碳化木耳多孔碳的制备及在硫正极中的应用

Preparation and research of carbonized agaric material for sulfur cathodes

以冷冻干燥的木耳为前体,在不同碳化温度下,制备了孔结构和表面化学性质可调的碳材料。测试结果表明,碳化温度在450~650℃时,所制备的碳材料含氧官能团丰富但缺乏孔道结构;而碳化温度在800~900℃时,所制备的碳材料富含微孔和介孔结构(795 m^(2)/g),但缺乏表面基团。将碳材料作为硫的载体制备碳硫复合材料。实验表明具有丰富微孔和小介孔结构的LD900材料,其微孔对含硫物种具有一定限制作用,使LD900-S呈现3个放电平台,由于微孔和小介孔在循环过程中易被阻塞,致使其循环稳定性较差。而富含极性含氧官能团的LD450材料,则对含硫物种表现出更强的化学吸附作用,所制备的LD450-S正极具有更优的循环稳定性和倍率性能,在0.1 C倍率下,100次循环后比容量仍有577 mA·h/g,在1 C倍率下仍有650 mA·h/g的放电比容量。

Carbon materials with adjustable pore structure and surface chemical properties were prepared at different carbonization temperatures using freeze-dried agaric as a precursor.The measured results show that carbon materials prepared at carbonization temperatures ranging from 450—650℃have oxygen-containing functional groups without pore structure.While carbon materials prepared at 800—900℃contain the amount of microporous and mesoporous(795 m^(2)/g)without surface groups.Carbon materials were used as sulfur hosts to prepare carbon-sulfur composite materials to analyze the relationship between the structural properties of the carbon materials and the electrochemical properties of the C/S composites.It was found that LD900 material with plenty of microporous and mesoporous shows three discharge platforms due to the limitation of microporous structure towards sulfur-containing species.However,the micropores and small mesopores are easily blocked during the cycle process,resulting in LD900-S's poor cycle stability.While the LD450 has plenty of polar oxygen-containing functional groups,it has plenty of chemisorption towards sulfur-containing species.In addition,the prepared LD450-S cathode exhibits improved cycle stability and rate performance.After 100 cycles at 0.1 C,the specific discharge capacity is 577 mA·h/g,and at 1 C,the specific discharge capacity is still 650 mA·h/g.