双金属MOFs碳化工艺对锂硫电池正极材料性能的影响

Influence of carbonizing process of bimetal-MOFs on the property of Li-S battery

利用Co(NO_(3))_(2)和K_(3)Fe(CN)_(6)在水溶液中沉淀反应,制备了三维双金属有机框架前驱体,并在氩气氛退火获得碳化产物。通过改变碳化温度、前驱体包覆等工艺条件获得系列样品。利用X射线衍射、扫描电镜、透射电镜、热重仪进行形貌和结构分析;以产物制备硫碳复合材料作为正极,组装扣式锂硫电池并测试电化学性能。结果表明:前驱体碳化过程为多步放热收缩过程,为了获得良好的材料结构,需要对前驱体包覆并选择适当的碳化温度。CoFeCN@C-750具有完整的核壳结构,表现出最佳的综合电化学性能。在1C电流密度下,300次循环平均每圈循环衰减率0.10%。

The 3D-bimetal-organic frameworks precursors were obtained by precipitation reaction in aqueous solution using Co(NO_(3))_(2)and K_(3)Fe(CN)_(6).And the series of carbonizing products were obtained by additional polydopamine envelope and annealing at different temperature,which used as the cathode material of lithium-sulfur(Li-S)battery.The morphology and structure of the different samples were compared by X-ray diffractometer(XRD),scanning electron microscope(SEM),transmission electron microscope(TEM),thermal gravimetric analyzer(TG),etc.And the difference in carbonization process of different samples were analysis.The Electrochemical performance of Li-S batteries with different samples as cathode materials were tested by electrochemical impedance test(EIS),cyclic voltampere test(CV),and charge and discharge performance test.The results shown that the polydopamine envelope and annealing temperature can affect the carbonization product structure.The polydopamine coating can prevent material reunion during carbonization.And the spatial domain restriction of the intact shell was helpful to anchor S and polysulfide inside the structure.Excessive annealing temperature can disrupt the integrity of the nuclear shell structure,and too low annealing temperatures can cause incomplete carbonization of the material.As the best one,the Li-S batteries with CoFeCN@C-750 cathode performed excellent cycling stability with the capacity decay rate of 0.1%per cycle at 1C after 300 cycles.