Working principle of lithium battery

Lithium ion migration between positive and negative electrodes
The working principle of lithium-ion battery is based on the reversible migration of lithium ions between positive and negative electrodes, and the mutual conversion of electrical energy and chemical energy is realized through electrochemical reactions. ‌ The specific process is as follows: ‌
Core principle and charging and discharging process
‌ When charging: The external power source drives lithium ions to be deintercalated from the positive electrode material (such as lithium cobalt oxide, lithium iron phosphate), and penetrate the electrolyte to embed into the layered graphite structure of the negative electrode. At the same time, electrons flow to the negative electrode through the external circuit to form a current. ‌ When discharging: Lithium ions are deintercalated from the graphite negative electrode, and return to the positive electrode material through the electrolyte. Electrons flow to the positive electrode through the external circuit to power external devices.
Key materials and reaction mechanisms ‌ Positive electrode material: Commonly used lithium cobalt oxide, lithium iron phosphate, etc., release lithium ions through oxidation reactions. ‌ Negative electrode material: Graphite is mostly used, and its layered structure can reversibly store lithium ions. ‌ Electrolyte: As an ion transport medium, it allows lithium ions to move but blocks electrons.
Voltage dynamics
Battery voltage fluctuates with charge and discharge status:
‌Initial charging‌: voltage is low, internal resistance and polarization effects are significant; voltage continues to rise during constant current phase (e.g. ternary lithium battery rises from 3.0V to 4.2V).
‌Discharge process‌: voltage gradually decreases until it reaches the cut-off voltage (usually ≥2.5V) to avoid collapse of the negative electrode structure.