Microwave-enhanced Leaching Of Ni, Co And Mn From Cathode Materials Of Waste Ternary Lithium-ion Batteries

Lithium-ion battery is a kind of secondary battery with high specific energy and good safety.Its rapid development has also led to a blowout increase in the number of used lithium-ion batteries.Waste lithium ion batteries contain a large amount of valuab le metals Co,Ni,Mn,Cu,Al,Li,as well as some toxic organic electrolytes and binders.Therefore,recycling lithium-ion batteries can not only relieve the pressure on resource demand,but also reduce the environmental hazards of toxic substances.Based on the current research status of the existing technology,combined with the characteristics of microwave selective heating,environmental protection and energy saving,this research proposes a new technology of microwave pretreatment and microwave enhance d leaching;the apparent density and temperature of the microwave absorption performance of the cathode material are studied The influence of the positive electrode material and the thermal behavior of the cathode material in the microwave field;the influ ence of microwave pretreatment and microwave-enhanced leaching on metal recovery was explored,and compared with conventional leaching,the conclusions obtained are as follows:(1)The effect of apparent density and temperature on the dielectric properties of the positive electrode material was measured by the high-temperature dielectric test system,and it was found that as the apparent density of the positive electrode material increases,the dielectric constant also increases.However,the diel ectric loss factor and loss tangent reach the maximum when the apparent density is 1.484g/cm3.The high-temperature dielectric properties of the positive electrode material show that the dielectric constant of the positive electrode material is 6.86 at roo m temperature.As the temperature increases,the dielectric constant of the positive electrode material also increases,and reaches the maximum value of 11.96 at 400°C.The dielectric loss factor and the loss tangent also show a similar trend.The microwav e thermal behavior of the cathode material is closely related to the change of the dielectric properties.It only takes10 minutes for the cathode material to heat from room temperature to 700°C,and the maximum heating rate can reach 4.75°C/s.The shorter heating time and higher heating rate indicate the cathode material Has excellent absorbing properties.At the same time,the changing trend of dielectric properties is consistent with penetration depth,reflection loss and microwave heating characteristics.(2)Under normal conditions,the influence of the leaching time,leaching temperature,solid-to-liquid ratio,and sulfuric acid concentration of the positive electrode material on the leaching rate of the positive electrode material was explored.The best leaching conditions for the positive electrode material are as follows: leaching time 1h,leaching temperature 80?,solid-liquid ratio 1/10(g/m L),sulfuric acid concentration 5mol/L.Under the best conditions,the concentrations of Ni,Co,and Mn were 14.58g/L,6.62g/L,36.01g/L,1.87g/L,and the final calculated leaching rates were99.76%,99.71%,99.84%.(3)Combined with the thermogravimetric analysis results of the cathode material,the influence of microwave pretreatment on the leaching effect was studied by controlling the temperature and holding time of microwave pretreatment.The results show that when the microwave pretreatment temperature is low,the binder and carbon in the positive electrode material cannot be removed well,and will cover the surface of the positive electrode material,which is not conducive to the leaching of valuable metals in the acid solution.High,after reaching the binder volatilization and carbon oxidation temperature,the leaching efficiency of valuable metals begins to incre ase.At the same time,the longer the pretreatment holding time,the better the leaching effect.The final result shows that when the pretreatment temperature is 600°C and the holding time is 30 minutes,the binder and carbon can be effectively removed,thereby realizing the efficient leaching of valuable metals in the positive electrode material.The SEM and XRD analysis of the pretreatment product showed that no matter whether the holding time or the holding temperature was changed,the spherical material structure in the cathode material did not change.(4)By controlling the leaching time,leaching temperature,solid-to-liquid ratio,and sulfuric acid concentration,the influence of microwave-enhanced leaching on the leaching rate of cathode materials was studied.From the perspective of leaching rate,the best leaching conditions for cathode materials are: leaching time 0.5h,The leaching temperature is 70°C,the solid-liquid ratio is 1/8,and the sulfuric acid concentration is5mol/L.Under the optimal leaching conditions,the concentrations of Ni,Co,Mn,and Li are 18.03g/L,8.19g/L,44.64g/L,and 2.32g/L respectively.Finally,the leaching rates of them are calculated to be 99.21%.98.91%,99.23%,99.73%.