活性炭载硫材料的超临界二氧化碳制备及在锂硫电池中的应用

Abstract

锂硫(Li-S)电池因其理论比容量和能量密度分别高达1675mAh/g和2600wh/Kg而备受关注，但硫与放电最终产物Li2S的电子绝缘性以及“穿梭效应”使其实际应用存在较大困难。为寻求上述问题的潜在解决方案，本工作发展了一种新颖的Li-S电池正极材料制备技术，即通过超临界CO2(SCCO2)辅助沉积，将硫负载到商业活性碳(QR1500)。SCCO2近似气体的低粘度、低表面张力与高扩散性和类似液体的密度与溶剂化能力，使得硫均匀分散在活性炭孔道结构并与碳接触充分。以所得材料为正极的锂硫电池，展现出良好的循环性能。0.5C倍率下循环第一圈比容量达到810mAh/g，循环150圈后容量保持在55%，而用常规熔融渗透法制备的碳硫复合材料，其首次充放电比容量为139mAh/g。 On account of its surpassing theoretical specific capacity (1675mAh/g) and energy density (2600wh/Kg), lithium-sulfur (Li-S) battery has attracted extensive attention nowadays. However, its practical application is hindered by the electric insulativity of sulfur and Li2S as well as the well-known shuttle effect. In this work, a novel method, supercritical CO2(SCCO2) assisted precipitation, is reported to load sulfur onto commercial activated carbon (QR1500) as cathode material of Li-S battery, which exhibits improved cycling performance. SCCO2 provides low viscosity, low surface tension and high diffusivity like gas as well as appreciable density and solvation power like liquid, enabling uniform dispersion of sulfur into porous QR1500 and intimate contact of sulfur with carbon. As cathode materials of Li-S battery, the resultant composite gives rise to an initial discharge capacity of 810mAh/g at 0.5˚C, which is higher than that of 139mAh/g for its counterpart prepared by traditional melting infiltration. Furthermore, 55% of capacity was preserved after 150 cycles.