MnO_2制备尖晶石LiMn_2O_4及其电化学性能研究

Preparation of Spinel LiMn_2O_4 from Manganese Oxide and Its Electrochemical Performance

前驱体Mn O_2的性质对产物锰酸锂性能影响显著。采用液相沉淀法制备不同性质birnessite型层状Mn O_2,研究发现,以中性条件制得的Mn O_2为前驱体,最终产物中存在Mn O_2杂相且无表面碳包覆,而以酸性条件制得的Mn O_2为前驱体可以得到碳包覆的纯相尖晶石Li Mn_2O_4。后者在0.2 C的充放电倍率下,首次放电比容量为129.7 m Ah/g,远高于前者的58.5 m Ah/g;在30 C的大倍率下,容量高达117.8 m Ah/g,经1500次循环后容量保持率约为92%。因此,将液相沉淀法条件优化为酸性得到的Li Mn_2O_4产物表现出优异的大倍率性能和循环稳定性,具有市场应用前景。

The property of Mn O_2 precursor has a great effect on the performance of Li Mn_2O_4 product.In this study,birnessite-type layered Mn O_2 was obtained through liquid phase coprecipitation reaction under neutral and acidic conditions.After heat treatment,the final product synthesized from Mn O_2 under neutral conditions has an impurity phase Mn O_2 without any carbon layer,while the product synthesized from Mn O_2 under acidic conditions is proved to be pure spinel Li Mn_2O_4 with a thin carbon layer.The latter carbon-coated Li Mn_2O_4 delivers the initial discharge capacity of 129.7 m Ah/g at 0.2 C,which is higher than 58.5 m Ah/g of the former product;even at a higher rate of 30 C,the discharge capacity can reach 117.8 m Ah/g and retain about 92%capacity after 1500 cycles.The results show that when precursor Mn O_2 is optimized under acidic conditions,the as-synthesized spinel Li Mn_2O_4 can exhibit superior high-rate capability and long-life cycling stability,which proves to be a promising cathode material for market applications.