CoSe2/C复合电催化材料修饰隔膜对高载量锂硫电池性能的影响

以具有菱形十二面体结构的ZIF-67为模板, 采用两步烧结法合成了CoSe₂/C复合材料, CoSe₂纳米颗粒直径约30 nm, 均匀分散在碳骨架上. 电化学测试结果表明, CoSe₂/C复合材料在放电过程中可以加快可溶性聚硫离子的还原反应动力学, 还能够促进不溶性Li₂S的沉积过程, 同时加速充电过程中Li₂S的氧化分解. 将CoSe₂/C作为电催化材料与碳材料混合后用于隔膜修饰, 修饰层面载量仅为0.15 mg/cm², 其中CoSe₂/C的质量分数仅占30%时, 电池依然表现出优异的电化学性能; 当硫载量为4.8 mg/cm²时, 在0.2C倍率下电池初始放电比容量为756 mA·h/g, 经过180次循环后, 容量依然能够维持715 mA·h/g, 每次衰减率仅为0.031%.

Enhance of CoSe2/C Composites Modified Separator on Electrochemical Performance of Li-S Batteries at High Sulfur Loading

Herein， CoSe₂/C composite was obtained by a simple two-step calcining method with the rhombohedral dodecahedral ZIF-67 as the template. The CoSe₂ nanoparticles with diameters of approximately 30 nm were dispersed in the carbon skeleton maintaining the structure of the template. Systematically electrochemical results demonstrated that the CoSe₂/C composite could fasten the kinetics of the soluble lithium polysulfides， as well as guide the deposition of the insoluble Li₂S during the discharge process. In addition， the CoSe₂/C could also boost the oxidation of Li₂S. It was loaded on commercial Celgard 2400 separators as the electrocatalytic materials. It is worth to note that the mass loading of the modified layer is only 0.15 mg/cm²， in which the CoSe₂/C composite only accounts for 30%（mass fraction）. Consequently， the cells with CoSe₂/C-modified separator delivered a superior electrochemical performance， which with a high sulfur loading of 4.8 mg/cm² gave an initial specific capacity of 756 mA·h/g at 0.2C and maintained at 715 mA·h/g after 180 cycles， with a capacity decay rate of 0.031% per cycle.