为研究制备工艺对LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2正极材料微结构及电化学性能的影响,采用共沉淀法,在搅拌速度分别为500、600、700、800 r/min下合成前驱体,再经850℃焙烧制得LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2正极材料。采用X射线衍射仪(X...为研究制备工艺对LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2正极材料微结构及电化学性能的影响,采用共沉淀法,在搅拌速度分别为500、600、700、800 r/min下合成前驱体,再经850℃焙烧制得LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2正极材料。采用X射线衍射仪(XRD)和扫描电子显微镜(SEM)等表征了样品的微结构;以CV阻抗测试、恒流充放电等技术测试了样品的电化学性能。结果表明,所有样品均为单一的六方晶系相,没有其他杂相。前驱体的搅拌速度为500、600、700、800 r/min时制备的LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2正极材料的首次充电比容量分别为167.4、185.8、169.4、149.6 m Ah/g,首次放电比容量分别为147.9、165.6、141.9、122.6 m Ah/g,首次库仑效率分别为88.3%、89.12%、83.6%、82.0%。可见,前驱体的搅拌速度为600 r/min、焙烧温度为850℃时所制备的LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2正极材料具有较好的电化学性能。展开更多
This work reports a comprehensive study of a novel polyol method that can successfully synthesize layered LiNi0.4Mn0.4Co0.2O2,spinel LiNi0.5Mn1.5O4,and olivine LiCoPO4 cathode materials.When properly designed,polyol m...This work reports a comprehensive study of a novel polyol method that can successfully synthesize layered LiNi0.4Mn0.4Co0.2O2,spinel LiNi0.5Mn1.5O4,and olivine LiCoPO4 cathode materials.When properly designed,polyol method offers many advantages such as low cost,ease of use,and proven scalability for industrial applications.Most importantly,the unique properties of polyol solvent allow for greater morphology control as shown by all the resulting materials exhibiting monodispersed nanoparticles morphology.This morphology contributes to improved lithium ion transport due to short diffusion lengths.Polyol-synthesized LiNi0.4Mn0.4Co0.2O2 delivers a reversible capacity of 101 and 82 mAh.g-1 using high current rate of 5C and 10C,respectively.It also displays surprisingly high surface structure stability after chargedischarge processes.Each step of the reaction was investigated to understand the underlying polyol synthesis mechanism.A combination of in situ and ex situ studies reveal the structural and chemical transformation of Ni-Co alloy nanocrystals overwrapped by a Mn-and Li-embedded organic matrix to a sedes of intermediate phases,and then eventually to the desired layered oxide phase with a homogeneous distribution of Ni,Co,and Mn.We envisage that this type of analysis will promote the development of optimized synthesis protocols by establishing links between experimental factors and important structural and chemical properties of the desired product.The insights can open a new direction of research to synthesize high-performance intercalation compounds by allowing unprecedented control of intermediate phases using experimental parameters.展开更多
The constructed potential-pH diagrams of Li-Ni(Co,Mn)-H2O system indicate that the LiNiO2,LiCoO2 and LiMnO2 are thermodynamically stable in aqueous solution within the temperature range of 25-200°C and the activi...The constructed potential-pH diagrams of Li-Ni(Co,Mn)-H2O system indicate that the LiNiO2,LiCoO2 and LiMnO2 are thermodynamically stable in aqueous solution within the temperature range of 25-200°C and the activity range of 0.01-1.00.A predominant co-region of LiNiO2,LiCoO2 and LiMnO2 oxides(Li-Ni-Co-Mncomposite oxide)is found in the Li-Ni-Co-Mn-H2O potential-pH diagrams,in which the co-precipitation region expands towards lower pH with rising temperature,indicating the enhanced possibility of synthesizing Li-Ni-Co-Mn composite oxide in aqueous solution.The experimental results prove that it is feasible to prepare the LiNi0.5Co0.2Mn0.3O2 cathode materials(NCM523)by an aqueous routine.The as-prepared lithiated precursor and NCM523 both inherit the spherical morphology of the hydroxide precursor and the obtained NCM523 has a hexagonalα-NaFeO2 structure with good crystallinity.It is reasonable to conclude that the aqueous routine for preparing NCM cathode materials is a promising method with the guidance of the reliable potential-pH diagrams to some extent.展开更多
Several lithium-ion batteries of 18650-type were assembled with pristine or Al2O3-coated LiNi0.4Co0.2Mn0.4O2（NCM） as cathode material and mesocarbon microbeads（MCMB） as anode material.The cycling performance of th...Several lithium-ion batteries of 18650-type were assembled with pristine or Al2O3-coated LiNi0.4Co0.2Mn0.4O2（NCM） as cathode material and mesocarbon microbeads（MCMB） as anode material.The cycling performance of the batteries was examined under 25 °C at a 2C rate within a potential range of 2.75―4.20 V.The changes of the crystal structure,the lattice parameter,the mean crystallite size,and the mean micro-strain of pristine NCM and Al2O3-coated NCM during the charge-discharge cycling were determined by X-ray diffraction（XRD）.The results indicate that the bulk structure of Al2O3-coated NCM is more stable than that of pristine NCM,which leads to the better cycling performance of Al2O3-coated NCM compared to that of pristine NCM.展开更多
采用共沉淀法制备了三元材料LiNi0.4Co0.2Mn0.4O2,掺杂不同比例铷进行改性,对其进行了结构表征,考察了其电化学性能.结果表明,Li0.97Rb0.03Ni0.4Co0.2Mn0.4O2样品的结晶度较好,铷掺杂起到了稳定三元材料晶体结构的作用,有效改善了材料...采用共沉淀法制备了三元材料LiNi0.4Co0.2Mn0.4O2,掺杂不同比例铷进行改性,对其进行了结构表征,考察了其电化学性能.结果表明,Li0.97Rb0.03Ni0.4Co0.2Mn0.4O2样品的结晶度较好,铷掺杂起到了稳定三元材料晶体结构的作用,有效改善了材料的电化学性能,5C倍率下放电比容量达130 m A×h/g.展开更多
文摘为研究制备工艺对LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2正极材料微结构及电化学性能的影响,采用共沉淀法,在搅拌速度分别为500、600、700、800 r/min下合成前驱体,再经850℃焙烧制得LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2正极材料。采用X射线衍射仪(XRD)和扫描电子显微镜(SEM)等表征了样品的微结构;以CV阻抗测试、恒流充放电等技术测试了样品的电化学性能。结果表明,所有样品均为单一的六方晶系相,没有其他杂相。前驱体的搅拌速度为500、600、700、800 r/min时制备的LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2正极材料的首次充电比容量分别为167.4、185.8、169.4、149.6 m Ah/g,首次放电比容量分别为147.9、165.6、141.9、122.6 m Ah/g,首次库仑效率分别为88.3%、89.12%、83.6%、82.0%。可见,前驱体的搅拌速度为600 r/min、焙烧温度为850℃时所制备的LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2正极材料具有较好的电化学性能。
文摘This work reports a comprehensive study of a novel polyol method that can successfully synthesize layered LiNi0.4Mn0.4Co0.2O2,spinel LiNi0.5Mn1.5O4,and olivine LiCoPO4 cathode materials.When properly designed,polyol method offers many advantages such as low cost,ease of use,and proven scalability for industrial applications.Most importantly,the unique properties of polyol solvent allow for greater morphology control as shown by all the resulting materials exhibiting monodispersed nanoparticles morphology.This morphology contributes to improved lithium ion transport due to short diffusion lengths.Polyol-synthesized LiNi0.4Mn0.4Co0.2O2 delivers a reversible capacity of 101 and 82 mAh.g-1 using high current rate of 5C and 10C,respectively.It also displays surprisingly high surface structure stability after chargedischarge processes.Each step of the reaction was investigated to understand the underlying polyol synthesis mechanism.A combination of in situ and ex situ studies reveal the structural and chemical transformation of Ni-Co alloy nanocrystals overwrapped by a Mn-and Li-embedded organic matrix to a sedes of intermediate phases,and then eventually to the desired layered oxide phase with a homogeneous distribution of Ni,Co,and Mn.We envisage that this type of analysis will promote the development of optimized synthesis protocols by establishing links between experimental factors and important structural and chemical properties of the desired product.The insights can open a new direction of research to synthesize high-performance intercalation compounds by allowing unprecedented control of intermediate phases using experimental parameters.
基金Project(FA2019015) supported by the Government of Chongzuo,Guangxi Zhuang Autonomous Region,ChinaProject(AD18281073) supported by Science and Technology Department of Guangxi Zhuang Autonomous Region,China
文摘The constructed potential-pH diagrams of Li-Ni(Co,Mn)-H2O system indicate that the LiNiO2,LiCoO2 and LiMnO2 are thermodynamically stable in aqueous solution within the temperature range of 25-200°C and the activity range of 0.01-1.00.A predominant co-region of LiNiO2,LiCoO2 and LiMnO2 oxides(Li-Ni-Co-Mncomposite oxide)is found in the Li-Ni-Co-Mn-H2O potential-pH diagrams,in which the co-precipitation region expands towards lower pH with rising temperature,indicating the enhanced possibility of synthesizing Li-Ni-Co-Mn composite oxide in aqueous solution.The experimental results prove that it is feasible to prepare the LiNi0.5Co0.2Mn0.3O2 cathode materials(NCM523)by an aqueous routine.The as-prepared lithiated precursor and NCM523 both inherit the spherical morphology of the hydroxide precursor and the obtained NCM523 has a hexagonalα-NaFeO2 structure with good crystallinity.It is reasonable to conclude that the aqueous routine for preparing NCM cathode materials is a promising method with the guidance of the reliable potential-pH diagrams to some extent.
基金Supported by the Project of Shanghai Committee of Science and Technology,China(Nos.1052nm00100,09ZR1437600)
文摘Several lithium-ion batteries of 18650-type were assembled with pristine or Al2O3-coated LiNi0.4Co0.2Mn0.4O2（NCM） as cathode material and mesocarbon microbeads（MCMB） as anode material.The cycling performance of the batteries was examined under 25 °C at a 2C rate within a potential range of 2.75―4.20 V.The changes of the crystal structure,the lattice parameter,the mean crystallite size,and the mean micro-strain of pristine NCM and Al2O3-coated NCM during the charge-discharge cycling were determined by X-ray diffraction（XRD）.The results indicate that the bulk structure of Al2O3-coated NCM is more stable than that of pristine NCM,which leads to the better cycling performance of Al2O3-coated NCM compared to that of pristine NCM.
文摘采用共沉淀法制备了三元材料LiNi0.4Co0.2Mn0.4O2,掺杂不同比例铷进行改性,对其进行了结构表征,考察了其电化学性能.结果表明,Li0.97Rb0.03Ni0.4Co0.2Mn0.4O2样品的结晶度较好,铷掺杂起到了稳定三元材料晶体结构的作用,有效改善了材料的电化学性能,5C倍率下放电比容量达130 m A×h/g.
