Abstract
As the explosive growth of the electric vehicle market leads to an increase in spent lithium-ion batteries (LIBs), the disposal of LIBs has also made headlines. In this study, we synthesized the cathode active materials Li[Ni1/3Mn1/3Co1/3]O2 (NMC) and Li[Ni1/3Mn1/3Co1/3Fe0.0005Al0.0005]O2 (NMCFA) via hydroxide co-precipitation and calcination processes, which simulate the resynthesis of NMC in leachate containing trace amounts of iron and aluminum from spent LIBs. The effects of iron and aluminum on the physicochemical and electrochemical properties were investigated and compared with NMC. Trace amounts of iron and aluminum do not affect the morphology, the formation of O3-type layered structures, or the redox peak. On the other hand, the rate capability of NMCFA shows high discharge capacities at 7 C (110 mAh g−1) and 10 C (74 mAh g−1), comparable to the values for NMC at 5 C (111 mAh g−1) and 7 C (79 mAh g−1), respectively, due to the widened interslab thickness of NMCFA which facilitates the movement of lithium ions in a 2D channel. Therefore, iron and aluminum, which are usually considered as impurities in the recycling of LIBs, could be used as doping elements for enhancing the electrochemical performance of resynthesized cathode active materials.
Highlights
Lithium-ion batteries (LIBs) are suitable for portable IT devices, energy storage systems, and electric vehicles (EVs) due to their excellent electrochemical performance, related to their long cycling life and high energy density [1]
Both NMC and NMCFA have spherical secondary particles consisting of granular primary particles, which indicates that trace amounts of iron and aluminum do not affect the morphological properties of precursors
This result is consistent with the previous literature that has investigated the effects of iron or aluminum on the morphology of NMC [10,11]
Summary
Lithium-ion batteries (LIBs) are suitable for portable IT devices, energy storage systems, and electric vehicles (EVs) due to their excellent electrochemical performance, related to their long cycling life and high energy density [1]. Spent LIBs contain considerable impurities such as iron, aluminum, and copper, in addition to the valuable metals included in the cathode active materials, such as lithium, nickel, and cobalt. Trace impurities such as zinc, magnesium, calcium, and sodium can emerge during the LIB recycling process [5]. We synthesized iron and aluminum co-doped NMC (NMCFA) cathode active materials via the co-precipitation method, which simulates the resynthesis of NMC in leachate containing trace amounts of iron and aluminum from spent LIBs. A tolerance level of 0.05 mol% for iron and aluminum was introduced during the co-precipitation, aiming at the synergetic effect of enhancing the structural and electrochemical properties. A series of electrochemical analyses including the galvanostatic intermittent titration technique (GITT), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) were systematically conducted to elucidate the effects of co-doping process
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