Preparation And Modification Of Li_1.2Mn_0.54Co_0.13Ni_0.13O₂ Cathode Material For Lithium Ion Batteries

xLi₂MnO₃·??1-x?LiMO₂??M=Ni,Co,Mn,etc.?material was first discovered in 1997 by Numata,Sakaki et al^[39],it was found that Li₂MnO₃·LiCoO₂ layered solid solution material can be used as the cathode material of lithium ion battery,the first discharge capacity can reach 280mAh g^-1,and its theoretical capacity can reach 300mAh g^-1.Future requirements for lithiumion ion batteries are high energy density,high power density,so the Rich lithium manganese cathode materialhas a promising future.In this paper,Ni_1/6Co_1/6Mn_4/6CO₃precursors were prepared by using Na₂CO₃ as the Coprecipitation agent and ammonia as the Chelating agent.The precursors of Ni_1/6Co_1/6Mn_4/6CO₃ were prepared by carbonate coprecipitation.Li_1.2Mn_0.54Co_0.13Ni_0.13O₂ cathode material,the more systematic study of the effect of sintering temperature and chelating agent concentration on structure,morphology and electrochemical performance of materials;The Li_1.2Mn_0.54Co_0.13Ni_0.13O₂ cathode material was modified by Al₂O₃+Li₂O coatingto improve its electrochemical performance.The composite LMNCO was made by compounding with GN?graphene?,CNT?carbon nanotube?and Li_1.2Mn_0.54Co_0.13Ni_0.13O₂ to improve its electrochemical performance and rate performance.When the chelating agent concentration is 0.05mol/L and the sintering temperature is900?,the prepared Li_1.2Mn_0.54Co_0.13Ni_0.13O₂ cathode material has excellent lamella structure and relatively low cation mixing.The discharge capacity of 238.3mAh g^-1,1C rate charge and discharge conditions,the first ring discharge capacity of 167.2mAh g^-1(the charge and discharge process without constant voltage charging,coupled with constant voltage charging,the discharge capacity can be Increasing 20-30mAh g^-1).After 100 cycles,the specific discharge capacity of the material decayed to 146.5mAh g^-1,and the capacity retention rate was 87.62%.In this paper,the Li_1.2Mn_0.54Co_0.13Ni_0.13O₂ cathode material was modified by coating Al₂O₃+Li₂O.The first-cycle discharge specific capacity of the sample at current rate 1C of the coated cathode material was 173.2mAh g^-1.After 100 cycles,the discharge capacity decayed to 158.9mAh g^-1,the capacity retention rate of up to 91.74%(the sample is under 1C rate cycle test is carried out without constant voltage charging conditions,if combined with constant voltage charging,The discharge capacity can be increased by 20-30mAh g^-1).The discharge specific capacity at 10C rate is higher than that of blank control by nearly 1/3,which can reach 99.4mAh g^-1.After being coated and modified,the rate performance and cycle performance of the material are obviously improved.The multiply depolarized composite cathode consisted of Li_1.2Mn_0.54Ni_0.13Co_0.13O₂?LMNCO?and a combinatory conductive network of graphene?GN?+carbon nanotubes?CNTs?in the active material and GN coating at the interface of current collector is synthesized via pasting LMNCO/GN/CNTs composite slurry on GN coated Al foil.The interlaced GN+CNTs conductive network improves both the electronic conductivity and Li ion transport and stabilizes the structure of composite.The GN coating at the interface of current/active materials interlaces with GN+CNTs in the active materials and improves the adhesion and reduces the resistance between the active material and current collector.Consequently,the LMNCO composite cathode exhibits superior rate capacities of 132mAh g^-11 at 5C and 97mAh g^-11 at 10C,high cycling capacity retentions of 86%at 1C and 85%at 2C after 100 cycles,respectively and lower voltage fading.This combinatory conductive network is much more efficient for reducing the resistance and polarization of electrode than any single conductive network of GN+CNTs,CNTs,GN or GN coating.