Considering the necessity of green and sustainable recycling of spent lithium-ion batteries (LIBs). Herein, a green closed-loop leaching process based on electrolysis of sodium sulfate solution for recycling spent LIBs is demonstrated. Electrolysis technology and LIBs recycling technology are combined together in this work. The H2SO4 and NaOH obtained by electrolysis of sodium sulfate solution are used as leachate, and the generated O2 and H2 can be recycled due to the high added value. Under the optimal condition, the leaching efficiencies for Al, Ni, Co, Mn, and Li can all reach more than 99%, then high pure Al(OH)3, Li2CO3, and spherical Ni0.5Co0.2Mn0.3CO3 precursor are obtained from the recycled solution. Moreover, the spherical regenerated LiNi0.5Co0.2Mn0.3O2 is synthesized by using recycled-Li2CO3 and Ni0.5Co0.2Mn0.3CO3 precursor, and it has excellent electrochemical performance with the highest discharge specific capacity of 167.04 mAh g-1, good rate performance and cycle stability (87% capacity retention after 100 cycles). The remained acid-based solution in the

recycling process can be neutralized to form sodium sulfate and reused for electrolysis, which constitutes a closed-loop cycling process. Finally, it is calculated that an economic outcome of $6992 is obtained by recycling one ton spent lithium-ion batteries. These results show this closed-loop hydrometallurgical strategy is environment green and industrial valuable, which can be further extended to recycle other transition metal layered oxide cathode batteries.