In this study, the evolution trends in various hydrogen storage properties as well as kinetics performance of LaNi5-xCox (x = 0, 0.25, 0.50 and 0.75) alloys up to 1000 cycles are studied, and the effects of Co on the long-term hydrogen absorption/desorption properties are revealed. The alloys have single LaNi 5 phase structure. The cell volume increases with increasing Co content, resulting in a lower hydrogen absorption/desorption plateau pressure and a more stable hydride phase. The alloys have good kinetics performance and can fully absorb hydrogen within 300 s. The hydrogen absorption rate increases with either cycling or Co addition, but neither of them changes the rate limiting step which remains to be diffusion controlled model in the temperature range of 343-383 K. With cycling, an intermediate gamma phase emerges with the coexistence of alpha and beta phases indicated by an extra higher plateau in P-C-T curves. This gamma phase acts as a buffer releasing the microstrains which is reflected from the slower capacity degradation, and the significant decrease in hysteresis and slope factor upon its appearance. Moreover, the c/a value increases after 1000 cycles which also relieves the microstrains in the alloys. Co addition not only enhances the buffer effect of gamma phase by partially combining it with beta phase, but also promotes the increasing degree of c/a value, contributing to a better crystal structure, bigger particle size and higher cycle stability during long-term cycling. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.