Watch lithium ions swim between a graphite anode and a layered-oxide cathode in a transparent cell cutaway while electrons, blocked by the separator, take the long way around the external circuit. Reverse the flow between discharge and charge, and see the share lost to heat grow as you raise the rate.
The battery was packed under the floor of the EV. Open one grain of it — one cell — and there are only four rooms. Graphite anode on the left, layered-oxide cathode on the right, a thin separator dividing them, and the external circuit crossing above. The green grains are lithium ions. Right now the cell is charged: most of the ions are sitting between the layers of graphite in the anode. The energy is stored neither as a liquid nor as a flame, but as where the ions get to sit.
Turn the cell and find all four rooms: anode, separator, cathode, external circuit.
