微波强化浸出废旧三元锂离子电池正极材料中的Ni、Co和Mn

【作者】 李宁；

【导师】 刘秉国；

【作者基本信息】 昆明理工大学 ， 有色金属冶金， 2021， 硕士

【摘要】 锂离子电池是一种比能量高、安全性好的二次电池,它的快速发展也导致废旧锂离子电池的数量出现井喷式的上涨。废旧锂离子电池中含有大量的有价金属Co、Ni、Mn、Cu、Al、Li,也含有一些有毒的有机电解质和粘结剂。因此,回收锂离子电池不仅可以缓解资源需求的压力,也能减少其中有毒物质对环境的危害。本研究针对现有工艺的研究现状,结合微波选择性加热、绿色环保和节能的特点,提出了微波预处理以及微波强化浸出的新工艺;研究了表观密度和温度对正极材料的微波吸收性能的影响以及正极材料在微波场中的热行为;探索了微波预处理以及微波强化浸出对金属回收率的影响,并与常规浸出进行了对比,得到的结论如下:(1)通过高温介电测试系统测量了表观密度和温度对正极材料介电特性的影响,发现随着正极材料表观密度的增加,介电常数也随之增加。但介电损耗因子和损耗角正切在表观密度为1.484g/cm~3时,达到最大。正极材料的高温介电特性研究表明,正极材料在室温下介电常数为6.86,随着温度的升高,正极材料的介电常数也随之增加,并在400℃时达到最大值11.96。介电损耗因子和损耗角正切也呈现了相似的变化趋势。正极材料的微波热行为与介电性能变化密切相关,正极材料从室温加热到700℃仅需要10min,最高加热速率可达到4.75℃/s,较短的加热时间和较高的加热速率说明正极材料具有优良的吸波性能。同时,介电性能的变化趋势与穿透深度、反射损耗以及微波加热特性相吻合。(2)常规条件下,探究了正极材料的浸出时间、浸出温度、固液比、硫酸浓度对正极材料浸出率的影响。得出正极材料的最佳浸出条件为:浸出时间1h,浸出温度80℃,固液比为1/10(g/m L),硫酸浓度为5mol/L。在最佳条件下在最佳条件下Ni、Co、Mn的浓度分别14.58g/L、6.62g/L、36.01g/L、1.87g/L,最后计算的出它们的浸出率分别为99.76%,99.71%,99.84%。(3)结合正极材料的热重分析结果,通过控制微波预处理的温度和保温时间,研究了微波预处理对浸出效果的影响。结果表明在微波预处理温度较低时,正极材料中的粘结剂和碳不能很好地除去,会覆盖在正极材料的表面,不利于有价金属在酸溶液中的浸出,随着温度升高,达到粘结剂挥发以及碳的氧化温度后,有价金属的浸出效率开始增加。同时预处理保温时间越长,浸出效果越好。最终结果表明在预处理温度为600℃,保温时间为30分钟时,可以有效除去粘结剂和碳,从而实现正极材料中的有价金属的高效浸出。对预处理产物的SEM和XRD分析表明,无论是改变保温时间还是保温温度,正极材料中球形的物质结构并没有发生改变。(4)通过控制浸出时间、浸出温度、固液比、硫酸浓度,研究了微波强化浸出对正极材料浸出率的影响,从浸出率的角度来看,正极材料的最佳浸出条件为:浸出时间0.5h,浸出温度70℃,固液比为1/8,硫酸浓度为5mol/L。在最佳浸出条件下Ni、Co、Mn和Li的浓度分别为18.03g/L、8.19g/L、44.64g/L、2.32g/L,最后计算得出它们的浸出率分别为99.21%,98.91%,99.23%,99.73%。更多还原

【Abstract】 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%.更多还原