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.