盐+碱协同对多孔碳电极材料电化学性能的影响

Synergistic Effect of Salt+Alkali on the Electrochemical Performance of Carbon Electrode Materials

摘要:

超级电容器作为一类新兴的能量存储转换器件，因其充放电速度快、寿命长和安全环保的特点而受到推崇。其中，用于超级电容器的电极材料一直是人们的研究重点，综合原料来源、价格和制备工艺等因素，多孔碳电极材料成为首选。盐模板法和KOH化学活化法都是制备多孔碳电极常用的方法，前者产物的孔结构以介孔为主，但操作复杂；后者活化产物比表面积大，可以精确控制多孔碳电极的孔径分布和孔体积，但该法活化后的多孔碳多以微孔为主。若将两者结合，形成优势互补，协同构建合理的碳材料结构，有助于提升多孔碳电极的电化学性能。以锂电负极行业的固废——针状焦的生焦粉为原料，利用模板和化学活化相结合的方法制备电极材料，探索盐（KCl）和碱（KOH）的添加比例对碳电极材料电化学性能的影响。研究结果表明，两种方法相结合制备得到的多孔碳样品的碳结构以表面缺陷较多的无定型碳为主。随着KOH加入量的增加，无定型结构的碳增加，但是加入过量的KOH并不能提高无定型碳的含量。三电极测试分析发现，样品PC-2表现出优异的电容性能，在1 A·g^-1的电流密度下，质量比电容达到266.9 A·g^-1；在10 A·g^-1的高电流密度下，容量保持率高达79.4%。该电极材料的内阻仅为0.67 Ω，并且双电层电容性能有极短的响应时间。当m(生焦粉)∶m(KCl)∶m(KOH)=1∶3∶2时，KCl和KOH的协同活化效果达到了最佳，显著提高了碳电极材料电荷的传输能力，且能有效地缩短电解质离子在材料内部的扩散路径，表现出较快的充放电速度。

Abstract:

As a new type of energy storage and conversion device， supercapacitors are highly praised for their fast charging and discharging speed， long service life， safety and environmental protection. Among them， electrode materials for supercapacitors have always been the focus of research. Considering the factors such as raw material source， price and preparation process， porous carbon electrode materials have become the first choice. Salt template method and KOH chemical activation method are common methods for preparing porous carbon electrodes. The former has complex operation， but the pore structure of the product is mainly mesoporous. The latter activation product has a large specific surface area， which can accurately control the pore size distribution and pore volume of the porous carbon electrode， but the porous carbon activated by this method is mainly micropores. If the two are combined to form complementary advantages and jointly construct a reasonable carbon material structure， it will help to improve the electrochemical performance of porous carbon electrodes. The electrode materials were prepared by a combination of template and chemical activation using the raw coke powder of needle coke， a solid waste in the lithium battery anode industry， as raw material. The effects of the addition ratio of salt （KCl） and alkali （KOH） on the electrochemical properties of carbon electrode materials were investigated. The results show that the carbon structure of the porous carbon samples prepared by the combination of the two methods is mainly amorphous carbon with more surface defects， and the amorphous carbon increases with the increase of KOH addition， but the addition of excessive KOH does not increase the content of amorphous carbon.In the three-electrode test analysis， it was found that the sample PC-2 showed excellent capacitance performance， and the mass specific capacitance reached 266.9 A·g^-1 at a current density of 1 A·g^-1. At a high current density of 10 A·g^-1， the capacity retention rate is as high as 79.4%. The internal resistance of the electrode material is only 0.67 Ω， and the electric double layer capacitance performance has a very short response time. Therefore， when the mass ratio of raw material， KCl and KOH is 1∶3∶2， the synergistic activation effect of KCl and KOH is the best， which greatly improves the charge transport capacity of carbon electrode materials， and can effectively shorten the diffusion path of electrolyte ions in the material， showing a faster charge and discharge rate.