying about spilling its contents.
With this analogy, it is plainly obvious why both the positive and negative ends of a battery must be connected in a circuit. If, say, you connect only the negative electrode to ground, there is no current because there is no electricity coming in on the positive electrode that can be pumped out.
The anode is the negative electrode of a discharging battery. The electrolyte has high ionic conductivity but low electrical conductivity. For this reason, during discharge of a battery, ions flow from the anode to the cathode through the electrolyte. Meanwhile, electrons are forced to flow from the anode to the cathode through the load.