摘要
二氧化锡(SnO2)材料因具有储量丰富、理论容量高、嵌脱锂电位安全等一系列优点,在锂离子电池负极材料研究中受到广泛关注.然而, SnO2纳米材料在锂化反应过程中的机理,尤其是第一步转化反应是否可逆尚存在争议.本文利用常规水热法成功制备了平均粒径为4.4 nm的SnO2纳米颗粒,并在透射电子显微镜中构建了微型锂离子电池原型器件,对SnO2纳米颗粒在充放电过程中的微观形貌和物相演变进行原位表征.实验结果表明, SnO2纳米颗粒在嵌锂过程中率先生成了纳米尺寸的中间相Sn,随后发生了合金化反应转变为Li22Sn5相.脱锂反应后, Li22Sn5相转变为SnO2.分析认为,纳米晶界阻碍了Sn颗粒的聚集长大,使得Sn和Li2O能够充分接触,进而使脱锂反应能够完全进行,生成SnO2.研究结果对于如何提高SnO2基电极材料可逆比容量和循环性能具有一定的指导意义.
Tin oxide(SnO2)has attracted a lot of attention among lithium ion battery anode materials due to its rich reserves,high theoretical capacity,and safe potential.However,the mechanism of the SnO2 nano materials in the lithiation-delithiation reaction,especially whether the first-step conversion reaction is reversible,is still controversial.In this paper,SnO2 nanoparticles with an average particle size of 4.4 nm are successfully prepared via a simple hydrothermal method.A nanosized lithium ion battery that enables the in situ electrochemical experiments of SnO2 nanoparticles is constructed to investigate the electrochemical behavior of SnO2 in lithiation-delithiation process.Briefly,the nanosized electrochemical cell consists of a SnO2 working electrode,a metal lithium(Li)counter electrode on a sharp tungsten probe,and a solid electrolyte of lithium oxide(Li2O)layer naturally grown on the surface of metal Li.Then,the whole lithiation-delithiation process of SnO2 nanocrystals is tracked in real time.When a constant potential of–2 V is applied to the SnO2 with respect to lithium,lithium ions begin to diffuse from one side of the nanoparticles,which is in contact with the Li/Li2O layer,and gradually propagate to the other side.Upon the lithiation,a two-step conversion reaction mechanism is revealed:SnO2 is first converted into intermediate phase of Sn with an average diameter of 4.2 nm which is then further converted into Li22Sn5.Upon the delithiation,a potential of 2 V is applied and Li22Sn5 phase can be reconverted into SnO2 phase when completely delithiated.It is because the interfaces and grain boundaries of nano-sized SnO2 may impede the Sn diffusing from one grain into another during lithiation/delithiation and then suppress the coarsening of Sn,and enable the Li2O and Sn to be sufficiently contacted with each other and then converted into SnO2.This work provides a valuable insight into an understanding of phase evolution in the lithiation-delithiation process of SnO2 and the results are of great significance for improving the reversible capacity and cycle performance of lithium ion batteries with SnO2 electrodes.
作者
熊雨薇
尹奎波
文一峰
辛磊
姚利兵
朱重阳
孙立涛
Xiong Yu-Wei;Yin Kui-Bo;Wen Yi-Feng;Xin Lei;Yao Li-Bing;Zhu Chong-Yang;Sun Li-Tao(SEU-FEI Nano-Pico Center,Key Laboratory of MEMS of Ministry of Education,Southeast University,Nanjing 210096,China)
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
2019年第15期324-330,共7页
Acta Physica Sinica
基金
国家重点基础研究发展计划(批准号:2017YFA0204800)
国家自然科学基金(批准号:11674052,11525415,51420105003)资助的课题~~
关键词
SnO2纳米颗粒
锂化反应机理
原位表征
SnO2 nanoparticles
lithium reaction mechanism
in situ characterization
