ABSTRACT
Copper ions are one of the major associated metal ions present in the precursors of the synthesis of Li[NiCoMn]1/3O2 from the recovery of spent Li-ion batteries by wet chemical processes. To evaluate the feasibility of reusing Cu(2+) as a favourable dopant in Li[NiCoMn]1/3O2 instead of as usual removing it as an undesirable impurity, the effect of Cu-doping on the electrochemical behaviour of Li[NiCoMn]1/3O2 is investigated in this work. Li[NiCo1-xCuxMn]1/3O2 (x = 0, 0.02, 0.04, 0.06 and 0.08) is synthesized through two steps, roasting the precursors obtained from carbonate co-precipitation, and their structures and electrochemical performances are systemically investigated. The results indicate that substitution of Co with Cu was successfully achieved without any detectable second phases. The initial discharge capacity of Li[NiCo1-xCuxMn]1/3O2 gradually dropped with an increase of x but the rate property and capacity retention were remarkably enhanced. In particular, the capacity retention of the Li[NiCo0.94Cu0.06Mn]1/3O2 sample reached 95.87% within 50 cycles at a current density of 160 mA g(-1). CV and EIS revealed that such improvements are ascribed to a higher Li(+) diffusion coefficient and lower charge-transfer resistance derived from Cu(2+) doping. The results suggest that Cu can be used as a beneficial dopant to partially substitute Co in synthesizing Li[NiCoMn]1/3O2 from spent LIBs instead of having to remove it as an impurity.
ABSTRACT
A novel strategy of waste-cleaning-waste is proposed in the present work. A metals-doped ZnO (M-ZnO, M = Fe, Mg, Ca and Al) nanomaterial has been prepared from a metallurgical zinc-containing solid waste "fabric filter dust" by combining sulfolysis and co-precipitation processes, and is found to be a favorable photocatalyst for photodegradation of organic substances in wastewater under visible light irradiation. All the zinc and dopants (Fe, Mg, Ca and Al) for preparing M-ZnO are recovered from the fabric filter dust, without any addition of chemical as elemental source. The dust-derived M-ZnO samples deliver single phase indexed as the hexagonal ZnO crystal, with controllable dopants species. The photocatalytic activity of the dust-derived M-ZnO samples is characterized by photodegradation of phenol aqueous solution under visible light irradiation, giving more prominent photocatalytic behaviors than undoped ZnO. Such enhancements may be attributed to incorporation of the dust-derived metal elements (Fe, Mg, Ca and Al) into ZnO structure, which lead to the modification of band gap and refinement of grain size. The results show a feasibility to utilize the industrial waste as a resource of photodegradating organic substances in wastewater treatments.