Study On Synthesis And Modification Of Li-rich Spherical Cathode Material Li_1.3[Ni_0.35Mn_0.65]O₂as Lithium Ion Batteries

The Li-rich layered cathode materials, xLi2MnO3·(l-x)LiMO2(M=Ni, Co, Mn,0<x <1), have been the focus of research as a new generation of positive electrodematerials in high-energy lithium-ion batteries due to their much higher capacity ofmore than250mAh g-1，lower cost and higher safety. However, there are someproblems, such as the lower initial efficiency during the first charge/discharge process,poor rate capability, and fast capacity fading, which should be solved so as to putthem into application as soon as possible.This paper aims to improve the electrochemical performance of Li-rich sphericalLi1.3[Ni0.35Mn0.65]O2,which was prepared via a simple co-precipitation method. Inaddition, the effect of calcining temperature and time on morphology, structure andelectrochemical performance has been studied in detail. The as-prepared samples werecharacterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) andcharge/discharge tests. The results reveal that Li1.3[Ni0.35Mn0.65]O2show the bestelectrochemical properties when it is calcined at850℃for12h, which delivers aninitial discharge capacity of229.1mAh g-1and the first coulombic efficiency is up to84.8%at a rate of0.1C in the voltage range of2.0~4.6V. And the capacity retentionof the sample is61.1%at0.33C after100cycles.Al2O3coating can effectively improve the electrochemical performance ofLi-rich spherical Li1.3[Ni0.35Mn0.65]O2, especially, the2wt%-Al2O3coated sampleshows the best electrochemical properties, which delivers the initial dischargecapacity and coulombic efficiency are228.2mAh g-1and89.6%, respectively, at arate of0.1C in the voltage of2.0~4.6V. Furthermore, the2wt%-Al2O3coated samplerepresents excellent cycling stability with a capacity retention of90.9%at0.33C after100cycles. Particularly, herein the typical inferior rate capability of Li-rich layeredcathode is apparently improved, and the2wt%-Al2O3coated sample also shows a highrate capability, which can deliver a capacity of101.3mAh g-1even at10C, muchhigher than that of the pristine one (48.4mAh g-1).Mg-F co-substitution can effectively improve the electrochemical performanceof Li-rich spherical Li1.3[Ni0.35Mn0.65]O2, and Li1.3(Ni0.35Mn0.65)1-0.03Mg0.03O2-0.03F0.03exhibits the best electrochemical performance compared to the pristine sample, whichdelivers an initial discharge capacity of215.4mAh g-1at a rate of0.1C in the voltageof2.0~4.6V, and the first coulombic efficiency is up to88.1%. Additionally, the Li1.3(Ni0.35Mn0.65)1-0.03Mg0.03O2-0.03F0.03shows excellent cycling stability with acapacity retention of86.3%at0.33C after100cycles.And the materials also shows ahigh rate capability of88.3mAh g-1even at10C.