When the battery is being used — and its stored energy is being discharged — tiny particles (called ions) inside the battery travel from the anode to the cathode, through a chemical solution called the electrolyte, creating an electrical current.
When the battery is being recharged, those particles then flow back from cathode to anode.
Image Credit: Battery University
Lithium’s role
Because lithium is stored in both cathode and anode, these cells are generally known as lithium ion. The separator, as its name implies, keeps the cathode and anode from touching each other and causing an electrical short.
Anode, separator
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