摘要
锂硫二次电池因具有非常高的理论比容量(1675 mAh/g)和能量密度(2600 Wh/kg)而备受关注。然而,锂硫电池的正极材料单质硫因导电性差和在充放电过程中生成的多硫化物Li_(2)S_(n)(4≤n≤8)极易发生“穿梭效应”等问题,严重降低了对活性硫的利用效率,造成电极材料不可逆的容量损失。因此寻找成本低、可循环利用、热稳定性好的碳载体基质是提高锂硫电池电化学性能最有效的方法之一。在本研究中,以天然木质素作为碳源,首先经过萃取和碳化过程制备了多孔碳纳米球,再通过熔融过程,将单质硫成功地包裹进木质素基碳纳米球的孔隙中,制备得到多孔球状结构的碳/硫复合材料(LS-C/S)。当该复合材料用作锂硫电池正极材料时,在0.1 C电流密度下,硫含量为59.41%(质量分数)的电极材料的首次放/充电比容量分别为800.3 mAh/g和758.8 mAh/g,对应库仑效率为94.8%,在经过200次充放电循环后,其比容量稳定在647.4 mAh/g,容量保持率为84.3%,相当于每循环一圈容量平均损失为0.0785%。此外,在经过高倍率的充放电循环后,比容量仍能恢复并稳定在620 mAh/g,展现出良好的可逆倍率稳定性。这种木质素基碳纳米球具有的高比表面积和多孔结构,促进了锂离子和电子的传输,有效地抑制了中间产物多硫化锂的溶解扩散,提高了单质硫作为正极材料的利用效率,因此,复合材料表现出优异的循环稳定性和可逆倍率性能。
Lithium-sulfur batteries(Li-S)have attracted extensive attention as energy storage devices owing to their high theoretical capacities(1675 mAh/g)and specific energy densities(2600 Wh/kg).However,the poor electronic conductivity of elemental sulfur and the"shuttle effect"of the intermediates polysulfides(Li_(2)S_(n),4≤n≤8)occurring during the discharge/charge processes lead to the lower utilization of active sulfur and an irreversible capacity loss of the cathode materials.Therefore,finding a cost-effective,recyclable,and thermally stable carrier matrix is crucial in improving the utilization of elemental sulfur and enhancing the electrochemical performance of Li-S batteries.In this work,a three-dimensional porous carbon-sulfur nanosphere composite material was prepared using the facile chemical method through natural lignin as the carbon source.First,the carbon nanospheres were prepared using sodium lignosulfonate as a carbon source through extraction and carbonization.Then,elemental sulfur was successfully impregnated into the voids of lignin-based carbon nanospheres in the melting process to obtain the LS-C/S nanosphere composites.When used as the cathode material for the Li-S batteries,the nanocomposite material with 59.41%sulfur content delivered the first discharge/charge capacities of 800.3 mAh/g and 758.8 mAh/g at the current density of 0.1 C,showing the Coulombic efficiency of 94.8%.The capacity stabilized at 647.4 mAh/g after 200 repeated discharge/charge cycles with a capacity retention rate of 84.3%,corresponding to an average capacity loss of 0.0785%per cycle.Additionally,after multiple high-rate discharge/charge cycles,the specific capacity of the LS-C/S nanocomposites still recovered and stabilize at 620 mAh/g,showing excellent reversible rate capability.The lignin-based carbon nanospheres with high specific surface areas and porous structures effectively promote the transport of Li+and e−,suppress the"shuttle effect"of lithium polysulfides,and improve the utilization of sulfur materials.Hence,the composite electrode showed superior cycling stability and rate performance when employed as a cathode for Li-S batteries.
作者
李顺
黄建国
何桂金
LI Shun;HUANG Jianguo;HE Guijin(College of Chemistry and Materials Engineering,Zhejiang A&F University,Hangzhou 311300,Zhejiang,China;Department of Chemistry,Zhejiang University,Hangzhou 310027,Zhejiang,China)
出处
《储能科学与技术》
CSCD
北大核心
2024年第1期270-278,共9页
Energy Storage Science and Technology
基金
浙江省自然科学基金项目(LQ20B030003)
国家自然科学青年基金(22203073)。
关键词
锂硫电池
木质素
碳纳米球
正极材料
电化学性能
lithium-sulfur batteries
lignin
carbon nanosphere
cathode material
electrochemical performance
