Effects of Na content on structure and electrochemical performances of Na_xMnO_2+d cathode material

来源期刊：中国有色金属学报(英文版)2010年第10期

论文作者：杨顺毅 王先友 王莹 陈权启 李姣姣 杨秀康

文章页码：1892 - 1898

Key words：lithium-ion battery; cathode material; sodium manganese oxides; electrochemical properties; sol-gel technology

Abstract: Sodium manganese oxides, Na_xMnO_2+d (x = 0.4, 0.5, 0.6, 0.7, 1.0; d = 0-0.3), were synthesized by solid-state reaction routine combined with sol-gel process. The structure, morphology and electrochemical performances of as-prepared samples were characterized by XRD, SEM, CV, EIS and galvanostatic charge/discharge experiments. It is found that Na_0.6MnO_2+d and Na_0.7MnO_2+d have high discharge capacity and good cycle performance. At a current density of 25 mA/g at the cutoff voltage of 2.0-4.3 V, Na_0.6MnO_2+d gives the second discharge capacity of 188 mA·h/g and remains 77.9% of second discharge capacity after 40 cycles. Na_0.7MnO_2+d exhibits the second discharge capacity of 176 mA·h/g and shows better cyclic stability; the capacity retention after 40 cycles is close to 85.5%. Even when the current density increases to 250 mA/g, the discharge capacity of Na_0.7MnO_2+d still approaches to 107 mA·h/g after 40 cycles.