凝胶燃烧法合成Li_(1.07)Mn_(1.93)O_4纳米片及其高倍率放电和循环稳定性(英文)

High Rate Capability and Cycling Stability of Li_(1.07)Mn_(1.93)O_4 Nanoflakes Synthesized via Gel-Combustion Method

利用聚乙烯吡咯烷酮(PVP)作为聚合物配位剂和燃料,通过凝胶-燃烧法合成了Li1.07Mn1.93O4纳米片.采用热重/差热分析(TG/DTA)研究了凝胶的燃烧过程.采用X射线多晶衍射(XRD)分析了材料的结构,结果表明合成的Li1.07Mn1.93O4结晶完整,无杂质相.扫描电镜(SEM)结果显示材料的二次形貌为厚度约100nm的片状,由大小约100nm的一次颗粒构成.充放电测试表明Li1.07Mn1.93O4纳米片具备极佳的倍率放电性能和优秀的循环性能.0.5C(1C=120mA.g-1)倍率的初始放电容量为115.4mAh.g-1,即使倍率增大到40C,放电容量仍有105.3mAh.g-1.在10C倍率的放电条件下,循环850次容量保持率为81%.电化学阻抗谱(EIS)测试表明Li1.07Mn1.93O4纳米片的界面电荷转移电阻(Rct)远小于同类商业材料.

Li1.07Mn1.93O4 nanoflakes were synthesized by a gel-combustion method using polyvinylpyrrolidone （PVP） as the polymer chelating agent and fuel. Thermogravimetric and differential thermal analyses （TG/DTA） were used to investigate the combustion process of the gel precursor. X-ray diffraction （XRD） analysis indicated that the as-prepared Li1.07Mn1.93O4 was a pure, highly crystalline phase. Scanning electron microscopy （SEM） results showed that most of the secondary particles were nanoflakes, about 100 nm in thickness, and the primary particle of the nanoflakes was about 100 nm in size. Charge and discharge tests suggested that the Li1.07Mn1.93O4 nanoflakes had excellent rate capability and good cycling stability. The initial discharge capacity was 115.4 mAh g-1 at a rate of 0.5C （1 C=120 mAh. g-1） and the capacity was maintained at 105.3 mAh g-1 at the high discharge rate of 40C. When cycling at 10C, the material retained 81% of its initial capacity after 850 cycles. Electrochemical impedance spectroscopy （EIS） tests indicated that the charge-transfer resistance （Rct） of the Li1.07Mn1.93O4 nanoflakes was much less than that of commercial Li1.07Mn1.93O4.