Recovery of valuable metals from spent lithium-ion battery (LIB) is of both environmental and economic importance. Acidic leaching usually encounters issues of low selectivity or slow kinetics with considerable secondary waste generation during further purification. In this research, a closed-loop process with improved leaching selectivity for recycling of spent LiNixCoyMn1-x-yO2 battery using weak acidic leachant was demonstrated. To obtain optimal conditions of the leaching process, the effects of acid concentration, solid to liquid (S/L) ratio, temperature and reductant content were systematically investigated. Almost all Co, Li, Mn and Ni could be effectively recovered into the solution while Al remained in the residue as metallic form, after one-step leaching. The role of reductant during leaching was further evaluated which was found to be critical for the leaching kinetics. It is clear that the addition of reductant could alter the rate-controlling step of leaching from the ion diffusion in the residue layer to the surface chemical reactions. With high selectivity against impurities, this research proposed and verified a process to recover high purity Li2CO3 from the cathode scrap of LIBs, and more than 90% of the global recovery rate of valuable metals can be achieved. Display omitted •A selective leaching process for recycling spent lithium-ion battery was proposed.•Acetic acid leaches all metals out except Al whose leaching rate is only 2.36%.•The effect of reductant on the leaching kinetics was quantitatively evaluated.•The introduction of reductant alters the rate-controlling step of leaching process.•High purity of Li2CO3 is recovered with more than 90% of recovery rate for metals.