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多孔生物质碳硫复合正极材料的制备及其电化学性能研究
首发时间：2018-05-14
摘要：理论比容量高达1675 mah/g，质量比能量可达2600 wh/kg的锂硫电池,被认为是新一代最具竞争力的二次电池之一。但单质硫本身不导电,且放电过程中会形成多硫化物等中间产物溶于电解液,导致"穿梭效应"，严重降低了电池的充放电比容量及库伦效率，需加入高导电性的多孔碳进行改善。鉴于传统碳基材料昂贵的成本因素，本文以废弃莲杆为原料制备导电性较高的生物质多孔碳材料，并通过简单的高温热解法和koh活化法与单质硫形成活化碳硫复合材料(alc/s)。利用扫描电子显微镜(sem)、x射线衍射(xrd)对复合材料进行形貌、结构分析，表明单质硫均分散至莲杆碳基体中。由比表面积测试(bet)和孔径分布测试得alc比表面积为2966 m2/g，平均孔径为2.697 nm，具有强物理吸附作用以显著抑制多硫化物的溶解和扩散。电化学测试显示0.2 c倍率下alc/s电极首次放电比容量高达1358 mah/g，硫的利用率达到了81％，循环50次后比容量还保持在1064 mah/g,较之普通硫电极其电化学性能得到显著改善。
关键词： 生物质碳;单质硫;正极材料;锂硫电池
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preparation and electrochemical performance of porous biomass carbon/sulfur composite cathode materials
abstract：lithium-sulfur (li-s) batteries are nominated as one of the most promising next-generation electrochemical storage systems due to their relatively low cost, high capacity and theoretical energy density. however, the insulation of sulfur and the dissolution of intermediates polysulfide necessitate the addition of high conductivity matrices to enhance the active-material utilization, which are usually high-cost. in this work, the biomass-derived porous carbon (alc) is fabricated by carbonizing bio-waste lotuspetiole and subsequently activating the material with koh. the morphology, structure of the composites are characterized by scanning electron microscopy (sem), x-ray diffraction (xrd). the as-prepared alc possesses a large specific surface area of 2966 m2/g and an average pore size of 2.697 nm, introducing strong physical adsorption to significantly suppress the dissolution and diffusion of polysulfide. herein, a high initial discharge capacity of 1358 mah/g at 0.2 c with the utilization of sulfur is up to 81%, and large reversible capacity of 1064 mah/g after 50 cycles at 0.2 c, meaning its outstanding prospects for the better cyclability and electrochemical performance as application of li-s battery.
keywords： biomass carbon elemental sulfur cathode material lithium-sulfur batteries
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多孔生物质碳硫复合正极材料的制备及其电化学性能研究
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