富锂Li_1+x(Ni_1/3Co_1/3Mn_1/3)O_2+x/2和锰基正极材料Li(Li_1/3-2x/3Ni_xMn_2/3-x/3)O₂的制备与性能

【作者】 喻东；

【导师】 钟盛文；

【作者基本信息】 江西理工大学 ， 应用化学， 2008， 硕士

【摘要】 富锂正极材料具有比容量高,结构稳定,造价低廉,污染小等特点,近年来受到广泛的关注。本论文主要研究了富锂三元正极材料Li1+x[Ni1/3Co1/3Mn1/3]O2+x/2 （x=0.2,0.4,0.6）与富锂锰基镍锰正极材料Li[Li_1/3-2x/3Ni_xMn_2/3-x/3]O₂ （x=0.125,0.2,0.35,0.5）的实验室合成以及它们的电性能。采用碳酸盐共沉淀法合成了三元材料前驱体,并研究了合成条件对合成的前驱体形貌及振实密度的影响,确定了最优化合成条件:pH = 8,过渡金属离子浓度2 mol·L-1 ,反应时间12 13 h。在此研究的基础上,合成了富锂三元正极材料Li1+x[Ni1/3Co1/3Mn1/3]O2+x/2（x=0.2,0.4,0.6）。通过扫描电镜（SEM）,X衍射（XRD）分析研究了它们的形貌与结构,通过电性能测试仪检测了它们的充放电性能。采用硝酸盐法合成的富锂锰基镍锰正极材料Li[Li_1/3-2x/3Ni_xMn_2/3-x/3]O₂ （x=0.125,0.2,0.35,0.5）制成AA电池,在电性能测试仪上进行充放电测试发现:在2.0 4.6 V ,0.2 C,25℃条件下当x = 0.2时合成的正极材料Li[Li0.2Ni0.2Mn0.6]O2表现出较好的比容量与循环性能:初始放电比容量为220 mAh·g-1 ,经过50次循环后,放电比容量仍然可以保持在157 mAh·g-1。对于电化学性能表现较好的Li[Li0.2Ni0.2Mn0.6]O2材料,分别研究了不同锂配比（锂比为0.97,1.00,1.03,1.06）以及不同烧成温度（760℃,860℃,950℃）对材料性能的影响。研究表明:锂比为1.03 ,在760℃条件下合成的Li[Li0.2Ni0.2Mn0.6]O2材料表现出较为优异的电性能。最后,研究了通过碳酸盐共沉淀法合成富锂锰基镍锰正极材料Li[Li_1/3-2x/3Ni_xMn_2/3-x/3]O₂ （x=0.125,0.2,0.35,0.5）。并通过扫描电镜（SEM）,X衍射（XRD）检测了材料的形貌及结构。测试了它们的电化学性能。研究表明当x = 0.2时合成的正极材料Li[Li0.2Ni0.2Mn0.6]O2表现出较好的充放电性能与循环性能:初始放电比容量为243 mAh·g-1 ,经过20次循环后,放电比容量仍然可以保持在182 mAh·g-1。更多还原

【Abstract】 High lithium cathode materials had these performances with high specific capacity, structural stability, and low cost, lower pollution and so on. It was gotten an extensive attention in recent years. two cathode materials were synthesized, the high lithium cathode material Li1+x[Ni1/3Co1/3Mn1/3]O2+x/2 （x=0.2,0.4,0.6） and the high lithium manganese-base cathode materials Li[Li_1/3-2x/3Ni_xMn_2/3-x/3]O₂ （x=0.125,0.2,0.35,0.5）, and they electrochemical performances were analysed in the paper.The precursor of Li1+x[Ni1/3Co1/3Mn1/3]O2+x/2 was prepared with co-precipitation of carbonate method. The influences of synthesis conditions for precursors on morphology, density were studied. The optimal synthesis conditions were that, pH was at 8, transition metal ion concentration was 2 mol·L-1, the reaction time was about 12 13 h. The morphology and structure for the cathode materials Li1+x[Ni1/3Co1/3Mn1/3]O2+x/2（x=0.2,0.4,0.6）were determined by scanning electron microscopy （SEM） and X-ray diffraction （XRD） analysis. And the charge and discharge performance were measured by electrochemical performances test.Nitrate of Li, Mn, Ni with different ratios were mixed and then the high lithium manganese-base cathode material Li[Li_1/3-2x/3Ni_xMn_2/3-x/3]O₂ （x=0.125,0.2,0.35,0.5）were cacined at high temperture. AA-size batteries were assembled and electrochemical performances were tested. Test results show that, Li[Li_1/3-2x/3Ni_xMn_2/3-x/3]O₂ had better charge-discharge performance and cycle performance while x = 0.2, work pressure at 2.0 4.6 V, and charging current at 0.2 C and testing temperature at 25℃, for cathode materials synthesis of Li[Li0.2Ni0.2Mn0.6]O2. The optimal cathode material was Li[Li0.2Ni0.2Mn0.6]O2. It had an initial discharge capacity of 220 mAh·g-1 and could still be maintained discharge capacity over 157 mAh·g-1 after 50 cycles. The influence of lithium ratios （1+δ） were studied for cathode materials Li1+δ[Li0.2Ni0.2Mn0.6]O2 （lithium ratio were selected at 0.97, 1.03,1.06,1.09） and the different calcining temperature （760℃, 860℃, 950℃were choiced） were tested on the properties of cathode materials. The optimal synthesis conditions were that, the lithium ratio at 1.03 and calcining temperature at 760℃could obtain more excellent electrochemical performances.The precursors of Li[Li_1/3-2x/3Ni_xMn_2/3-x/3]O₂ （x=0.125,0.2,0.35,0.5）were prepared by co-precipitation of carbonate. The study also showed that, cathode materials Li[Li0.2Ni0.2Mn0.6]O2 had better electrochemical performances for x=0.2. Its initial discharge capacity of 243 mAh·g-1, after 20 cycles, the discharge capacity can still be maintained at 182 mAh·g-1.更多还原