At a fundamental level the mixture and layers of the active chemistry need to stay in position and intact. Within the cathode and anode mixture binders are used to hold the particles together and to adhere them to the electrode.
During charge and discharge the active layers change in thickness and this can put a significant strain on the active layers.
Cell Expansion – as you charge a cell it expands, when you discharge a cell it contracts and as the cell ages over its lifetime we see a continuing cell expansion. Thus the cell expansion can be divided into:
- Irreversible cell expansion
- Reversible cell expansion
The extent of microcracking can be controlled via a variety of different particle-based strategies, the relevance of which depends upon if fracture arises from nonuniform lithiation due to fast charging or anisotropic swelling of primary grains. These strategies include limiting active material strains through control of the voltage or composition, decreasing the size of primary or secondary particles and enhancing their ionic conductivity.
See also: Cathode Contact Resistance: The Overlooked Lever Behind Single-Crystal NMC811 Longevity