How a Lithium-Ion Battery Works

Concept — reversible lithium shuttling

A lithium-ion cell stores energy by moving Li⁺ ions between two electrodes. Discharging lets Li⁺ drift from the graphite anode to the layered-oxide cathode through the electrolyte, forcing electrons through your device — that electron flow is the current. Charging uses an external source to push everything back. The same ions shuttle back and forth, so the cell is rechargeable.

What the animation shows

Both electrodes sit immersed in one electrolyte, split by a porous separator. Watch the Li⁺ ions cross the electrolyte and the electrons travel the outer circuit — always in the direction the mode arrow shows. As Li⁺ leaves the anode the state of charge and voltage fall; charging reverses it. At the limits the current stops: Empty (all Li⁺ at the cathode) and Full (all back in the anode).

Quantities

• SOC — state of charge, 0–100% (fraction of Li⁺ held in the anode).
• Voltage — terminal voltage, modelled as V = 3.00 + 1.20·SOC (3.00 V empty → 4.20 V full).
• Current I — I = C-rate × Q, with cell capacity Q = 2.5 Ah; zero at Empty/Full.
• E_density = 250 Wh/kg — representative gravimetric energy density.
• r_Li⁺ = 76 pm — ionic radius of Li⁺ (Shannon, 6-coordinate).
• F = 96485 C/mol — Faraday constant, charge per mole of electrons.

Sources

Linden & Reddy, Handbook of Batteries; Tarascon & Armand, Nature 414 (2001); Shannon ionic radii (1976); CODATA 2018 (F). V(SOC) is a teaching model, not a datasheet curve.