Full Cell Voltage Boundary Calibration to Prevent Crystalline Lithium Silicide Nucleation
Upper full cell voltage cutoff calibration limits local anode lithiation potential above 50 mV vs Li/Li+ to prevent crystalline silicon phase breakdown.
Phase Transition Potential
Meaning
Specific electrical potential at which an electrode material undergoes a fundamental change in crystal structure during charge or discharge. Observation of the phase transition potential allows for the identification of the precise moment lithium ions reorganize the host lattice. This event usually appears as a flat plateau or a sharp peak in the differential capacity curve.
Equilibrium Potential
Stability occurs when the chemical potential of the lithium in the electrode matches the electrical potential of the terminal. The phase transition potential marks the boundary between two stable configurations of the material.
Atomic Structure
Internal layers within the cathode or anode shift to accommodate the incoming or outgoing ions. At the phase transition potential, the material might change from a hexagonal to a monoclinic structure. These changes often involve mechanical stress which can lead to cracks in the electrode over many cycles.
Modern coatings attempt to suppress these transitions to improve the long term durability of the battery by keeping the structure in a single phase for as long as possible.
Operating Boundary
Voltage ranges can be set to avoid the most damaging structural shifts. Designers often set the cutoff voltages just before a phase transition potential to maximize the number of cycles the battery can survive.