Lithium-rich layered oxides always suffer from low initial Coulombic efficiency,poor rate capability and rapid voltage fading.Herein,engineering oxygen vacancies in hierarchically Li1.2Mn0.54Ni0.13Co0.13O2 porous micr...Lithium-rich layered oxides always suffer from low initial Coulombic efficiency,poor rate capability and rapid voltage fading.Herein,engineering oxygen vacancies in hierarchically Li1.2Mn0.54Ni0.13Co0.13O2 porous microspheres(L@S)is carried out to suppress the formation of irreversible Li20 during the initial discharge process and improve the Li+diffusion kinetics and structural stability of the cathode mateiral.As a result,the prepared L@S cathode delivers high initial Coulombic efficiency of 92.3%and large specific capacity of 292.6 mA h g^-1 at 0.1 C.More importantly,a large reversible capacity of 222 mA h g^-1 with a capacity retention of95.7%can be obtained after 100 cycles at 10 C.Even cycled at ultrahigh rate of 20 C,the L@S cathode can deliver stable reversible capacity of 153 mA h g^-1 after 100 cycles.Moreover,the full cell using L@S as cathode and Li4 Ti5 O12 as anode exhibits a relatively high reversible capacity of 141 mA h g^-1 with an outstanding voltage retention of 97%after 400 cycles at a large current density of 3 C.These results may shed light on the improvement of electrochemical performances of lithiumrich layered oxides via the multiscale coordinated design based on atomic defects,microstructure and composition.展开更多
Lithium-rich layered oxides(LrLOs) deliver extremely high specific capacities and are considered to be promising candidates for electric vehicle and smart grid applications. However, the application of LrLOs needs fur...Lithium-rich layered oxides(LrLOs) deliver extremely high specific capacities and are considered to be promising candidates for electric vehicle and smart grid applications. However, the application of LrLOs needs further understanding of the structural complexity and dynamic evolution of monoclinic and rhombohedral phases, in order to overcome the issues including voltage decay, poor rate capability, initial irreversible capacity loss and etc. The development of aberration correction for the transmission electron microscope and concurrent progress in electron spectroscopy, have fueled rapid progress in the understanding of the mechanism of such issues. New techniques based on the transmission electron microscope are first surveyed, and the applications of these techniques for the study of the structure, migration of transition metal, and the activation of oxygen of LrLOs are then explored in detail, with a particular focus on the mechanism of voltage decay.展开更多
采用喷雾干燥法合成了富锂层状氧化物正极材料0.6Li[Li_(1/3)Mn_(2/3)]O2·0.4LiNi_(5/12)Mn_(5/12)Co_(1/6)O_2(简称LNMCO),并使用Zr(CH3COO)4进行ZrO_2的包覆改性。TEM测试结果显示纳米级的ZrO_2颗粒附着在LNMCO的表面。包覆质量...采用喷雾干燥法合成了富锂层状氧化物正极材料0.6Li[Li_(1/3)Mn_(2/3)]O2·0.4LiNi_(5/12)Mn_(5/12)Co_(1/6)O_2(简称LNMCO),并使用Zr(CH3COO)4进行ZrO_2的包覆改性。TEM测试结果显示纳米级的ZrO_2颗粒附着在LNMCO的表面。包覆质量分数为1.5%的ZrO_2包覆样品的首圈库伦效率和放电比容量有着显著提升,在室温下其首圈库伦效率和放电比容量(电流密度:20 m A·g-1,电压:2.0~4.8 V)分别为87.2%,279.3 m Ah·g-1,而原样则为75.1%,224.1 m Ah·g-1,循环100圈之后,1.5%ZrO_2包覆样品的放电比容量为248.3 m Ah·g-1,容量保持率为88.9%,高于原样的195.9 m Ah·g-1和87.4%。展开更多
基金support from the National Key R&D Program of China(2016YFA0202602 and2016YFA0202604)the National Natural Science Foundation of China(51701169 and 51871188)+2 种基金the Natural Science Foundation of Fujian Province(2017J05087)the Key Projects of Youth Natural Foundation for the Universities of Fujian Province of China(JZ160397)the“Double-First Class” Foundation of Materials and Intelligent Manufacturing Discipline of Xiamen University
文摘Lithium-rich layered oxides always suffer from low initial Coulombic efficiency,poor rate capability and rapid voltage fading.Herein,engineering oxygen vacancies in hierarchically Li1.2Mn0.54Ni0.13Co0.13O2 porous microspheres(L@S)is carried out to suppress the formation of irreversible Li20 during the initial discharge process and improve the Li+diffusion kinetics and structural stability of the cathode mateiral.As a result,the prepared L@S cathode delivers high initial Coulombic efficiency of 92.3%and large specific capacity of 292.6 mA h g^-1 at 0.1 C.More importantly,a large reversible capacity of 222 mA h g^-1 with a capacity retention of95.7%can be obtained after 100 cycles at 10 C.Even cycled at ultrahigh rate of 20 C,the L@S cathode can deliver stable reversible capacity of 153 mA h g^-1 after 100 cycles.Moreover,the full cell using L@S as cathode and Li4 Ti5 O12 as anode exhibits a relatively high reversible capacity of 141 mA h g^-1 with an outstanding voltage retention of 97%after 400 cycles at a large current density of 3 C.These results may shed light on the improvement of electrochemical performances of lithiumrich layered oxides via the multiscale coordinated design based on atomic defects,microstructure and composition.
基金finically supported by the National Key Research and Development Program of China (Grant No. 2016YFB0100100)Strategic Priority Research Program of Chinese Academy of Sciences (CAS, Grant No. XDA09010101)Ningbo Key Science and Technology Projects "Industrial Application Development of Graphene" (Grant No. 2014S10008)
文摘Lithium-rich layered oxides(LrLOs) deliver extremely high specific capacities and are considered to be promising candidates for electric vehicle and smart grid applications. However, the application of LrLOs needs further understanding of the structural complexity and dynamic evolution of monoclinic and rhombohedral phases, in order to overcome the issues including voltage decay, poor rate capability, initial irreversible capacity loss and etc. The development of aberration correction for the transmission electron microscope and concurrent progress in electron spectroscopy, have fueled rapid progress in the understanding of the mechanism of such issues. New techniques based on the transmission electron microscope are first surveyed, and the applications of these techniques for the study of the structure, migration of transition metal, and the activation of oxygen of LrLOs are then explored in detail, with a particular focus on the mechanism of voltage decay.
文摘采用喷雾干燥法合成了富锂层状氧化物正极材料0.6Li[Li_(1/3)Mn_(2/3)]O2·0.4LiNi_(5/12)Mn_(5/12)Co_(1/6)O_2(简称LNMCO),并使用Zr(CH3COO)4进行ZrO_2的包覆改性。TEM测试结果显示纳米级的ZrO_2颗粒附着在LNMCO的表面。包覆质量分数为1.5%的ZrO_2包覆样品的首圈库伦效率和放电比容量有着显著提升,在室温下其首圈库伦效率和放电比容量(电流密度:20 m A·g-1,电压:2.0~4.8 V)分别为87.2%,279.3 m Ah·g-1,而原样则为75.1%,224.1 m Ah·g-1,循环100圈之后,1.5%ZrO_2包覆样品的放电比容量为248.3 m Ah·g-1,容量保持率为88.9%,高于原样的195.9 m Ah·g-1和87.4%。
