核桃壳衍生活性炭孔结构的调控及其对锂硫电池性能的影响

Walnut Shell-based Activated Carbon for Li—S Batteries and the Effect of Pore Structure on the Performance

以核桃壳(WS)为碳源,KOH为活化剂,通过改变KOH/初级碳化物的质量比(碱碳比)来调控核桃壳活性炭孔结构,进而考察孔结构与硫/碳复合正极材料电化学性能的关系。研究表明,提高碱碳比,核桃壳活性炭的比表面积、总孔容与介孔孔容比例都明显增大,其复合正极的初始放电比容量与倍率性能都随着其比表面积、总孔容、介孔孔容比例均有先提高后降低的趋势。当碱碳比为6∶1时,比表面积(3913 m^(2)/g)、总孔容(2.26 cm^(3)/g)、介孔孔容比例(59.4%)较大的WSAC-6/S在0.2 C(1 C=279 mAh/g)下有最高的初始放电比容量(1397 mAh/g)与良好的循环稳定性,在循环100圈后放电比容量可维持在869 mAh/g,尤其在0.5 C下,仍然具有较好的电化学性能,在循环200圈后放电比容量可维持在707 mAh/g.

Walnut shell(WS)was used as carbon source and KOH as activator.A series of activated carbon with different pore structures were produced by changing the mass ratio of KOH to carbonized precursor from walnut shell(KOH/carbonized precursor ratio),so as to reveal the relationship between the pore structure and the electrochemical performance.The result shows that the specific surface area,total pore volume,and percentage of mesoporous volume of activated carbon increased obviously with rising KOH/carbonized precursor ratio.Both the initial discharge specific capacity and the scaling performance of the composite cathode increased of first and then decreased slightly with the increase of specific surface area,total pore volume,and percentage of mesoporous volume.When the KOH/carbonized precursor ratio was 6∶1,WSAC-6/S with large specific surface area(3913 m^(2)/g),total pore volume(2.26 cm^(3)/g),and percentage of mesoporous volume(59.4%)showed high initial specific capacity(1397 mAh/g)and stable charge/discharge performance(869 mAh/g after 100 cycles at 0.2 C).Especially,at 0.5 C,it still exhibited excellent electrochemical performance,and the specific discharge capacity maintained at 707 mAh/g after 200 cycles.