The present invention relates to zero waste process for the recovery of energy grade critical materials from spent oxide-based libs of  spent Lithium-Ion battery (LIBs) cathode system by semi hydrometallurgical recovery route. More particularly, the present invention  relates to extraction of metal values (Co, Mn, Cu, Ni, Al, Li) from the spent Lithium-Ion battery (LIBs) using a mild reductive acid  leaching medium. Subsequently the metals are recovered through a three-step chemical precipitation route. The transition metals (Co,  Mn, Cu, Ni, Al, Li) are obtained as mix metal dicarboxylate in the first step, while aluminum is separated as aluminum phosphate in  the second step, and lithium is recovered in the third step as ß-lithium phosphate with 99% purity. The reagents used in leaching and  precipitation of the valuable metals are efficiently recovered after third step, resulting in a fully sustainable process with zero waste.  Further the mix metal dicarboxylate and ß-lithium phosphate can be used directly or as precursor for energy applications.