"The degradation rate of lithium-ion battery is not a linear process with respect tonumber of cycles, battery aging tests (Fig. 1) have shown that in cycling tests the degradation rate is significantly higher during the early cycles than during the later cycles, and then increases rapidly when reaching the end of life (EoL)."

Actually, 80% is considered effectively 'end of life':

"Battery end of life is typically defined as the point at which the battery only provides 80% of its rated maximum capacity"

* https://www.researchgate.net/publication/303890624_Modeling_...