高性能、低成本的多孔碳材料是理想的锂硫电池硫宿主材料,但利用廉价的原料实现其规模化制备仍面临巨大挑战。以资源丰富的高硫煤为原料,采用氧化镁和氢氧化钾作为模板剂和活性剂,制备了煤基多孔碳材料,并研究了其作为锂硫电池硫宿主材料的构效关系。研究发现,煤基碳材料制备过程中,模板剂MgO作用下产生介孔(占比74%);活性剂KOH主要导致微孔(占72%)生成;MgO和KOH共同作用制备的碳材料PCMgO+KOH比表面积大(1616m2/g)、孔容高(1.02m3/g)、孔结构丰富(介孔54%、微孔46%)。电化学性能测试结果表明,S@PCMgO+KOH具有良好的倍率性能和优异的循环稳定性,在1C充放电倍率循环500圈后容量仍能保留553.2mAh/g,容量保持率达65.5%,每个循环的衰减率低至0.069%;在2C下,循环500圈后容量为484.0mAh/g,容量保持率为63%,每圈衰减率仅0.075%,具有良好的倍率性能和优异的循环稳定性。PCMgO+KOH优异的电化学性能主要来自其较小的欧姆电阻和电荷转移电阻、快速的多硫化物氧化还原反应动力学及对多硫化锂优异的束缚能力。本研究为价廉性高的锂硫电池硫宿主材料的制备提供了可选择的路线。

Porous carbon materials with superior performance and low-cost have emerged as the preferred sulfur host materials in lithium-sulfur batteries, however, utilizing cheap raw materials to achieve large-scale preparation still faces great challenge. In this study, porous carbon materials were synthesized using abundant high sulfur coal as the feedstock and magnesium oxide and potassium hydroxide bothas templates and activators. The study delved into the investigation of structure-activity relationship of these materials when employed assulfur host materials in lithium sulfur batteries. It is observed that mesoporous (constituting 74%) are predominantly generated due to thetemplating action of MgO. KOH serves as an active agent primarily responsible for the formation of micropores ( constituting 72%).The combined use of MgO and KOH leads to the creation of carbon material, PCMgO+KOH, characterized by large specific surface area(1 616 m2 / g),high pore volume (1.02 m3 / g),and rich pore structure (54% mesoporous and 46% microporous). The results of electrochemical performance test show that the S@ PCMgO+KOH has good rate performance and excellent cycle stability. After 500 cycles of chargingang discharging at 1 C, it can still retain 553.2 mAh/ g, with a capacity retention rate of 65.5% and a decay rate of only 0.075% per cycle, demonstrating good rate performance and excellent cycling stability. The excellent electrochemical properties of PCMgO+KOH can be attributed mainly to its low ohmic resistance and charge transfer resistance, rapid polysulfide redox reaction kinetics, and exceptional capability in binding lithium polysulfide. This study provides an alternative route for the preparation of low-cost and high-performance host materials for lithium-sulfur batteries.

0 引言

1 试验

   1.1 材料的制备

   1.2 扣式电池的组装

   1.3 硫化锂的沉积与成核测试

   1.4 可视化吸附试验

   1.5 测试仪器及方法

2 结果与讨论

   2.1 高硫煤基碳材料的结构表征

   2.2 电化学性能

   2.3 电化学作用机理

3 结论