Research On Synthesis And Modification Of Li₂MnsiO₄Cathode Material For Lithium Ion Batteries

As the potential cathode material for lithium ion batteries, Li₂MnSiO₄had beensystematically introducted and synthesized via solution reflux method and sol-gelmethod. Moreover, the effects of cation doping on the electrochemical performance ofLi₂MnSiO₄/C were also investigated.1. CH₃COOLi·2H₂O、（CH₃COO）₂Mn·4H₂O and TEOS as raw materials, citricacid and ethylene glycol as carbon source, solution reflux method was used tosynthesize Li₂MnSiO₄/C cathode materials. In addition, the optimal calcinationtemperature and time were also studied. Sintered at650℃for12h, Li₂MnSiO₄/Cexhibits excellent electrochemical performance. Its initial discharge specific capacityat0.1C and0.2C are104.84mA·h/g and103.49mA·h/g in the range of1.5⁴.8V,respectively. Besides,46.33mA·h/g and36.29mA·h/g are still obtained in the20thcycle.2. In the sol-gel method, citric acid and ethylene glycol as carbon source, thestoichiometric ratio of CH₃COOLi·2H₂O、（CH₃COO）₂Mn·4H₂O and nano-SiO₂wereused as the starting materials to synthesize Li₂MnSiO₄/C cathode material. In addition,the optimal preparation conditions such as the pH value of sol system, calcinationtemperature and time were also studied. When the pH is6, the excellentelectrochemical performace is obtained by Li₂MnSiO₄/C prepared at600℃for12h.The initial discharge specific capacity at0.1C and0.2C are122.26mA·h/g and106.64mA·h/g in the range of1.5⁴.8V, respectively. Besides, it also delivers34.42mA·h/g and33.98mA·h/g in the20th cycle.3. Based on the solution reflux method, Mg²⁺, Fe²⁺and Li⁺were doped intoLi₂MnSiO₄/C cathode material. The results show that all the doping have an importanteffect on the electrochemical performance of the as-prepared samples. The initialdischarge specific capacity of Li₂Mn_0.9Mg_0.1SiO₄/C are162.67mA·h/g and134.23mA·h/g at0.1C and0.2C, while69.76mA·h/g and65.63mA·h/g are still obtainedafter20cycles; The Fe²⁺doped sample with10%shows the high capacity and cyclicperformance, at0.1C and0.2C the initial discharge specific capacity are138.05mA·h/g and118.06mA·h/g, respectively, and retain a discharge specific capacity of 56.11mA·h/g and53.38mA·h/g for20cycles; However, Li_2.05MnSiO₄/C cathodematerial presents the initial discharge specific discharge capacity of119.17mA·h/gand112.08mA·h/g at0.1C and0.2C, after charge/discharge for20cycles, the restare46.92mA·h/g and46.48mA·h/g respectively.4. Based on the sol-gel method, Cu²⁺and Ni²⁺were doped into Li₂MnSiO₄/Ccathode material. The electrochemical performances of the as-prepared samples havechanged by doping.4%Cu²⁺doped sample Li₂Mn_0.96Cu_0.04SiO₄/C can stabilize thestructure of Li₂MnSiO₄/C, the initial discharge specific capacity are89.2mA·h/g and64.4mA·h/g at0.1C and0.2C, respectively. While the capacity retaintion of44.42%and50.76%are obtained after20cycles; However, The initial dischargespecific capacity of Li₂Mn_0.94Ni_0.06SiO₄/C are107.46mA·h/g and97.35mA·h/g at0.1C and0.2C, respectively, after charge/discharge for20cycles, the rest are41.54mA·h/g and39.10mA·h/g respectively.