Meaning
Voltage threshold at which an electrolyte undergoes irreversible chemical breakdown marks the end of its stable operation. Cell designers use decomposition potential to establish the maximum safe charging voltage of a lithium-ion or sodium-ion battery. Beyond this electrical limit, the solvent or salt molecules oxidise or reduce on the electrode surfaces.
This value defines the boundary of the electrolyte working window.
Electrochemical Limit
Molecular orbital energy levels dictate the resistance of a formulation to electrical stress. The highest occupied molecular orbital governs the oxidation limit at the cathode, while the lowest unoccupied molecular orbital dictates the reduction limit at the anode. Sourcing teams compare these theoretical levels against the practical working voltage of the high-energy active materials to select compatible liquid mixtures.
When the cell potential exceeds these boundaries, electron transfer occurs directly between the electrodes and the electrolyte molecules, causing rapid decay. This electrochemical oxidation degrades the surface of nickel-rich cathode active materials and generates insulating byproducts that choke lithium ion transport during subsequent cycles.
Cell Degradation
Gas evolution and solid deposits are the immediate consequences of exceeding the electrochemical limits. When the organic carbonates break down, they release carbon dioxide, ethylene, or other volatile species that cause pouch swelling or cell venting. This reaction consumes active lithium ions and solvent, which increases internal resistance.
Over time, the decomposition potential transition is crossed, and the battery loses its power capability.
Measurement Method
Linear sweep voltammetry provides the standard way to determine the electrochemical stability limits of a liquid mixture. A working electrode is held in a test cell and the potential is slowly swept upward or downward while monitoring the current response. The point where the current increases exponentially defines the decomposition potential of the solution.
This test operates under inert conditions to prevent moisture contamination from skewing the results.
