利用红土镍矿非目标元素Fe、Si制备LiFePO4/C和Li2FeSiO4/C正极材料的基础研究

Lateritic nickel ore has become the main resource of extracting nickel, which accounts for 70% nickel resources of the world. It can not be effectively and cleanly treated by the conventional wet processing, which due to a great deal of waste gas, waste water and industrial residues, serious environmental pollution and low value added of the non-target element Fe and Si. In this research, we focus on lateritic nickel ore and propose ammonium sulfate roasting-ammonioiarosite separation iron-hydrolyze and alkali calcination dissolving slag-chemical precipitation method to synthesize the raw material Fe2O3, SiO2 of the LiFePO4/C, Li2FeSiO4/C electrode material. The precipitation principal and regulation mechanism have been illuminated by the precipitation behavior of ammonioiarosite and SiO2. The reduction kinetics characteristics of Fe2O3 in the process of synthesizing LiFePO4/C has been discussed, which reveal that the influence rule of microstructure of ammonioiarosite and SiO2 to the LiFePO4/C and Li2FeSiO4/C prepared by carbothermal reduction reaction and hydrothermal method. We also research the doping behaviors of single element (Cr、Mg) and multielement in the lateritic nickel ore for the performance of battery material, and bulid the inner connection between the microstructure and lithiation-delithiation behavior of lithium ion. The high value added lithium ion battery LiFePO4/C and Li2FeSiO4/C anode materials are synthesized from the lateritic nickel ore, which provide new technology and theoretical support for comprehensive utilization of lateritic nickel ore resources

占世界镍资源70%的红土镍矿成为提取镍的主要资源。常规湿法工艺难以高效处理，三废排放多，环境污染严重，非目标元素Fe、Si附加值较低。本项目以红土镍矿为研究对象，提出硫酸铵焙烧-黄铵铁矾沉铁-水解、碱焙烧溶出渣-化学沉淀工艺，获得制备电极材料LiFePO4/C、Li2FeSiO4/C的原料Fe2O3、SiO2。通过黄铵铁矾和SiO2的析出行为，阐明其析出规律和调控机制；探讨LiFePO4/C碳热还原制备过程中Fe2O3的还原动力学特征，揭示黄铵铁矾和SiO2的微观状态对LiFePO4/C和水热法制备Li2FeSiO4/C性能的影响规律；探究红土镍矿中Cr、Mg等单元素掺杂及多元素掺杂对两种电池材料性能的影响，建立掺杂后微观结构与锂离子脱/嵌行为的内在联系。由红土镍矿为原料合成了高附加值锂离子电池LiFePO4、Li2FeSiO4正极材料，为红土镍矿资源高效、综合利用提供新技术及理论支持。

以红土镍矿为原料，采用硫酸铵焙烧—溶出—黄铵铁矾法沉铁，然后再以黄胺铁矾水解所得Fe2O3为原料，加入一定比例的Li2CO3、NH4H2PO4和蔗糖进行还原焙烧制备锂离子电池正极材料LiFePO4/C，经过参数的探索，给出最佳的工艺制备参数：红土镍矿矿料与硫酸铵摩尔比1:1.05、焙烧温度为600℃、焙烧时间5 h，黄氨铁矾的反应时间4 h、反应温度95 ℃、终点pH值为2.5、搅拌速度为400 r/min，正极材料制备温度750℃，烧结时间14 h，在0.05 C倍率下，放电比容量164.56 mAh/g，是磷酸铁锂电池理论容量的94%，在0.05 C倍率下经过100次循环后，电池的放电比容量为162.78 mAh/g，容量保持率为98%；采用氢氧化钠水热—溶出—化学法法沉硅，得到SiO2，固相法制备锂离子电池正极材料Li2FeSiO4/C，经过参数研究，得到最佳工艺制备参数：氢氧化钠与矿石摩尔比1.2:1、反应温度250℃、反应时间2 h，纳米SiO2制备在硫酸浓度10%、熟化温度70 °C、熟化时间1 h、搅拌速度600 r/min、表面活性剂为PEG400最佳，正极材料在900°C煅烧10 h制备的样品，其电化学性能最佳，以0.05 Ｃ倍率进行充放电测试，Li2FeSiO4/C复合材料的初始放电比容量为137.5 mAh/g，室温下循环50次后，其放电比容量保持率为98.2%。研究结果可为红土镍矿资源的高效、综合利用提供新技术及理论支持。