镍系锂离子电池正极材料的制备及改性研究
发布时间：2019-01-14 11:10
【摘要】：镍系正极材料因其容量高,资源广以及环境友好等优势而成为最具有应用前景的锂离子电池正极材料之一。然而,化学计量比的镍酸锂难以制备,同时在充电过程中高氧化态的镍离子易与电解质发生副反应,从而恶化材料的循环寿命和热稳定性。通过合适的掺杂与包覆等手段可有效地提高镍系正极材料的电化学性能。本论文采用控制结晶共沉淀法制备了Co掺杂的LiNi0.8Co0.2O2正极材料和Co-Al共掺杂的正极材料LiNi0.8Co0.15Al0.05O2,探讨了制备条件对材料形貌、结构和电化学性能的影响。此外,通过对LiNi0.8Co0.15Al0.05O2正极材料进行导电聚合物聚苯胺包覆来进一步改善其电化学性能。论文的主要工作如下:(1)通过控制结晶共沉淀法制备了球形前驱体Ni0.8Co0.2(OH)2,再将其与氢氧化锂进行混合,经过高温固相反应得到LiNi0.8Co0.2O2正极材料。探讨了共沉淀反应体系中pH值和搅拌速率对前躯体的影响,结果表明:pH值为10.8,搅拌速率为800 rpm时,所得到的前躯体颗粒球形度好、粒径分布均匀;同时,研究了高温固相反应过程中煅烧气氛、Li/M、煅烧温度和煅烧时间对材料性能的影响。当氧气流速为60 m L/min,锂金属比1.06时,在750℃温度下煅烧12 h所得到的材料性能最优。在3.0~4.3 V、0.1 C(18 mA g-1)充放电条件下,其首次放电容量可达195.3 mAh?g-1,并且经过50次循环后容量保持率为82.6%。(2)以EDTA为Al3+螯合剂,通过控制结晶共沉淀法制备了球形前驱体Ni0.8Co0.15Al0.05(OH)2,考察了Li/M、煅烧温度以及煅烧时间对所制备的LiNi0.8Co0.15Al0.05O2正极材料的影响,结果显示最佳的工艺条件为:氧气流速60m L/min,锂金属比1.06,煅烧温度750℃和煅烧时间12 h。最佳工艺条件下制备的LiNi0.8Co0.15Al0.05O2正极材料,在3.0~4.3 V、0.1 C条件下首次放电容量为193.4mAh?g-1,经过50次循环后容量保持率仍然为90.1%。(3)为了进一步改善Li Ni0.8Co0.15Al0.05O2正极材料的电化学性能,采用导电聚合物聚苯胺对其进行表面包覆,探讨了聚苯胺包覆量对材料性能的影响。结果表明,聚苯胺包覆量为10 wt%时所得到的材料具有最佳的电化学性性。在3.0~4.3 V电压范围内,以0.1 C倍率进行充放电时,其首次放电容量为195.6 mAh?g-1,并且首次库伦效率高达90.3%。此外,在0.1 C倍率下循环50次后容量仍然保持有181.3mAh/g,容量保持率高达92.6%;并且2.0 C倍率下的放电比容量仍为143.5mAh?g-1,显示材料具有优异的循环稳定性和倍率性能。
[Abstract]:Nickel cathode materials have become one of the most promising cathode materials for lithium ion batteries due to their advantages of high capacity, wide resources and environmental friendliness. However, the stoichiometric lithium nickelate is difficult to be prepared, and the high oxidized nickel ion can easily react with the electrolyte during the charging process, thus worsening the cycle life and thermal stability of the material. The electrochemical properties of nickel cathode materials can be improved by appropriate doping and coating. In this paper, Co doped LiNi0.8Co0.2O2 cathode materials and Co-Al co-doped cathode materials LiNi0.8Co0.15Al0.05O2, were prepared by controlled crystallization coprecipitation. The effects of preparation conditions on the morphology, structure and electrochemical properties of the materials were investigated. In addition, the electrochemical properties of LiNi0.8Co0.15Al0.05O2 cathode materials were further improved by coating the conductive polymer Polyaniline. The main work of this paper is as follows: (1) the spherical precursor Ni0.8Co0.2 (OH) _ 2 was prepared by controlled crystallization coprecipitation method, and then mixed with lithium hydroxide. The LiNi0.8Co0.2O2 cathode material was prepared by solid state reaction at high temperature. The effects of pH value and stirring rate on the precursor in coprecipitation reaction system were discussed. The results showed that when the pH value was 10.8 and the stirring rate was 800 rpm, the particle size distribution was uniform and spherical. At the same time, the effects of calcination atmosphere, Li/M, calcination temperature and calcination time on the properties of the materials during high temperature solid state reaction were studied. When the oxygen flow rate is 60 mL / min, the ratio of lithium to metal is 1.06, and the calcined temperature is 750 鈩，
本文编号：2408633
[Abstract]:Nickel cathode materials have become one of the most promising cathode materials for lithium ion batteries due to their advantages of high capacity, wide resources and environmental friendliness. However, the stoichiometric lithium nickelate is difficult to be prepared, and the high oxidized nickel ion can easily react with the electrolyte during the charging process, thus worsening the cycle life and thermal stability of the material. The electrochemical properties of nickel cathode materials can be improved by appropriate doping and coating. In this paper, Co doped LiNi0.8Co0.2O2 cathode materials and Co-Al co-doped cathode materials LiNi0.8Co0.15Al0.05O2, were prepared by controlled crystallization coprecipitation. The effects of preparation conditions on the morphology, structure and electrochemical properties of the materials were investigated. In addition, the electrochemical properties of LiNi0.8Co0.15Al0.05O2 cathode materials were further improved by coating the conductive polymer Polyaniline. The main work of this paper is as follows: (1) the spherical precursor Ni0.8Co0.2 (OH) _ 2 was prepared by controlled crystallization coprecipitation method, and then mixed with lithium hydroxide. The LiNi0.8Co0.2O2 cathode material was prepared by solid state reaction at high temperature. The effects of pH value and stirring rate on the precursor in coprecipitation reaction system were discussed. The results showed that when the pH value was 10.8 and the stirring rate was 800 rpm, the particle size distribution was uniform and spherical. At the same time, the effects of calcination atmosphere, Li/M, calcination temperature and calcination time on the properties of the materials during high temperature solid state reaction were studied. When the oxygen flow rate is 60 mL / min, the ratio of lithium to metal is 1.06, and the calcined temperature is 750 鈩，
本文编号：2408633
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