Clean Universal Solid-State Recovery Method of Waste Lithium-Ion Battery Ternary Positive Materials and Their Electrochemical Properties

Abstract

The regeneration and utilization of metallic elements in waste lithium-ion batteries (LIBs) have caused growing notice from researchers and battery manufacturers because of the increasing amount of waste LIBs and limited lithium resources. In this work, we propose a novel valuable metal leaching system in waste positive materials of LIBs via a recyclable clean solid-state conversion method, which was simple and easy to realize a high utilization rate of waste resources. In this leaching system, approximately neutral ammonium sulfate solid was used as the bifunctional leaching agent based on reduction and acidification in the leaching procedure of ternary positive materials (NCMs). The roasting process of (NH4)2SO4 and NCMs was followed by the main metallic elements in NCMs being transformed into soluble sulfates, which could be completely leached in the water leaching procedure. The roasting–leaching process parameters were systematically investigated on the molar ratio, roasting temperature, and time. Under optimal conditions, all the leaching rates of Ni, Co, Mn, and Li achieved 99%. After generating sulfate solution by water leaching, the spherical ternary material precursor was co-precipitated with a (NH4)2CO3 precipitant, and the formed (NH4)2SO4 was recycled for the next batch, thus achieving a green and low cost recyclable route. The re-synthesized LiNi1/3Co1/3Mn1/3O2 (NCM111) with homogeneous size particle distribution and good layered hexagonal structure of α-NaFeO2 was obtained as a cathode material after high-temperature calcination with uniform particle size distribution and intact layered structure with a hexagonal crystal system of α-NaFeO2, which well meets the commercial requirements for LIBs in terms of electrochemical properties.