MnO_(2)@ACFF中间层强化高载量硫电极性能稳定性作用

Effect of an Interlayer Derived from MnO_(2) Modification of Activated Carbon Fiber Felt on Cycle Stability of Sulfur Electrode with High Sulfur Loadings

为提高碳材料对聚硫化物的吸附能力,将MnO_(2)原位化学沉积于活性碳纤维炭毡(ACFF)的碳纤维表面,得到了聚硫化物吸附强化的多孔导电材料(MnO_(2)@ACFF)。将其作为中间层设置于隔膜和硫电极之间,有效控制了高载量硫电极的聚硫离子穿梭,提高了活性物质利用率和库伦效率,降低了电极极化和电化学反应阻抗,提高了电极循环稳定性,避免了锂硫电池的突然失效。在2 mA/cm^(2)的电流密度下,载硫量为15 mg/cm^(2)的硫电极经过350次充放电循环仍保有430 mA·h/g的比容量。提高硫电极载硫量虽然使电极的循环稳定性下降,但载量为20 mg/cm^(2)和30 mg/cm^(2)的硫电极0.1 C下经过100次循环,仍分别保有736 mA·h/g和446 mA·h/g的比容量,比容量保持率为65%,而且面积比容量和面积比能量也能分别保持64%和42%,高于当前锂离子电池的面积比容量和面积比能量。

In order to improve the adsorption capability of carbon materials toward polysulfides,a porous conductive material was prepared by in-situ deposition of MnO_(2) on surfaces of activated carbon fiber in its felt(ACFF),named MnO_(2)@ACFF.The MnO_(2)@ACFF was placed between separator and sulfur electrode as an interlayer.The existence of MnO_(2)@ACFF interlayer effectively controlled polysulfide shuttle when using heavy S-loaded electrode,thereby promoting utilization of active substance and coulombic efficiency,improving the electrode cyclability ascribed to the decrease in electrode polarization and electrochemical impedance,preventing the electrode from sudden failure.The sulfur electrode with an S-loading of 15 mg/cm^(2),delivered a discharge capacity of 430 mA·h/g after 350 evaluation cycles at a current density of 2 mA/cm^(2).Though increase in S-loading led to the deterioration of sulfur electrode,the sulfur electrodes with S-loading of 20 mg/cm^(2) and 30 mg/cm^(2) presented the discharge capacities of 736 mA·h/g and 446 mA·h/g after 100 cycles at 0.1 C,respectively,meanwhile the retention rate of specific capacity reached 65%,the areal specific capacity and energy density kept 64%and 42%,higher than those of lithium-ion batteries.