Synthesis And Performance Research Of Lithium-rich Manganes-based Li_1.2Mn_0.54Ni_0.13O₂

In recent years, lithium-rich manganes-based material has attract much attention ofparties scientists for its advantage of high capacity、high voltage、low cost,but the lowerfirst-time coulomb efficiency and poor rate performance with lower cycle performance of ithave greatly hinder its practical application. In this paper, we synthesized sphericalLi_1.2Mn_0.54Ni_0.13Co_0.13O₂with carbonate co-precipitation method after the study of themanganese-based lithium-rich material. This article analysised and studyed the structure andmorphology, composition and electrochemical properties, and its concentration-gradientcoating modification and carbon nanotubes doping modificationits resolve performanceissues.The uniform spherical precursor particles Mn_0.66Co_0.17Ni_0.17CO₃was synthesized bycarbonate co-precipitation method, then the material was used to synthesize cathode materialLi_1.2Mn_0.54Ni_0.13Co_0.13O₂through optimized high-temperature calcination process. By meansof SEM, XRD, TG were used to characterize the composition and structure of the material,the results show that the material has a layered structure and spherical morphology. Thecharge-discharge test results showed that the first discharge capacity Li_1.2Mn_0.54Ni_0.13Co_0.13O₂of0.1C rate was283.9mAh/g and the first coulomb efficiency was76.3%, after50charge-discharge cycles the capacity retention rate of92.2%. The rate performance wasgenerally but the cycle performance under different rate is excellent.We synthesized concentration-gradient GC-LMO material to enhance the cyclingperformance of Li_1.2Mn_0.54Ni_0.13Co_0.13O₂. The spherical material was constituted by a highspecific energy core of Li_1.2Mn_0.54Ni_0.13Co_0.13O₂, a high cycle performance Li_1.13Mn_0.47-Ni_0.2Co_0.2O2shell layer and an intermediate concentration-gradient transition layer for thepurpose of maintainingenhance the cycle performance of the material on the basis of thehigher capacity. The EDX test proved the prepared material having the design of aconcentration gradient through the cross-section, while the material at the0.1C rate50timesthe cycle capacity retention rate was98%, the capacity retention rate was91.4%after500cycles at1C, raterepresenting an72.1%capacity retention rate of Li_1.2Mn_0.54Ni_0.13Co_0.13O₂has been greatly improved.We also synthesized carbon nanotubes doped precursor to prepare of CNT&x=0.5LMO with3D pore structure for the purpose of upgrading the first coulombic efficiency and ratecapability of Li_1.2Mn_0.54Ni_0.13Co_0.13O₂. The charge-discharge test results showed that the firstdischarge capacity CNT&x=0.5LMO of0.1C rate was303.2mAh/g and the first coulombefficiency was90.4%, the first coulomb efficiency has been greatly improved. The1C rateinitial discharge capacity of CNT&x=0.5LMO is218.7mAh/g, compared to1C rate initialdischarge capacity of Li_1.2Mn_0.54Ni_0.13Co_0.13O₂（190.6mAh/g） increased14.7%. Electro-chemical tests prove that f-CNTs doped precursor preparation with3D pore structure of thecathode material can improve the the first Coulomb efficiency and magnificationperformance.