Meaning
Mechanical failure of active material grains caused by the propagation of cracks along specific crystallographic directions. During the charge and discharge cycles, the lattice dimensions of the material change, creating internal stress. Particle cleavage occurs when this stress exceeds the fracture toughness of the crystal.
Interfacial Degradation
Exposure of fresh surfaces to the electrolyte following a fracture leads to further side reactions. When particle cleavage creates new cracks, the electrolyte penetrates the interior of the grain and forms additional solid electrolyte interphase. This process consumes lithium and increases the overall resistance of the electrode.
Capacity Loss
Separation of a grain into smaller fragments can isolate portions of the active material from the conductive network. If a fragment loses electrical contact with the binder or carbon black, it can no longer store energy. Particle cleavage is thus a major contributor to the gradual decline in battery capacity during long-term use.
Stress Mitigation
Engineering the particle size and shape can help reduce the likelihood of mechanical failure. Smaller grains tend to experience lower internal gradients and are less prone to particle cleavage. Coatings that provide mechanical reinforcement or buffers that absorb volume changes are also used to prolong the life of the electrode.
