生物质炭基硫正极材料的制备及其电化学性能研究

Study on Preparation and Electrochemical Performance of Biomass Carbon-based Sulfur Cathode Material

锂硫电池因较高的理论比容量和能量密度在动力汽车和储能装置等领域具有广阔的应用前景,因此设计制备低成本和高性能的锂硫电池正极材料具有重要研究价值。以廉价易得且可再生的红薯淀粉为生物质碳源,经水热反应、高温石墨化以及碱活化等方法,得到表面富含多孔的碳材料。再将其与硫单质按不同比例混合,通过熔融扩散法制备锂硫电池正极材料。运用X射线衍射、氮气吸附、X射线光电子能谱等手段对材料的表面形貌和结构进行了表征。另外,对利用该材料组装的电池进行电化学测试,结果显示碳/硫比为1∶2时,电池具有更优良的循环及倍率等电化学性能,其在0.1 A g^(-1)下的初始放电容量为1 470.6 mAhg^(-1),恒电流循环300圈后容量为754.6 mAhg^(-1);并在3 C下的放电容量达到864.1 mAhg^(-1)。研究成果为自然界中生物质转化为功能性碳材料提供了一种新思路。

Lithium-sulfur batteries have broad application prospects in power vehicles and energy storage de⁃vices due to their higher theoretical specific capacity and energy density.Therefore,it is urgent to design and prepare low-cost and high-performance cathode materials for lithium-sulfur batteries.In this paper,the cheap,easily available and renewable sweet potato starch is used as the biomass carbon source.After simple hydrothermal reaction,high-temperature graphitization and alkali activation,a carbon-based material with rich porous surface is obtained.Then it is mixed with the elemental sulfur in different proportions,and the cathode material of the lithium-sulfur battery is prepared by the melt diffusion method.The surface morphol⁃ogy and structure of the materials were characterized by X-ray diffraction,nitrogen adsorption desorption and X-ray photoelectron spectroscopy.In addition,the electrochemical test of the battery showed that when the carbon/sulfur ratio is 1∶2,the battery has better electrochemical performance such as cycle and rate,and its initial discharge capacity at 0.1 A g^(-1) is 1470.6 mAh g^(-1),after 300 cycles of constant current,the capacity is 754.6 mAh g^(-1),and the discharge capacity reaches 864.1 mAh g^(-1) at 3 C.On this basis,this paper also pro⁃vides a new idea for the conversion of biomass into functional carbon materials in nature.