Meaning
Features in a differential capacity plot that identify specific stages of lithium staging within the anode material. These graphite intercalation peaks correspond to the transitions between different crystalline phases as ions occupy spaces between the carbon sheets. Scientists use these markers to assess the state of health and the degree of degradation in the negative electrode.
Phase Staging
Orderly insertion of ions creates distinct energy levels within the hexagonal lattice. When graphite intercalation peaks shift to higher or lower potentials, it indicates a change in the thermodynamic environment of the host material. This shift often occurs due to the expansion or contraction of the carbon layers.
Voltage Signature
Differential capacity analysis (dQ/dV) transforms a standard charge curve into a series of distinct humps. Each of the graphite intercalation peaks represents a peak in electrochemical activity at a specific voltage plateau. A decrease in the height of these peaks correlates with the loss of active lithium or accessible carbon sites.
The relative distance between these features reveals the kinetics of the intercalation process and the stability of the electrolyte interface.
Anode Health
Mechanical stress from repeated expansion can fracture the particles and blur the signal. Clear and well-defined graphite intercalation peaks suggest that the structural integrity of the anode remains intact. Continuous monitoring of these peaks allows for the early detection of capacity fade mechanisms.
