The effect of microcrack on the capacity fading of nickel-rich NCA cathode material

Abstract

The mechanism for capacity fading of Ni-rich cathode material is inspected through Li[Ni1-x-yCoxAly]O2 (NCA) (1-x-y = 0.8, 0.88, and 0.95) which synthesized for this research. However, the discharge capacity is enhanced as Ni content increase, the capacity retention and thermal property is degraded. This properties degradation could relate well with H2-H3 phase transition, where the anisotropic volume change takes place, and resulting growth of microcracks. Even though the microcracks start to propagate at 3.9V in all particle core of three cathodes, the microcracks, reached to outer surface, increases with Ni fraction increases during further charging process. Theses severe microcracks can be the pathway of electrolyte and deliver electrolyte into the particle center, that accelerates degradation of the surface of primary particles. Therefore, suppressing H2-H3 phase transition, which mainly causes microcracks, should be the first step to develop the next generation lithium ion battery.