锂离子电池新型正极材料xLiF-(Ni1/6Co1/6Mn4/6)3O4的制备及电化学性能研究

采用高能球磨法通过不同球磨时间合成 xLiF-(Ni1/6Co1/6Mn4/6)3O4新型正极材料，并对材料进行石墨烯复合改性，提高其性能。结合X-射线衍射(XRD)、扫描电镜(SEM)、电化学性能测试和X-射线电子能谱（XPS）对xLiF-(Ni1/6Co1/6Mn4/6)3O4正极材料性能进行表征。研究表明，球磨24小时产物的放电容量最高，为157.3 mAh g-1。并且LiF与(Ni1/6Co1/6Mn4/6)3O4比例为1.5:1(x=1.5)时放电容量最高。此外正极材料添加石墨烯能改善材料的电化学性能，石墨烯复合量为20%，在室温、0.05 C(1C=250 mAh g-1)、1.5 -4.8 V下，材料首圈的放电比容量为235 mA hg -1，相较于无石墨烯的材料，在1 C和5 C倍率下，放电比容量分别为151和114 mAh g-1。同时分析了正极材料放电容量随截止电压的变化，确定了复合正极材料在高电压下有获得更高放电容量的潜力。

Synthesis and electrochemical properties of xLiF-(Ni1/6Co1/6Mn4/6)3O4composite as a novel cathode material for Li-ion batteries

A novel cathode material xLiF-(Ni1/6Co1/6Mn4/6)3O4composites are synthesized by the high energy mechanical milling with different time and the prepared compound were modified by the graphene to improve electrochemical performance. X-ray diffraction (XRD), scanning electron microscopy (SEM), electrochemical test and X-ray photoelectron spectroscopy (XPS) are employed to further characterize the properties of the composites. The resultant cathode demonstrates the highest discharge capacity of 157.3 mAh g-1 when the time of ball milling is 24h. The xLiF-(Ni1/6Co1/6Mn4/6)3O4 composites add 20% graphene exhibit a discharge capacity of 235 mAh g-1 (1C = 250 mAh g-1) at 0.05 C from 1.5-4.8 V. The rate capability is also promoted as the discharge specific capacity reaching 151 and 114 mAh g-1 at 1 C and 5 C respectively. Moreover, the variation of the discharge capacity of the composite cathode along with the cut-off voltage are analyzed, which confirms the potential of higher discharge capacity of the cathode at higher voltage.