Meaning
Electrochemical phases occurring during the insertion of lithium ions into a carbon matrix define the sequential thermodynamic steps of anode charging. These graphite lithiation stages represent distinct ordered structures, commonly designated from stage four to stage one as the concentration of lithium increases. Each phase transition correlates with a specific change in the crystalline structure of the host material.
Structural Transition
Host layers shift from random distributions to highly ordered configurations to accommodate the intercalating ions. During the transition between different graphite lithiation stages, the spacing between graphene sheets expands to prevent structural collapse. This expansion must be managed to avoid particle cracking.
Voltage Profile
Distinct plateaus in the open circuit potential curve indicate the coexistence of two phases at a given state of charge. Understanding the graphite lithiation stages helps identify when the anode is approaching full capacity and running a higher risk of lithium plating.
Design Influence
Cell designers use these phase transition limits to optimise fast-charging protocols without triggering anode degradation. High charging rates can cause non-uniform distribution across the graphite lithiation stages, creating localized over-lithiation. This mismatch accelerates capacity fade and can lead to internal short circuits if dendritic lithium grows through the separator.
