Meaning
Lithium-ion electrochemical cells experience reversible and irreversible dimensional changes in their active materials during charge and discharge cycles. This physical deformation, referred to as electrode strain, occurs as lithium ions insert into and extract from the host crystal lattice. It develops within both the anode and cathode, creating mechanical stresses that propagate through the cell layers.
The magnitude of this displacement depends on the chemistry of the active material and the state of charge.
Damage Mechanism
Repetitive volume expansion and contraction generate internal stress gradients that exceed the cohesive strength of the binder. Under these conditions, electrode strain leads to microcracking within individual active material particles. This cracking exposes fresh surfaces to the electrolyte, which accelerates the consumption of active lithium.
The electrical contact between the particles and the current collector eventually degrades.
Performance Degradation
Impedance growth occurs when the conductive network within the electrode is disrupted by mechanical action. Accumulated electrode strain causes macroscopic swelling of the battery pack, which requires structural containment to prevent cell damage. This swelling reduces the round-trip efficiency of the energy storage system.
It also shortens the operational life of the battery.
Mitigation Strategy
Cell design relies on composite formulations that accommodate volume shifts. Incorporating elastic binders and conductive additives helps absorb electrode strain. These materials maintain the electronic path during cycling.
