摘要
使用电解液成膜添加剂是一种简单高效的提高电池循环稳定性的方法。氟代碳酸乙烯酯(FEC)的最低未被占据分子轨道(LUMO)能量较低,易被还原,通常被认为是很好的负极成膜添加剂,但因其最高占据分子轨道(HOMO)能量也较低,抗氧化性较好,故其被认为不在正极上发生作用。本工作结合电化学,形貌分析,化学成分表征,原位结构分析等方法研究了FEC添加剂在钠离子电池中的作用。我们发现适量的FEC添加剂不仅可以显著抑制电解液溶剂碳酸丙烯酯(PC)的分解,而且会在正极上形成一层富NaF的保护层,提高循环过程中正极晶格结构稳定性,从而提高电池的循环稳定性。密度泛函理论(DFT)计算表明,FEC之所以能在正极上形成保护层,可能与其容易在正极界面与钠盐阴离子ClO4-结合反应有关。
Driven by the wide-scale implementation of intermittent renewable energy generating technologies,such as wind and solar,sodiumion batteries have recently attracted attention as an inexpensive energy storage system due to the abundance,low cost,and relatively low redox potential of sodium.However,in comparison with lithium-ion batteries,which are known for long cycle life,sodium-ion batteries usually suffer from significant capacity fading during long-term cycling due to the large volume expansion/contraction of the electrode active materials caused by insertion/extraction of the large sodium ion.In recent years,intense effort has been focused on the search for high performance electrode materials and electrolytes to improve the cyclability of sodium-ion batteries,and some progress has been achieved.The incorporation of additives into the electrolyte is a simple and efficient method of improving the cycle stability of sodium-ion batteries.Fluoroethylene carbonate(FEC)is generally considered to be a suitable additive for the formation of the anode solid electrolyte interphase(SEI),due to a relatively lowlying lowest unoccupied molecular orbital(LUMO).However,it is suggested that FEC it will not be oxidized on the cathode since it also has a relatively low highest occupied molecular orbital(HOMO).In this study,we investigated the effect of FEC as an additive on the cycle life of a sodium-ion battery with a P2-NaxCo0.7Mn0.3O2(x≈1)layered sodium transition metal oxide as the cathode active material,a sodium metal foil anode,a glass fiber separator,and an electrolyte composed of NaC lO 4 and a varying mass content of FEC dissolved in propylene carbonate(PC).We analyzed the effect of the FEC additive on the morphology and chemical composition of the separator and cathode electrode surface using scanning electron microscopy(SEM),transmission electron microscopy(TEM),infrared spectroscopy,and X-ray photoelectron spectroscopy(XPS),and studied the evolution of the crystalline structure of the cathode active material durin
作者
程振杰
毛亚云
董庆雨
金锋
沈炎宾
陈立桅
CHENG Zhenjie;MAO Yayun;DONG Qingyu;JIN Feng;SHEN Yanbin;CHEN Liwei(School of Nano Technology and Nano Bionics,University of Science and Technology of China,Hefei230026,P.R.China;i-Lab,CAS Center for Excellence in Nanoscience,Suzhou Institute of Nano-Tech and Nano-Bionics,Chinese Academy ofSciences,Suzhou215123,Jiangsu Province,P.R.China;School of Materials Science and Engineering,Shanghai University,Shanghai200444,P.R.China.)
出处
《物理化学学报》
SCIE
CAS
CSCD
北大核心
2019年第8期868-875,共8页
Acta Physico-Chimica Sinica
基金
国家科技部(2016YFB0100102)
中国科学院战略性先导专项(XDA09010600,XDA09010303)
国家自然科学基金(21625304,21733012)资助项目~~
