基于柠檬酸盐自模板法碳纳米片的制备及其在钠离子电容器中的应用

Self-template synthesis of carbon nanosheets based on salts citrate for sodium ion capacitors

由于电容型材料较低的比电容使得提高钠离子电容器(SICs)的能量密度成为目前研究的一大挑战.在此,文中通过直接碳化柠檬酸钠和柠檬酸钾制备了具有不同孔径分布的碳纳米片.所得的2种碳材料分别作为负极材料和正极材料时都表现出高的倍率性能和长的循环寿命.为了弥补电容材料比电容低的缺陷,以NaI作为氧化还原添加剂提供额外的容量.相比于未添加剂的SICs,NaI的加入可将SICs的能量密度从84.3 Wh·kg^-1提高到118.1 Wh·kg^-1,同时,功率密度最大可达40 kW·kg^-1.在充放电循环10000圈后,SICs的比容量仍可保持初始值的74%.这一策略对提升电化学储能器件的能量密度具有重要的指导意义.

It is a big challenge to enhance the energy density of sodium ion capacitors(SICs)in current research because of the low capacitance of capacitive materials.Herein,we prepare carbon nanosheets with different pore size distributions by directly carbonizing sodium citrate and potassium citrate,respectively.Both two kinds of carbon materials as anode and cathode materials deliver high rate capability and long cycle stability.In order to make up for the defect of low capacitance of capacitive materials,NaI is acted as redox additive to provide extra capacitance.Compared with SICs without the addition of NaI,the presence of NaI can enhance the energy density from 84.3 Wh·kg^-1 to 118.1 Wh·kg^-1,as well as a maximum power density of 40 kW kg^-1.After cycling 10000 cycles,the capacitance of SICs can retain 74%of initial value.This strategy has an important guiding effect on the improvement of energy density for energy storage devices.