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
富锂层状氧化物材料是一种具有类固溶体结构的锂离子电池正极材料,放电比容量可达250 m Ah/g,且价格低廉。因此,富锂层状氧化物材料被认为是最有希望的下一代正极材料之一。然而,富锂层状材料还存在诸多问题,如首次库仑效率低、倍率性...富锂层状氧化物材料是一种具有类固溶体结构的锂离子电池正极材料,放电比容量可达250 m Ah/g,且价格低廉。因此,富锂层状氧化物材料被认为是最有希望的下一代正极材料之一。然而,富锂层状材料还存在诸多问题,如首次库仑效率低、倍率性能差以及容量和电压平台衰减严重,这些问题阻碍其在商业中的应用。本文从富锂层状材料的晶型结构和首次充放电特性出发,主要介绍了离子掺杂、表面包覆以及表面氧空位修饰的作用机理,并进一步分析了不同掺杂离子和不同包覆材料作用于富锂层状材料后性能差异的原因,以及双掺杂和双包覆的优势。最后,本文针对单纯的离子掺杂、表面包覆、表面氧空位修饰在富锂层状材料改性中的不足,提出了基于上述三种改性方式的联合改性机制,并对该机制进行了简要介绍。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.
文摘富锂层状氧化物材料是一种具有类固溶体结构的锂离子电池正极材料,放电比容量可达250 m Ah/g,且价格低廉。因此,富锂层状氧化物材料被认为是最有希望的下一代正极材料之一。然而,富锂层状材料还存在诸多问题,如首次库仑效率低、倍率性能差以及容量和电压平台衰减严重,这些问题阻碍其在商业中的应用。本文从富锂层状材料的晶型结构和首次充放电特性出发,主要介绍了离子掺杂、表面包覆以及表面氧空位修饰的作用机理,并进一步分析了不同掺杂离子和不同包覆材料作用于富锂层状材料后性能差异的原因,以及双掺杂和双包覆的优势。最后,本文针对单纯的离子掺杂、表面包覆、表面氧空位修饰在富锂层状材料改性中的不足,提出了基于上述三种改性方式的联合改性机制,并对该机制进行了简要介绍。
