As the chemical reaction within the battery initiates, electrons flow from the negative electrode to the positive electrode. Simultaneously, lithium-ion migrates from the positive electrode to the negative electrode, engendering a redox reaction that converts electrical energy into chemical energy.
When charging the battery, the charger sucks electrons out of the cathode ('+' terminal), and pushes electrons into the anode ('-' terminal). This 'pumps' lithium ions through the electrolyte from the cathode (+) to the anode (-). The electrons can't move through the electrolyte, so they all 'pile up' at the anode.
Why is an anode a negative electrode of a discharging battery?
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.
When discharging a battery, the cathode is the positive electrode, at which electrochemical reduction takes place. As current flows, electrons from the circuit and cations from the electrolytic solution in the device move towards the cathode.
The electrons can't move through the electrolyte, so they all 'pile up' at the anode. When an external circuit is connected the electrons flow through the wires from the anode back to the cathode, and the lithium ions move back through the electrolyte to meet them. It is the ions inside the battery that transport charge.
The electrons don't pass through the battery. They come out from the negative terminal and go back into the positive terminal, and that's it. Here's an illustration of how it works in a Li-ion battery:- When charging the battery, the charger sucks electrons out of the cathode ('+' terminal), and pushes electrons into the anode ('-' terminal).
The electron excess in the zinc and the electron deficiency in the copper electrode drive electron flow through the external circuit, from zinc (too many electrons, hence the negative electrode) to copper (with an electron deficit, hence the positive lead of the battery).