The mechanism of particle synergetic effect is attributed to the compensating property of blending components, which improves the inter-particles diffusibility of Li+, therefore reduces the particle impedance of blended materials promoting rate performance.
An equivalent circuit model is proposed to interpret the electrochemical behaviors showed in electrochemical impedance spectroscopy. The model analysis of charging-discharging characters shows that LiMn2O4 releases more reversible capacity in the blended materials than when it is alone at the same electrochemical condition. A synergetic effect, a capacity increasing at high discharging rate referring to the linear superposition of blending components, is observed in a wide blending ratio for blended materials. This work reports a systematic study of LiNi1/3Co1/3Mn1/3O2–LiMn2O4 blended materials incorporated with characterizations of particles, calculations of charging-discharging characters, and analysis of cyclic voltammetry. The proposed process obeys the principles of circular economy and green chemistry.īlended cathode materials generally suffer from capacity loss impacting on their power performance in lithium-ion batteries. Moreover, the emission of toxic gases SO2 and NOx generated in the acid roasting was avoided.
Through the precise regulation of NCM phases during the synergistic roasting process, the efficient cascade extraction of Li and TMs from spent NCM batteries was realized, and a new way for the comprehensive utilization of the Na2SO4 byproducts was determined. During the self-reduction roasting of graphite anode, the addition of Na2SO4 transformed Li from Li2CO3 to LiNaSO4 with higher solubility and also prevented the overreduction of Ni and Co oxides to the metallic states, which are prone to the deterioration of their acid leaching performance. Subsequently, >95% Ni, >99% Mn and >99% Co were leached by H2SO4 solution without additional reductant. >85% Li was selectively extracted from the roasted product by water leaching. The NCM cathode was transformed into water-soluble LiNaSO4 and acid-dissolved divalent oxides of (NiO)m(MnO)n and CoO based on the synergy between self-reduction of graphite anode and Na2SO4 roasting. A novel process was developed for the selective extraction of Li and efficient leaching of transition metals (TMs) from spent LiNixCoyMnzO2 (NCM) batteries coupled with the synergistic disposal of Na2SO4 byproducts generated from lithium battery industry.
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