Synthesis And Electrochemical Performance Of Manganese Based Lithium-rich Oxide Cathode Material For Lithium-ion Batteries

Lithium-rich cathode materials attracted widely attention due to their high specific capacity, structural stability, low cost and lower pollution, in recent years. However, for the first time the material discharge embedded lithium ion is far less than in the process of charging process, resulting in the first week the irreversible capacity loss. Therefore, this paper used doping methods to improve the electrochemical performance of lithium-rich manganese-based oxide cathode material. The physical properties of materials were investigated by current charge-discharge, cyclic voltammetry and electrochemical impedance spectrochemical performances.Li-ion cathnode materials Li Mn O2, Li Mn2O4 and Li2 Mn O3 were synthesized by hot solvent method, microwave solid-phase method and sol-gel method, respectively. And this three typical Li-Mn-O were tested, severally by phase characterization and electrochemical performance, and it is concluded that: Using solvent hot method to prepare Li Mn O2,180 ℃ for 12 h, the first week charge specific capacity is 164 m Ah·g-1, the fifteenth week charge specific capacity is 80.9 m Ah·g-1, following the electrochemical cycling process, O-Li Mn O2 turns into Li Mn2O4 pahse. The capacity fading resulting from structural changes in material. Using microwave solid state method to prepare Li Mn2O4 material, at 460 W for 15 min, the first week charge specific capacity is 122.3 m Ah·g-1, the fifteenth week charge specific capacity is 83 m Ah·g-1, the electrochemical performance data shows that it has a good ratio performance. Using sol-gel method to prepare Li2 Mn O3 meterial, 700 ℃ for 12 h, 0.2C the first week charge specific capacity is 221.6 m Ah·g-1. After 50 cycles, the capacity remains at 178.9 m Ah·g-1. the electrochemical performance data shows that it has high charge and discharge specific capacity and good cycle stability.Using high temperature solid state method synthese new design ternary material, pick out the good ternary material and it is concluded that: among them there were three tipes of ternary materials, shows up well electrochemical performance. They were namely, Li Mn1/3Ni1/3Co1/3O2 、 Li Mn1/2Ni1/4Co1/4O2 、 Li Mn1/2Ni3/10Co1/5O2. Investigate the influence of reaction temperature on the electrochemical properties of the sample. 750 ℃ for 12 h, the first week charge specific capacity of these samples were 167.1 m Ah·g-1,102.3 m Ah·g-1,133.6m Ah·g-1. All in all, the electrochemical performance of Li Mn1/3Ni1/3Co1/3O2 is the best.Using high temperature solid state method synthesis three lithium-rich manganese based materials respectively. Look further into ternary material: firstly, testing electrochemical performance of Li2 Mn O3·Li Mn1/3Ni1/3Co1/3O2, Li2 Mn O3·Li Mn1/2Ni1/4Co1/4O2 and Li2 Mn O3·Li Mn1/2Ni3/10Co1/5O2 one by one, we can concluded that Li2 Mn O3·Li Mn1/3Ni1/3Co1/3O2 is the best. At 900 ℃ for 12 h, the first week charge specific capacity of these samples were 286.9m Ah·g-1. The material shows high discharge capacity, however it has first week irreversible problem.In the case of element-doping of lithium-rich manganese based materials. Using high temperature solid state method, and doping Al3+ into Li2Mn1-x O3·Li Mn1/3Ni1/3Co1/3 Alx O2(x=0.01,0.03,0.05) materials to explore the effects on the electrochemical properties. Investigate suitable amount of doping element. The result of electrochemical properties test showed that, while the doping amount is 3%, the lithium-rich manganese based materials has well electrochemical performance, first week irreversible problem has been solved as well.