12. Batteries: thermo-electro-chemical modeling#
A battery is an electrochemical system that converts chemical energy directly into electrical energy via spontaneous reduction-oxidation (redox) reactions. It acts as an electrochemical reactor where the spatial separation of the oxidation and reduction steps forces electrons to flow through an external load to perform work.
Core components.
Anode (negative electrode): the electrode where oxidation (loss of electrons) occurs during discharge.
Cathode (positive electrode): the electrode where reduction (gain of electrons) occurs during discharge.
Electrolyte: a medium containing mobile ions that carries ionic current inside the cell while remaining electronically insulating.
Separator: a permeable membrane that prevents physical contact between the anode and cathode to avoid internal short circuits.
Classification.
Primary (non-rechargeable): the underlying chemical reactions are thermodynamically irreversible or physically difficult to reverse. Once the reactants are depleted, the battery cannot be recharged (e.g., Alkaline, Zinc-carbon).
Secondary (rechargeable): the redox reactions are highly reversible. Applying an external electrical potential drives the current in reverse, regenerating the initial chemical reactants (e.g., Lithium-ion, Lead-acid, NiMH).
Examples.