Surface residual lithium compounds severely affected the preparation and application of LiNi0.80Co0.15Al0.05O2(NCA)cathode materials.Coating the NCA surface with Li-reactant agents is an efficient method for transforming these residual lithium compounds.Nonetheless,a singular coating technique is insufficient to satisfy all specified requirements.In this paper,the liquid phase and solid phase were combined.First,the LiOH on the surface of the NCA cathode material was washed with ethanol,and then Al2O3was added.Combined with XRD,SEM,TEM and XPS analysis,the added Al2O3reacted with the washed LiOH,not only generating a β-LiAlO2coating on the surface of the NCA cathode material,but also effectively reducing the amount of residual LiOH on the surface.Electrochemical performance tests revealed thatβ-LiAlO2coating could enhance the first discharge performance,rate capability,and cycle stability of the NCA cathode material.The capacity retention rate of LiAlO2-NCA samples remained at 68.4%,after 200 cycles at 1 C.CV and EIS analyses showed that the improvement in the electrochemical performance of the LiAlO2-NCA sample was attributed to the β-LiAlO2coating,which can not only enhance Li+diffusion kinetics and conductivity of the cathode material but also reduce the interface side reactions between the electrode and electrolyte,thereby decreasing the Rct.
In this study,composite solid-state electrolytes(CSEs)were fabricated by incorporating 20%,50%,and 80% of Li1.3Al0.3Ti1.7(PO4)3solid electrolyte powder into a poly(ethylene oxide)(PEO)-based solid polymer electrolyte(SPE)matrix via a solution casting method.The microstructural characteristics,ionic conductivity,Young’s modulus,and interfacial electrochemical stability with lithium metal anodes of the LATP/SPE composite electrolytes were systematically investigated.Experimental results demonstrated that the CSE containing 50%LATP exhibited optimal electrochemical performance,achieving stable cycling for 1600 h at a current density of 0.5 mA/cm2.This performance significantly surpassed that of composites with 0,20%,and 80%LATP additions.Furthermore,the interfacial failure mechanisms between lithium metal and CSEs with varying LATP contents were thoroughly elucidated.
The efficient recovery of valuable metal resources,such as iron,nickel,cobalt and copper,from iron-rich nickel slag represents a key technical bottleneck in the comprehensive utilization of nickel slag resources.This study focused on metallized pellets produced by the reduction of modified nickel slag.Firstly,the thermodynamic analysis of the CaO-MgO-SiO2 slag system for these pellets was carried out using FactSage software,and the composition of secondary slags and melt characteristics were determined through phase diagrams and equilibrium calculations.Then,the effects of melting temperature,alkalinity and other factors on the recovery rates of valuable metals,such as iron,nickel,cobalt and copper in metallized pellets were investigated through experiments.The migration and enrichment characteristics of the target metals were also explored during the melting separation process,the optimal processing parameters were identified,and the underlying mechanism was analyzed.Thermodynamic calculations showed that when the slag system alkalinity of modified nickel slag metallized pellets was within the range of 0.70.9,the melting temperature was lower than 1400℃,the viscosity was 0.20.4 Pa·s,and the secondary slag phase was the pyroxene phase.Experimental results showed that when the melting temperature was 1600℃,and the alkalinity was 0.9,the recovery ratio of melted iron reached 95.31%.The enrichment and recovery ratios of nickel,cobalt and copper were all satisfactory.
Aiming at a zinc sulfate solution containing a Fe2+concentration of 20.3 g/L produced by a zinc hydrometallurgical plant,a new process was developed to oxidize Fe2+to Fe3+using pure oxygen in an autoclave.Secondary zinc oxide powder was utilized as a neutralizing agent to neutralize the acid generated during the iron precipitation stage.The reaction pH value was rigorously controlled within the range of 3.0 to 4.0.Under the conditions of oxygen partial pressure of 0.35 MPa,reaction temperature of 80℃,agitation speed of 450 r/min,and neutralizing agent dosage of 55 g/L,the oxidation and removal of Fe2+from the zinc sulfate solution were achieved within 50 min.The total iron(TFe)concentration in the solution after iron precipitation was less than 2 g/L,and the iron removal efficiency reached 92%.
The primary impurity minerals in microcrystalline graphite include quartz,mica,chlorite,and sulfide minerals(such as pyrite).Current acid leaching purification processes face challenges,including the low solubility of impurities and the occurrence of secondary precipitation.In this study,hydrochloric acid(HCl)and hydrofluoric acid(HF)were used as the primary leaching agents,and ammonium persulfate((NH4)2S2O8)was introduced to enhance the oxidative properties of the leaching system,thereby strengthening the purification effect.Acid leaching experiments demonstrated that the fixed carbon content of graphite increased from 98.0% to 98.4% with the addition of ammonium persulfate,indicating a significant improvement in the purification efficiency.Thermodynamic analysis revealed that while pyrite cannot spontaneously react with HF and HCl at ambient temperature,the addition of ammonium persulfate promoted its dissolution.Furthermore,it was found that the reaction of mica and chlorite with HF tended to generate potassium hexafluorosilicate(K2SiF6)precipitates.However,the presence of hydrochloric acid in the mixed acid system effectively suppressed the formation of these precipitates to a certain extent,thereby enhancing the purification efficiency.Structural characterization of the purified graphite indicated that the introduction of ammonium persulfate did not adversely affect the surface morphology or the crystalline structure of the microcrystalline graphite.
The efficient recovery of valuable metal resources,such as iron,nickel,cobalt and copper,from iron-rich nickel slag represents a key technical bottleneck in the comprehensive utilization of nickel slag resources.This study focused on metallized pellets produced by the reduction of modified nickel slag.Firstly,the thermodynamic analysis of the CaO-MgO-SiO2 slag system for these pellets was carried out using FactSage software,and the composition of secondary slags and melt characteristics were determined through phase diagrams and equilibrium calculations.Then,the effects of melting temperature,alkalinity and other factors on the recovery rates of valuable metals,such as iron,nickel,cobalt and copper in metallized pellets were investigated through experiments.The migration and enrichment characteristics of the target metals were also explored during the melting separation process,the optimal processing parameters were identified,and the underlying mechanism was analyzed.Thermodynamic calculations showed that when the slag system alkalinity of modified nickel slag metallized pellets was within the range of 0.70.9,the melting temperature was lower than 1400℃,the viscosity was 0.20.4 Pa·s,and the secondary slag phase was the pyroxene phase.Experimental results showed that when the melting temperature was 1600℃,and the alkalinity was 0.9,the recovery ratio of melted iron reached 95.31%.The enrichment and recovery ratios of nickel,cobalt and copper were all satisfactory.
Aiming at a zinc sulfate solution containing a Fe2+concentration of 20.3 g/L produced by a zinc hydrometallurgical plant,a new process was developed to oxidize Fe2+to Fe3+using pure oxygen in an autoclave.Secondary zinc oxide powder was utilized as a neutralizing agent to neutralize the acid generated during the iron precipitation stage.The reaction pH value was rigorously controlled within the range of 3.0 to 4.0.Under the conditions of oxygen partial pressure of 0.35 MPa,reaction temperature of 80℃,agitation speed of 450 r/min,and neutralizing agent dosage of 55 g/L,the oxidation and removal of Fe2+from the zinc sulfate solution were achieved within 50 min.The total iron(TFe)concentration in the solution after iron precipitation was less than 2 g/L,and the iron removal efficiency reached 92%.
The primary impurity minerals in microcrystalline graphite include quartz,mica,chlorite,and sulfide minerals(such as pyrite).Current acid leaching purification processes face challenges,including the low solubility of impurities and the occurrence of secondary precipitation.In this study,hydrochloric acid(HCl)and hydrofluoric acid(HF)were used as the primary leaching agents,and ammonium persulfate((NH4)2S2O8)was introduced to enhance the oxidative properties of the leaching system,thereby strengthening the purification effect.Acid leaching experiments demonstrated that the fixed carbon content of graphite increased from 98.0% to 98.4% with the addition of ammonium persulfate,indicating a significant improvement in the purification efficiency.Thermodynamic analysis revealed that while pyrite cannot spontaneously react with HF and HCl at ambient temperature,the addition of ammonium persulfate promoted its dissolution.Furthermore,it was found that the reaction of mica and chlorite with HF tended to generate potassium hexafluorosilicate(K2SiF6)precipitates.However,the presence of hydrochloric acid in the mixed acid system effectively suppressed the formation of these precipitates to a certain extent,thereby enhancing the purification efficiency.Structural characterization of the purified graphite indicated that the introduction of ammonium persulfate did not adversely affect the surface morphology or the crystalline structure of the microcrystalline graphite.
The efficient recovery of valuable metal resources,such as iron,nickel,cobalt and copper,from iron-rich nickel slag represents a key technical bottleneck in the comprehensive utilization of nickel slag resources.This study focused on metallized pellets produced by the reduction of modified nickel slag.Firstly,the thermodynamic analysis of the CaO-MgO-SiO2 slag system for these pellets was carried out using FactSage software,and the composition of secondary slags and melt characteristics were determined through phase diagrams and equilibrium calculations.Then,the effects of melting temperature,alkalinity and other factors on the recovery rates of valuable metals,such as iron,nickel,cobalt and copper in metallized pellets were investigated through experiments.The migration and enrichment characteristics of the target metals were also explored during the melting separation process,the optimal processing parameters were identified,and the underlying mechanism was analyzed.Thermodynamic calculations showed that when the slag system alkalinity of modified nickel slag metallized pellets was within the range of 0.70.9,the melting temperature was lower than 1400℃,the viscosity was 0.20.4 Pa·s,and the secondary slag phase was the pyroxene phase.Experimental results showed that when the melting temperature was 1600℃,and the alkalinity was 0.9,the recovery ratio of melted iron reached 95.31%.The enrichment and recovery ratios of nickel,cobalt and copper were all satisfactory.
