摘要
正极是锂-氧气(Li-O_(2))电池的电化学反应场所,其直接决定了电池性能。本研究采用泡桐木为原材料,在NaCl/CoCl_(2)混合熔融盐介质中,以三聚氰胺和硫脲为氮源和硫源,一步热解炭化制备出Co、N、S共掺杂的三维自支撑多孔炭材料(wd-NSC),并直接用作Li-O_(2)电池正极。利用X射线衍射、扫描电镜、透射电镜、氮气吸脱附、拉曼光谱、X射线光电子能谱等对所获三维自支撑多孔炭材料的形貌、晶体结构与化学成分进行了表征。研究结果表明,Co、N、S共掺杂的三维自支撑多孔炭材料表现出高比容量(在0.05mA/cm^(2)的电流密度下,放电比容量可达12.83mA·h/cm^(2))和出色的循环稳定性(在电流密度为0.1mA/cm^(2)和限定容量为0.5mA·h/cm^(2)下,循环寿命可达125次),优异的电池性能可归因于三维分级多孔结构及Co、N、S共掺杂的协同作用。
Lithium-oxygen(Li-O_(2))batteries are considered as the most promising new generation energy storage devices because of their high theoretical energy density and environmental friendliness.However,large overpotential,low practical energy density and poor cycle life are the huge obstacles to their practical application.Since the insoluble and insulating discharge products(Li_(2)O_(2))gradually form on the surface or in the pores of cathode during the discharging process,these products will block the diffusion channel of O_(2)/electrolyte and cover the catalytic active sites.In addition,the sluggish kinetics of oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)require noble-metal-based materials as catalyst to reduce the overpotential and achieve high electrochemcial efficiency.However,high cost and scarcity of the noble-metal catalysts hinder their large scale applications.Development of economically viable and highly efficient noble-metal-free electrocatalysts is extremely urgent,especially for heteroatom doped carbons as the most promising candidates.In this paper,a novel Co,N and S co-doped three dimensional self-standing porous carbon(wd-NSC)was prepared as cathode for Li-O_(2)battery using melamine and thiourea as nitrogen and sulfur sources via one-step pyrolysis of paulownia wood in NaCl/CoCl_(2)mixed molten salt medium.X-ray diffraction(XRD)and scanning electron microscopy(SEM)results found that the wd-NSC inherited the original vertical channel structure of paulownia wood,and formed porous carbon fiber network on the surface and inside the channels of wd-NSC.Transmission electron microscopy(TEM)and X-ray photoelectron spectroscopy(XPS)confirmed that N and S were successfully doped into the C skeleton,while Co might exist in the form of single atom or clusters.Nitrogen adsorption/desorption isotherms showed that the wd-NSC possess hierarchical porous structure with pore sizes ranging from micropore to macropore.Raman spectra certified that the introduction of S increased the defect degree of wd-NSC.At a current density of 0.05mA/cm^(2),the discharge specific capacity of wd-NSC reached to 12.83mA·h/cm^(2),and exhibited a good rate capability and cycling stability(at a current density of 0.1mA/cm^(2)and a limited capacity of 0.5mA·h/cm^(2),the cell can maintain 125 cycles).The excellent electrochemical performance of wd-NSC in the Li-O_(2)battery could be attributed to the synergistic effect of three-dimensional hierarchical porous structure and Co,N,S heteroatoms co-doping.The above results demonstrated that this study provided a promising strategy to produce efficiency and low-cost cathodes for practical application in Li-O_(2)batteries.
作者
梁华根
齐正伟
贾林辉
盖泽嘉
荆胜羽
尹诗斌
LIANG Huagen;QI Zhengwei;JIA Linhui;GAI Zejia;JING Shengyu;YIN Shibin(Low Carbon Energy Institute,China University of Mining and Technology,Xuzhou 221008,Jiangsu,China;School of Information and Control Engineering,China University of Mining and Technology,Xuzhou 221008,Jiangsu,China;College of Chemistry and Chemical Engineering,MOE Key Laboratory of New Processing Technology for Non-ferrous Metals and Materials,Guangxi Key Laboratory of Processing for Non-ferrous Metals and Featured Materials,Guangxi University,Nanning 530004,Guangxi,China)
出处
《化工进展》
EI
CAS
CSCD
北大核心
2022年第5期2555-2565,共11页
Chemical Industry and Engineering Progress
基金
国家自然科学基金(21908242,21872040)
广西大学有色金属及特色材料加工重点实验室开放基金(2021GXYSOF10)。
关键词
锂-氧气电池
空气电极
三维自支撑
熔融盐
掺杂
电化学
纳米结构
制备
lithium-oxygen(Li-O_(2))battery
air electrode
three-dimensional self-standing
molten salt
doped
electrochemistry
nanostructure
preparation
